RESUMO
PURPOSE: Transplantation of retinal stem cells (RSCs) is a potential therapy for retinal degeneration. However, success critically depends on whether RSCs can differentiate into fully functional daughter cells. METHODS: Whole-cell patch clamp techniques were used to characterize the postinduction developmental profile of membrane potentials and ionic currents in RSCs cultured from embryonic day 17 Long Evans rats. These results were compared to recordings obtained from cultured cells obtained from postnatal day 1 rat pups. RESULTS: Outward rectifying potassium currents (I(K+)) were observed in approximately 15% of cells at day 3 and in all cells by day 7. Voltage-dependent sodium currents took longer to emerge (day 7), and TTX-sensitive channels were not fully mature until day 15. Broad excitatory potentials, characteristic of immature action potentials, could be reliably stimulated by day 10, and spontaneous action potentials were recorded at day 25, which were indistinguishable, in terms of width and amplitude, from the comparison group of developing retinal neurons. CONCLUSIONS: The maturation of presumptive retinal ganglion cell electrophysiological properties appears to take at least 15 days under these culture conditions. Knowledge of the timing of voltage-dependent ion channel development could improve the success rate in future transplantation protocols.