Density-dependent differentiation in nontransformed XXXX retinal progenitor cells in response to basic fibroblast growth factor- and transforming growth factor-alpha.

@entity1 @entity1603 @entity310 @entity7790 @entity540 @entity2788 @entity35 @entity10185
Multipotential retinal precursors give rise to all cell types seen in @entity2788 . The generation of differentiation and diversity of neuronal cell types is determined by both extrinsic regulatory signals and endogenous genetic programs. We have previously reported that cell commitment in @entity1 retinal precursor cells (SV-40T) can be modified in response to exogenous growth factors, basic fibroblast growth factor, and @entity310 ( @entity540 and @entity7790 ). We report in this study that nontransformed @entity1 retinal precursors differentiate into photoreceptors by a cell density-dependent mechanism, and the effects were potentiated by @entity540 and @entity7790 alone or in combination. A larger proportion of multipotential precursors plated at a density of 1 x 10(4) cells/cm(2) differentiated into neurons (photoreceptors) compared to cells plated @entity35 x 10(4)/cm(2) and 1 x 10(5) cells/cm(2) under serum-free conditions and the effects were amplified seven- to eightfold in response to growth factors. Basic fibroblast growth factor ( @entity540 ) and @entity7790 can induce 90% of the cells to assume a photoreceptor phenotype at a lower cell density, compared to only 30 and 25% of the cells acquiring a photoreceptor phenotype at intermediate and higher cell densities. Furthermore, at a lower cell density, 60-70% of the cells incorporate @entity1603 (Brdu), suggesting that cells in a cell cycle may make a commitment to a specific fate in response to neurotrophins. Neurons with a photoreceptor phenotype were positive for three different sets of antibodies for rods/cones. Cells also exhibited upregulation of other proteins such as a D4 receptor protein expressed in photoreceptors, protein kinase Calpha ( @entity10185 ) expressed in rod bipolars and blue cones, and some other neuronal cell types. This was also confirmed by Western blot analysis. Newly derived photoreceptors survive for a few days before significant cell death ensues under serum-free conditions. To summarize, differentiation in precursors is density dependent, and growth factors amplify the effects.
