[Show abstract][Hide abstract] ABSTRACT: Keratocytes, the quiescent cells of the corneal stroma, play a crucial role in corneal wound healing. Neuropeptides and neurotransmitters are usually associated with neuronal signaling, but have recently been shown to be produced also by non-neuronal cells and to be involved in many cellular processes. The aim of this study was to assess the endogenous intracellular and secreted levels of the neuropeptides substance P (SP) and neurokinin A (NKA), and of the neurotransmitters acetylcholine (ACh), catecholamines (adrenaline, noradrenaline and dopamine), and glutamate, as well as the expression profiles of their receptors, in human primary keratocytes in vitro and in keratocytes of human corneal tissue sections in situ. Cultured keratocytes expressed genes encoding for SP and NKA, and for catecholamine and glutamate synthesizing enzymes, as well as genes for neuropeptide, adrenergic and ACh (muscarinic) receptors. Keratocytes in culture produced SP, NKA, catecholamines, ACh, and glutamate, and expressed neurokinin-1 and -2 receptors (NK-1R and NK-2R), dopamine receptor D2, muscarinic ACh receptors, and NDMAR1 glutamate receptor. Human corneal sections expressed SP, NKA, NK-1R, NK-2R, receptor D2, choline acetyl transferase (ChAT), M3, M4 and M5 muscarinic ACh receptors, glutamate, and NMDAR1, but not catecholamine synthesizing enzyme or the α1 and β2 adrenoreceptors, nor M1 receptor. In addition, expression profiles assumed significant differences between keratocytes from the peripheral cornea as compared to those from the central cornea, as well as differences between keratocytes cultured under various serum concentrations. In conclusion, human keratocytes express an array of neuropeptides and neurotransmitters. The cells furthermore express receptors for neuropeptides/neurotransmitters, which suggests that they are susceptible to stimulation by these substances in the cornea, whether of neuronal or non-neuronal origin. As it has been shown that neuropeptides/neurotransmitters are involved in cell proliferation, migration, and angiogenesis, it is possible that they play a role in corneal wound healing.
PLoS ONE 07/2015; 10(7):e0134157. DOI:10.1371/journal.pone.0134157 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Corneal dystrophies are a clinically and genetically heterogeneous group of inherited disorders that bilaterally affect corneal transparency. They are defined according to the corneal layer affected and by their genetic cause. In this study we identified a dominantly inherited Epithelial Recurrent Erosion Dystrophy (ERED)-like disease that is common in northern Sweden. Whole-exome sequencing resulted in the identification of a novel mutation, c.2816C>T, p.T939I, in the COL17A1 gene which encodes collagen type XVII alpha 1. The variant segregated with disease in a genealogically expanded pedigree dating back 200 years. We also investigated a unique COL17A1 synonymous variant, c.3156C>T, identified in a previously reported unrelated dominant ERED-like family linked to a locus on chromosome 10q23-q24 encompassing COL17A1. We show that this variant introduces a cryptic donor site resulting in aberrant pre-mRNA splicing and is highly likely to be pathogenic. Bi-allelic COL17A1 mutations have previously been associated with a recessive skin disorder, junctional epidermolysis bullosa, with recurrent corneal erosions being reported in some cases. Our findings implicate presumed gain of function COL17A1 mutations causing dominantly inherited ERED and improve understanding of the underlying pathology. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
Human Mutation 02/2015; 36(4). DOI:10.1002/humu.22764 · 5.14 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Introduction The presence or absence of inflammatory cells in chronic Achilles tendinopathy has been a controversial subject in previous studies. Macrophages, T lymphocytes, and neutrophils have previously been detected in tendinopathic human Achilles tendons, whereas other authors have reported that there is no evidence for their occurrence. This controversy may stem from the fact that human Achilles tendon overuse injuries usually develop gradually over time, and the time course of inflammation in response to overuse has been difficult to establish in clinical populations. The aim of this study was to examine the presence of inflammatory cells in the Achilles tendon of rabbits that were subjected to repetitive mechanical loading of defined durations.
Methods In this study, tissue blocks of Achilles tendon taken from a cohort of rabbits on which we previously reported1 were used to analyse the presence of inflammatory cells. Twenty-Four New Zealand male rabbits were subjected to repetitive mechanical loading of the Achilles tendon and grouped into four groups, according to the exercise time period: 0, 1, 3, and 6 weeks. Achilles tendons were harvested at the end of each time period. T-lymphyocytes and neutrophils were examined using immunohistochemistry, and macrophages were identified with Prussian blue staining. All areas of positively labelled cells were captured in digital micrographs using a 20x objective lens and expressed as cell density / viewing field.
Results Macrophages, T-lymphocytes, and neutrophils were detected in tendon sections from groups 0, 1, 3, 6 weeks. While there was no apparent change in the density of neutrophils over the 6 week time course, the density of lymphocytes (n.s.) and macrophages (p < 0.05) increased over the 6 weeks of overuse (Figure 1). Qualitatively speaking, the evidence of inflammation was not evenly distributed, as some tissue sections from the same groups showed no evidence of inflammatory cells. Inflammatory cells were observed primarily in the paratendon rather than the tendon proper.
Discussion An increasing number of macrophages and lymphocytes were detected in the Achilles tendons of animals subjected to repetitive mechanical loading, with an absence of the same types of cells in some sections from the same groups for unknown reasons. Future studies are needed to (1) confirm these findings using a corroborating technique, e.g. qPCR, and (2) examine the influence of additional variables including tendon region and sex.2 Future studies could examine whether inhibiting inflammation would lessen the extent of tendinopathy in this overuse model.
References Andersson, et al. Br J Sports Med. 2011;45(13):1017–2
Huisman, et al. J Anat. 2014;224(5):538–47
British Journal of Sports Medicine 09/2014; 48(Suppl_2):A60-A61. DOI:10.1136/bjsports-2014-094114.92 · 5.03 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Substance P (SP) is a neuropeptide, predominantly released from sensory nerve fibers, with a potentially protective role in diabetic corneal epithelial wound healing. However, the molecular mechanism remains unclear. We investigated the protective mechanism of SP against hyperglycemia-induced corneal epithelial wound healing defects, using type 1 diabetic mice and high glucose-treated corneal epithelial cells. Hyperglycemia induced delayed corneal epithelial wound healing, accompanied with attenuated corneal sensation, mitochondrial dysfunction, and impairments of Akt-, EGFR-, and Sirt1-activation, as well as decreased reactive oxygen species (ROS) scavenging capacity. However, SP application promoted the epithelial wound healing, the recovery of corneal sensation, the improvement of mitochondrial function, and the reactivation of Akt, EGFR and Sirt1, as well as increased ROS scavenging capacity, in both diabetic mouse corneal epithelium and high glucose-treated corneal epithelial cells. The promotion of SP on diabetic corneal epithelial healing was completely abolished by a NK-1 receptor antagonist. Moreover, the subconjunctival injection of NK-1 receptor antagonist also caused diabetic corneal pathological changes in normal mice. In conclusion, the results suggest that SP-NK-1 receptor signaling plays a critical role in the maintenance of corneal epithelium homeostasis, and that SP signaling through the NK-1 recssssseptor contributes to the promotion of diabetic corneal epithelial wound healing by rescued activation of Akt, EGFR, and Sirt1, improvement of mitochondrial function, and increased ROS scavenging capacity.
[Show abstract][Hide abstract] ABSTRACT: It has been hypothesised that an upregulation of the neuropeptide substance P (SP) and its preferred receptor, the neurokinin-1 receptor (NK-1 R), is a causative factor in inducing tenocyte hypercellularity, a characteristic of tendinosis, through both proliferative and antiapoptotic stimuli. We have demonstrated earlier that SP stimulates proliferation of human tenocytes in culture.
The aim of this study was to investigate whether SP can mediate an antiapoptotic effect in tumour necrosis factor-α (TNF-α)-induced apoptosis of human tenocytes in vitro.
A majority (approximately 75%) of tenocytes in culture were immunopositive for TNF Receptor-1 and TNF Receptor-2. Exposure of the cells to TNF-α significantly decreased cell viability, as shown with crystal violet staining. TNF-α furthermore significantly increased the amount of caspase-10 and caspase-3 mRNA, as well as both BID and cleaved-poly ADP ribosome polymerase (c-PARP) protein. Incubation of SP together with TNF-α resulted in a decreased amount of BID and c-PARP, and in a reduced lactate dehydrogenase release, as compared to incubation with TNF-α alone. The SP effect was blocked with a NK-1 R inhibitor.
This study shows that SP, through stimulation of the NK-1 R, has the ability to reduce TNF-α-induced apoptosis of human tenocytes. Considering that SP has previously been shown to stimulate tenocyte proliferation, the study confirms SP as a potent regulator of cell-turnover in tendon tissue, capable of stimulating hypercellularity through different mechanisms. This gives further support for the theory that the upregulated amount of SP seen in tendinosis could contribute to hypercellularity.
British Journal of Sports Medicine 08/2013; 48(19). DOI:10.1136/bjsports-2013-092438 · 5.03 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Studies on human patellar and Achilles tendons have shown that tendon cells not only have the capacity to produce acetylcholine (ACh) but also express muscarinic ACh receptors (mAChRs), of subtype M2 (M2R), and that both the production and receptor expression seem to be increased in tendinosis. Hypercellularity and angiogenesis are key histopathologic features in tendinosis tissue. In this study, we aimed at testing the hypothesis that ACh increases the proliferation rate of tenocytes through mAChR stimulation, as well as investigating whether this mechanism is mediated by the extracellular activation (phosphorylation) of the epidermal growth factor receptor (EGFR), which has been shown to elicit DNA synthesis and cell proliferation in other fibroblastic cells types, through an intracellular pathway including activation/phosphorylation of the mitogen activated protein kinases ERK1/2.
Human Achilles tenocytes were seeded in cell culture plates and incubated in serum-starved conditions. The cells were pre-treated with the EGFR inhibitor AG1478, the matrix metalloproteinase (MMP) inhibitor GM6001 or the mAChR antagonist atropine. The cells were then stimulated with ACh (10(-6) M) or the vehicle. To determine the levels of phospho-ERK1/2 and phospho-EGFR, Western blot analysis was performed. 5-Bromo-2'-deoxy-uridine (BrdU) and crystal violet staining were used to assess cell proliferation and cell viability, respectively.
The primary human tendon cells in culture expressed enzymes related to ACh synthesis (choline acetyltransferase and vesicular acetylcholine transporter), along with vimentin and tenomodulin, which confirm the tenocyte phenotype. The cells also expressed the M2R. By administering exogenous ACh, the tenocytes were stimulated to significantly proliferate and increase in viability. In addition, Western blot showed that ACh stimulation resulted in increased phosphorylation of both EGFR and ERK1/2. When the cells were exposed to atropine, or the EGFR-blocking substance, the proliferative effect of ACh decreased. Simultaneously, the increase in ERK1/2 phosphorylation induced by incubation with ACh was effectively blocked in the presence of the mAChR antagonist atropine. Inhibition of either EGFR or MMP with specific blockers reduced the phosphorylation of ERK1/2.
Based on the results of the present study, as well as from previously established studies, we propose that human tenocytes, with their innate ability to produce ACh, increase ACh production during tendinosis development. Via an autocrine loop, the ACh produced by tenocytes stimulates mAChRs on the cell surface, thereby activating MMPs to cleave a cell surface-associated EGFR ligand. The ligand then binds to EGFR which in turn after activation increases ERK1/2 phosphorylation, leading to the increased cell proliferation and hypercellularity as seen in tendinosis (figure 1). In an early stage of tendinosis, hypercellularity might be a part of a healing or adaptive response, but in the chronic stage excessive tenocyte proliferation could be detrimental to tendon structure and function. The non-neuronal cholinergic system of tendon tissue is thus a possible target for future modulation of these processes in tendinosis. Figure 1.Schematic drawing of proposed cellular pathways involved in ACh-induced proliferation of human tendon cells. ACh stimulates membrane bound muscarinic ACh receptors (mAChRs) that in turn activate matrix metalloproteinases (MMPs) to cleave a cell surface-associated EGFR ligand. The ligand then binds to EGFR which in turn increases cell proliferation through phosphorylation of the mitogen-activated protein kinases ERK1/2.
British Journal of Sports Medicine 06/2013; 47(9):e2. DOI:10.1136/bjsports-2013-092459.7 · 5.03 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Substance P (SP) and its receptor, the neurokinin-1 receptor (NK-1 R), are expressed by human tenocytes, and they are both up-regulated in cases of tendinosis, a condition associated with excessive apoptosis. It is known that SP can phosphorylate/activate the protein kinase Akt, which has anti-apoptotic effects. This mechanism has not been studied for tenocytes. The aims of this study were to investigate if Anti-Fas treatment is a good apoptosis model for human tenocytes in vitro, if SP protects from Anti-Fas-induced apoptosis, and by which mechanisms SP mediates an anti-apoptotic response. Anti-Fas treatment resulted in a time- and dose-dependent release of lactate dehydrogenase (LDH), i.e. induction of cell death, and SP dose-dependently reduced the Anti-Fas-induced cell death through a NK-1 R specific pathway. The same trend was seen for the TUNEL assay, i.e. SP reduced Anti-Fas-induced apoptosis via NK-1 R. In addition, it was shown that SP reduces Anti-Fas-induced decrease in cell viability as shown with crystal violet assay. Protein analysis using Western blot confirmed that Anti-Fas induces cleavage/activation of caspase-3 and cleavage of PARP; both of which were inhibited by SP via NK-1 R. Finally, SP treatment resulted in phosphorylation/activation of Akt as shown with Western blot, and it was confirmed that the anti-apoptotic effect of SP was, at least partly, induced through the Akt-dependent pathway. In conclusion, we show that SP reduces Anti-Fas-induced apoptosis in human tenocytes and that this anti-apoptotic effect of SP is mediated through NK-1 R and Akt-specific pathways.
British Journal of Sports Medicine 06/2013; 47(9):e2. DOI:10.1136/bjsports-2013-092459.6 · 5.03 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Treatment of midportion Achilles tendinopathy has been known to be difficult. Recent ultrasound(US) and Doppler(CD) findings (high blood flow outside ventral tendon), together with results of immunohistochemical analyses (marked presence of blood vessels accompanied by nerve fascicles in the ventral peritendinous tissue) have led to new treatment approaches like sclerosing polidocanol injections, where US and CD-guided injections in the region with high blood flow and nerves outside the tendon have shown good results. However, for satisfying pain relief multiple injection treatments were often needed. Therefore, based on the same principles as for the sclerosing injections, a more radical and one stage mini-surgical procedure has been invented.
107 patients (66 men, 41 women), mean age 43 years (range 24-77), with tendinosis in 125 Achilles tendons were, in local anaesthesia, treated with a US+CD-guided new surgical approach outside the ventral tendon. Pain during tendon loading activity (VAS) and satisfaction with treatment, were evaluated.
Before surgery, the mean VAS was 77. After surgery (follow up mean 18 months, range 6-33) the mean VAS was 2 in 111 tendons (89%) from satisfied patients back in full Achilles tendon loading activity.
US+CD-guided scraping/tenolysis in the region with rich vascularity and innervation outside the ventral tendon shows good short term clinical results in midportion Achilles tendinopathy.
British Journal of Sports Medicine 06/2013; 47(9):e2. DOI:10.1136/bjsports-2013-092459.32 · 5.03 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The biochemical micromilieu of human tendons has gained increasing interest during the last decade. Partly prompted by microdialysis studies of both Achilles and patellar tendons, demonstrating an unexpectedly augmented level of the neurotransmitter glutamate in tendinopathy,1 2 Khan et al first suggested a new paradigm concerning tendinopathy pathogenesis,3 in part contradicting already established theories. They suggested that the underlying mechanism of tendinopathy might be biochemical rather than structural. Since then, much contemporary research has been directed towards trying to answer the question of the possible role of biochemical agents in the development of tendon pain and degenerative-like tissue changes, that is, tendinosis. At the cellular level, tendon cells in tendinosis tissue have indeed been shown to produce an array of signal substances that were once thought to be restricted to neurones. Although the functional importance of such biochemical agents in tendinopathy remains to be determined, evidence of a dramatic change in local cell signalling within chronically painful tendons exists. Studies have demonstrated that there is a local, non-neuronal production in the tenocytes of traditionally neuronal mediators, like neuropeptides. These findings include acetylcholine,4(-)6 catecholamines,7(-)9 glutamate,10 and the neuropeptide substance P (SP).11 Furthermore, the receptors for several of these signal substances have been found on nerve fascicles and in blood vessel walls (as well as on the tenocytes themselves) of the tendon tissue. These results suggest that locally produced neuromodulators may influence pain signalling, angiogenesis and vascular regulation, as well as cellular and tissue changes, like cell proliferation and/or apoptosis and matrix remodelling, in tendinopathy.12 Results of novel experimental studies on both in vivo13 and in vitro14 models of tendinopathy have revealed the neuropeptide SP as a key player in cellular regulation of tendinosis. Endogenous production of SP by tendon tissue/cells is significantly increased after mechanical load14 15 and SP furthermore contributes to development of tendinosis tissue characteristics; promoting hypercellularity and angiogenesis.14 16 Very recent unpublished data, presented at this conference, further underline the role of SP, but also acetylcholine, as important mediators in tendinosis. Not least interesting in this respect is the fact that SP inhibits tenocyte apoptosis and consequently prevents self-regulatory mechanisms that should limit the amount of collagen producing cells and prohibit excessive collagen accumulation in tendinosis. All these studies strengthen the biochemical hypothesis,3 suggesting that the underlying pathology of tendinopathy is primarily of biochemical origin rather than mechanical (albeit perhaps indirectly through mechanotransduction). We believe that such a biochemical paradigm of tendinopathy can complement, rather than replace, existing theories. We furthermore believe that this hypothesis fits a theoretical model, put forth by Cook and Purdam, in which tendon pathology is proposed to exist on a continuum that at various points involves several tendon tissue abnormalities.17 This key note lecture aims at giving a brief orientation of the evidence to date in favour of the 'biochemical model of tendinopathy'.
British Journal of Sports Medicine 06/2013; 47(9):e2. DOI:10.1136/bjsports-2013-092459.2 · 5.03 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In September 2010, the first International Scientific Tendinopathy Symposium (ISTS) was held in Umeå, Sweden, to establish a forum for original scientific and clinical insights in this growing field of clinical research and practice. The second ISTS was organised by the same group and held in Vancouver, Canada, in September 2012. This symposium was preceded by a round-table meeting in which the participants engaged in focused discussions, resulting in the following overview of tendinopathy clinical and research issues. This paper is a narrative review and summary developed during and after the second ISTS. The document is designed to highlight some key issues raised at ISTS 2012, and to integrate them into a shared conceptual framework. It should be considered an update and a signposting document rather than a comprehensive review. The document is developed for use by physiotherapists, physicians, athletic trainers, massage therapists and other health professionals as well as team coaches and strength/conditioning managers involved in care of sportspeople or workers with tendinopathy.
British Journal of Sports Medicine 04/2013; 47(9). DOI:10.1136/bjsports-2013-092329 · 5.03 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Trichostatin A (TSA) has been shown to prevent fibrosis in vitro and in vivo. The present study aimed at investigating the role of reactive oxygen species (ROS) scavenging by TSA on TGF-β-induced myofibroblast differentiation of corneal fibroblasts in vitro. Human immortalized corneal fibroblasts were treated with TGF-β in the presence of TSA, the NAD(P)H oxidase inhibitor diphenyleneiodonium (DPI), antioxidant N-acetyl-cysteine (NAC), the NF-E2-related factor 2-antioxidant response element (Nrf2-ARE) activator sulforaphane, or small interfering RNA. Myofibroblast differentiation was assessed by α-smooth muscle actin (α-SMA) expression, F-actin bundle formation and collagen gel contraction. ROS, H(2)O(2), intracellular glutathione (GSH) level, cellular total antioxidant capacity and the activation of Nrf2-ARE signaling were determined with various assays. Treatment with TSA and the Nrf2-ARE activator resulted in increased inhibition of the TGF-β-induced myofibroblast differentiation as compared with treatment with DPI or NAC. Furthermore, TSA also decreased cellular ROS and H(2)O(2) accumulation induced by TGF-β, whereas it elevated intracellular GSH level and cellular total antioxidant capacity. In addition, TSA induced Nrf2 nuclear translocation and up-regulated the expression of Nrf2-ARE downstream antioxidant genes, whereas Nrf2 knockdown by RNA interference blocked the inhibition of TSA on myofibroblast differentiation. In conclusion, this study provides the first evidence implicating that TSA inihibits TGF-β-induced ROS accumulation and myofibroblast differentiation via enhanced Nrf2-ARE signaling.
[Show abstract][Hide abstract] ABSTRACT: Studies of human patellar and Achilles tendons have shown that primary tendon fibroblasts (tenocytes) not only have the capacity to produce acetylcholine (ACh) but also express muscarinic ACh receptors (mAChRs) through which ACh can exert its effects. In patients with tendinopathy (chronic tendon pain) with tendinosis, the tendon tissue is characterised by hypercellularity and angiogenesis, both of which might be influenced by ACh. In this study, we have tested the hypothesis that ACh increases the proliferation rate of tenocytes through mAChR stimulation and have examined whether this mechanism operates via the extracellular activation of the epidermal growth factor receptor (EGFR), as shown in other fibroblastic cells. By use of primary human tendon cell cultures, we identified cells expressing vimentin, tenomodulin and scleraxis and found that these cells also contained enzymes related to ACh synthesis and release (choline acetyltransferase and vesicular acetylcholine transporter). The cells furthermore expressed mAChRs of several subtypes. Exogenously administered ACh stimulated proliferation and increased the viability of tenocytes in vitro. When the cells were exposed to atropine (an mAChR antagonist) or the EGFR inhibitor AG1478, the proliferative effect of ACh decreased. Western blot revealed increased phosphorylation, after ACh stimulation, for both EGFR and the extracellular-signal-regulated kinases 1 and 2. Given that tenocytes have been shown to produce ACh and express mAChRs, this study provides evidence of a possible autocrine loop that might contribute to the hypercellularity seen in tendinosis tendon tissue.
Cell and Tissue Research 12/2012; 351(3). DOI:10.1007/s00441-012-1530-5 · 3.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Brain derived neurotrophic factor (BDNF) is a multipotent neurotrophin known for its growth-influencing and apoptosis-modulating functions, as well as for its function to interact with neurotransmitters/neuromodulators. BDNF is reported to be mainly produced in the brain. BDNF can be absorbed into peripheral tissue from the blood stream. Expression of this neurotrophin at the protein level, as well as of the neurotrophin receptor p75, has been previously shown for the principal cells (tenocytes) of the Achilles tendon. However, there is no proof at the mRNA level that BDNF is produced by the tenocytes. As the Achilles tendon tenocytes show "neuronal-like" characteristics, in the form of expressions favouring synthesis of several neuromodulators/neurotransmitters, and as BDNF especially is produced in neurons, it is of interest to confirm this. In the present study, therefore, in situ hybridization for demonstration of BDNF mRNA was performed on biopsies from Achilles tendons of patients with tendinosis and pain-free non-tendinosis individuals. The results showed that the tenocytes of both groups exhibited BDNF mRNA reactions. These observations indeed favour the idea that BDNF is produced by tenocytes in the human Achilles tendon, why Achilles tendon tissue is a tissue in which BDNF can be locally produced. BDNF can have modulatory functions for the tenocytes, including apoptosis-modifying effects via actions on the p75 receptor and interactive effects with neurotransmitters/neuromodulators produced in these cells. This possibility should be further studied for Achilles tendon tissue.
Histology and histopathology 09/2012; 27(9):1239-46. · 2.10 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The histopathology of tendons with painful tendinopathy is often tendinosis, a fibrosis-like condition of unclear pathogenesis characterized by tissue changes including hypercellularity. The primary tendon cells (tenocytes) have been shown to express adrenoreceptors (mainly alpha-2A) as well as markers of catecholamine production, particularly in tendinosis. It is known that adrenergic stimulation can induce proliferation in other cells. The present study investigated the effects of an exogenously administered alpha-2 adrenergic agonist in an established in vivo Achilles tendinosis model (rabbit) and also in an in vitro human tendon cell culture model. The catecholamine producing enzyme tyrosine hydroxylase and the alpha-2A-adrenoreceptor (α(2A) AR) were expressed by tenocytes, and alpha-2 adrenergic stimulation had a proliferative effect on these cells, in both models. The proliferation was inhibited by administration of an α(2A) AR antagonist, and the in vitro model further showed that the proliferative alpha-2A effect was mediated via a mitogenic cell signaling pathway involving phosphorylation of extracellular-signal-regulated kinases 1 and 2. The results indicate that catecholamines produced by tenocytes in tendinosis might contribute to the proliferative nature of the pathology through stimulation of the α(2A) AR, pointing to a novel target for future therapies. The study furthermore shows that animal models are not necessarily required for all aspects of this research.
Scandinavian Journal of Medicine and Science in Sports 01/2012; 23(6). DOI:10.1111/j.1600-0838.2011.01442.x · 2.90 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Patellar tendinopathy (PT) is one of the most common reasons for sport-induced pain of the knee. Low ankle dorsiflexion range might predispose for PT because of load-bearing compensation in the patellar tendon.
The purpose of this 1-year prospective study was to analyze if a low ankle dorsiflexion range increases the risk of developing PT for basketball players.
Cohort study (prognosis); Level of evidence, 2.
Ninety junior elite basketball players were examined for different characteristics and potential risk factors for PT, including ankle dorsiflexion range in the dominant and nondominant leg. Data were collected over a 1-year period and follow-up, including reexamination, was made at the end of the year.
Seventy-five players met the inclusion criteria. At the follow-up, 12 players (16.0%) had developed unilateral PT. These players were found to have had a significantly lower mean ankle dorsiflexion range at baseline than the healthy players, with a mean difference of -4.7° (P = .038) for the dominant limb and -5.1° (P = .024) for the nondominant limb. Complementary statistical analysis showed that players with dorsiflexion range less than 36.5° had a risk of 18.5% to 29.4% of developing PT within a year, as compared with 1.8% to 2.1% for players with dorsiflexion range greater than 36.5°. Limbs with a history of 2 or more ankle sprains had a slightly less mean ankle dorsiflexion range compared to those with 0 or 1 sprain (mean difference, -1.5° to -2.5°), although this was only statistically significant for nondominant legs.
This study clearly shows that low ankle dorsiflexion range is a risk factor for developing PT in basketball players. In the studied material, an ankle dorsiflexion range of 36.5° was found to be the most appropriate cutoff point for prognostic screening. This might be useful information in identifying at-risk individuals in basketball teams and enabling preventive actions. A history of ankle sprains might contribute to reduced ankle dorsiflexion range.
The American Journal of Sports Medicine 09/2011; 39(12):2626-33. DOI:10.1177/0363546511420552 · 4.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Physical activity affects the pain symptoms for Achilles tendinosis patients. Brain-derived neurotrophic factor (BDNF), tumor necrosis factor-alpha (TNF-α) and their receptors have been detected in human Achilles tendon. This pilot study aimed to compare serum BDNF and soluble tumor necrosis factor receptor I (sTNFRI) levels in Achilles tendinosis patients and healthy controls and to examine the influence of physical activity, and BMI and gender, on these levels. Physical activity was measured with a validated questionnaire, total physical activity being the parameter analyzed. Physical activity was strongly correlated with BDNF among tendinosis women [Spearman's rho (ρ)=0.90, P<0.01] but not among control women (ρ=-0.08, P=0.83), or among tendinosis and control men. Physical activity was significantly correlated with sTNFRI in the entire tendinosis group and among tendinosis men (ρ=0.65, P=0.01), but not in the entire control group or among control men (ρ=0.04, P=0.91). Thus, the physical activity pattern is related to the TNF and BDNF systems for tendinosis patients but not controls, the relationship being gender dependent. This is new information concerning the relationship between physical activity and Achilles tendinosis, which may be related to pain for the patients. This aspect should be further evaluated using larger patient materials.
Scandinavian Journal of Medicine and Science in Sports 08/2011; 21(6):e430-8. DOI:10.1111/j.1600-0838.2011.01358.x · 2.90 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To quantify the intratendinous levels of substance P (SP) at different stages of overload in an established model for Achilles tendinopathy (rabbit). Also, to study the distribution of the SP-receptor, the NK-1R, and the source of SP, in the tendon.
Animals were subjected to the overuse protocol for 1, 3 or 6 weeks. One additional group served as unexercised controls. Immunoassay (EIA), immunohistochemistry (IHC), and in situ hybridisation (ISH) were performed.
EIA revealed increased SP-levels in the Achilles tendon of the exercised limb in all the experimental groups as compared to in the controls (statistically significant; p=0.01). A similar trend in the unexercised Achilles tendon was observed but was not statistically significant (p=0.14). IHC and in ISH illustrated reactions of both SP and NK-1R mainly in blood vessel walls, but the receptor was also found on tenocytes.
Achilles tendon SP-levels are elevated already after 1 week of loading. This shows that increased SP-production precedes tendinosis, as tendinosis-like changes occur only after a minimum of 3 weeks of exercise, as shown in a recent study using this model. We propose that central neuronal mechanism may be involved as similar trends were observed in the contralateral Achilles tendon.