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I. Ahmad, A.V. Das, K.H. Cowan; Are Ciliary Epithelial Stem Cells Astrocytic in Nature? . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1017.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The adult mammalian ciliary epithelium (CE) harbors quiescent population of neural stem cells. The observation that proliferating CE stem cells express GFAP prompted us to investigate if these cells were astrocytic in nature like those in the sub ventricular zone (SVZ) of the adult brain. Methods: CE stem cells were isolated and cultures as previously described (Ahmad et al., 2000, Biochem. Biophys. Res. Commun. 270: 517-521). Double immunocytochemical analyses were carried out using antibodies against GFAP and neural progenitor markers such as nestin, Pax6 and Notch1. Proliferating cells were detected by their ability to incorporate BrdU. Stem cells were exposed to ganciclovir (GCV) following infection with adenovirus expressing HSV-TK gene under GFAP promoter and the effect on their survival and proliferation was assayed. Results: Co-localization of nestin and GFAP in CE stem cells revealed three sub-populations; GFAP-positive cells, nestin-positive cells and GFAP- and nestin-positive cells. While GFAP-positive cells displayed glial morphology, those co-expressing GFAP and nestin were bipolar or looked morphologically similar to immature neurons. The progenitor nature of a subset of GFAP-positive cells was further suggested by the fact that they incorporated BrdU and expressed Pax6/Notch1 in addition to nestin. Exposure of cells to GCV following adenovirus infection led to a decrease in the survival and proliferation suggesting that a subpopulation of stem cells can be sensitive to GCV due to their ability to activate GFAP promoter. Conclusions: Preliminary studies suggest that a sub-population of CE stems that co-expresses GFAP and neural progenitor markers may be similar to astrocytic stem cells found in the SVZ of the adult brain.
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