A tissue-engineered approach towards retinal repair: Scaffolds for cell transplantation to the subretinal space

Several mechanisms of retina degeneration result in the deterioration of the outer retina and can lead to blindness. Currently, with the exception of anti-angiogenic treatments for wet age-related macular degeneration, there are no treatments that can restore lost vision. There is evidence that photoreceptors and embryonic retinal tissue, transplanted to the subretinal space, can form new synapses with surviving host neurons. However, these transplants have yet to result in a clinical treatment for retinal degeneration. This article reviews the current literature on the transplantation of scaffolds with retinal and retinal pigmented epithelial (RPE) cells to the subretinal space. We discuss the types of cells and materials that have been investigated for transplantation to the subretinal space, summarize the current findings, and present opportunities for future research and the next generation of scaffolds for retinal repair. Challenges to cell transplantation include limited survival upon implantation and the formation of abnormal cell architectures in vivo. Scaffolds have been shown to enhance cell survival and direct cell differentiation and organization in a number of models of retinal degeneration. The transplantation of cells within a scaffold represents a possible treatment to repair retinal degeneration and restore vision in effected patients. Materials have been developed for the delivery of retinal and RPE cells separately however, the development of a combined tissue-engineered scaffold targeting both cell populations represents a promising direction for retinal repair.