Aim: To evaluate the expression pattern of glial cell line-derived neurotrophic factor (GDNF) with its receptors GDNF family receptor alpha-1 (GFRα-1) and Ret in the human corneal and limbal tissues, as well as in the primary human limbal epithelial cultures (PHLEC).
Methods: 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.
Results: GDNF and GFRα-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 GFRα-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.
Conclusion: These findings indicate that GDNF and GFRα-1 may represent a property for the phenotype of human corneal epithelial precursor cells. GDNF may signal independently of Ret through GFRα-1 in the stem cell-containing limbal epithelium.
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This study was presented in part as abstract at the Annual Meeting of the Association for Research in Vision and Ophthalmology, 6–10 May 2007, Fort Lauderdale, Florida.
Funding: This study was supported by NIH Grants, EY11915 (SCP) and EY014553 (DQL), National Institutes of Health, Bethesda, MD; Department of Defense Congressionally Directed Medical Research Programs (CDMRP) grant FY06 PR064719 (DQL); a grant from Lions Eye Bank Foundation (HQ); an unrestricted grant from Research to Prevent Blindness, the Oshman Foundation and the William Stamps Farish Fund.
Competing interests: None.