Generation of Storable Retinal Organoids and Retinal Pigmented Epithelium from Adherent Human iPS Cells in Xeno-Free and Feeder-Free Conditions.

Human induced pluripotent stem cells (hiPSCs) are potentially useful in regenerative therapies for retinal disease. For medical applications, therapeutic retinal cells, such as retinal pigmented epithelial (RPE) cells or photoreceptor precursors, must be generated under completely defined conditions. To this purpose, we have developed a two-step xeno-free/feeder-free (XF/FF) culture system to efficiently differentiate hiPSCs into retinal cells. This simple method, relies only on adherent hiPSCs cultured in chemically defined media, bypassing embryoid body formation. In less than 1 month, adherent hiPSCs are able to generate self-forming neuroretinal-like structures containing retinal progenitor cells (RPCs). Floating cultures of isolated structures enabled the differentiation of RPCs into all types of retinal cells in a sequential overlapping order, with the generation of transplantation-compatible CD73+ photoreceptor precursors in less than 100 days. Our XF/FF culture conditions allow the maintenance of both mature cones and rods in retinal organoids until 280 days with specific photoreceptor ultrastructures. Moreover, both hiPSC-derived retinal organoids and dissociated retinal cells can be easily cryopreserved while retaining their phenotypic characteristics and the preservation of CD73+ photoreceptor precursors. Concomitantly to neural retina, this process allows the generation of RPE cells that can be effortlessly amplified, passaged, and frozen while retaining a proper RPE phenotype. These results demonstrate that simple and efficient retinal differentiation of adherent hiPSCs can be accomplished in XF/FF conditions. This new method is amenable to the development of an in vitro GMP-compliant retinal cell manufacturing protocol allowing large-scale production and banking of hiPSC-derived retinal cells and tissues. Stem Cells 2017;35:1176-1188.