A biodegradable scaffold enhances differentiation of embryonic stem cells into a thick sheet of retinal cells.

Retinal degeneration is a leading cause of blindness in developed countries. Stem cells can be differentiated into retinal organoids to study mechanisms of retinal degeneration, develop therapeutic agents, and potentially serve as replacement tissues. The spherical nature of these retinoids limits their utility, because the investigator lacks ready access to both sides of the neo-tissue. For tissue-replacement, spherical retinoids are unable to interact simultaneously with the host retinal pigment epithelium and remaining neurosensory retina. To attempt making a planar retinoid, we developed a biodegradable scaffold that simulates the extracellular matrix of the neurosensory retina. Human embryonic stem cells were seeded on the scaffold. Differentiation into retinal cells was confirmed by quantitative RT-PCR, confocal immunocytochemistry, and immunoblotting. The scaffold favored differentiation into retinal cell types over other anterior forebrain cells, but retinal lamination was rudimentary. The cultures elicited a minimal immune response when implanted into the subretinal space of a mouse model of retinal degeneration. The implants survived for at least 12 weeks, but there was evidence of cytoplasmic transfer rather than implantation into the outer nuclear layer (photoreceptor layer). However, some implanted cells migrated to the inner layers of the retina and established elaborate arbors of neurites.