Photoreceptor precursors derived from three-dimensional embryonic stem cell cultures integrate and mature within adult degenerate retina

Irreversible blindness caused by loss of photoreceptors may be amenable to cell therapy. We previously demonstrated retinal repair(1) and restoration of vision through transplantation of photoreceptor precursors obtained from post-natal retinas into visually impaired adult mice(2,3). Considerable progress has been made in differentiating embryonic stem cells (ESCs) in vitro toward photoreceptor lineages(4-6). However, the capability of ESC-derived photoreceptors to integrate after transplantation has not been demonstrated unequivocally. Here, to isolate photoreceptor precursors fit for transplantation, we adapted a recently reported three-dimensional (3D) differentiation protocol that generates neuroretina from mouse ESCs(6). We show that Rhop.GFP-selected rod precursors derived by this protocol integrate within degenerate retinae of adult mice and mature into outer segment–bearing photoreceptors. Notably, ESC-derived precursors at a developmental stage similar to postnatal days 4-8 integrate more efficiently than cells at other stages. This study shows conclusively that ESCs can provide a source of photoreceptors for retinal cell transplantation.