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The trabecular meshwork: Structure, function and clinical implications. A review of the literature
Abstract
Glaucoma is a blinding optic neuropathy, the main risk factor for which is increased intraocular pressure (IOP). The trabecular meshwork, located within the iridocorneal angle, is the main pathway for drainage of aqueous humor (AH) out of the eye, and its dysfunction is responsible for the IOP elevation. The trabecular meshwork is a complex, fenestrated, three-dimensional structure composed of trabecular meshwork cells (TMC) interdigitated into a multilayered organization within the extracellular matrix (ECM). The purpose of this literature review is to provide an overview of current understanding of the trabecular meshwork and its pathophysiology in glaucoma. Thus, we will present the main anatomical and cellular bases for the regulation of aqueous humor outflow resistance, the pathophysiological mechanisms involved in trabecular dysfunction in the various types of glaucoma, as well as current and future therapeutic strategies targeting the trabecular meshwork.
... It is produced daily by the ciliary body processes in the posterior chamber of the eye [21,22]. After fulfilling its functions, the aqueous humor is drained from the eye through the trabecular meshwork located in the iridocorneal angle or through the uveoscleral outflow into the episcelar space [20][21][22][23]. Therefore, if additional elements, such as blood, inflammatory cells, pigment cells, and other metabolic products, appear in the fluid, they block the sieve and the fluid cannot drain freely from the eye [24,25]. ...
... However, in glaucoma, the outflow is most often obstructed without any apparent cause [24,26]. The outflow process of the aqueous humor is as follows: after being drained through the pupil, it flows through the trabecular meshwork in front of the scleral spur and the iris implant to the Schlemm's canal, then to the episcleral venous system, the orbital venous system, and finally, to the systemic venous circulation [21,23,24]. ...
... The impeded drainage of the AH results in elevated intraocular pressure, exerting stress on the optic nerve, which is widely considered to be a major factor contributing to the development of glaucoma [21,23,24,26]. This condition ultimately leads to the degeneration of nerve fibers and contributes to a gradual reduction in the visual field [15,22,27]. ...
The study of the aqueous humor (AH) plays a key role in understanding the pathophysiology of glaucoma. The AH provides nutrition, maintains the appropriate intraocular pressure, and provides important information about the mechanisms of the disease. The development of modern technologies has allowed the use of more accurate analytical methods, which has proven to be a key factor in determining the changes occurring in the proteome of the aqueous humor of glaucoma patients. Recently, researchers have observed changes in the levels of proteins associated with inflammation, oxidative stress, the complement system, and extracellular matrix remodeling. They have also shown that these changes may be variable for different types of glaucoma. The objective of this review is to collect and summarize the current knowledge on the potential biomarkers and pathomechanisms involved in the pathogenesis of glaucoma. We hope that our review will contribute to the improvement of current diagnostic methods in this illness and, through a better understanding of the changes occurring during the progression of the disease, will enable the development of more effective preventive and therapeutic strategies in the future.
... The TM has three layers: the inner uveal meshwork, the middle corneoscleral meshwork, and the outer juxtacanalicular meshwork, as shown in Figure 4 [102]. The trabecular outflow pathway is the main one for aqueous humour to drain out of the eye [102]. ...
... The TM has three layers: the inner uveal meshwork, the middle corneoscleral meshwork, and the outer juxtacanalicular meshwork, as shown in Figure 4 [102]. The trabecular outflow pathway is the main one for aqueous humour to drain out of the eye [102]. Via this pathway, aqueous flows through the trabecular meshwork (TM), Schlemm's canal, and the collector channels, and enter the aqueous veins [35,102]. ...
... The trabecular outflow pathway is the main one for aqueous humour to drain out of the eye [102]. Via this pathway, aqueous flows through the trabecular meshwork (TM), Schlemm's canal, and the collector channels, and enter the aqueous veins [35,102]. Pseudoexfoliative material can be found on the trabecular meshwork and downstream of the trabecular outflow pathway i.e., Schlemm's canal, the collector channels, aqueous, and episcleral veins [18,64,103]. ...
Pseudoexfoliation syndrome (PXS) is an age-related fibrillopathy where fibrillar exfoliation material accumulates and deposits in ocular and extra-ocular tissue. Within the eye, this substance accumulates on the ocular surface and in the anterior segment of the eye, impacting ocular structures such as the conjunctiva, Tenon’s capsule, sclera, cornea, iris, ciliary body, trabecular meshwork, and lens. This review aims to collate the current literature on how each anatomical part of the eye is affected by PXS, with a strong focus on molecular changes. We also summarise the current understanding of the key genetic factors influencing the development of PXS.
... The trabecular meshwork is a 3-dimensional structure located within the iridocorneal angle. It is composed of trabecular meshwork cells within a multilayered extracellular matrix [21]. The trabecular meshwork affects intraocular pressure by regulating the drainage of aqueous humor. ...
... The trabecular meshwork affects intraocular pressure by regulating the drainage of aqueous humor. This pathway works by draining the humor from the anterior chamber of the eye into the adjacent Schlemm's canal and then via aqueous vein collector channels and into the venous system [21]. ...
... Studies have shown that the increased resistance is related to a mechanism of trabecular stiffening involving senescence and apoptosis of trabecular meshwork cells and remodeling of the extracellular matrix [21]. Uveoscleral outflow is considered the less conventional pathway of aqueous humor drainage but is in fact of significance as a pharmacologic target. ...
... At day 0 before injection and days 2, 4, 6,7,9,11,13,14,16,18,20,22, and 29 after first injection, mice were delivered 2% isoflurane (RWD life science company, Shenzhen, China) at an oxygen delivery rate of 0.6 L/min using an anesthesia machine (R500IE, RWD life science company, China). IOP readings were noted in the morning simultaneously for all subjects with a rebound tonometer (ICare Tonolab, Espoo, Finland), and the average of five readings was calculated and used for further analysis. ...
... High IOP is a key risk factor for glaucoma, and trabecular meshwork is responsible for the aqueous humor circulation. 20 To investigate the effect of IFN-β on IOP levels and trabecular meshwork in vivo, we established a model by injecting 5000 U/mL IFN-β in the anterior chamber of mouse eyes. IOP was measured before injection and at the same intervals for 28 days after injection ( Figure 6A). ...
... 23,24 Changes in this 3D structure result in pathological IOP elevation and further cause open-angle glaucoma. 20 In patients with open-angle glaucoma, marked loss of TM cells was observed in the anterior chamber, leading to fusion and thickening of the trabecular lamellae. 25,26 This suggests that normal TM cell activity and function maintenance is essential for IOP stability. ...
Singleton–Merten syndrome (SMS) is a rare immunogenetic disorder affecting multiple systems, characterized by dental dysplasia, aortic calcification, glaucoma, skeletal abnormalities, and psoriasis. Glaucoma, a key feature of both classical and atypical SMS, remains poorly understood in terms of its molecular mechanism caused by DDX58 mutation. This study presented a novel DDX58 variant (c.1649A>C [p.Asp550Ala]) in a family with childhood glaucoma. Functional analysis showed that DDX58 variant caused an increase in IFN‐stimulated gene expression and high IFN‐β‐based type‐I IFN. As the trabecular meshwork (TM) is responsible for controlling intraocular pressure (IOP), we examine the effect of IFN‐β on TM cells. Our study is the first to demonstrate that IFN‐β significantly reduced TM cell viability and function by activating autophagy. In addition, anterior chamber injection of IFN‐β remarkably increased IOP level in mice, which can be attenuated by treatments with autophagy inhibitor chloroquine. To uncover the specific mechanism underlying IFN‐β‐induced autophagy in TM cells, we performed microarray analysis in IFN‐β‐treated and DDX58 p.Asp550Ala TM cells. It showed that RSAD2 is necessary for IFN‐β‐induced autophagy. Knockdown of RSAD2 by siRNA significantly decreased autophagy flux induced by IFN‐β. Our findings suggest that DDX58 mutation leads to the overproduction of IFN‐β, which elevates IOP by modulating autophagy through RSAD2 in TM cells.
... Trabecular meshwork (TM) represents the tissue of primary damage in any form of glaucoma. [1][2][3][4] Several molecular events precede the onset of structural or functional damage in the tissue resulting in manifest clinical features like raised intraocular pressure (IOP) and optic nerve/visual field damage. Decreased cellularity and loss of regular compact arrangement of the trabecular beams with epithelial-mesenchymal transition (EMT) changes are some structural changes that have been reported on histologic analysis, with majority of these studies being on cadaveric eyes with end-stage glaucoma. ...
... Decreased cellularity and loss of regular compact arrangement of the trabecular beams with epithelial-mesenchymal transition (EMT) changes are some structural changes that have been reported on histologic analysis, with majority of these studies being on cadaveric eyes with end-stage glaucoma. [3][4][5][6][7][8] Yet studying TM in vivo is challenging since the TM specimens obtained from routine trabeculectomy done in moderate-severe glaucoma contain very few viable cells, precluding useful tissue analysis by any molecular method like transcriptome or immunoblotting. [3,4,7,[8][9][10][11] Early glaucoma patients are rarely offered surgery, keeping in mind the catastrophic complications associated with routine trabeculectomy, which makes it impossible to study the molecular events in the tissue in early disease stages. ...
... [3][4][5][6][7][8] Yet studying TM in vivo is challenging since the TM specimens obtained from routine trabeculectomy done in moderate-severe glaucoma contain very few viable cells, precluding useful tissue analysis by any molecular method like transcriptome or immunoblotting. [3,4,7,[8][9][10][11] Early glaucoma patients are rarely offered surgery, keeping in mind the catastrophic complications associated with routine trabeculectomy, which makes it impossible to study the molecular events in the tissue in early disease stages. This mandates a study of in vitro models for studying disease pathogenesis, with clinical in vivo validation of in vitro being a challenge. ...
Purpose
To report the histopathologic correlates of trabecular meshwork (TM) specimens procured by microincisional trabeculectomy (MIT) for different severities of glaucoma (early glaucoma: visual field mean deviation [MD] <−6 dB, moderate glaucoma: MD from − 6 to − 12 dB, and advanced glaucoma: MD <−12 dB).
Methods
TM specimens from four patients undergoing MIT with or without cataract surgery were analyzed by routine histopathology for structural changes. The number of cells, the number of cells with spindle-shaped nuclei suggestive of epithelial–mesenchymal transformation (EMT), and the distance between the trabecular beams were calculated using different tools on freely available ImageJ software using the line or pint/count tool.
Results
The TM specimens procured from two early and two advanced glaucoma cases showed decreasing cellularity and decreased compact arrangement of the trabecular beams in severe disease stages. The number of cells and preserved architecture in all four specimens were evident, with > 50 cells being present per section in all four cases despite the glaucoma being of advanced disease stage in two patients.
Conclusion
The TM specimens obtained from MIT can be utilized for downstream analysis using different molecular methods for studying the molecular events in the tissue from early to severe glaucoma.
... It is well established that intraocular pressure (IOP) is maintained by a delicate balance between aqueous humor production in the ciliary body and its drainage via two outflow pathways. Approximately 75% of aqueous humor outflow occurs through the trabecular meshwork (TM) and Schlemm's canal [11]. There is evidence that a dysfunction of the TM is one of the primary contributory factors that leads to elevated IOP and subsequent retinal damage and vision loss [11]. ...
... Approximately 75% of aqueous humor outflow occurs through the trabecular meshwork (TM) and Schlemm's canal [11]. There is evidence that a dysfunction of the TM is one of the primary contributory factors that leads to elevated IOP and subsequent retinal damage and vision loss [11]. Compounds that lower IOP exert their pharmacological effects through various mechanisms, one of which is by modulating TM outflow facility [12]. ...
Background:
Hydrogen sulfide (H2S)-releasing compounds can reduce intraocular pressure in normotensive rabbits by increasing aqueous humor (AH) outflow through the trabecular meshwork. In the present study, we investigated the contribution of endogenous H2S and the role of intramurally generated prostaglandins in the observed increase in AH outflow facility in an ex vivo porcine ocular anterior segment model.
Material and methods:
Porcine ocular anterior segment explants were perfused with Dulbecco's Modified Eagle's Medium maintained at 37 °C and gassed with 5% CO2 and 95% air under an elevated pressure of 15 mmHg for four hours. Perfusates from the anterior segment explants were collected and immediately assayed for their H2S and prostaglandin E2 content.
Results:
Elevating perfusion pressure from 7.35 to 15 mm Hg significantly (p < 0.001) increased H2S concentration in the perfusate from 0.4 ± 0.1 to 67.6 ± 3.6 nM/µg protein. In the presence of an inhibitor of cystathionine ß-synthase/cystathionine γ-lyase, aminooxyacetic acid (AOAA, 30 µM), or an inhibitor of 3-mercaptopyruvate sulfurtransferase, α-ketobutyric acid (KBA, 1 mM), the effects of elevated pressure on H2S levels in the perfusate was significant (p < 0.001). Furthermore, flurbiprofen (30 µM) and indomethacin (10 µM) attenuated the elevated pressure-induced increase in H2S levels in the perfusate. Interestingly, elevating perfusion pressure had no significant effect on PGE2 concentrations in the perfusate. While the inhibition of H2S biosynthesis by AOAA or KBA did not affect PGE2 levels in perfusate, flurbiprofen (30 µM) caused a significant (p < 0.05) decrease in the concentration of PGE2 under conditions of elevated perfusion pressure.
Conclusions:
We conclude that the elevated perfusion pressure-induced increase in H2S concentrations depends upon the endogenous biosynthesis of H2S and intramurally produced prostaglandins in the porcine anterior segment explants. While the concentration of PGE2 in the perfusate under elevated perfusion pressure was unaffected by pretreatment with inhibitors of H2S biosynthesis, it was reduced in the presence of an inhibitor of cyclooxygenase.
... Although steroid-induced glaucoma accounts for a minor fraction of clinical cases, stimulation of Trabecular Meshwork Cells (TMCs) with GCs in vitro is often adopted as an experimental model to investigate the global metabolism of this cell type and the molecular mechanisms underscoring glaucoma onset [7]. In fact, TMCs serve key roles in regulating the composition and turnover of the trabecular meshwork (TM), which is the main outflow pathway of aqueous humor (AH), a fluid which shapes the globe of the eye and nourishes the tissues of the anterior chamber [8,9]. The balance between AH production by the ciliary body and its drainage through the TM are the major determinants of IOP regulation. ...
... Additionally, it is worth underscoring the fact that Ub-peptides of proteins involved in cell proliferation and cell-cycle control were identified as downregulated in dexa-treated cells. This finding may have implications in interpreting the reduced proliferation and lower TMC count and density documented in animal disease models [3,8,9]. Moreover, this finding is consistent with the upregulation of the p21 protein, which is a master regulator of the G1/S transition, and of cyclin D, under the same experimental condition, previously reported by us [21,43]. ...
Glaucoma is chronic optic neuropathy whose pathogenesis has been associated with the altered metabolism of Trabecular Meshwork Cells, which is a cell type involved in the synthesis and remodeling of the trabecular meshwork, the main drainage pathway of the aqueous humor. Starting from previous findings supporting altered ubiquitin signaling, in this study, we investigated the ubiquitin-mediated turnover of myocilin (MYOC/TIGR gene), which is a glycoprotein with a recognized role in glaucoma pathogenesis, in a human Trabecular Meshwork strain cultivated in vitro in the presence of dexamethasone. This is a validated experimental model of steroid-induced glaucoma, and myocilin upregulation by glucocorticoids is a phenotypic marker of Trabecular Meshwork strains. Western blotting and native-gel electrophoresis first uncovered that, in the presence of dexamethasone, myocilin turnover by proteasome particles was slower than in the absence of the drug. Thereafter, co-immunoprecipitation, RT-PCR and gene-silencing studies identified STUB1/CHIP as a candidate E3-ligase of myocilin. In this regard, dexamethasone treatment was found to downregulate STUB1/CHIP levels by likely promoting its proteasome-mediated turnover. Hence, to strengthen the working hypothesis about global alterations of ubiquitin-signaling, the first profiling of TMCs ubiquitylome, in the presence and absence of dexamethasone, was here undertaken by diGLY proteomics. Application of this workflow effectively highlighted a robust dysregulation of key pathways (e.g., phospholipid signaling, β-catenin, cell cycle regulation) in dexamethasone-treated Trabecular Meshwork Cells, providing an ubiquitin-centered perspective around the effect of glucocorticoids on metabolism and glaucoma pathogenesis.
... The iridocorneal angle is a structure at the periphery of the anterior chamber of the eye, between the iris and the cornea-the anterior wall of the angle pertains to the sclera, the posterior wall is the anterior face of the iris, and between the two we may find the ciliary body and the trabecular meshwork (a filtering structure connecting the anterior chamber and Schlemm's canal-a circular channel, situated in the scleral sulcus, with a lymphatic-like structure) [7][8][9]. This ocular structure is important in glaucoma classification and pathophysiology because it houses the two aqueous humor (AH) outflow pathways: ...
... In PACG, there is contact between the peripheral iris and the trabecular meshwork, which impairs the capacity of AH to reach the trabecular meshwork and filter through. In POAG, due to a remodeling of the extracellular matrix and cell aging and death in the trabecular meshwork, there is increased resistance in the trabecular meshwork; therefore, the outflow is lowered [8]. ...
Glaucoma is a widespread ophthalmological disease, with a high impact and frequent visual morbidity. While the physiopathology of the two types of primary glaucoma (open angle and angle closure) has been studied, there seems to be little relationship between the two. In this study, we gather clinical and preclinical data to support the idea that the two primary glaucomas are “mirrored” in terms of morphological parameters and disease physiopathology. In short, primary angle closure glaucoma (PACG) is associated with hyperopia and low axial length, and primary open angle glaucoma (POAG) is associated with myopia and high axial length. Moreover, in PACG and in primary angle closure or primary angle closure suspect cases, while there is extensive iridotrabecular contact, the intraocular pressure (IOP) is still maintained in the lower half of the normal range throughout the evolution of the disease, which suggests a baseline trabecular hyperfiltration in PACG. In the opposite case, myopic eyes with open angles and a higher risk of developing POAG often have a baseline IOP in the upper half of the normal range, suggesting a baseline trabecular hypofiltration. As we explore clinical, genetic and animal model data regarding these opposing aspects, we hypothesize the existence of a mirroring relationship between PACG and POAG. Defining the relationship between the two potentially blinding diseases, with a high prevalence worldwide, may aid in understanding the mechanisms better and refining diagnosis and treatment. Thus, our theory has been named the Mirror Theory of Primary Glaucomas.
... The TM is a complex structure with properties of endothelial cells, myofibroblasts, and macrophages. It plays a crucial role in secreting extracellular matrix (ECM) proteins and maintaining ECM remodeling and renewal, which are essential for the normal regulation of resistance [7]. ...
... This stiffening is correlated with the apoptosis of TM cells, alterations in the ECM, and reorganization of the actin cytoskeleton [8,9]. These changes in the TM resemble age-related changes but progress more rapidly in individuals with glaucoma [7,10]. Traditional anti-glaucoma agents do not target the TM. ...
Glaucoma is a chronic neurodegenerative disease that poses a significant threat of irreversible blindness worldwide. Current treatments for glaucoma focus on reducing intraocular pressure (IOP), which is the only modifiable risk factor. Traditional anti-glaucomatous agents, including carbonic anhydrase inhibitors, beta-blockers, alpha-2 agonists, and prostaglandin analogs, work by either improving uveoscleral outflow or reducing aqueous humor production. Rho kinase (ROCK) inhibitors represent a novel class of anti-glaucomatous drugs that have emerged from bench to bedside in the past decade, offering multifunctional characteristics. Unlike conventional medications, ROCK inhibitors directly target the trabecular meshwork outflow pathway. This review aims to discuss the mechanism of ROCK inhibitors in reducing IOP, providing neuroprotection, and preventing fibrosis. We also highlight recent studies and clinical trials evaluating the efficacy and safety of ROCK inhibitors, compare them with other clinical anti-glaucomatous medications, and outline future prospects for ROCK inhibitors in glaucoma treatment.
... Pseudoexfoliative material is made of abnormal fibrotic fiber [8]. Histologically those fibers are very similar to fibrous tissue fibers. ...
... PEXs are the most commonly present at iris pupillary margin ( Figure 1) and anterior lens capsule ( Figure 2). In the body PEX is accumulated in visceral organs as well as in blood vessels [8]. The aim of this study was to determine an incidence of patients with PEX in two different regions of Serbia. ...
Introduction /Objective. Pseudoexfoliation (PEX) is an age-related systemic disorder, which can affect the whole body, as well as the eye. It is characterized by abnormal production and accumulation of pseudoexfoliative material. When present in the eye, it can cause different difficulties, but most common are PEX glaucoma (XFG) and intraoperative and postoperative complications of cataract surgeries. The aim of this study was to determine an incidence of patients with PEX in two different regions of Serbia. Methods. The study included 7451 patients scheduled for cataract surgery in two regions of Serbia. It was designed as a multicentric, retrospective study with evaluation of the medical records of all patients who underwent cataract surgery. Thu study evaluated: incidence of PEX syndrome and PEX glaucoma, age and gender of patients, as well as preoperative antiglaucomatous therapy and intraoperative and postoperative cataract surgery complications. Results. XFS was recorded in 676 patients (407 females and 269 males), while 243 patients had XFS. It represented 3.26% of patients included in the study. Mean age of XFG patients was 78.1 ? 2.1 years with a statistically significant difference (p<0.05) among incidence of XFG in females compared to males. Intraoperative and postoperative complications during cataract surgery were significantly commonly in patients with PEX (p<0.05) Conlusion. PEX can complicate cataract surgery, while on the other hand XFG is more difficult to treat and control than most other glaucomas. Therefore, patients with PEX require special treatment during follow-up and treatment.
... Trabecular meshwork is a sieve-like structure, which acts as a filter between the anterior chamber and Schlemm´s canal, a circular canal that collects the aqueous and evacuates it into the extraocular circulation. Which bridges the scleral sulcus, inserts anteriorly into the peripheral cornea at the level of Schlemm´s line, posteriorly; the trabecular lamellae are connected to the junction between the ciliary body, iris and scleral spur (17). The uveal meshwork is in indirect communication with the aqueous humor, pillars extending from the iris root and ciliary body to Schlemm´s line, the corneoscleral meshwork, represent most of the trabecular meshwork, lamellae transverse by orifices, which extend and grow from the anterior wall of the scleral sulcus to the scleral spur (18). ...
Introduction: Glaucoma is the first cause of irreversible blindness. Endocyclophotocoagulation is a cyclodestructive procedure that reduces the production of aqueous humour partially. To know the presence of ultramicroscopic changes on the ciliary body after endocyclophotocoagulation. Material and methods: This is a prospective and longitudinal study about 10 eyes (9 patients). They were undergone to phacoemulsification and endocyclophotocoagulation doing an ultramicroscopic measurement before surgery, one week and three months after surgery. Measurements were compared with ANOVA and Friedman test. The statistical significance was p < 0.05. Results: The values CBT0, CBTMAX, CBT 100 presented a reduction in all the measurements presenting statistical significance after 90 days. There were no changes in LV and ACD in the postoperative measurements. Conclusion: There are changes in the anatomical measurements of the ciliary body after endocyclophotocoagulation.
... Trabecular meshwork is a sieve-like structure, which acts as a filter between the anterior chamber and Schlemm´s canal, a circular canal that collects the aqueous and evacuates it into the extraocular circulation. Which bridges the scleral sulcus, inserts anteriorly into the peripheral cornea at the level of Schlemm´s line, posteriorly; the trabecular lamellae are connected to the junction between the ciliary body, iris and scleral spur (17). The uveal meshwork is in indirect communication with the aqueous humor, pillars extending from the iris root and ciliary body to Schlemm´s line, the corneoscleral meshwork, represent most of the trabecular meshwork, lamellae transverse by orifices, which extend and grow from the anterior wall of the scleral sulcus to the scleral spur (18). ...
Introducción: La cardiopatía isquémica es la principal causa de mortalidad en el mundo y México. La rehabilitación cardiaca ambulatoria es una medida no farmacológica de prevención secundaria, cuya aplicación y estudio es limitado en población mexicana. Por lo anterior, el objetivo del presente estudio fue identificar el nivel de conocimiento en rehabilitación cardiaca ambulatoria en adultos mexicanos. Material y métodos: Estudio observacional, transversal y descriptivo en una unidad de medicina familiar en México. Se incluyeron hombre y mujeres, de 40 a 80 años, con enfermedad coronaria crónica. Se realizó un cálculo de muestra por una prevalencia con una n=240 adultos. Se aplicó el “Coronary Artery Disease Education Questionnaire Short Versión (CADE-Q SV) y cédula de datos sociodemográficos. El análisis univariado de variables cualitativas fue a través de frecuencias y porcentajes. Para variables cuantitativas se determinó su tipo de distribución, mediante criterio de prueba estadística (Komogorov- Smirnof, considerando una p > 0.05) empleándose mediana y rangos intercuartilares (RIC 25, 75). Resultados: De un total de 240 participantes, el 72.2% fue de sexo masculino, la mediana de edad fue de 69 años y el 93% presento hipertensión arterial sistémica. El 57.3% y 30.4% presentaron un nivel de conocimiento de rehabilitación cardiaca ambulatoria bueno y genial, respectivamente. Conclusiones: El nivel de conocimiento sobre rehabilitación cardiaca ambulatoria es bueno en la población estudiada, sin embargo, se requieren estudios longitudinales con modelos multivariados que puedan constatar los factores que influyen en el nivel de conocimiento de rehabilitación cardiaca.
... A literatura já demonstra que os conservantes presentes na maioria dos hipotensores oculares podem ter efeito negativo e deletério para as células trabeculares, agravando e acelerando o adoecimento trabecular, agravando o GAA. (5)(6)(7)(8) Além dos fatores relacionados aos efeitos adversos, existe um alto custo relacionado ao uso crônico de medicamentos, com enorme impacto econômico tanto do ponto de vista individual quanto da perspectiva dos sistemas de saúde. (9)(10)(11)(12) A trabeculoplastia seletiva a laser (SLT) consiste na aplicação de um laser específico (Nd-YAG laser de dupla frequência de 532 nm) diretamente sobre a malha trabecular, agindo intrinsicamente na célula trabecular, com o mínimo de dano tecidual, visando melhorar o fluxo de escoamento do humor aquoso. ...
... 15 The trabecular meshwork, a key structure in the anterior chamber, is responsible for regulating aqueous humor outflow. 16 When the ability of the trabecular meshwork to regulate outflow is compromised, drainage efficiency decreases, leading to elevated IOP. 17 TMCs are crucial for maintaining the structure and function of the trabecular meshwork, primarily through the production and remodeling of the extracellular matrix (ECM), which provides the structural framework of the meshwork. 18 In cases of glaucoma, dysregulation of TMC activity can result in the accumulation of excessive ECM material, thereby increasing resistance to aqueous humor outflow. ...
Purpose
Silicone oil (SiO) is commonly employed as an intravitreal tamponade to manage complex retinal detachments associated with proliferative diabetic retinopathy, trauma, or severe myopia and to facilitate retinal reattachment. Nevertheless, SiO usage is linked to several complications, notably secondary glaucoma, which constitutes a significant proportion of adverse effects. This study investigated the impact of SiO on trabecular meshwork cells, given their pivotal role in regulating aqueous humor outflow.
Methods
Human trabecular meshwork cells (HTMCs) were co-cultured with SiO. The impact on proliferation, fibrosis-related markers, and ferroptosis levels on these cells was evaluated using 5-ethynyl-2′-deoxyuridine (EdU), western blot, and immunofluorescence assays. Further gene knockdown experiments with NOX4 and Smad3 were conducted to elucidate the underlying mechanisms of SiO-induced changes.
Results
SiO intervention inhibited HTMC proliferation, upregulated fibrosis-related markers, and elevated ferroptosis levels. Gene knockdown experiments revealed that SiO-induced ferroptosis and reactive oxygen species (ROS) increase were mediated through NOX4 upregulation and Smad3 activation.
Conclusions
These findings highlight the significance of ferroptosis and the ROS/NOX4/Smad3 axis in the mechanism of SiO-induced intraocular pressure elevation. The insights gained from this study identify potential therapeutic targets to mitigate postoperative complications associated with SiO tamponade in ophthalmic surgery.
... The ICA forms a peripheral portion of the anterior chamber, where the cornea, sclera, and the base of the iris meet (16, 30). The ICA is composed of a reticular network of connective tissue beams, known as trabeculae, which are lined either partially or entirely by a single layer of cells (16,31,32). ...
In this review, we explore the transformative role of Ultrasound Biomicroscopy (UBM) in veterinary ophthalmology, focusing on its utility in evaluating the iridocorneal angle and ciliary body in dogs. We begin by outlining UBM’s foundational principles, providing a holistic understanding of its operational mechanics. This is followed by an exploration of the techniques and considerations for optimal UBM imaging, including the use of topical anesthesia, probe positioning, and maintaining a controlled measurement environment. A major section is dedicated to the detailed anatomy of the anterior segment, emphasizing the iridocorneal angle and ciliary body in controlling aqueous humor dynamics within canine and feline eyes. By comparing anatomical structures in humans and animals, we highlight the need for distinct parameters in veterinary medicine. The review also analyzes the parameters obtainable via UBM, emphasizing its potential in monitoring drug-induced ocular changes, gaging post-cataract surgical outcomes, and observing inter-species variations. We conclude by encapsulating the current state of research, addressing existing challenges, and suggesting future research avenues. This synthesis underscores the pivotal role of UBM in advancing veterinary ophthalmic diagnostics and research.
... therefore, for patients undergoing glaucoma filtration surgery, timely and regular treatment of scar formation in the filtration channel is crucial [10]. currently, corticosteroids are the main method for preventing and treating scar formation in the filtration channel after glaucoma surgery [11]. however, the long-term use of corticosteroids can lead to complications such as high intraocular pressure and cataracts, which limits their clinical use [12]. ...
Purpose
To prepare a polyglycolic acid-loaded mitomycin drug (MMC-ATS-@PLGA) to inhibit scar proliferation after glaucoma filtering surgery (GFS) via an anti-inflammatory mechanism that minimally affected intraocular pressure, which provided another therapeutic strategy for this disease.
Methods
We first detected the physicochemical properties of MMC-ATS-@PLGA. Next, we tested the biosafety of MMC-ATS-@PLGA in vivo and in vitro. Then, we assessed the therapeutic effects of MMC-ATS-@PLGA by laboratory and clinical examinations.
Results
In this study, we synthesized a new type of nanomedicine (MMC-ATS-@PLGA) with good stability and biocompatibility for inhibiting scar proliferation after GFS. The break-up time (BUT), Schimer test and intraocular pressure changes in GFS rabbits before and after treatment with MMC-ATS-@PLGA were not significantly different. Three weeks after GFS, the MMC-ATS-@PLGA group displayed significant decreases in nuclear volume, corneal cell oedema, type I and III collagen fibre expression, normal organelle morphology and collagen fibre arrangement. Compared with those in the FML and MMC groups, the α-SMA, CTGF and type III collagen fibres in the MMC-ATS-@PLGA group decreased more significantly, indicating that MMC-ATS-@PLGA can effectively inhibit the expression of these inflammatory factors during the inhibition of scar proliferation after GFS.
Conclusion
We successfully synthesized MMC-ATS-@PLGA, which could effectively inhibit scar proliferation after GFS via anti-inflammatory effects but had little effect on intraocular pressure. This new type of nanomedicine has good biosafety and stability and is worthy of further exploration in clinical practice.
... HTM cells from the anterior meshwork region and the inner uveal beams stain positively for neuronal-specific enolase. In contrast, cells of the posterior region do not 50 , and functional differences within the TM depend on localization 51 . Staining for neuronal-specific enolase could be used to identify the origin of TM cells in cell culture, eliminating this variable in further research. ...
The trabecular meshwork (TM) is crucial for regulating intraocular pressure (IOP), and its dysfunction significantly contributes to glaucoma, a leading cause of vision loss and blindness worldwide. Although rodents are commonly used as animal models in glaucoma research, the applicability of these findings to humans is limited due to the insufficient understanding of murine TM. This study aimed to compare primary human TM (hTM) and murine TM (mTM) cells in vitro to enhance the robustness and translatability of murine glaucoma models. In this in vitro study, we compared primary hTM and mTM cells under simulated physiological and pathological conditions by exposing both cell types to the glucocorticoid dexamethasone (DEX) and Transforming Growth Factor β (TGFB2), both of which are critical in the pathogenesis of several ophthalmological diseases, including glaucoma. Phagocytic properties were assessed using microbeads. Cells were analyzed through immunocytochemistry (ICC) and Western blot (WB) to evaluate the expression of extracellular matrix (ECM) components, such as Fibronectin 1 (FN1) and Collagen IV (COL IV). Filamentous-Actin (F-Act) staining was used to analyze cross-linked actin network (CLAN) formation. Additionally, we evaluated cytoskeletal components, including Vimentin (VIM), Myocilin (MYOC), and Actin-alpha-2 (ACTA2). Our results demonstrated significant similarities between human and murine TM cells in basic morphology, phagocytic properties, and ECM and cytoskeletal component expression under both homeostatic and pathological conditions in vitro. Both human and murine TM cells exhibited epithelial-to-mesenchymal transition (EMT) after exposure to DEX or TGFB2, with comparable CLAN formation observed in both species. However, there were significant differences in FN1 and MYOC induction between human and murine TM cells. Additionally, MYOC expression in hTM cells depended on fibronectin coating. Our study suggests that murine glaucoma models are potentially translatable to human TM. The observed similarities in ECM and cytoskeletal component expression and the comparable EMT response and CLAN formation support the utility of murine models in glaucoma research. The differences in FN1 and MYOC expression between hTM and mTM warrant further investigation due to their potential impact on TM properties. Overall, this study provides valuable insights into the species-specific characteristics of TM and highlights opportunities to refine murine models for better relevance to human glaucoma.
... Most aqueous humor outflow flows through the trabecular meshwork and the canal of Schlemm, which are parts of the trabecular pathway. [21] In the uveoscleral pathway, aqueous humor passes into the supraciliary and suprachoroidal spaces through the ciliary muscle. [22] Both routes drain the aqueous humor into the venous circulation. ...
Juvenile glaucoma, or primary juvenile open-angle glaucoma (JOAG), is a rare yet significant form of glaucoma seen in individuals younger than 40. The condition is distinguished by increased intraocular pressure, optic nerve damage, and loss of vision in the field of view. Inadequate treatment can result in permanent vision loss. JOAG arises from the abnormal development of trabecular meshwork. Besides clinical evaluation, the diagnosis of JOAG may involve measuring intraocular pressure with tonometry, examining the drainage angle with gonioscopy, checking for optic nerve damage with ophthalmoscopy, assessing peripheral vision with a visual field test, and obtaining detailed images of the optic nerve and retinal layers with optical coherence tomography. As in other forms of glaucoma, this condition is typically managed with topical medical drops, laser treatments, or surgery. Treatment aims to reduce intraocular pressure to halt or slow the progression of functional and anatomical disease-related defects.
This activity for healthcare professionals is designed to enhance learners' competence when evaluating and managing JOAG. Participants gain a better understanding of the condition's overall features, anatomical factors, natural development, and progression patterns. The etiology, pathophysiology, and best practices for diagnosing and managing JOAG will also be emphasized. Greater proficiency equips learners to collaborate within an interprofessional team caring for patients with this condition.
... IOP builds up mainly in response to resistance provided throughout the HTM to the aqueous humor (AH) outflow [1]. The HTM is made up of connective tissue containing collagenous and elastic fibers, and it is covered by flat cells [2]. This permeable tissue is located around the cornea and is composed of three different layers: the uveoscleral region (UVM), with pore sizes varying from 70 to 100 µm; the corneoscleral region (CTM), with pore sizes of 30 µm; and the juxtacanalicular region (JTC), with pore sizes of 4-7 µm (Figure 1) [3]. ...
The human trabecular meshwork (HTM) is responsible for regulating intraocular pressure (IOP) by means of gradient porosity. Changes in its physical properties, like increases in stiffness or alterations in the extracellular matrix (ECM), are associated with increases in the IOP, which is the primary cause of glaucoma. The complexity of its structure limits the engineered models to one-layered and simple approaches, which do not accurately replicate the biological and physiological cues related to glaucoma. Here, a combination of melt electrowriting (MEW) and solution electrospinning (SE) is explored as a biofabrication technique used to produce a gradient porous scaffold that mimics the multi-layered structure of the native HTM. Polycaprolactone (PCL) constructs with a height of 20–710 µm and fiber diameters of 0.7–37.5 µm were fabricated. After mechanical characterization, primary human trabecular meshwork cells (HTMCs) were seeded over the scaffolds within the subsequent 14–21 days. In order to validate the system’s responsiveness, cells were treated with dexamethasone (Dex) and the rho inhibitor Netarsudil (Net). Scanning electron microscopy and immunochemistry staining were performed to evaluate the expected morphological changes caused by the drugs. Cells in the engineered membranes exhibited an HTMC-like morphology and a correct drug response. Although this work demonstrates the utility of combining MEW and SE in reconstructing complex morphological features like the HTM, new geometries and dimensions should be tested, and future works need to be directed towards perfusion studies.
... [50] When OAG in a patient is attributed to elevated IOP, the cause of this increase in IOP is commonly thought to occur due to dysfunction in aqueous outflow through the trabecular meshwork of the eye. [51] This may occur as a result of partial obstruction due to foreign material (eg, accumulated mucopolysaccharides in the trabecular meshwork), a reduction in the number of trabecular endothelial cells, a decreased density of trabecular pores, number of vacuoles, or size of the inner wall endothelium of the canal of Schlemm, loss of phagocytic activity, or dysfunction in the neurological feedback loop involved in drainage of aqueous humor. ...
... It also causes a dilation of retinal veins and optic disc swelling that can concurrently damage optic nerve fibers. [15] Glaucomatocyclitic Crisis manifests as recurrent acute attacks of increased intraocular pressure that resolve without treatment but with repeated attacks, has been reported to cause glaucomatous damage to the optic nerve over time. [16][17] ...
... The AH may encounter various degrees of resistance through the different layers of the TM and across the inner wall of Schlemm's canal. [9] 2. About 20% of the AH passes from the chamber angle into the suprachoroidal space and ciliary muscle and through the scleral substance and enters uveal venous circulation in the ciliary body, choroid, and sclera. ...
... [74,75] The TM, as a significant site of drainage resistance, is predominantly composed of multiple layers of crossed, flattened collagen bundles surrounded by endothelium cells, myofibroblasts, and macrophages. [76] Within the peri-canalicular region of TM, the myoblasts, under cellular deformation monitoring mechanisms, [77] work in tandem with the anterior ciliary muscles in the SC wall to modulate resistance. [78] As part of the endothelial-like cell family, TMCs exhibit phagocytic capabilities and play a role in inflammation mediation. ...
Glaucoma, a blind‐leading disease largely since chronic pathological intraocular high pressure (ph‐IOP). Hitherto, it is reckoned incurable for irreversible neural damage and challenges in managing IOP. Thus, it is significant to develop neuroprotective strategies. Ferroptosis, initially identified as an iron‐dependent regulated death that triggers Fenton reactions and culminates in lipid peroxidation (LPO), has emerged as a focal point in multiple tumors and neurodegenerative diseases. Researches show that iron homeostasis play critical roles in the optic nerve (ON) and retinal ganglion cells (RGCs), suggesting targeted treatments could be effective. In glaucoma, apart from neural lesions, disrupted metal balance and increased oxidative stress in trabecular meshwork (TM) are observed. These disturbances lead to extracellular matrix excretion disorders, known as sclerotic mechanisms, resulting in refractory blockages. Importantly, oxidative stress, a significant downstream effect of ferroptosis, is also a key factor in cell senescence. It plays a crucial role in both the etiology and risk of glaucoma. Moreover, ferroptosis also induces non‐infectious inflammation, which exacerbate glaucomatous injury. Therefore, the relevance of ferroptosis in glaucoma is extensive and multifaceted. In this review, the study delves into the current understanding of ferroptosis mechanisms in glaucoma, aiming to provide clues to inform clinical therapeutic practices.
... Thus, the rationale for GATT is to remove TM and the inner wall of Schlemm's canal (SC), which is the major site of the resistance. [4][5][6][7][8] The ab interno approach of GATT allows direct visualization of the "trabecular shelf," which indicates an open, cleaved collector system. However, it is critical to remember that it destroys the entire TM circumferentially, and that is the crux of its efficacy. ...
How to cite this article: Bhartiya S, Aktas Z, Ichhpujani P. Is GATT the Answer? J Curr Glaucoma Pract 2023;17(4):167–168.
... Dysfunction of the trabecular mesh (TM), which regulates the aqueous humor (AqH) outflow from the anterior chamber, is the main cause of elevated IOP [145]. Once the function of trabecular meshwork is impaired, it loses its ability to self-repair [146]. Studies have demonstrated that iPSCs, BMSCs, and ADSCs are reliable sources of cells for stem cell replacement therapy in the trabecular network of glaucoma due to their ability to differentiate and regenerate TM cells [147]. ...
With the rapid and groundbreaking development in 21st century medicine on a global scale, new possibilities have emerged for addressing eye diseases, that can be blindness, and that conventional pharmaceuticals and surgical interventions have not hitherto been able to adequately treat. Gene enhancement/supplementation, gene editing, and stem cell therapies have now emerged as key subdisciplines. Here we discuss the current state and prospects of regenerative therapy in the field of ophthalmology, with a primary focus on diseases affecting the cornea, retina, and optic nerve. Our review summarizes the latest advances, challenges, and opportunities in these fields, as well as the potential applications and limitations of different strategies. The review also highlights the importance of interdisciplinary and collaborative innovation models for achieving breakthroughs in therapeutic development for sight‐loss diseases worldwide.
... Dividing the groups into mild and moderate glaucoma, one might presume that early-stage glaucoma cases exhibit a lower degree of trabecular damage (due to a shorter disease duration), potentially resulting in a higher likelihood of achieving lower IOP levels and, consequently, a more pronounced treatment success. 30,31 In addition, it could be anticipated that eyes with higher baseline IOP would experience a more substantial reduction in their initial IOP levels. 32 However, despite the moderate glaucoma group having slightly elevated mean IOP values compared with the mild glaucoma group, our analyses, encompassing parameters such as absolute or relative success, the impact of IOP reduction, and the quantity of eye drops used, did not reveal statistically significant differences. ...
Précis
Selective laser trabeculoplasty can be used as a substitute for medications in patients with mild-to-moderate glaucoma, reducing the cost of eye drop distribution in the Brazilian public health system.
Purpose
To observe the effectiveness of selective laser trabeculoplasty (SLT) as a substitute for eye drops in patients with open-angle glaucoma in the Brazilian Public Health System.
Materials and methods
SLT was performed bilaterally after medication washout. This is a prospective interventional study, comparing intraocular pressure (IOP) when using eye drops, at baseline (post-washout), and at 12-month follow-up, after SLT. Medication was added if the target IOP was not achieved, following the Brazilian Public Health System eye drops protocol, based on medication costs. Absolute (without eye drops) and qualified (with eye drops) success were measured with IOP ≤ 21, IOP ≤ 18, IOP ≤ 15 and IOP ≤ 12 mmHg. Besides IOP evolution, ability to reduce IOP (in %), and eye drops reduction were evaluated.
Results
92 eyes of 46 patients were included, 70 eyes with mild glaucoma and 22 with moderate glaucoma, mean number of eye drops 2.26±1.06 (82.6% were using a prostaglandin analogue) and post-washout IOP of 21.10±5.24 mmHg. There was relative success at IOP ≤18 mmHg, where the mild group had greater success than the moderate group (88.1% vs. 71.4%, P =0.824). The average IOP reductions were 23.04% and 25.74% at 6 and 12 months, respectively. The average number of eye drops was 1.02, with 1.1% using a prostaglandin analogue. Furthermore, 68.19% of the patients had a decrease in the quantity of eye drops used.
Conclusion
SLT is effective in reducing IOP and replacing eye drops in patients in the Brazilian Public Health System. Moreover, there was a significant reduction in the use of prostaglandin analogues.
... Altered TM cells elevate outflow resistance, leading to increased IOP and POAG. This pathomechanism puts TM cells at the focus of glaucoma research [2]. Frequently used TM cells in studies are human, bovine, and porcine due to their easy accessibility [3]. ...
Purpose
The outflow pathway, especially trabecular meshwork (TM), plays an essential role in glaucoma, and the availability of TM cells is crucial for in vitro research. So far, the isolation of TM cells from mice has been anything but manageable due to the small size of the eye. Direct isolation using a stereomicroscope and forceps requires a high grade of dexterity. Indirect isolation is based on the phagocytic properties of TM cells and involves injecting magnetic microspheres into the anterior chamber of live mice followed by isolation. Therefore, a simpler, less expensive, and nonexperimental strategy for isolating mouse TM cells would be desirable.
Methods
After enucleation, the eyes were cut in half anterior-to-posteriorly. The lens and posterior segment were removed. Iris and the attached ciliary body were gently pulled backward and disconnected from the remaining tissue to expose the TM. By incising through the cornea anteriorly and posteriorly of the TM, the cornea/TM stripe could be isolated. The cornea/TM stripe was cultured with the pigmented side down in a 6-well. The outgrowing pigmented cells were analyzed by immunocytochemistry and mRNA expression for previously described TM cell markers. The phagocytic properties of the cells were additionally confirmed using fluorescent microspheres.
Results
Pigmented phagocytic cells were the first to grow out of the cornea/TM strips after approximately 4–7 days. Cells were positive for Collagen IV, Fibronectin1, Vimentin, and Actin alpha 2 and could phagocytize fluorescent microbeads. Cross-linked actin networks were visible after 9 days of exposure to TGFB2 (transforming growth factor-beta 2). Additionally, treatment with 500 nM Dexamethasone for one week increased myocilin expression, as previously reported for TM cells. In addition, we proved that this method can also be used in albino mice, which lack pigmentation of the trabecular meshwork.
Conclusions
The isolated cells show phagocytic properties and specific expression of markers reported in TM cells. Therefore, our dissection-based method is inexpensive and reproducible for isolating TM cells in mice.
... Human trabecular meshwork cells (HTMCs), situated in the iridocorneal angle, are primarily responsible for the drainage of aqueous humor. Elevated IOP is a consequence of HTMC dysfunction or the resistance of HTMCs to aqueous humor outflow [4]. Increasing evidence supports that oxidative stress plays an essential role in the pathophysiological changes in HTMCs [5,6] that lead to the suppression of aqueous humor outflow, thus upregulating the IOP. ...
Purpose
Human trabecular meshwork cell (HTMC) dysfunction results in imbalanced aqueous humor inflow and outflow, leading to an increase in intraocular pressure (IOP). Uncontrolled high IOP can promote the occurrence of glaucoma, an irreversible optic neuropathy. Here, we explored whether the long non-coding RNA plasmacytoma variant translocation 1 (lncRNA PVT1)/microRNA-29a-3p (miR-29a-3p) axis could ameliorate HTMC dysfunction under oxidative stress by modulating the expression of the proangiogenic factor vascular endothelial growth factor (VEGFA) and the profibrotic factor metalloproteinase-2 (MMP-2).
Methods
HTMCs were cultured under H2O2-induced oxidative stress for 48 h. The expression of lncRNA PVT1, miR-29a-3p, VEGFA, MMP-2, intracellular adhesion molecule-1 (ICAM-1), and alpha-smooth muscle actin (α-SMA) was detected by reverse transcription quantitative real-time polymerase chain reaction, western blotting, and immunofluorescence. Interference experiments were conducted via the transfection of HTMCs with small interfering RNA (siRNA) targeting lncRNA PVT1 or miR-29a-3p mimics. A luciferase reporter assay was undertaken to identify the presence of a miR-29a-3p binding site in lncRNA PVT1. Flow cytometry and Transwell and Cell Counting Kit-8 assays were employed to evaluate HTMC functions under oxidative stress with different treatments.
Results
In HTMCs, the expression of lncRNA PVT1 was induced by H2O2 treatment, whereas that of miR-29a-3p was inhibited. The levels of angiogenic factors (VEGFA, ICAM-1) and fibrosis-associated mediators (MMP-2, α-SMA) were upregulated in HTMCs under oxidative stress. The siRNA-mediated suppression of lncRNA PVT1 or the upregulation of miR-29a-3p significantly suppressed the expression of VEGFA, MMP-2, ICAM-1, and α-SMA. A luciferase reporter assay confirmed that lncRNA PVT1 directly targeted miR-29a-3p and acted as a miR-29a-3p sponge. The knockdown of lncRNA PVT1 restored the level of miR-29a-3p in H2O2-treated HTMCs, thereby inhibiting VEGFA and MMP-2, its target mRNAs. HTMC dysfunction, including increased apoptosis and decreased cell mobility and viability, could be effectively ameliorated by lncRNA PVT1 downregulation or miR-29a-3p overexpression under oxidative stress.
Conclusion
LncRNA PVT1 has potential as a therapeutic target for inhibiting VEGFA and MMP-2, thus protecting HTMCs, suppressing the progression of fibrosis, and, consequently, improving the outcome of glaucoma filtration surgery.
... Furthermore, due to anatomical differences in the position of the trabecular meshwork, between humans and dogs, it is not appropriate to utilize ICA or anterior chamber angle opening distance (AOD), commonly used in human studies, to investigate the potential causes of glaucoma following cataract surgery in dogs (12,13). ...
Introduction
Glaucoma is one of the most serious complications that causes irreversible blindness after phacoemulsification in dogs; however, a clear mechanism has not been elucidated. This study aimed to analyse the possible anatomical factors associated with glaucoma after phacoemulsification using parameters that reflect the anatomical characteristics of dogs.
Materials and methods
A total of 69 eyes of 48 dogs were included in this study. The patients were divided into three groups: normal eye (n = 18), cataract (n = 39), and post-phacoemulsification for at least 2 months after surgery (post-phaco, n = 12). For further analysis, the dogs were subdivided into two groups according to cataract stage: phacoemulsification non-candidate and candidate groups. Non-cataracts and incipient cataracts were categorized into the non-candidate group, whereas immature and mature cataracts were categorized into the candidate group. Measurements of the ciliary cleft parameters, including the area of the ciliary cleft (CCA), length of the ciliary cleft (CCL), width of the ciliary cleft (CCW), iridocorneal angle, and angle opening distance, were obtained using ultrasound biomicroscopy.
Results
CCA, CCL, and CCW were significantly higher in the candidate group than in the non-candidate group. CCA, CCL, and CCW were significantly reduced in the post-phaco group compared to those in the cataract group. Based on these results, we found that the ciliary cleft expanded in cataract-affected eyes and narrowed after phacoemulsification. This may indicate that the space between the trabecular meshworks became narrower, potentially leading to an increase in the resistance of the aqueous humor.
Conclusion
A narrowed ciliary cleft after phacoemulsification may be an anatomical factor associated with glaucoma.
This study aims to examine ferroptosis-associated genes in primary open-angle glaucoma (POAG) and offer new insights into the underlying disease mechanisms and potential therapeutic approaches. Differentially expressed genes (DEGs) between the POAG and control groups were identified using bioinformatics analysis and subsequently intersected with a ferroptosis gene set to isolate ferroptosis-related DEGs (Ferr DEGs). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were conducted to examine their biological functions. Core genes were identified through protein-protein interaction (PPI) network and Friends analysis. The diagnostic potential of core Ferr DEGs was assessed using receiver operating characteristic (ROC) curve analysis, while immune cell infiltration was examined using the CIBERSORT algorithm. Additionally, Spearman correlation analysis was used to examine the relationships between the identified genes and immune cell populations. A total of 25 Ferr DEGs were identified, with DDIT4, GDF15, NAMPT, HBA1, and IGFBP7 recognized as key core genes. ROC analysis demonstrated that these genes exhibited high diagnostic accuracy, with an AUC > 0.7. Additionally, the infiltration levels of memory B cells and macrophage_M2 were significantly elevated in POAG tissues compared to the control group. Notably, the core genes revealed significant correlations with various immune cell types. Our findings underscore the involvement of ferroptosis-related genes in POAG pathogenesis and highlight their potential as diagnostic biomarkers and therapeutic targets. Future research should focus on validating these findings in clinical settings and exploring the therapeutic modulation of ferroptosis in POAG management.
Background Recent studies have found that ferroptosis may be involved in the process of trabecular meshwork injury in glaucoma. This study aims to reveal ferroptosis-related gene signature in primary open-angle glaucoma (POAG) and identify small molecule drugs as new direction of therapy. Methods Ferroptosis-related indicators in POAG patients and chronic ocular hypertension (COH) rats were detected by ELISA kits. The dataset (GSE27276) from GEO database and ferroptosis-related genes from FerrDb were downloaded for analysis. Small molecule drugs targeting ferroptosis-related signature components were predicted via CMap database and CB-Dock2. H 2 O 2 -induced human trabecular meshwork cells (HTMCs) oxidative stress model was constructed to validate the expression of hub genes and efficacy of drugs. Digoxin was made into eye drops to verify its intraocular pressure (IOP) lowering effect in vivo. Results Ferroptosis levels were enhanced in POAG patients and COH eyes of rats. A total of 14 ferroptosis-related differentially expressed genes were identified. PPI analysis and in vitro experiments showed HBA1, SLC2A3 and SCD played an important role in ferroptosis-mediated POAG. CMap and molecular docking indicated that ATPase inhibitors digoxin might be considered as potential therapeutic drugs for POAG. Digoxin administration alleviated H 2 O 2 -induced HTMCs ferroptosis and lowered IOP of COH eyes. Conclusions This study clarified the ferroptosis-related gene signature in the pathogenesis of POAG, which provide a theoretical basis for the prevention and early diagnosis of POAG. Translation of specific small molecule drugs will propose new ideas for therapy of POAG.
The cornea is a vital tissue of the human body. The health status of the cornea has a great impact on the quality life of person. There has been a great deal of research on the human cornea biomechancis. However, the difficulty in obtaining the human cornea has greatly limited the research of cornea biomechancis. Using finite element modelling has become a very effective and economical means for studying mechanical properties of human cornea. In this review, the geometrical and constitutive models of the cornea are summarised and analysed, respectively. Some factors affecting of the finite element calculation are discussed. In addition, prospects and challenges for the finite element model of the human cornea are presented. This review will be helpful to researchers performing studies in the relevant fields of human cornea finite element analysis.
Purpose
Acute ocular hypertension (AOH) is the defining feature of acute glaucoma. The mechanical stress and excessive production of reactive oxygen species (ROS) during episodes can directly or indirectly damage the trabecular meshwork (TM). Despite its significance, a clear understanding of its pathogenesis and an effective therapeutic target remain lacking in acute glaucoma. In the present study, we explored the potential molecular mechanisms underlying TM cell death following oxidative damage and AOH. The use of NAC/VX-765 as a potential pharmaceutical intervention for reducing intraocular pressure (IOP) was discussed.
Methods
The levels of NLRP3 and caspase-1 were compared between normal and glaucomatous TM samples. An in vitro oxidative damage model and an AOH rat model were used to investigate the potential molecular mechanism behind TM cell death. The ROS scavenger N-acetyl-L-cysteine (NAC) and caspase-1 inhibitor VX-765 were used to counteract TM damage.
Results
Elevated levels of NLRP3 and caspase-1 were observed in patients with acute glaucoma. H2O2 exposure decreased the viability of human trabecular meshwork (HTM) cells and increased intracellular ROS levels. Both Gene and protein expressions of NLRP3, caspase-1, GSDMD-N, and IL-1β were notably upregulated in H2O2-induced HTM cells and the rodent AOH model. Both NAC and VX-765 demonstrated protective effects against TM injury by inhibiting pyroptosis. The IOP-lowering effects of NAC and VX-765 persisted for 7 days.
Conclusions
Our findings indicate that the classical pyroptosis pathway, NLRP3/caspase-1/IL-1β, plays a key role in acute glaucomatous TM injury. Targeting pyroptosis provides novel therapeutic avenues for treating AOH-induced irreversible TM injury. This provides not only a promising therapeutic target for glaucoma but also introduces a new approach to intervention.
Glaucoma is the primary factor underlying irreversible blindness. Recent studies suggest that the risk of glaucoma significantly increases in patients with systemic lupus erythematosus (SLE); however, the mechanism underlying this association remains unclear. Therefore, this study aimed to identify novel common biomarkers and potential therapeutic drugs for SLE and glaucoma. GSE27276, GSE50772, and GSE148371 datasets were sourced from the gene expression omnibus (GEO) database. An integrated analysis of the datasets for both diseases identified biomarkers and thoroughly examined their biological roles and molecular mechanisms using differential expression analysis (DEA), weighted gene co‐expression network analysis (WGCNA), gene enrichment analysis, machine learning, microRNA (miRNA) and transcription factor analyses, immune infiltration analyses, and single‐cell transcriptome analysis. Concurrently, molecular docking was used to forecast potential drugs targeting these biomarkers. Finally, reverse transcription quantitative real‐time polymerase chain reaction (RT‐qPCR) was performed in human trabecular meshwork stem cells to validate the five identified biomarkers. The 10 key genes identified through DEA and WGCNA were predominantly involved in immune, inflammatory, and autophagy pathways. Additionally, machine learning identified five biomarkers, and we established associated transcription factors and miRNA regulatory networks. Immune infiltration analysis indicated an elevated presence of immune cells, including macrophages, T cells, and B cells, in both conditions. Furthermore, the DSigDB database yielded 10 potential therapeutic agents, three of which showed strong binding potential to the biomarkers via molecular docking. The RT‐qPCR results confirmed the trend in gene expression. This study uncovered a new link between SLE and primary open‐angle glaucoma, identifying biomarkers and mechanisms of immunopathogenesis for future research and treatment strategies.
Glaucoma presents a significant global health concern and affects millions of individuals worldwide and predicted a high increase in prevalence of about 111 million by 2040. The current standard treatment involves hypotensive eye drops; however, challenges such as patient adherence and limited drug bioavailability hinder the treatment effectiveness. Nanopharmaceuticals or nanomedicines offer promising solutions to overcome these obstacles. In this manuscript, we summarized the current limitations of conventional antiglaucoma treatment, role of nanomedicine in glaucoma treatment, rational design, factors effecting the performance of nanomedicine and different types of nanocarriers in designing of nanomedicine along with their applications in glaucoma treatment from recent literature. Current clinical challenges that hinder real-time application of antiglaucoma nanomedicine are highlighted. Lastly, future directions are identified for improving the therapeutic potential and translation of antiglaucoma nanomedicine into clinic.
This literature review evaluates any possible links between primary open-angle glaucoma (POAG) and caloric restriction (CR), body mass index (BMI), and exercise, aiming to map the extent of the literature. Its primary objective is to recognise the nature and breadth of research evidence, identify possible gaps in these topics and develop future studies. The databases searched were MEDLINE (PudMed), Scopus and ScienceDirect, in April 2023 for articles published in English, with no date restriction. A total of 447 search results were retrieved. Of these, 73 were related to CR, 249 to BMI, and 125 to exercise. Records identified included systematic reviews, meta-analyses, randomised controlled trials, cohort studies and animal studies. CR has been shown to halt the degeneration of retinal ganglion cells and protect against various glaucomatous processes in animal models. Low BMI has been shown to be associated with an increased risk of POAG and a faster rate of visual field deterioration in POAG. However, the association between high BMI and POAG is not consistent. Exercise has been shown to cause mechanical, vascular, and neurobiological changes affecting the pathophysiology of POAG. The present review helps identify key characteristics and factors relating to the impacts of CR, BMI, or exercise on POAG.
Aim
The purpose of this study was to determine the real-world efficacy of early phacoemulsification cataract surgery and goniotomy with a Sinskey hook in patients with glaucoma.
Methods
This study was conducted at Advanced Eye Care of New York, a private practice located in Manhattan, NY. This was a single-center, retrospective study of predominantly Black and Afro-Latino patients with glaucoma. These patients underwent early phacoemulsification cataract surgery and goniotomy using an affordable and reusable straight Sinskey hook (Ambler 200-μm tip). Patients who underwent the aforementioned procedure with 6 months of follow-up were included in this study. Investigated parameters were intraocular pressure, number of medications, mean deviation on visual field test, visual acuity, adverse events, and pre/postoperative spherical refractive error.
Results
Among all 38 eyes that were enrolled in the study and underwent surgery (goniotomy using a Sinskey hook with phacoemulsification), mean intraocular pressure was reduced from 16.45 mmHg at baseline to 13.24 mmHg at month 6, a 19.5% reduction. The mean number of topical intraocular pressure-lowering medications used was reduced from 1.81 at baseline to 0.52 at month 6, a 71% reduction in topical medications.
Conclusion
Combined early cataract surgery and goniotomy performed with a Sinskey hook is an affordable microinvasive surgery and an effective way to reduce intraocular pressure and the number of ocular hypertensive medications used in Black and Afro-Latino patients with primary open-angle glaucoma.
Precis
Long-term success was achievable after GATT. GATT performed at early stage of glaucoma had better surgery outcomes. Trabeculoplasty may compromise surgery success.
Purpose
To evaluate the long-term effectiveness of prolene suture gonioscopy assisted transluminal trabeculotomy (GATT) and identify factors that may affect surgical outcomes.
Patients and Methods
This is a retrospective cohort study of adult patients with prolene suture GATT performed by a single surgeon at one medical center.
Results
Of the 145 eyes from 124 patients studied, intraocular pressure was reduced from 22.1±7.8 to 15.1±3.2 and 15.1±3.5 mmHg, and the number of glaucoma medications was reduced from 3.2±1.1 to 1.3±1.4 and 1.4±1.5 at postoperative years 3 and 4, respectively. 93 and 71 eyes completed a 3 and 4-year follow-up, with 44% of the eyes at year 4 remaining medication free. Compared to eyes with combined GATT/cataract extraction (CE), eyes with GATT alone had significantly more preoperative medications and a higher reoperation rate (31% vs. 16.5%). Eyes with prior trabeculoplasty had a higher reoperation rate (28.8%) than those without (16.1%). Kaplan-Meier survival analysis revealed that GATT/CE eyes without trabeculoplasty had a longer median time to failure (48 mo) than GATT/CE eyes with trabeculoplasty (18 mo), and GATT eyes with or without trabeculoplasty (9 mo and 12 mo, respectively).
Conclusion
Prolene suture GATT successfully reduced IOP. Eyes with more preoperative medications responded less well to GATT. Prior laser trabeculoplasty was associated with poorer outcomes. Further study is needed to verify these findings.
Purpose
To evaluate abnormalities in serum and aqueous humor uric acid (UA) levels in primary angle closure glaucoma (PACG).
Methods
Patients with PACG and age-similar and gender-similar controls (patients scheduled for cataract extraction) were enrolled prospectively. Serum UA levels were determined by enzymatic colorimetry; aqueous humor UA levels by Enzyme-Linked ImmunoSorbent Assay. A t-test was used to compare UA levels between PACG patients and controls, with one-way ANOVA used to compare levels across PACG subgroups with differing disease severity. Comparisons between PACG patients and controls were adjusted for systemic and ocular confounding factors using binary logistic regression.
Results
In all, 131 PACG patients and 112 controls were included. The serum UA level was 266 ± 69 μmol/L in the PACG group and 269 ± 73 μmol/L in the control group (p = 0.71). The aqueous humor UA level was 35.4 ± 8.2 μmol/L in the PACG group and 53.9 ± 18.6 μmol/L in the control group (p < 0.001). This difference remained significant after adjusting for age, gender, systolic blood pressure, diastolic blood pressure, body mass index, axial length, central corneal thickness, anterior chamber depth, lens thickness, white-to-white distance, corneal endothelial cell density, and serum UA level (odds ratio: 0.88, 95 % confidence interval: 0.83–0.93, p < 0.001).
Conclusion
Aqueous humor UA levels differ between PACG patients and controls, but serum UA levels do not. This indicates that local UA plays a role in the pathogenesis of PACG, but systemic UA does not.
Given the widespread application of glucocorticoids in ophthalmology, the associated elevation of intraocular pressure (IOP) has long been a vexing concern for clinicians, yet the underlying mechanisms remain inconclusive. Much of the discussion focuses on the extracellular matrix (ECM) of trabecular meshwork (TM). It's widely agreed that glucocorticoids impact the expression of Matrix metalloproteinases (MMPs), leading to ECM deposition. Since Zn ²⁺ is vital for MMPs, we explored its role in ECM alterations induced by dexamethasone (DEX). Our study revealed that in human TM cells treated with DEX, the level of intracellular Zn ²⁺ significantly decreased and accompanied by impaired extracellular Zn ²⁺ uptake. This correlated with changes in several Zrt-, Irt-related proteins (ZIP) and metallothionein. ZIP8 knockdown impaired extracellular Zn ²⁺ uptake, but Zn ²⁺ chelation didn't affect ZIP8 expression. Resembling DEX's effects, chelating Zn ²⁺ decreased MMP2 expression, increased the deposition of ECM proteins, and induced structural disarray of ECM. Conversely, supplementation of exogenous Zn ²⁺ to DEX-treated cells ameliorated these outcomes. Inspiringly, dietary zinc supplementation in mice significantly reduced DEX-induced IOP elevation and collagen content in TM, thereby rescuing the visual function of the mice. These findings underscore zinc's pivotal role in ECM regulation, providing a novel perspective on the pathogenesis of glaucoma.
Glaucoma is one of the leading causes of irreversible blindness in developed countries, and intraocular pressure (IOP) is primary and only treatable risk factor, suggesting that to a significant extent, glaucoma is a disease of IOP disorder and pathological mechanotransduction. IOP-lowering ways are limited to decreaseing aqueous humour (AH) production or increasing the uveoscleral outflow pathway. Still, therapeutic approaches have been lacking to control IOP by enhancing the trabecular meshwork (TM) pathway. Trabecular meshwork cells (TMCs) have endothelial and myofibroblast properties and are responsible for the renewal of the extracellular matrix (ECM). Mechanosensitive cation channels, including Piezo1 and TRPV4, are abundantly expressed in primary TMCs and trigger mechanostress-dependent ECM and cytoskeletal remodelling. However, prolonged mechanical stimulation severely affects cellular biosynthesis through TMC mechanotransduction, including signaling, gene expression, ECM remodelling, and cytoskeletal structural changes, involving outflow facilities and elevating IOP. As for the functional coupling relationship between Piezo1 and TRPV4 channels, inspired by VECs and osteoblasts, we hypothesized that Piezo1 may also act upstream of TRPV4 in glaucomatous TM tissue, mediating the activation of TRPV4 via Ca2+ inflow or Ca2+ binding to phospholipase A2(PLA2), and thus be involved in increasing TM outflow resistance and elevated IOP. Therefore, this review aims to help identify new potential targets for IOP stabilization in ocular hypertension and primary open-angle glaucoma by understanding the mechanical transduction mechanisms associated with the development of glaucoma and may provide ideas into novel treatments for preventing the progression of glaucoma by targeting mechanotransduction.
Matrix metalloproteinases (MMPs) are a family of proteolytic enzymes that degrade extracellular matrix (ECM) components such as collagen and have important roles in multiple biological processes, including development and tissue remodeling, both in health and disease. The activity of MMPs is influenced by the expression of MMPs and tissue inhibitors of metalloproteinase (TIMPs). In the eye, MMP-mediated ECM turnover in the juxtacanalicular region of the trabecular meshwork (TM) reduces outflow resistance in the conventional outflow pathway and helps maintain intraocular pressure (IOP) homeostasis. An imbalance in the MMP/TIMP ratio may be involved in the elevated IOP often associated with glaucoma. The prostaglandin analog/prostamide (PGA) class of topical ocular hypotensive medications used in glaucoma treatment reduces IOP by increasing outflow through both conventional and unconventional (uveoscleral) outflow pathways. Evidence from in vivo and in vitro studies using animal models and anterior segment explant and cell cultures indicates that the mechanism of IOP lowering by PGAs involves increased MMP expression in the TM and ciliary body, leading to tissue remodeling that enhances conventional and unconventional outflow. PGA effects on MMP expression are dependent on the identity and concentration of the PGA. An intracameral sustained-release PGA implant (Bimatoprost SR) in development for glaucoma treatment can reduce IOP for many months after expected intraocular drug bioavailability. We hypothesize that the higher concentrations of bimatoprost achieved in ocular outflow tissues with the implant produce greater MMP upregulation and more extensive, sustained MMP-mediated target tissue remodeling, providing an extended duration of effect.
Human trabecular meshwork (TM) cells play pivotal roles in maintaining homeostasis of intraocular pressure via regulation of aqueous humor outflow. These cells are capable of phagocytosis, which is considered to be essential for their regulatory function. In addition, there is a strong expression of the gap junction protein connexin43 (Cx43) in the TM. Here, we investigated functional relationships between phagocytosis activity of TM cells and their expression of Cx43. Phagocytosis was measured by showing the ability of TM cells to engulf inert fluorescent particles consisting of pHrodo. We found that internalized pHrodo was partially co-localized with Cx43 and that the phagocytic activity was dramatically reduced after knockdown of Cx43 using lentiviral Cx43 shRNA. These results suggest that Cx43 is involved in the regulation of phagocytosis by TM cells.
IntroductionNew open-angle glaucoma (OAG) and ocular hypertension (OHT) therapies that reduce treatment burden and improve outcomes relative to currently available agents are needed. Netarsudil, a novel Rho kinase inhibitor approved by the US Food and Drug Administration, reduces intraocular pressure (IOP) by increasing trabecular outflow. Two phase 3 superiority studies compared a fixed-dose combination (FDC) of netarsudil and the prostaglandin latanoprost with each active component for IOP-lowering efficacy.Methods
Pooled efficacy and safety data were analyzed from MERCURY-1 and -2 studies in patients with OAG or OHT. Patients instilled one drop of netarsudil (0.02%)/latanoprost (0.005%) FDC (n = 483), netarsudil (0.02%, n = 499), or latanoprost (0.005%, n = 486) into each eye once-daily between 20:00 and 22:00. IOP was measured at 08:00, 10:00, and 16:00 at weeks 2, 6, and the primary endpoint at month 3.ResultsBaseline mean diurnal IOP was 23.6, 23.6, and 23.5 mmHg in netarsudil/latanoprost FDC, netarsudil, and latanoprost groups, respectively. Mean diurnal IOP in each group was 15.3, 18.1, and 17.5 mmHg at week 2, 15.7, 18.4, and 17.4 mmHg at week 6, and 15.8, 18.4, and 17.3 mmHg at week 12. The netarsudil/latanoprost FDC met criteria for superiority compared with each active component (p < 0.0001 for all nine time points). At month 3, among patients randomized to netarsudil/latanoprost FDC or latanoprost, 58.4% vs 37.3% (p < 0.0001) achieved IOP ≤ 16 mmHg. Among patients randomized to netarsudil/latanoprost FDC or netarsudil or latanoprost, 30.9% vs 5.9% (p < 0.0001) vs 8.5% (p < 0.0001) achieved at least a 40% reduction from baseline in mean diurnal IOP. Pooled safety results were consistent with individual MERCURY studies.Conclusion
Once-daily netarsudil/latanoprost FDC produced statistically significant and clinically relevant reductions in mean IOP that were statistically superior to IOP reductions achieved by netarsudil and latanoprost monotherapy. Results of the pooled efficacy and safety analyses were consistent with the individual studies.Trial registrationClinicalTrials.gov identifiers, NCT02558400 and NCT02674854.
The trabecular meshwork’s (TM) physiological role is to maintain normal intraocular pressure by regulating aqueous humor outflow. With age, and particularly in eyes with primary open angle glaucoma, the number of cells residing within the TM is markedly decreased and the function of the tissue is compromised. Here we evaluate if transplantation of induced pluripotent stem cell derived TM like cells (iPSC-TM) restores TM cellularity and function in human eyes obtained from older human donors. Human iPSC were differentiated into iPSC-TM and compared to primary TM cells by RNAseq. iPSC-TM were then injected into the anterior segments of human eyes maintained in perfusion culture. Seven and 14 days eyes after injection eyes that received iPSC-TM contained significantly more cells in the TM. Fewer than 1% of all cells appeared to be iPSC-TM, but significantly more cells in these eyes were immunopositive for Ki 67 and incorporated BrdU. Our study demonstrates that transplantation iPSC-TM stimulates proliferation of endogenous TM cells in perfusion cultured human eyes from aged donors. These data, in concert with our previous findings in animal models, suggest that functional regeneration of the TM may be possible in human eyes with primary open angle glaucoma.
Purpose:
To image the human trabecular meshwork (TM) in vivo using adaptive optics gonioscopy (AOG) with approximately 2-μm lateral resolution.
Methods:
An existing Indiana University adaptive optics scanning laser ophthalmoscope was altered by adding a 12-mm button lens to a clinical gonioscopic lens allowing high-resolution imaging of the human iridocorneal angle. First an anatomic model eye was used to refine the imaging technique and then nine participants (7 controls and 2 participants with pigment dispersion syndrome) were imaged.
Results:
All nine participants were successfully imaged without adverse events. High-resolution imaging of the human TM was achieved allowing for visualization of the TM beams, and presumed endothelial cells. Uveal meshwork beams in controls averaged 25.5 μm (range, 15.2-44.7) in diameter with pores averaging 42.6 μm (range, 22.3-51.4) while the corneoscleral meshwork pores averaged 8.9 μm (range, 7.7-12.1). Differences in appearance of the uveal and corneoscleral meshwork were noted between the two participants with pigment dispersion syndrome and the controls. These included nearly absent spacing between the beams and enlarged endothelial cells with hyperreflective areas.
Conclusions:
AOG allows for near cellular level resolution of the human TM in vivo. This may allow for further understanding of age-related changes that occur as well as provide a deeper understanding of medical and surgical alterations for the treatment of glaucoma.
Translational relevance:
Further development of this approach may allow for direct measurements at a micometer level in vivo of changes that occur in the human trabecular meshwork with glaucoma and therapeutic interventions.
Purpose:
POAG is a progressive optic neuropathy that is currently the leading cause of irreversible blindness worldwide. While the underlying cause of POAG remains unclear, TGF-β2-dependent remodeling of the extracellular matrix (ECM) within the trabecular meshwork (TM) microenvironment is considered an early pathologic consequence associated with impaired aqueous humor (AH) outflow and elevated IOP. Early studies have also demonstrated markedly elevated levels of oxidative stress markers in AH from POAG patients along with altered expression of antioxidant defenses. Here, using cultured primary or transformed human TM cells, we investigated the role oxidative stress plays at regulating TGF-β2-mediated remodeling of the ECM.
Methods:
Primary or transformed (GTM3) human TM cells conditioned in serum-free media were incubated in the absence or presence of TGF-β2 and relative changes in intracellular reactive oxygen species (ROS) were measured using oxidation-sensitive fluorogenic dyes CellROX green or 6-carboxy-2',7'-dichlorodihydrofluorescein diacetate (carboxy-H2DCFDA). TGF-β2-mediated changes in the content of connective tissue growth factor (CTGF) and collagen types 1α1 (COL1A1) and 4α1 (COL4A1) mRNA or collagens I and IV isoform proteins were determined in the absence or presence of mitochondrial-targeted antioxidants (XJB-5-131 or MitoQ) and quantified by quantitative PCR or by immunoblot and immunocytochemistry. Smad-dependent canonic signaling was determined by immunoblot, whereas Smad-dependent transcriptional activity was quantified using a Smad2/3-responsive SBE-luciferase reporter assay.
Results:
Primary or transformed human TM cells cultured in the presence of TGF-β2 (5 ng/mL; 2 hours) exhibited marked increases in CellROX or fluorescein fluorescence. Consistent with previous reports, challenging cultured human TM cells with TGF-β2 elicited measurable increases in regulated Smad2/3 signaling as well as increases in CTGF, COL1A1, and COL4A1 mRNA and collagen protein content. Pretreating human TM cells with mitochondrial-targeted antioxidants XJB-5-131 (10 μM) or MitoQ (10 nM) attenuated TGF-β2-mediated changes in Smad-dependent transcriptional activity.
Conclusions:
The multifunctional profibrotic cytokine TGF-β2 elicits a marked increase in oxidative stress in human TM cells. Mitochondrial-targeted antioxidants attenuate TGF-β2-mediated changes in Smad-dependent transcriptional activity, including marked reductions in CTGF and collagen isoform gene and protein expression. These findings suggest that mitochondrial-targeted antioxidants, when delivered directly to the TM, exhibit potential as a novel strategy by which to slow the progression of TGF-β2-mediated remodeling of the ECM within the TM.
Purpose of review
In this review, we overview the pathophysiology of primary open-angle glaucoma as it relates to the trabecular meshwork (TM), exploring modes of TM dysfunction and regeneration via stem cell therapies.
Recent Findings
Stem cells from a variety of sources, including trabecular meshwork, mesenchymal, adipose, and induced pluripotent stem cells, have shown the potential to differentiate into TM cells in vitro or in vivo and to regenerate the TM in vivo, lowering intraocular pressure (IOP) and reducing glaucomatous retinal ganglion cell damage.
Summary
Stem cell therapies for TM regeneration provide a robust and promising suite of treatments for eventual lowering of IOP and prevention of glaucomatous vision loss in humans in the future. Further investigation into stem cell homing mechanisms and the safety of introducing these cells into human anterior chamber, for instance, are required before clinical applications in treating glaucoma patients.
Glaucoma leads to irreversible blindness. Numerous anti-glaucoma eye drops have been developed. Unfortunately, many patients with glaucoma still suffer from progressive visual disorders. Recently, ripasudil hydrochloride hydrate, a selective Rho-associated protein kinase inhibitor, was launched for the treatment of glaucoma. However, adverse events, such as conjunctival hyperemia, are often noted in clinical trials using healthy subjects. Therefore, we investigated the onset, offset, and kinetic changes of conjunctival hyperemia induced by ripasudil ophthalmic solution in patients with open-angle glaucoma or ocular hypertension who had already been treated with anti-glaucoma eye drops other than ripasudil. Conjunctival hyperemia was evaluated by both clinical grading by 3 ophthalmic physicians and pixel coverage of conjunctival blood vessels determined by conjunctival hyperemia-analyzing software. Conjunctival hyperemia appeared within 10 min post-instillation in most of the participants. Clinical grade and pixel coverage increased significantly 10 min post-instillation and then decreased. In most of the participants, hyperemia resolved within 2 h. Median conjunctival hyperemia offset was 90 min. A tendency of monotonic increase was observed between clinical grade and pixel coverage. Taken altogether, hyperemia induced by ripasudil was transient in glaucoma patients who had already been treated with anti-glaucoma eye drops other than ripasudil.
Purpose
This study investigated the hypotensive effect of RKI-1447, a Rho kinase inhibitor, in a porcine ex vivo pigmentary glaucoma model.
Methods
Twenty-eight porcine anterior chambers were perfused with medium supplemented with 1.67 × 10⁷ pigment particles/ml for 48 h before treatment with RKI-1447 (n = 16) or vehicle control (n = 12). Intraocular pressure (IOP) was recorded and outflow facility was calculated. Primary trabecular meshwork cells were exposed to RKI-1447 or vehicle control; effects on the cytoskeleton, motility, and phagocytosis were evaluated.
Result
Compared to baseline, the perfusion of pigment caused a significant increase in IOP in the RKI-1447 group (P = 0.003) at 48 h. Subsequent treatment with RKI-1447 significantly reduced IOP from 20.14 ± 2.59 to 13.38 ± 0.91 mmHg (P = 0.02). Pigment perfusion reduced the outflow facility from 0.27 ± 0.03 at baseline to 0.18 ± 0.02 at 48 h (P < 0.001). This was partially reversed with RKI-1447. RKI-1447 caused no apparent histological changes in the micro- or macroscopic TM appearance. RKI-1447-treated primary TM cells showed significant disruption of the actin cytoskeleton both in the presence and absence of pigment (P < 0.001) but no effect on TM migration was observed. Pigment-treated TM cells exhibited a reduction in TM phagocytosis, which RKI-1447 reversed.
Conclusion
RKI-1447 significantly reduces IOP by disrupting TM stress fibers and increasing TM phagocytosis. These features may make it useful for the treatment of secondary glaucomas with an increased phagocytic load.
Purpose
The aim of this study was to compare intraocular pressure (IOP) outcomes in eyes with cataract and glaucoma undergoing phacoemulsification (phaco) in combination with goniotomy using the Kahook Dual Blade (KDB) or implantation of a single iStent trabecular bypass device.
Methods
Retrospective analysis of IOP and IOP-lowering medication reduction in eyes undergoing phaco-goniotomy with KDB (n=237) or phaco-iStent (n=198). Preoperative, intraoperative, and postoperative data were collected through 6 months of follow-up. Outcome measures included mean IOP reduction, mean reduction in IOP-lowering medications, and the proportion of eyes achieving ≥20% IOP reduction or ≥1 medication reduction from baseline.
Results
Mean IOP in the phaco-goniotomy with KDB group decreased from 17.9±4.4 mmHg at baseline to 13.6±2.7 mmHg at Month 6 (P<0.001), with mean medication use decreasing from 1.7±0.9 to 0.6±1.0 (P<0.001). In the phaco-iStent group, mean IOP decreased from 16.7±4.4 mmHg to 13.9±2.7 mmHg (P<0.001), with mean IOP-lowering medication use decreasing from 1.9±0.9 to 1.0±1.0 (P<0.001). Mean IOP reduction from baseline was significantly greater in the phaco-goniotomy with KDB group at Month 6 (phaco-goniotomy with KDB −4.2 mmHg [23.7%] vs phaco-iStent −2.7 mmHg [16.4%]; P<0.001). IOP-lowering medication reduction was greater in the phaco-goniotomy with KDB group compared to the phaco-iStent group (1.1 vs 0.9 medications, respectively; P=0.001). The most common adverse event was IOP spikes occurring in 12.6% of phaco-iStent eyes and 6.3% of phaco-goniotomy with KDB eyes (P=0.024).
Conclusion
Goniotomy with the KDB combined with cataract surgery significantly lowers both IOP and the need for IOP-lowering medications compared to cataract extraction with iStent implantation in glaucomatous eyes through 6 months of postoperative follow-up.
Purpose
The trabecular meshwork (TM) has an important role in the regulation of aqueous humor outflow and IOP. Regulation of the extracellular matrix (ECM) by TGFβ2 has been studied extensively. Bone morphogenetic protein (BMP) and activin membrane-bound inhibitor (BAMBI) has been shown to inhibit or modulate TGFβ2 signaling. We investigate the role of TGFβ2 and BAMBI in the regulation of TM ECM and ocular hypertension.
Methods
Mouse TM (MTM) cells were isolated from B6;129S1-Bambitm1Jian/J flox mice, characterized for TGFβ2 and dexamethasone (DEX)–induced expression of fibronectin, collagen-1, collagen-4, laminin, α-smooth muscle actin, cross-linked actin networks (CLANs) formation, and DEX-induced myocilin (MYOC) expression. MTM cells were transduced with Ad5.GFP to identify transduction efficiency. MTM cells and mouse eyes were transduced with Ad5.Null, Ad5.Cre, Ad5.TGFβ2, or Ad5.TGFβ2 + Ad5.Cre to evaluate the effect on ECM production, IOP, and outflow facility.
Results
MTM cells express TM markers and respond to DEX and TGFβ2. Ad5.GFP at 100 MOI had the highest transduction efficiency. Bambi knockdown by Ad5.Cre and Ad5.TGFβ2 increased fibronectin, collagen-1, and collagen-4 in TM cells in culture and tissue. Ad5.Cre, Ad5.TGFβ2, and Ad5.TGFβ2 + Ad5.Cre each significantly induced ocular hypertension and lowered aqueous humor outflow facility in transduced eyes.
Conclusions
We show for the first time to our knowledge that knockdown of Bambi alters ECM expression in cultured cells and mouse TM, reduces outflow facility, and causes ocular hypertension. These data provide a novel insight into the development of glaucomatous TM damage and identify BAMBI as an important regulator of TM ECM and ocular hypertension.
Pigment dispersion can lead to pigmentary glaucoma, a poorly understood condition of younger myopic eyes with fluctuating high intraocular pressure. It has been difficult to investigate its pathogenesis without a model similar to human eyes in size and behavior. Here we present a porcine ex vivo model that recreates several features of pigmentary glaucoma, including intraocular hypertension, accumulation of pigment in the trabecular meshwork, and declining phagocytosis. We found that trabecular meshwork cells regulate outflow, form actin stress fibers, and have a decreased phagocytic activity. Gene expression microarrays and a pathway analysis of TM monolayers as well as ex vivo anterior segment perfusion cultures indicated that RhoA plays a central role in regulating the cytoskeleton, motility, and phagocytosis in the trabecular meshwork, providing new insights and targets to investigate in pigmentary glaucoma.
Purpose:
To report 1-year treatment outcomes in the Primary Tube Versus Trabeculectomy (PTVT) Study.
Design:
Multicenter, randomized clinical trial.
Participants:
Two hundred forty-two eyes of 242 patients with medically uncontrolled glaucoma and no previous incisional ocular surgery, including 125 in the tube group and 117 in the trabeculectomy group.
Methods:
Patients were enrolled at 16 clinical centers and assigned randomly to treatment with a tube shunt (350-mm2Baerveldt glaucoma implant) or trabeculectomy with mitomycin C (MMC; 0.4 mg/ml for 2 minutes).
Main outcome measures:
Intraocular pressure (IOP), glaucoma medical therapy, visual acuity, visual fields, surgical complications, and failure (IOP of more than 21 mmHg or reduced by less than 20% from baseline, IOP of 5 mmHg or less, reoperation for glaucoma, or loss of light perception vision).
Results:
The cumulative probability of failure during the first year of follow-up was 17.3% in the tube group and 7.9% in the trabeculectomy group (P = 0.01; hazard ratio, 2.59; 95% confidence interval, 1.20-5.60). Mean ± standard deviation IOP was 13.8±4.1 mmHg in the tube group and 12.4±4.4 mmHg in the trabeculectomy group at 1 year (P = 0.01), and the number of glaucoma medications was 2.1±1.4 in the tube group and 0.9±1.4 in the trabeculectomy group (P < 0.001). Postoperative complications developed in 36 patients (29%) in the tube group and 48 patients (41%) in the trabeculectomy group (P = 0.06). Serious complications requiring reoperation or producing a loss of 2 Snellen lines or more occurred in 1 patient (1%) in the tube group and 8 patients (7%) in the trabeculectomy group (P = 0.03).
Conclusions:
Trabeculectomy with MMC had a higher surgical success rate than tube shunt implantation after 1 year in the PTVT Study. Lower IOP with use of fewer glaucoma medications was achieved after trabeculectomy with MMC compared with tube shunt surgery during the first year of follow-up. The frequency of serious complications producing vision loss or requiring reoperation was lower after tube shunt surgery relative to trabeculectomy with MMC.
Purpose
Dysfunction of the trabecular meshwork (TM) in pigmentary glaucoma contributes to increased aqueous humor outflow resistance and intraocular pressure. In this study, we investigated the effect of pigment dispersion on trabecular meshwork cells.
Methods
Porcine TM cells from ab interno trabeculectomy specimens were exposed to pigment dispersion, then, analyzed for changes in morphology, immunostaining, and ultrastructure. Their abilities to phagocytose migrate, and contraction was quantified. An expression microarray, using 23,937 probes, and a pathway analysis were performed.
Results
Stress fiber formation was increased in the pigment dispersion group (P) (60.1 ± 0.3%, n = 10) compared to control (C) (38.4 ± 2.5%, n = 11, p < 0.001). Phagocytosis declined (number of cells with microspheres in P = 37.0 ± 1.1% and in C = 68.7 ± 1.3%, n = 3, p < 0.001) and migration was reduced after 6 h (cells within the visual field over 6 h in P = 28.0.1 ± 2.3 (n = 12) and in C = 40.6 ± 3.3 (n = 13), p < 0.01). Pigment induced contraction at 24 h onwards (p < 0.01). Microarray analysis revealed that Rho signaling was central to these responses.
Conclusion
Exposure of TM cells to pigment dispersion resulted in reduced phagocytosis and migration, as well as increased stress fiber formation and cell contraction. The Rho signaling pathway played a central and early role, suggesting that its inhibitors could be used as a specific intervention in treatment of pigmentary glaucoma.
Purpose:
To evaluate the efficacy and ocular and systemic safety of netarsudil 0.02% ophthalmic solution, a rho-kinase inhibitor and norepinephrine transporter inhibitor, in patients with open-angle glaucoma and ocular hypertension.
Design:
Double-masked, randomized non-inferiority clinical trials.
Methods:
After a washout of all pre-study ocular hypotensive medications, eligible patients were randomized to receive netarsudil 0.02%, q.d., timolol 0.5% b.i.d., and (ROCKET-2 only), netarsudil 0.02%, b.i.d. Data through 3 months from both studies are provided in this report.
Results:
Enrolled into the two studies were 1,167 patients. Treatment with netarsudil q.d. produced clinically and statistically significant reductions from baseline intraocular pressure (p < 0.001), and was non-inferior to timolol in the per-protocol population with maximum baseline IOP < 25 mmHg in both studies (ROCKET-2, primary outcome measure and population, ROCKET-1, post hoc outcome measure). Netarsudil b.i.d. was also non-inferior to timolol (ROCKET-2). The most frequent adverse event was conjunctival hyperemia, the incidence of which ranged from 50% (126/251, ROCKET-2) to 53% (108/203, ROCKET-1) for netarsudil q.d., 59% (149/253, ROCKET-2) for netarsudil b.i.d., and 8% (17/208, ROCKET-1) to 11% (27/251, ROCKET-2) for timolol (p < 0.0001for netarsudil vs. timolol).
Conclusions:
In two large, randomized, double-masked trials reported here, once-daily dosing of netarsudil 0.02% was found to be effective and well-tolerated for the treatment of patients with ocular hypertension and open-angle glaucoma. The novel pharmacology and aqueous humor dynamic effects of this molecule suggest it may be a useful addition to the armamentarium of ocular hypotensive medications.
Background
MIGS have been developed as a surgical alternative for glaucomatous patients.
Purpose
To analyze the change in intraocular pressure (IOP) and glaucoma medications using different MIGS devices (Trabectome, iStent, Excimer Laser Trabeculotomy (ELT), iStent Supra, CyPass, XEN, Hydrus, Fugo Blade, Ab interno canaloplasty, Goniscopy-assisted transluminal trabeculotomy) as a solo procedure or in association with phacoemulsification.
Methods
Randomized control trials (RCT) and non-RCT (non randomized comparative studies, NRS, and before-after studies) were included. Studies with at least one year of follow-up in patients affected by primary open angle glaucoma, pseudoexfoliative glaucoma or pigmentary glaucoma were considered. Risk of Bias assessment was performed using the Cochrane Risk of Bias and the ROBINS-I tools. The main outcome was the effect of MIGS devices compared to medical therapy, cataract surgery, other glaucoma surgeries and other MIGS on both IOP and use of glaucoma medications 12 months after surgery. Outcomes measures were the mean difference in the change of IOP and glaucoma medication compared to baseline at one and two years and all ocular adverse events. The current meta-analysis is registered on PROSPERO (reference n° CRD42016037280).
Results
Over a total of 3,069 studies, nine RCT and 21 case series with a total of 2.928 eyes were included. Main concerns about risk of bias in RCTs were lack of blinding, allocation concealment and attrition bias while in non-RCTs they were represented by patients’ selection, masking of participants and co-intervention management. Limited evidence was found based on both RCTs and non RCTs that compared MIGS surgery with medical therapy or other MIGS. In before-after series, MIGS surgery seemed effective in lowering both IOP and glaucoma drug use. MIGS showed a good safety profile: IOP spikes were the most frequent complications and no cases of infection or BCVA loss due to glaucoma were reported.
Conclusions
Although MIGS seem efficient in the reduction of the IOP and glaucoma medication and show good safety profile, this evidence is mainly derived from non-comparative studies and further, good quality RCTs are warranted.
Purpose:
Primary open-angle glaucoma (POAG) is particularly common in older individuals and associated with pathologic degeneration of the trabecular meshwork (TM). We have shown previously that transplantation of induced pluripotent stem cell (iPSC) derived TM cells restores aqueous humor dynamics in young transgenic mice expressing a pathogenic form of human myocilin (Tg-MYOCY437H). This study was designed to determine if this approach is feasible in older mice with more pronounced TM dysfunction.
Methods:
Mouse iPSC were differentiated toward a TM cell phenotype (iPSC-TM) and injected into the anterior chamber of 6-month-old Tg-MYOCY437H or control mice. IOP and aqueous humor outflow facility were recorded for up to 3 months. Transmission electron microscopy, Western blot, and immunohistochemistry were performed to analyze TM morphology, quantify endoplasmic reticulum (ER) stress, and assess TM cellularity.
Results:
A 12 weeks after transplantation, IOP in iPSC-TM recipients was statistically lower and outflow facility was significantly improved compared to untreated controls. The number of endogenous TM cells increased significantly in iPSC-TM recipients along with the appearance of TM cells immmunopositive for a marker of cellular division. Morphologically, transplantation of iPSC-TM preserves ER structure 12 weeks after transplantation. However, myocilin and calnexin expression levels remain elevated in transplanted eyes of these 9-month-old Tg-MYOCY437H mice, indicating that ER stress persists within the TM.
Conclusions:
Transplantation of iPSC-TM can restore IOP and outflow facility in aged Tg-MYOCY437H mice. This type of stem cell-based therapy is a promising possibility for restoration of IOP control in some glaucoma patients.
Purpose
Increased expression of TGF-β2 in primary open-angle glaucoma (POAG) aqueous humor (AH) and trabecular meshwork (TM) causes deposition of extracellular matrix (ECM) in the TM and elevated IOP. Bone morphogenetic proteins (BMPs) regulate TGF-β2–induced ECM production. The underlying mechanism for BMP4 inhibition of TGF-β2–induced fibrosis remains undetermined. Bone morphogenic protein 4 induces inhibitor of DNA binding proteins (ID1, ID3), which suppress transcription factor activities to regulate gene expression. Our study will determine whether ID1and ID3 proteins are downstream targets of BMP4, which attenuates TGF-β2 induction of ECM proteins in TM cells.
Methods
Primary human TM cells were treated with BMP4, and ID1 and ID3 mRNA, and protein expression was determined by quantitative PCR (Q-PCR) and Western immunoblotting. Intracellular ID1 and ID3 protein localization was studied by immunocytochemistry. Transformed human TM cells (GTM3 cells) were transfected with ID1 or ID3 expression vectors to determine their potential inhibitory effects on TGF-β2–induced fibronectin and plasminogen activator inhibitor-I (PAI-1) protein expression.
Results
Basal expression of ID1-3 was detected in primary human TM cells. Bone morphogenic protein 4 significantly induced early expression of ID1 and ID3 mRNA (P < 0.05) and protein in primary TM cells, and a BMP receptor inhibitor blocked this induction. Overexpression of ID1 and ID3 significantly inhibited TGF-β2–induced expression of fibronectin and PAI-1 in TM cells (P < 0.01).
Conclusions
Bone morphogenic protein 4 induced ID1 and ID3 expression suppresses TGF-β2 profibrotic activity in human TM cells. In the future, targeting specific regulators may control the TGF-β2 profibrotic effects on the TM, leading to disease modifying IOP lowering therapies.
Members of the transforming growth factor beta (TGFβ) cytokine family have long been associated with affecting several cellular functions, including cell proliferation, differentiation and extracellular matrix (ECM) turnover. Of particular interest to this work, TGFβ2 has been linked to most types of glaucomas as a potential fibrotic agent that can cause elevation of intraocular pressure (IOP). Given that the trabecular meshwork (TM) provides most of aqueous humor outflow resistance in the eye, an in vitro bioengineered human TM (HTM) model has been created and validated by analyzing effects of TGFβ2 on transcellular pressure changes and outflow facility. These changes were correlated with several biological alterations induced by this cytokine, including ECM production and overexpression of HTM-marker myocillin. Furthermore, this TM model has been used to extend current knowledge of gene expression of cytokines involved in TGFβ-induced ECM turnover over time. In particular, the ability for a ROCK-inhibitor to diminish the effect of TGFβ on TM was demonstrated. This work supports the notion that anti-fibrotic activities of ROCK-inhibitors could counteract the elevation of IOP and increased strain observed in glaucomatous TM.
Chronic glaucoma is a multifactorial disease among which oxidative stress may play a major pathophysiological role. We conducted a systematic review and meta-analysis to evaluate the levels of oxidative and antioxidative stress markers in chronic glaucoma compared with a control group. The PubMed, Cochrane Library, Embase and Science Direct databases were searched for studies reporting oxidative and antioxidative stress markers in chronic glaucoma and in healthy controls using the following keywords: “oxidative stress” or “oxidant stress” or “nitrative stress” or “oxidative damage” or “nitrative damage” or “antioxidative stress” or “antioxidant stress” or “antinitrative stress” and “glaucoma”. We stratified our meta-analysis on the type of biomarkers, the type of glaucoma, and the origin of the sample (serum or aqueous humor). We included 22 case-control studies with a total of 2913 patients: 1614 with glaucoma and 1319 healthy controls. We included 12 studies in the meta-analysis on oxidative stress markers and 19 on antioxidative stress markers. We demonstrated an overall increase in oxidative stress markers in glaucoma (effect size = 1.64; 95%CI 1.20–2.09), ranging from an effect size of 1.29 in serum (95%CI 0.84–1.74) to 2.62 in aqueous humor (95%CI 1.60–3.65). Despite a decrease in antioxidative stress marker in serum (effect size = –0.41; 95%CI –0.72 to –0.11), some increased in aqueous humor (superoxide dismutase, effect size = 3.53; 95%CI 1.20–5.85 and glutathione peroxidase, effect size = 6.60; 95%CI 3.88–9.31). The differences in the serum levels of oxidative stress markers between glaucoma patients and controls were significantly higher in primary open angle glaucoma vs primary angle closed glaucoma (effect size = 12.7; 95%CI 8.78–16.6, P < 0.001), and higher in pseudo-exfoliative glaucoma vs primary angle closed glaucoma (effect size = 12.2; 95%CI 8.96–15.5, P < 0.001). In conclusion, oxidative stress increased in glaucoma, both in serum and aqueous humor. Malonyldialdehyde seemed the best biomarkers of oxidative stress in serum. The increase of some antioxidant markers could be a protective response of the eye against oxidative stress.
We previously demonstrated that an αvβ5 integrin/FAK- mediated pathway regulated the phagocytic properties of human trabecular meshwork (HTM) cells. Here we demonstrate that this process is mediated by Rac-1 and a previously unreported signaling pathway that utilizes the Tiam1 as well as a novel ILK/RhoG/ELMO2 signaling pathway. Phagocytosis in both a TM-1 cell line and normal HTM cells was mediated by Rac1 and could be significantly decreased by >75% using the Rac1 inhibitor EHop-016. Knockdown of Rac1 in TM-1 cells also inhibited phagocytosis by 40% whereas overexpression of a constitutively active Rac1 or stimulation with PDGF increased phagocytosis by 83% and 32% respectively. Tiam1 was involved in regulating phagocytosis. Knockdown of Tiam1 inhibited phagocytosis by 72% while overexpression of Tiam1 C1199 increased phagocytosis by 75%. Other upstream effectors of Rac1 found to be involved included ELMO2, RhoG, and ILK. Knockdowns of ELMO2, ILK, and RhoG caused a reduction in phagocytosis by 51%, 55% and 46% respectively. In contrast, knockdown of Vav2 and Dock1 or overexpression of Vav2 Y159/172F did not cause a significant change in phagocytosis. These data suggest a novel link between Tiam1 and RhoG/ILK /ELMO2 pathway as upstream effectors of the Rac1-mediated phagocytic process in TM cells.
Direct visualization and assessment of the iridocorneal angle (ICA) region with high resolution is important for the clinical evaluation of glaucoma. However, the current clinical imaging systems for ICA do not provide sufficient structural details due to their poor resolution. The key challenges in achieving high quality ICA imaging are its location in the anterior region of the eye and the occurrence of total internal reflection due to refractive index difference between cornea and air. Here, we report an indirect axicon assisted gonioscopy imaging probe with white light illumination. The illustrated results with this probe shows significantly improved visualization of structures in the ICA including TM region, compared to the current available tools. It could reveal critical details of ICA and expected to aid management by providing information that is complementary to angle photography and gonioscopy.
Intraocular pressure (IOP) is still the main treatment target for glaucoma. Outflow resistance mainly exists at the trabecular meshwork (TM) outflow pathway, which is responsible for IOP regulation. Changes of TM cellularity and TM extracellular matrix turnover may play important roles in IOP regulation. In this article, we review basic anatomy and physiology of the outflow pathway and TM stem cell characteristics regarding the location, isolation, identification and function. TM stem cells are localized at the insert region of the TM and are label-retaining in vivo. They can be isolated by side-population cell sorting, cloning culture, or sphere culture. TM stem cells are multipotent with the ability to home to the TM region and differentiate into TM cells in vivo. Other stem cell types, such as adipose-derived stem cells, mesenchymal stem cells and induced pluripotent stem cells have been discovered for TM cell differentiation and TM regeneration. We also review glaucomatous animal models, which are suitable to study stem cell-based therapies for TM regeneration.
Minimally invasive glaucoma surgery aims to provide a medication-sparing, conjunctival-sparing, ab interno approach to intraocular pressure reduction for patients with mild-to-moderate glaucoma that is safer than traditional incisional glaucoma surgery. The current approaches include: increasing trabecular outflow (Trabectome, iStent, Hydrus stent, gonioscopy-assisted transluminal trabeculotomy, excimer laser trabeculotomy); suprachoroidal shunts (Cypass micro-stent); reducing aqueous production (endocyclophotocoagulation); and subconjunctival filtration (XEN gel stent). The data on each surgical procedure for each of these approaches are reviewed in this article, patient selection pearls learned to date are discussed, and expectations for the future are examined.
The reactive oxygen species (ROS) form under normal physiological conditions and may have both beneficial and harmful role. We search the literature and current knowledge in the aspect of ROS participation in the pathogenesis of anterior and posterior eye segment diseases in adults. ROS take part in the pathogenesis of keratoconus, Fuchs endothelial corneal dystrophy, and granular corneal dystrophy type 2, stimulating apoptosis of corneal cells. ROS play a role in the pathogenesis of glaucoma stimulating apoptotic and inflammatory pathways on the level of the trabecular meshwork and promoting retinal ganglion cells apoptosis and glial dysfunction in the posterior eye segment. ROS play a role in the pathogenesis of Leber’s hereditary optic neuropathy and traumatic optic neuropathy. ROS induce apoptosis of human lens epithelial cells. ROS promote apoptosis of vascular and neuronal cells and stimulate inflammation and pathological angiogenesis in the course of diabetic retinopathy. ROS are associated with the pathophysiological parainflammation and autophagy process in the course of the age-related macular degeneration.
• Aim: To report a case of Charles Bonnet syndrome in advanced pseudoexfoliative glaucoma. • Methods: Case report. • Results: A 92-year-old Malay man presented visual hallucination for 2 years with worsening of his symptoms for the past 2 months. He claimed that he had seen people as well as hundreds of children on separate occasions vividly. He even saw a rabbit running across his room on a few occasions. However, he had insight that this was an abnormal experience. His cognitive function was normal for his age. Psychiatry evaluations including the mental status examination were normal. He was previously diagnosed as open angle glaucoma with history of uneventful cataract surgery and trabeculectomy over his left eye. His vision was hand movement in the right eye and 6/7.5 in the left eye with tunnel vision. Funduscopy of the left eye showed advanced glaucomatous optic disc cupping. He had right bullous keratopathy with absolute glaucoma and left advanced pseudoexfoliative glaucoma with functioning blebs. • Conclusion: Elderly patient who presented visual hallucination often poses a diagnostic dilemma especially when the criteria for diagnosis of dementia and psychosis are not conclusive. In such a group of patients who possess the insight into the unreality of what they are seeing with a deteriorating vision, ophthalmologists should therefore raise the suspicion of possible Charles Bonnet syndrome.
Introduction:
Glaucoma is a sight-threatening retinal neuropathy associated with elevated intraocular pressure (IOP) due to degeneration and fibrosis of the trabecular meshwork (TM). Glaucoma medications aim to reduce IOP without targeting the specific TM pathology, Bone-marrow mesenchymal stem cells (MSCs) are used today in various clinical studies. Here, we investigated the potential of MSCs therapy in an glaucoma-like ocular hypertension (OHT) model and decipher in vitro the effects of MSCs on primary human trabecular meshwork cells.
Methods:
Ocular hypertension model was performed by cauterization of 3 episcleral veins (EVC) of Long-Evans male rat eyes. MSCs were isolated from rat bone marrow, amplified in vitro and tagged with quantum dot nanocrystals. Animals were distributed as 1) MSCs group receiving 5.10(5)cells/6μl Minimum Essential Medium and 2) MEM group receiving 6μl MEM (n = 10 each). Injections were performed into the anterior chamber of 20 days-hypertensive eyes and IOP was monitored twice a week for 4 weeks. At the end of experiment, cell distribution in the anterior segment was examined in confocal microscopy on flat mounted corneas. Moreover, we tested in vitro effects of MSCs conditioned medium (MSC-CM) on primary human trabecular meshwork cells (hTM cells) using Akt activation, myosin phosphorylation and TGF-β2-dependent profibrotic phenotype in hTM cells.
Results:
We demonstrated a rapid and long-lasting in vivo effect of MSCs transplantation that significantly reduced IOP in hypertensive eyes induced by EVC. MSCs were located to the ciliary processes and the TM. Enumeration of RGCs on whole flat-mounted retina highlighted a protective effect of MSCs on RGCs death. In vitro, MSC-CM promotes: (i) hTM cells survival by activating the antiapoptotic pathway, Akt, (ii) hTM cells relaxation as analyzed by the decrease in myosin phosphorylation and (iii) inhibition of TGF-β2-dependent profibrotic phenotype acquisition in hTM cells.
Conclusions:
MSCs injection in the ocular anterior chamber in a rat model of OHT provides neuroprotective effect in the glaucoma pathophysiology via TM protection. These results demonstrate that MSCs constitute promising tool for treating ocular hypertension and retinal cell degeneration.
Transforming growth factor-β2 induces extracellular matrix (ECM) remodeling, which likely contributes to the defective function of the trabecular meshwork (TM) leading to glaucomatous ocular hypertension. Bone morphogenetic proteins (BMPs) inhibit these profibrotic effects of TGFβ2. The BMP antagonist gremlin is elevated in glaucomatous TM cells and increases IOP in an ex vivo perfusion culture model. The purpose of this study was to determine whether gremlin regulates ECM proteins in the TM, signals through the Smad3-dependent pathway, and induces ocular hypertension in mice.
Ad5.Gremlin or Ad5.TGFβ2 was injected intravitreally into one eye of each mouse. Intraocular pressure measurements were taken using a TonoLab tonometer. Gremlin, TGFβ2, fibronectin (FN), and collagen-1 (Col-1) expression in the TM was determined by immunofluorescence, Western immunoblot, and quantitative (q)PCR analyses.
Ad5.Gremlin or Ad5.TGFβ2 each caused significant IOP elevation in mice. Immunofluorescence and Western blot analysis demonstrated that gremlin and TGFβ2 reciprocally increased the expression of each other, and both increased FN expression in the TM and surrounding tissues. Ad5.Gremlin elevated IOP and increased Fn and Col-1 gene expression in the TM of Smad3 wild-type (WT) mice, but had no effect in Smad3 HET or Smad3 KO mice.
Our results demonstrate that intravitreal injections of either Ad5.Gremlin or Ad5.TGFβ2 elevate IOP and upregulate the ECM protein FN in the TM of mice. These data show that gremlin signals through the Smad3-dependent pathway in the TM to elevate IOP. We determined for the first time gremlin's role in inducing ocular hypertension in an in vivo model system.
Purpose:
Rho-associated kinase-inhibitor ripasudil 0.4% eye drops are reportedly effective for the reduction of intraocular pressure (IOP) in glaucoma patients. However, the previous studies investigated the efficacy of IOP reduction for only about 1 year. Here, we evaluated the safety and efficacy of long-term ripasudil instillation in Japanese open-angle glaucoma (OAG) patients.
Methods:
This study involved 312 eyes of 312 Japanese OAG patients newly initiated with ripasudil treatment at Kyoto Prefectural University of Medicine and Oike-Ikeda Eye Clinic, Kyoto, Japan. In all patients, adverse events leading to discontinuation of ripasudil treatment were investigated. Of the 312 patients, 129 patients able to continue ripasudil administration for over 12-months post-treatment initiation were enrolled to investigate the long-term efficacy. IOP data at 0-, 1-, 3-, 6-, 12-, 18-, and 24-months post initiation of continuous ripasudil use were obtained, and the IOP values at each time point were then compared. The first period (from 1-6 months) and second period (from 12-24 months) IOP data were also compared based on the mixed model.
Results:
IOP at each time-point post-treatment initiation was significantly reduced compared with that at pre initiation (P < 0.05). Differences in IOP between the first and second periods of the study were not statistically significant (P = 0.058). Adverse events leading to discontinuation of treatment included blepharitis (15.7%) and conjunctival hyperemia (9.0%).
Conclusions:
We found that in Japanese OAG patients, 24-month ripasudil eye drop instillation is both safe and effective for lowering IOP and that blepharitis is the primary adverse event for discontinuation of use.
Isolation of trabecular meshwork stem cells in vitro provides the foundation of a novel treatment for glaucoma. Trabecular meshwork stem cells (TMSCs) of the fetal calve were extracted and cultured for this experiment. TMSCs were isolated through side population cell sorting. TMSCs were then identified using immunofluorescent staining. Extracellular matrix (ECM) expression in TM cells derived from TMSCs was evaluated with Western blot. Our results showed a positive expression of stem cell markers Notch1 and OCT-3/4 in TMSCs, but no TM cells markers TIMP3 or AQP1. In contrast, primary TM cells expressed these TM cell markers but no stem cell markers. Our result confirmed that there are expression of ECM components, such as fibronectin, laminin, collagen I and collagen IV in TM cells differentiated from TMSCs.
Conclusion
TM cells derived from TMSCs can secrete ECM components which is important for sustain the physiological function.
The fixed-dose combination (FDC) of netarsudil 0.02%/ latanoprost 0.005% was approved by the United States Food and Drug Administration (FDA) on March 12, 2019, for the reduction of intraocular pressure (IOP) in patients with open-angle glaucoma (OAG) and ocular hypertension (OHT). Netarsudil is a Rho kinase (ROCK) inhibitor and latanoprost is a prostaglandin analogue (PGA). Once-daily administration of this FDC reduces IOP by enhancing aqueous outflow through both the trabecular pathways (ROCK inhibition) and uveoscleral pathways (PGA). Two phase III clinical trials, MERCURY-1 and MERCURY-2, confirmed significantly greater efficacy of the FDC than the individual components, with IOP reductions of 30% or greater observed in 59-65% of subjects treated with FDC compared with 29-37% of subjects treated with latanoprost alone and 21-29% of subjects treated with netarsudil alone. The FDC was well tolerated with mostly mild ocular side effects and limited systemic side effects. This paper will review the work leading to FDA approval and the clinical indications for the use of this combination.
Primary open-angle glaucoma is the leading cause of irreversible blindness worldwide, and intraocular pressure reduction remains the only proven treatment strategy. Elevated intraocular pressure occurs as the result of impaired aqueous humor outflow. Both a passive model and a dynamic model have been used to explain trabecular outflow resistance. The passive model posits that the trabecular meshwork acts as a static filter that exerts stable and passive resistance to outflow. In contrast, the dynamic model involves a "biomechanical pump." In recent years, the range of surgical management options for glaucoma has dramatically expanded, particularly the class of procedures known as microinvasive glaucoma surgery. These procedures typically target and enhance specific outflow routes. Optimal patient outcomes with microinvasive glaucoma surgery require a clear understanding of aqueous outflow and a surgical approach that is targeted to overcome the site of abnormal resistance in the individual. We review the anatomy and physiology of trabecular and suprachoroidal outflow that is of relevance to microinvasive glaucoma surgery-performing surgeons.
Once-daily (p.m.) netarsudil ophthalmic solution 0.02% (Rhopressa) is approved in the United States for lowering elevated intraocular pressure (IOP) in patients with open-angle glaucoma or ocular hypertension. Netarsudil, a Rho kinase (ROCK) inhibitor that lowers IOP primarily by increasing trabecular outflow, produces statistically and clinically significant reductions in mean IOP from baseline, with comparable effects on nocturnal and diurnal IOP. In three phase III trials of patients with elevated IOP, the ocular hypotensive efficacy of once-daily netarsudil 0.02% met the criteria for noninferiority to twice-daily timolol 0.5% at all time points over 3 months in patients with baseline IOP more than 25 mmHg. The most frequent adverse event (AE) was generally mild conjunctival hyperemia, the severity of which did not increase with continued dosing. Netarsudil was associated with minimal treatment-related serious or systemic AEs, likely due to the lack of systemic exposure. This report summarizes the available preclinical and clinical data on netarsudil.
Exfoliation glaucoma (XFG) is the most common identifiable cause of open-angle glaucoma worldwide, and results from the accumulation of extracellular fibrillary material (XFM) within the trabecular meshwork and the Schlemm canal leading to increased intraocular pressure and potential blindness. Immunohistochemical and mass spectrometry analyses have revealed that XFM is a highly glycosylated proteinaceous complex that is extremely resistant to degradation both within the body and under experimental conditions. The protein core contains a wide variety of proteins, including basement membrane proteins, elastic fiber proteins, latent TGFβ proteins, metalloproteinases, chaperone proteins, complement proteins, lysyl oxidase-like 1 (LOXL1), and apolipoprotein E (ApoE). This supplemental section identifies the advances in knowledge and current understanding of the components within XFM with a specific focus on the most recent work defining proteins within XFM and to pose several biological questions that remain unanswered.
Glaucoma is a progressive and chronic neurodegenerative disorder characterised by damage to the inner layers of the retina and deformation of the optic nerve head. The degeneration of retinal ganglion cells (RGCs) and their axons results in an irreversible loss of vision and is correlated with increasing age. Extracellular matrix (ECM) changes related to natural ageing generates a stiffer extracellular environment throughout the body. Altered age-associated ocular tissue stiffening plays a major role in a significant number of ophthalmic pathologies. In glaucoma, both the trabecular meshwork (TM) and the optic nerve head (ONH) undergo extensive ECM remodelling, characterised by fibrotic changes associated with cellular and molecular events (including myofibroblast activation) that drive further tissue fibrosis and stiffening. Here we review the literature concerning the role of age-related ocular stiffening in the TM, lamina cribrosa (LC), sclera, cornea, retina and Bruch membrane/choroid and discuss their potential role in glaucoma progression. Since TM and LC cells are both mechanosensitive, we then describe molecular mechanisms underlying tissue stiffening and cell mechanotransduction, and how these cellular activities can drive further fibrotic changes within ocular tissues. An improved understanding of the interplay between age-related tissue stiffening and biological responses in the TM and ONH could potentially lead to novel therapeutic strategies for glaucoma treatment.
Purpose:
To validate a new culture model of primary human trabecular meshwork cells (p-hTMCs) using Matrigel®, in order to mimic in vitro 3D-TM organization, and to investigate the proinflammatory effect of benzalkonium chloride (BAK) in 3D p-hTMC cultures.
Methods:
p-hTMCs, seeded onto Matrigel®-coated inserts were stimulated with BAK (10(-4)%), dexamethasone (DEX) (10(-6)M) or transforming growth factor-beta 2 (TGF-β2) (5ng/ml) for 48h and observed with confocal microscopy. The BAK effect at 10(-4)% or 5.10(-3)% on the gene expressions of interleukin-6 (IL-6), interleukin-8 (IL-8) and matrix metalloproteinase (MMP-9) was investigated using qRT-PCR in 2D and 3D p-hTMC cultures.
Results:
p-hTMCs seeded in Matrigel® were able to organize themselves in a 3D-spatial conformation in the different conditions tested with cross-linked actin network (CLAN) formation in presence of DEX or TGF-β2 and intercellular space contraction with TGF-β2. IL-6 and IL-8 gene expressions increased in presence of BAK in 2D and in 3D p-hTMC cultures. BAK 10(-4)% only showed a tendency to stimulate MMP-9 expression in p-hTMCs after 24h-recovery.
Conclusions:
We investigated this new 3D-TM in vitro model in Matrigel® matrix for pathophysiological and toxicological purposes. It appears as a new promising tool for a better understanding of TM behavior in physiological and stress conditions, as well as toxicological evaluations of antiglaucoma eyedrops and preservatives.
Purpose Description and evaluation of the technique and efficacy of canaloplasty ab interno (ABIC) in patients with open angle glaucoma (POAG). Methods In this monocentric series of consecutive cases, patients with cataract and open angle glaucoma (combined operation) and pseudophacic patients (mean age: 78 years, range 66-90 years), and suffering from POAG were included. All of them were operated with ABIC by using the iTrack™ 250 µ-microcatheter (Ellex Medical Lasers Pty Ltd, Adelaide, Australia), in order to circumferentially vasodilate Schlemm's canal without implanting a suture to increase tension. Primary endpoints were the mean IOP (intraocular pressure) after 1, 3, 6, 9 and 12 months surgery. Results Twenty-three patients (23 eyes) were included in the study. Mean IOP without a preoperative wash-out phase was reduced from 18.8 ± 5.63 mmHg preoperatively to 14.9 ± 2.90 mmHg (n = 22), 13.82 ± 2.98 (n = 19), 14.69 ± 2.36 mmHg (n = 13), 16.0 ± 2.09 (n = 11) and 14.73 ± 2.97 (n = 11) at 1, 3, 6, 9 and 12 months after surgery. Mean medication was reduced from 1.69 to 0.21 at the last follow-up. The only complication was limited descemetolysis near the limbus. Conclusion The initial results in this study indicate that ABIC reduces IOP and that the dependance on medication is comparable to that with ab externo canaloplasty.
Georg Thieme Verlag KG Stuttgart · New York.
Purpose:
To study the long-term clinical outcomes of uveitic glaucoma and to identify risk factors for progression.
Methods:
Retrospective study of uveitic glaucoma patients in two tertiary medical centers in 2003-2015. Patient- and disease-related data was retrieved. Clinical parameters and visual fields measured at predetermined time points were recorded. Outcome measures included maintaining intraocular pressure ≤21 mmHg and preserving visual fields.
Results:
Included were 34 patients (53 eyes), with a mean follow-up of 7 years. Idiopathic anterior uveitis and open-angle glaucoma were most common. In total, 62% of eyes were steroid responders. Higher IOP was associated with posterior synechiae, peripheral-anterior synechiae, steroidal, and immunomodulatory therapy (p<0.05). Glaucomatous field defects developed in 49%, with most showing no progression, despite elevation of cup-to-disc ratio (p<0.05).
Conclusions:
Chronic severe uveitis, expressed by structural complications and immunomodulatory therapy, was associated with high IOP and the need for more IOP lowering medications, but was unrelated to glaucomatous damage.
Purpose:
Glaucoma is closely linked with oxidative stress and inflammation, and difficult to treat. Its occurrence frequently is contributed by the failure of the trabecular meshwork (TM). Curcumin is known as an antioxidative and anti-inflammatory substance, possessing the potential to treat glaucoma.
Methods:
Using TM cells as the in vitro model system, we investigated the effects of curcumin on oxidative stress-induced markers for TM impairments, including cell death, production of intracellular reactive oxygen species (iROS), induction of proinflammatory proteins, activation of senescence marker, accumulation of carbonylated proteins, and apoptotic cell numbers.
Results:
Curcumin treatment protected TM cells against oxidative stress-induced cell death. Curcumin treatment at concentrations between 1 and 20 μM reduced the production of iROS in H2O2-exposed TM cells in a dose-dependent manner. Further studies demonstrated that curcumin treatment (20 μM) significantly inhibited proinflammatory factors, including IL-6, ELAM-1, IL-1α, and IL-8, whereas it decreased activities of senescence marker SA-β-gal, and lowered levels of carbonylated proteins and apoptotic cell numbers.
Conclusions:
Curcumin is capable of protecting TM cells against oxidative stress, shedding new light on potential treatment for glaucoma.
Glaucoma is the second leading cause of blindness worldwide and elevated intraocular pressure (IOP) is the most important risk factor. High IOP usually occurs as a result of an increase in aqueous humor outflow resistance at the trabecular meshwork (TM). An abnormal TM contributes to the development of glaucoma. Oxidative stress and vascular damage are considered two major cellular factors that lead to alterations in the TM. In this review, we discuss the findings related to oxidative damage to the TM, including the sources of oxidative stress in the TM such as the mitochondria, peroxisomes, endoplasmic reticulum, membrane, cytosol and exogenous factors. We also discuss antioxidants and clinical studies related to protection against oxidative stress in the TM. Although many questions remain unanswered, it is becoming increasingly clear that oxidative stress-induced damage to the TM is related to glaucoma. This may inspire new studies to find better and more stable antioxidants, and better models with which to elucidate the mechanisms involved, and to determine whether in vitro findings translate into in vivo observations. The regulation of the oxidative/redox balance may be the ultimate target for protecting the TM from oxidative stress and preventing glaucoma.
Aberrant expression and signaling of Transforming Growth Factor (TGF)-β is strongly associated with development of elevated intraocular pressure (IOP) and primary open-angle glaucoma (POAG). In cells of the trabecular meshwork, a key component of the conventional outflow pathway, TGF-β is well-known to promote expression of multiple ocular hypertensive mediators, including genes associated with fibrosis as well as cellular contractility. These effects are mediated by induction of canonical (Smad) as well as non-canonical (MAPK, Rho GTPase) signaling cascades. In the present review, we will highlight the non-canonical, Smad-independent signaling pathways activated by TGF-β2 in human TM cells, as well as the genes known to be induced by non-canonical TGF-β2 signaling.
Alterations in stiffness of the trabecular meshwork (TM) may play an important role in primary open-angle glaucoma (POAG), the second leading cause of blindness. Specifically, certain data suggest an association between elevated intraocular pressure (IOP) and increased TM stiffness; however, the underlying link between TM stiffness and IOP remains unclear and requires further study. We here first review the literature on TM stiffness measurements, encompassing various species and based on a number of measurement techniques, including direct approaches such as atomic force microscopy (AFM) and uniaxial tension tests, and indirect methods based on a beam deflection model. We also briefly review the effects of several factors that affect TM stiffness, including lysophospholipids, rho-kinase inhibitors, cytoskeletal disrupting agents, dexamethasone (DEX), transforming growth factor- (TGF- ), nitric oxide (NO) and cellular senescence. We then describe a method we have developed for determining TM stiffness measurement in mice using a cryosection/AFM-based approach, and present preliminary data on TM stiffness in C57BL/6J and CBA/J mouse strains. Finally, we investigate the relationship between TM stiffness and outflow facility between these two strains. The method we have developed shows promise for further direct measurements of mouse TM stiffness, which may be of value in understanding mechanistic relations between outflow facility and TM biomechanical properties.
With the combined purpose of facilitating useful vision over a lifetime, a number of ocular cells have evolved specialized features not found elsewhere in the body. The trabecular meshwork (TM) cell at the irido-corneal angle, which is a key regulator of intraocular pressure, is no exception. Examination of cells in culture isolated from the human TM has shown that they are unique in many ways, displaying characteristic features of several different cell types. Thus, these neural crest derived cells display expression patterns and behaviors typical of endothelia, fibroblasts, smooth muscle and macrophages, owing to the multiple roles and two distinct environments where they operate to maintain intraocular pressure homeostasis. In most individuals, TM cells function normally over a lifetime in the face of persistent stressors, including phagocytic, oxidative, mechanical and metabolic stress. Study of TM cells isolated from ocular hypertensive eyes has shown a compromised ability to perform their daily duties. This review highlights the many responsibilities of the TM cell and its challenges, progress in our understanding of TM biology over the past 30 years, as well as discusses unanswered questions about TM dysfunction that results in IOP dysregulation and glaucoma.
E-prostanoid receptor subtype 2 (EP2) agonists are currently under clinical development as hypotensive agents for the treatment of ocular hypertension. However, the effects of EP2 receptor agonists on trabecular meshwork (TM) alterations leading to primary open-angle glaucoma (POAG) are still unknown. Here, we evaluated whether EP2 receptor activation exhibits protective functions on TM cell death induced by endoplasmic reticulum (ER) stress. We show that the EP2 receptor agonist butaprost protects TM cell death mediated by the ER stress inducer tunicamycin through a cyclic AMP (cAMP)-dependent mechanism, but independent of the classical cAMP sensors, protein kinase A and exchange proteins activated by cAMP. The ER stress-induced intrinsic apoptosis inhibited by the EP2 receptor agonist was correlated with a decreased accumulation of the cellular stress sensor p53. In addition, p53 down-regulation was associated with inhibition of its transcriptional activity, which led to decreased expression of the pro-apoptotic p53-upregulated modulator of apoptosis (PUMA). The stabilization of p53 by nutlin-3a abolished butaprost-mediated cell death protection. In conclusion, we showed that EP2 receptor activation protects against ER stress-dependent mitochondrial apoptosis through down-regulation of p53. The specific inhibition of this pathway could reduce TM alterations observed in POAG patients.
Glaucoma patients have elevated aqueous humor and trabecular meshwork (TM) levels of transforming growth factor-beta2 (TGF-β2). TGF-β2 has been associated with increased extracellular matrix (ECM) deposition (i.e. fibronectin), which is attributed to the increased resistance of aqueous humor outflow through the TM. We have previously demonstrated that bone morphogenetic protein (BMP) 4 selectively counteracts the profibrotic effect of TGF-β2 with respect to ECM synthesis in the TM, and this action is reversed by the BMP antagonist gremlin. Thus, the BMP and TGF-β signaling pathways antagonize each other's antifibrotic and profibrotic roles. The purpose of this study was to determine whether cultured human TM cells: (a) express other BMP antagonists noggin, chordin, BMPER, BAMBI, Smurf1 and 2, and (b) whether expression of these proteins is regulated by exogenous TGF-β2 treatment. Primary human trabecular meshwork (TM) cells were grown to confluency and treated with TGF-β2 (5 ng/ml) for 24 or 48 h in serum-free medium. Untreated cell served as controls. qPCR and Western immunoblots (WB) determined that human TM cells expressed mRNAs and proteins for the BMP antagonists proteins: noggin, chordin, BMPER, BAMBI, and Smurf1/2. Exogenous TGF-β2 decreased chordin, BMPER, BAMBI, and Smurf1 mRNA and protein expression. In contrast, TGF-β2 increased secreted noggin and Smurf2 mRNA and protein levels. BMP antagonist members are expressed in the human TM. These molecules may be involved in the normal function of the TM as well as TM pathogenesis. Altered expression of BMP antagonist members may lead to functional changes in the human TM.
Purpose:
Prostaglandin F2α analogues are the first-line medication for the treatment of ocular hypertension (OHT), and prostanoid EP2 receptor agonists are under clinical development for this indication. The goal of this study was to investigate the effects of F prostanoid (FP) and EP2 receptor activation on the myofibroblast transition of primary trabecular meshwork (TM) cells, which could be a causal mechanism of TM dysfunction in glaucoma.
Methods:
Human primary TM cells were treated with either latanoprost or butaprost and TGF-β2. Trabecular meshwork contraction was measured in a three-dimensional (3D) TM cell-populated collagen gel (CPCG) model. Expression of α-smooth muscle actin (α-SMA) and phosphorylation of myosin light chain (MLC) were determined by Western blot. Assembly of actin stress fibers and collagen deposition were evaluated by immunocytochemistry. Involvement of p38, extracellular signal-regulated kinase (ERK), and Rho-associated kinase (ROCK) pathways as well as matrix metalloproteinase activation was tested with specific inhibitors.
Results:
In one source of validated adult TM cells, latanoprost induced cell contraction as observed by CPCG surface reduction and increased actin polymerization, α-SMA expression, and MLC phosphorylation, whereas butaprost inhibited TGF-β2-induced CPCG contraction, actin polymerization, and MLC phosphorylation. Both agonists inhibited TGF-β2-dependent collagen deposition. The latanoprost effects were mediated by p38 pathway.
Conclusions:
Latanoprost decreased TM collagen accumulation but promoted a contractile phenotype in a source of adult TM cells that could modulate the conventional outflow pathway. In contrast, butaprost attenuated both TM contraction and collagen deposition induced by TGF-β2, thereby inhibiting myofibroblast transition of TM cells. These results open new perspectives for the management of OHT.
Primary Open Angle Glaucoma (POAG) is an irreversible, vision-threatening disease that affects millions worldwide. The principal risk factor of POAG is increased intraocular pressure (IOP) due to pathological changes in the trabecular meshwork (TM). The TGFβ signaling pathway activator TGFβ2 and the Wnt signaling pathway inhibitor secreted frizzled-related protein 1 (SFRP1) are elevated in the POAG TM. In this study, we determined whether there is a crosstalk between the TGFβ/Smad pathway and the canonical Wnt pathway using luciferase reporter assays. Lentiviral luciferase reporter vectors for studying the TGFβ/Smad pathway or the canonical Wnt pathway were transduced into primary human non-glaucomatous TM (NTM) cells. Cells were treated with or without a combination of 5 μg/ml TGFβ2 and/or 100 ng/ml Wnt3a recombinant proteins, and luciferase levels were measured using a plate reader. We found that TGFβ2 inhibited Wnt3a-induced canonical Wnt pathway activation, while Wnt3a inhibited TGFβ2-induced TGFβ/Smad pathway activation (n = 6, p < 0.05) in 3 NTM cell strains. We also found that knocking down of Smad4 or β-catenin using siRNA in HTM5 cells transfected with similar luciferase reporter plasmids abolished the inhibitory effect of TGFβ2 and/or Wnt3a on the other pathway (n = 6). Our results suggest the existence of a cross-inhibition between the TGFβ/Smad and canonical Wnt pathways in the TM, and this cross-inhibition may be mediated by Smad4 and β-catenin.
Intraocular pressure (IOP), the critical risk factor for glaucoma, is generated and maintained by the aqueous humor circulation system. Aqueous humor is secreted from the epithelial layers of the ciliary body and exits the eye through the trabecular meshwork or the uveoscleral outflow pathways. IOP builds up in response to a resistance to aqueous humor flow in the trabecular outflow pathways. The trabecular outflow resistance is localized in the inner wall region, which comprises the juxtacanalicular connective tissue (JCT) and the inner wall endothelium of Schlemm's canal (SC). Outflow resistance in this region is lowered through the relaxation of contractile myofibroblast-like cells in trabecular meshwork and the adjacent scleral spur, or the contraction of the ciliary muscle. In primary open-angle glaucoma, the most frequent form of glaucoma, outflow resistance of the inner wall region is typically higher than normal. There is evidence that the increase in resistance is related to characteristic biological changes in the resident cells of the JCT, which more and more acquire the structural and functional characteristics of contractile myofibroblasts. The changes involve an augmentation of their actin cytoskeleton and of their surrounding fibrillary extracellular matrix, which connects to JCT cells via integrins. This scenario leads to an overall stiffening of the inner wall region, and is modulated by transforming growth factor-β/connective tissue growth factor signaling. Essentially comparable changes appear to occur in SC endothelial cells. Stiffening of JCT and SC cells is very likely a critical causative factor for the increase in trabecular outflow resistance in POAG.
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Treatment with corticosteroids can result in ocular hypertension and may lead to the development of steroid-induced glaucoma. The extent to which biomechanical changes in trabecular meshwork (TM) cells and extracellular matrix (ECM) contribute toward this dysfunction is poorly understood.
Primary human TM (HTM) cells were cultured for either 3 days or 4 weeks in the presence or absence of dexamethasone (DEX), and cell mechanics, matrix mechanics and proteomics were determined, respectively. Adult rabbits were treated topically with either 0.1% DEX or vehicle over 3 weeks, and mechanics of the TM were determined.
Treatment with DEX for 3 days resulted in a 2-fold increase in HTM cell stiffness, and this correlated with activation of extracellular signal-related kinase 1/2 (ERK1/2) and overexpression of α-smooth muscle actin (αSMA). Further, the matrix deposited by HTM cells chronically treated with DEX is approximately 4-fold stiffer, more organized, and has elevated expression of matrix proteins commonly implicated in glaucoma (decorin, myocilin, fibrillin, secreted frizzle-related protein [SFRP1], matrix-gla). Also, DEX treatment resulted in a 3.5-fold increase in stiffness of the rabbit TM.
This integrated approach clearly demonstrates that DEX treatment increases TM cell stiffness concurrent with elevated αSMA expression and activation of the mitogen-activated protein kinase (MAPK) pathway, stiffens the ECM in vitro along with upregulation of Wnt antagonists and fibrotic markers embedded in a more organized matrix, and increases the stiffness of TM tissues in vivo. These results demonstrate glucocorticoid treatment can initiate the biophysical alteration associated with increased resistance to aqueous humor outflow and the resultant increase in IOP.