Abstract
Abstract: :
Purpose:To demonstrate the potential utility of neuronal stem cell transplantation using a highly-inductive host retinal environment. Methods:For these studies we used a well-characterized source of neural progenitor cells derived from the adult rat hippocampus and labeled with green fluorescent protein (GFP; a generous gift from Dr. F. Gage). Neonatal rat retinas were isolated and explanted onto tissue culture well inserts with the mitotically-active germinal epithelium facing upward, and a suspension of cells (10µl of 1.5 X 105 cells/ml) was added to the surface of the explant. Explants were maintained in culture media for up to 14 days, a time that approximates maturation of retinal circuitry, in vivo. Explants were then harvested, fixed in 4% paraformaldehyde and cryosectioned for analysis. Some sections were stained for retinal cell type-specific markers, including rhodopsin, recoverin, PKC, calbindin, calretinin or parvalbumin, using the appropriate Cy3-conjugated secondary antibody. Results:After 7 days in culture (DIC), retinal explants displayed evidence of differentiation into discrete cellular and plexiform layers. Furthermore, widespread incorporation of GFP-labeled cells was observed. Most labeled cells were localized to the outer retina, but many cells had migrated to the inner retina where they contributed to a distinct layer, one to two cells in thickness, at the innermost boundary (presumptive ganglion cell layer); another more diffuse distribution was observed in the presumptive inner nuclear layer. Many GFP-labeled cells extended processes into the presumptive inner plexiform layer and displayed bipolar- and amacrine-like morphologies. After 10 and 14 DIC, further development of retinal lamination was evident. Likewise, further morphological differentiation of GFP-labeled cells was observed. At no time point examined, however, were cells observed that displayed evidence of end-stage phenotypic differentiation, as assessed by double label immunofluorescence microscopy. Conclusion:In a highly-inductive host environment, exogenously-applied neural progenitor cells can undergo extensive incorporation into the host tissue, migrate to specific cellular layers and undergo limited phenotypic differentiation. The results of these studies highlight the important role of local environmental cues in development and suggest that transplantation of adult neural stem cells are a potential therapeutic tool for retinal neuronal degenerative disease.
Keywords: 564 retinal development • 607 transplantation • 560 retinal culture