Abstract
Abstract: :
Purpose: Adult retinal stem cell harbors a cardinal feature of neural stem cell. However, different from neural stem cell progenies derived from other regions, the retinal stem cells can differentiate into retinal-specific cell types, suggesting that the stem cell state is maintained by the molecules needed for its maintenance and that intrinsic factors confer their regional specificity. In this study, the expressions of Notch pathway molecules and homeobox genes in adult retinal stem cells were investigated. Methods: Adult retinal stem cells were isolated in a neurosphere forming culture from the ciliary body of C57/Bl6 mice. The expressions of the Notch signaling molecules, Dalta1, Jagged, Notch1, numb, Hes1 and Hes5 and homeobox genes, Emx2, Dlx2, Otx1, Rx, Six3, Pax6 and Chx10, as well as region specific transcription factors, RORb and Foxn4, were examined using semi-quantative RT-PCR. Concomitantly, to investigate the proliferative capability and the percentage of the undifferentiated cells in the sphere colonies, the diameter of the sphere colonies was measured, and the percentage of nestin-positive cells was quantified by immunocytochemical analysis after short and long period culture. Results: Retinal stem cells expressed Emx2, Dlx2, Otx1, Rx, Six3, Pax6 and Chx10 even after passaging. The expressions of RORb and Foxn4 were not detected. Among the Notch pathway molecules, the expression levels of numb and HES1 did not change after two months of passaging, whereas the expression levels of Delta1, Jagged, Notch1 and Hes5 decreased after the passaging. The diameter of the sphere colonies and the percentage of nestin-positive cells also decreased after passaging. Conclusions: Adult retinal stem cells express region-specific homeobox genes even after passaging. However, the expression levels of Notch pathway molecules decrease after long passaging, which might lead to the attenuation of the expansionary growth in the neurosphere forming culture.
Keywords: retina • retinal development • transcription factors