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DR Whikehart, AC Vaughn, GP Holley, HF Edelhauser; Telomerase Activity in the Human Corneal Endothelial Limbus . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1627.
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Purpose: It is well-known that human corneal endothelial cells are reluctant to divide both in vivo and in culture. We considered the possibility that the endothelial limbus may contain progenitor cells for the endothelial layer. In this study we investigated the probability that these cells could have telomerase activity which would serve as an identifying stem cell marker. Methods: Young (less than 20 yr) and old (more than 40 yr) donors, obtained from the Georgia Eye Bank, were used for this study. Dissected endothelial tissues with and without the endothelial limbal area were included. All epithelial tissues were carefully excluded. After tissue extraction, telomerase activity was assayed by PCR amplification, gel electrophoresis and staining with SYBR green to detect the TRAP products of the enzyme. Results: When assays were performed with tissues containing the endothelial limbal area, telomerase activity was found in both the young and old groups. However, the young group demonstrated the presence of higher telomerase activity than the old group. When corneal endothelial tissues without the limbus were assayed (trephined central area), no telomerase activity was detected. Conclusion: Currently, in all human tissues that have been studied, only stem cells and carcinoma cells have been shown to have significant telomerase activity. This activity is necessary to maintain the continuous, high reproductive rate of these cells. The results of this study suggest that the corneal endothelial limbal area contains progenitor (stem) cells for the endothelium. It is possible that while endothelial cells within the central cornea may lose their ability to divide, they may also be renewed by endothelial, limbal progenitor cell division.
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