Abstract
Abstract: :
Purpose: To examine the fate of undifferentiated neural retina precursor cells (NRPCs) transplanted to the subretinal space of young adult RCS rats. Are NRPCs pre-programmed to a retinal cell pathway or affected differentially by the local host microenvironment if transplanted? Methods: NRPCs were isolated from E17 Long Evans or transgenic rats expressing human placental alkaline phosphatase (hPAP), cultured in media containing DMEM, F-12, N2, heparin, NT3, and FGF2 with or without 1% FBS and passaged to obtain proliferating populations of NRPCs in polyornithine and laminin-coated dishes. Long Evans-derived NRPCs were prelabeled with BrdU for 5 days before transplantation. Undifferentiated NRPCs were then engrafted into the subretinal space of young adult (5-8 wks) RCS rats, with or without fetal (E19) retinal sheets originated from Long Evans rats. Results: The passaged (P1 and P2) NRPCs derived from Long Evans rats were mostly nestin and BrdU-positive in vitro, indicating these cells are undifferentiated neural precursors. Previously it was shown that under differentiation conditions in vitro, the cells differentiated into 87% neurons (62% rhodopsin-positive) and 10% glia. In vivo, after transplantation, many cells survived and migrated into the host retinas and the fetal retinal sheets of donor origin (when the NRPCs and sheets were co-transplanted). Many NRPCs were integrated into various layers of the host retinas and expressed the neuronal marker neuron-specific enolase (NSE) or the astrocytic marker GFAP. No cells were found immunopositive for photoreceptor markers rhodopsin and S-antigen. Many cells were positive for protein kinase C alpha, a marker for retinal bipolar and amacrine cells. Only scattered cells were positive for calbindin and calretinin, markers for horizontal cells and amacrine cells. However, the majority of implanted NRPCs remain undifferentiated in the host retinas, the fetal sheets, and the choroid tissue surrounding the subretinal space. Conclusion: The much reduced differentiation observed in the NRPCs engrafted in the host retinas of young adult RCS rats suggests that the microenvironment of young adult RCS rats might rather have inhibitory than promoting effects over the donor NRPCs, in contrast to the predominant neuronal retinal cell differentiation observed in NRPCs in vitro. Support: An Anonymous Sponsor, Research to Prevent Blindness (MJS, RBA), and NS38665 (SRW).
Keywords: 607 transplantation • 560 retinal culture • 564 retinal development