Abstract
Abstract: :
Purpose: Embryonic stem cells are rich and renewable source of neural progenitors. We have shown previously that ES cell-derived neural progenitors have the potential to acquire retinal phenotypes (Zhao and Ahmad, 2001 ARVO Abstract 1066). We have studied these cells, generated by two different methods, in co:culture conditions and upon overexpression of photoreceptor regulating genes in order to improve the efficiency of their differentiation into retinal cell types. Methods: Mouse D3 ES cells were cultured and induced to generate neural progenitors using either retinoic acid (Bain et al., 1995 Dev. Bio. 168:342-357) or by ITSFn/FGF2 (Okabe et al., 1996 Mech. Dev. 59:89-102). ES cell-derived neural progenitors were co:cultured with excess of embryonic retinal cells. In addition, they were transfected with recombinant vector expressing Crx and Nrl, before co:culture. Results: Both ITSFn/FGF2- and RA- based methods caused neural induction in ES cells. However, the former generated more neural progenitors than the later (86.3% Vs 63%). A small subset of BrdU+, ES cell-derived neural progenitors expressed photoreceptor-specific markers, rhodopsin and IRBP, when co-cultured with retinal cells. The proportion of cells with photoreceptor-specific markers was higher in the ITSFn/ FGF2 group and increased from 0.7% to 2% when the duration of culture was extended from 5 days to 10 days. In addition, subsets of BrdU+ cells were detected that expressed retinal markers such as PKC, mGluR6, RPF1 and Islet1. However, these markers are also expressed in other brain regions. The proportion of BrdU+ cells, expressing one of these markers was considerably high than those expressing rhodopsin, at the end of 5th day of co:culture [ 1.3% (Islet1), 4% (RPF1), 6.4% (mGluR6) and 21.7% (PKC)]. Experiments are currently underway to analyze the effect of overexpression of Nrl and Crx on retina-specific differentiation of ES cell-derived neural progenitors. Conclusion: ES cell-derived neural progenitors can be induced to acquire retinal phenotypes, as ascertained by the expressing of photoreceptor specific markers. The efficiency of retinal differentiation improved with ITSFn/ FGF2-induced neural progenitors and by extending the duration of co:culture. Identification of conditions that promote retina-specific differentiation of ES cells will lead to a renewable source of retinal progenitors that can be used for understanding retinal development and for cell therapy to treat retinal degeneration. Supported by UNMC Dean's grant and Foundation Fighting Blindness.
Keywords: 564 retinal development • 523 proliferation • 340 cell-cell communication