Abstract
Purpose::
To explore the possibility that cultured RPE cells may serve as stem cells to generate photoreceptors.
Methods::
RPE was isolated from day 6 chick embryos, and its cells were dissociated and cultured. Cultured RPE cells were programmed to transdifferentiate with neuroD, a proneural bHLH gene important for photoreceptor development. Ectopic expression of neuroD in cultured RPE cells was achieved through infection with replication-competent retrovirus RCAS expressing neuroD.
Results::
From the otherwise non-neural, RPE cell culture arose cells that were transdifferentiating along the photoreceptor pathway. Immunostaining demonstrated that transdifferentiating cells synthesized red opsin and localized the photopigment protein to the apex. Electron microphotographs illustrated that the majority of these cells formed inner segments rich in mitochondria. Some transdifferentiating cells developed rudimentary outer segments, including electron-dense discs, analogous to those of developing photoreceptors in the retina. Calcium imaging with Fluo-4 AM showed that transdifferentiating cells responded to light by reducing their cellular, free calcium levels. Conclusions: The development of these advanced structural and functional properties supports the possibility of generating functional photoreceptors from guided RPE transdifferentiation.
Conclusions::
The development of these advanced structural and functional properties supports the possibility of generating functional photoreceptors from guided RPE transdifferentiation.
Keywords: regeneration • differentiation • transcription