[Show abstract][Hide abstract] ABSTRACT: There is a great interest in using epithelium generated in vitro for tissue bioengineering. Mouse 3T3 fibroblasts have been used as a feeder layer to cultivate human epithelia including corneal epithelial cells for more than 3 decades. To avoid the use of xeno-components, we evaluated human fibroblasts as an alternative feeder supporting human corneal epithelial regeneration. Five human fibroblast cell lines were used for evaluation with mouse 3T3 fibroblasts as a control. Human epithelial cells isolated from fresh corneal limbal tissue were seeded on these feeders. Colony forming efficiency (CFE) and cell growth capacity were evaluated on days 5-14. The phenotype of the regenerated epithelia was evaluated by morphology and immunostaining with epithelial markers. cDNA microarray was used to analyze the gene expression profile of the supportive human fibroblasts. Among 5 strains of human fibroblasts evaluated, two newborn foreskin fibroblast cell lines, Hs68 and CCD1112Sk, were identified to strongly support human corneal epithelial growth. Tested for 10 passages, these fibroblasts continually showed a comparative efficiency to the 3T3 feeder layer for CFE and growth capacity of human corneal epithelial cells. Limbal epithelial cells seeded at 1 × 10(4) in a 35-mm dish (9.6 cm(2)) grew to confluence (about 1.87-2.41 × 10(6) cells) in 12-14 days, representing 187-241 fold expansion with over 7-8 doublings on these human feeders. The regenerated epithelia expressed K3, K12, connexin 43, p63, EGFR and integrin β1, resembling the phenotype of human corneal epithelium. DNA microarray revealed 3 up-regulated and 10 down-regulated genes, which may be involved in the functions of human fibroblast feeders. These findings demonstrate that commercial human fibroblast cell lines support human corneal epithelial regeneration, and have potential use in tissue bioengineering for corneal reconstruction.
PLoS ONE 01/2012; 7(6):e38825. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: It is clear that the microenvironment or niche plays an important role in determining the fate of stem cells: being stem cells or differentiated. However, the intrinsic pathways controlling the fate of adult stem cells in different niches are largely unknown. This study was to explore the role of β-catenin/Tcf4/survivin signaling in determining the fate of human corneal epithelial stem cells in different media. We observed that the low calcium serum-free media, especially CnT-20, promoted proliferative capacity, colony forming efficiency and stem cell-like phenotype of human corneal epithelial cells (HCECs) when compared with the cells cultured in a high calcium serum-containing medium SHEM. Three key factors in Wnt signaling, β-catenin, Tcf4 and survivin, were found to be expressed higher by HCECs grown in CnT-20 than those cultured in SHEM, as evaluated by real-time PCR, Western blotting and immunostaining. Transfection of siRNA-Tcf4 at 10-50nM knocked down Tcf4, and also significantly suppressed its down stream molecule survivin at both mRNA and protein levels in HCECs. Furthermore, Tcf4 silencing significantly suppressed the proliferative capacity of HCECs, measured by WST-1 assay, compared with the control groups, untreated or transfected with non-coding sequence siRNA-fluorescein. These findings demonstrate that low calcium serum free media promote ex vivo expansion of corneal epithelial progenitor cells that retain a less differentiated phenotype and high proliferative capacity via β-catenin/Tcf4/survivin signaling, a novel intrinsic pathway. This study may have high impact and clinic implication on the expansion of corneal epithelial stem cells in regenerative medicine, especially for ocular surface reconstruction.
The international journal of biochemistry & cell biology 02/2011; 43(5):751-9. · 4.89 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Adult stem cells are well known for their self-renewal and regenerative capacity. The mechanisms protecting these cells from inflammatory damage have not been well elucidated. This study investigated the immunoprotective properties of corneal epithelial stem cells from inflammation by producing glial cell-derived neurotrophic factor (GDNF). Primary human limbal epithelial cells (HLECs) cultured from limbal explants were treated with interleukin (IL)-17A, tumor necrosis factor (TNF)-α, or hyperosmotic media, with or without GDNF or nuclear factor kappa B (NF-κB) inhibitor (NF-κB-I) for 4-48 hours. Inflammatory mediators and Th17-inducing cytokines were determined by real-time polymerase chain reaction, enzyme-linked immunosorbent assay, and immunobead assays. NF-κB activation was detected by p65 phosphorylation, immunostaining and Western blotting. GDNF and its receptor, GDNF family receptor α-1, were exclusively immunolocalized in the basal layer of limbal epithelium, whereas IL-17 receptor was negative in these cells. Exogenous IL-17A stimulated the expression and production of inflammatory cytokines (TNF-α, IL-6, and IL-1β) and chemokine IL-8 by HLECs. Th17-inducing cytokines, transforming growth factor (TGF)-β1, IL-6, IL-23, and IL-1β, were significantly increased at mRNA and protein levels by HLECs exposed to TNF-α or hyperosmotic media. IL-17 activated NF-κB by p65 phosphorylation at serine 536 and nuclear translocation. GDNF or NF-κB-I blocked IL-17-induced NF-κB p65 activation and production of inflammatory mediators. Furthermore, GDNF suppressed the production of Th17-inducing cytokines through inhibiting NF-κB activation. These findings demonstrate that limbal progenitor cell-produced neurotrophic factor GDNF suppresses IL-17-mediated inflammation via NF-κB signaling pathway. This may represent a unique immunoprotective property of limbal stem cells against inflammatory challenges on the ocular surface.
[Show abstract][Hide abstract] ABSTRACT: Identification and isolation of adult stem cells are still challenging for stem cell biologists. For example, no consensus exists yet regarding definitive markers for corneal epithelial stem cells, which have been identified to reside in the limbus for two decades. This study characterized the molecular signatures and biological pathways of limbal epithelial progenitors, the rapid adherent cells (RAC) isolated by adhesion on collagen IV, using human genome microarrays, real-time PCR and immunofluorescent staining. The microarrays produced highly reproducible data not only for all gene transcripts, but also for significantly changed genes, although the total 12 samples of 3 cell populations in 2 arrays were isolated from 4 separate experiments at different time period. The hierarchical clustering heatmap visually revealed that RAC progenitor population displayed distinguishably characteristic gene expression profile. With verification of 27 important genes by quantitative real-time PCR, the microarray data not only confirm the expression patterns of 15 known genes as stem cell associated markers representing limbal stem cell phenotype, but also identified many significantly regulated genes expressed by limbal progenitor cells. Transcription factor TCF4 and cell surface protein SPRRs were identified as potentially positive or negative markers, respectively, for corneal epithelial progenitor cells. Using GenMAPP and MAPPFinder, we have identified three patterns of biological pathway profiles, overexpressed, underexpressed and balanced, by RAC progenitors based on gene ontology categories. These genes and related pathways are interesting targets for further identification and isolation of limbal stem cells as well as other tissue-specific adult stem cells.
The international journal of biochemistry & cell biology 04/2010; 42(7):1142-53. · 4.89 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This study was to explore a potential role of epithelium-derived cytokines in Th17 differentiation. Th17 induction was evaluated by murine CD4(+) T cells treated with different combinations of five inducing cytokines, or conditioned media of human corneal epithelial cells (HCECs) exposed to a variety of stimuli. Th17 differentiation was determined by measuring Th17 associated molecules, IL-17A, IL-17F, IL-22, CCL-20, and STAT3 at mRNA and protein levels, and numbers of IL-17-producing T cells by real-time PCR, and cytokine immunobead and ELISPOT assays, respectively. IL-23 was the strongest inducer for expanding Th17 cells in the presence of TGF-beta1 + IL-6; and IL-1beta was the strongest Th17 amplifier in the presence of TGF-beta1 + IL-6 + IL-23. These inducing cytokines were found to be significantly stimulated in HCECs challenged by hyperosmotic media (450 mOsM), microbial components (polyI:C, flagellin, R837, and other TLR ligands) and TNF-alpha. Interestingly, when incubated with conditioned media of HCECs irritated by polyI:C or TNF-alpha, CD4(+) T cells displayed increased mRNA levels of IL-17A, IL-17F, IL-22, CCL-20, and STAT3, increased IL-17 protein in the supernatant, and increased numbers of IL-17-producing T cells (Th17 cells). These findings demonstrate for the first time that Th17 differentiation can be promoted by cytokines produced by corneal epithelium that are exposed to hyperosmotic, microbial, and inflammatory stimuli.
Journal of Cellular Physiology 09/2009; 222(1):95-102. · 4.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To evaluate production and activity of metalloproteinase (MMP)-9 on the ocular surface of patients with dysfunctional tear syndrome (DTS) and determine any correlation between MMP-9 activity and clinical parameters.
Forty-six patients with newly diagnosed DTS and 18 control subjects were recruited. Complete ocular surface examinations were performed. Tear MMP-9 activity was assessed with an MMP-9 activity assay in 1 microL of unstimulated tear fluid. Using conjunctival epithelial cells from 19 patients with DTS and 16 controls, levels of MMP-9 and its regulating cytokine mRNA transcripts were evaluated by semiquantitative real-time PCR.
Each of four DTS severity-based groups had significantly higher mean MMP-9 activities than did the control group, which was 8.39 +/- 4.70 ng/mL. The DTS4 group had the highest MMP-9 activity (381.24 +/- 142.83 ng/mL), for which the mean was significantly higher than that of other DTS groups. In addition, patients with DTS had significantly higher levels of IL-1beta, IL-6, TNF-alpha, and TGF-beta1 mRNA transcripts in their conjunctival epithelia than did the control subjects. Tear MMP-9 activities showed significant correlation with symptom severity scores, decreased low-contrast visual acuity, fluorescein tear break-up time, corneal and conjunctival fluorescein staining, topographic surface regularity index (SRI), and percentage area of abnormal superficial corneal epithelia by confocal microscopy.
Tear MMP-9 activity was significantly higher in patients with DTS. This activity was associated with increased mRNA expression of MMP-9 and its regulating genes and correlated strongly with clinical parameters. MMP-9 appears to be a potentially useful biomarker for diagnosing, classifying, and monitoring DTS.
[Show abstract][Hide abstract] ABSTRACT: To explore the crucial role of the human corneal epithelium-derived proallergic cytokine thymic stromal lymphopoietin (TSLP) in initiation and regulation of immune responses.
Primary corneal epithelial cells, established from donor limbal explants, were treated with 11 microbial ligands and proinflammatory and Th2 cytokines, alone or in combination. TSLP mRNA and protein were determined by real-time PCR and ELISA, respectively. NF-kappaB activation was detected by immunostaining and Western blot.
TSLP was found to be expressed by human corneal epithelium and its cultures. TSLP in corneal epithelial cells were largely induced in a concentration-dependent fashion by polyI:C, flagellin, and FSL-1, the ligands for toll-like receptor (TLR)-3, -5, and -6, respectively. Compared with the control, TSLP mRNA was increased by 60-, 12- and 8-fold and TSLP protein increased by 67-, 19- and 7-fold by these three ligands, respectively. The proinflammatory (TNF-alpha and IL-1beta) and Th2 (IL-4 and IL-13) cytokines moderately induced TSLP expression and production. IL-4 and -13 strongly synergized with PolyI:C, flagellin, and TNF-alpha to promote TSLP production in ex vivo tissues and in vitro cultures of corneal epithelium. PolyI:C, flagellin, or TNF-alpha also induced NF-kappaB p65 protein nuclear translocation. The NF-kappaB inhibitor quinazoline blocked p65 nuclear translocation and further suppressed TSLP expression and production induced by these stimuli.
These findings provide the first evidence of TSLP induction in the human eye and suggest the novel phenomenon that human corneal epithelium-derived TSLP may serve as a link between the innate and adaptive immune responses. TSLP may become a novel therapeutic target for allergic and inflammatory ocular surface diseases.
[Show abstract][Hide abstract] ABSTRACT: To evaluate the expression pattern of glial cell line-derived neurotrophic factor (GDNF) with its receptors GDNF family receptor alpha-1 (GFR alpha-1) and Ret in the human corneal and limbal tissues, as well as in the primary human limbal epithelial cultures (PHLEC).
Expression of GDNF and its receptors, and the co-localisation with stem cell associated and differentiation markers were evaluated by immunofluorescent staining, western blot analysis and real-time PCR in the fresh human corneoscleral tissues, as well as in the PHLEC. Single cell colony-forming and wound-healing assays were also evaluated in PHLEC.
GDNF and GFR alpha-1 were found to be expressed by a subset of basal cells and co-localised with ATP-binding cassette, subfamily G (WHITE), member 2 (ABCG2) and p63, but not with cytokeratin 3 in the human limbal basal epithelium. In PHLEC, they were expressed by a small population of cells in the less differentiated stage. The GDNF and GFR alpha-1-positive subpopulations were enriched for the expression of ABCG2 and p63 (p<0.01). Recombinant human GDNF promoted the proliferation and wound healing of epithelial cells in the PHLEC. In contrast, Ret was abundantly located in the human corneal epithelium except for the basal cells of the limbal epithelium.
These findings indicate that GDNF and GFR alpha-1 may represent a property for the phenotype of human corneal epithelial precursor cells. GDNF may signal independently of Ret through GFR alpha-1 in the stem cell-containing limbal epithelium.
The British journal of ophthalmology 10/2008; 92(9):1269-74. · 2.92 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To examine the effect of 4 commercially available contact lens multipurpose solutions (MPS) on the viability and barrier function of human corneal epithelial cells in vitro.
Immortalized human corneal epithelial cells were exposed to 4 solutions, MPS A, B, C, and D with culture medium and Hanks' Balanced Salt Solution as controls. MTT assay was used to evaluate cell viability. ApopTag Fluorescein Apoptosis assay was used to detect cell death in situ. Corneal epithelial barrier function was evaluated by fluorescein permeability and immunofluorescent staining for tight junction proteins zonula occludens (ZO)-1 and occludin.
Corneal epithelial survival rates, evaluated by MTT assay showed no statistical difference between MPS A and the culture medium or Hanks' Balanced Salt Solution controls. MPS B, C, and D were associated with significantly less cell survival than the controls after exposure for 6 hrs (all P<0.01). Compared with the controls, the MPS A did not increase cell apoptosis, whereas the other 3 caused higher apoptotic rates. The epithelial permeability after exposure to MPS A was similar to controls and significantly lower than MPS B and MPS D (P<0.01). The tight junction proteins ZO-1 and occludin were well maintained after exposure to MPS A. In contrast, the expression of ZO-1 and occludin were largely disturbed by the other 3 MPS solutions.
The current marketed contact lens MPS may have negative effects on human corneal epithelial viability and barrier function. Among 4 MPS studied, MPS A maintains the cell viability and barrier function significantly better than other 3 marketed products.