Cell-based therapy for degenerative retinal disease

Stem cell-derived retinal pigment epithelium (RPE) and photoreceptors (PRs) have restored vision in preclinical models of human retinal degenerative disease. This review discusses characteristics of stem cell therapy in the eye and the challenges to clinical implementation that are being confronted today. Based on encouraging results from Phase I/II trials, the first Phase II clinical trials of stem cell-derived RPE transplantation are underway. PR transplant experiments have demonstrated restoration of visual function in preclinical models of retinitis pigmentosa and macular degeneration, but also indicate that no single approach is likely to succeed in overcoming PR loss in all cases. A greater understanding of the mechanisms controlling synapse formation as well as the immunoreactivity of transplanted retinal cells is urgently needed. PRs and RPE cells can be grown from embryonic and induced pluripotent stem cells.Transplanted stem cell-derived PRs and RPE cells have been shown to integrate with host retinae and restore visual function in preclinical models of human retinal degenerative disease.PR transplants can integrate with host retinae even in late stages of retinal degeneration.Physical barriers, such as the external limiting membrane, and biochemical properties of the extracellular matrix, such as disease-related changes in Bruch's membrane and the interphotoreceptor matrix, may limit transplanted cell integration with host tissue.Phase I/II human clinical trials of stem cell-derived RPE for age-related macular degeneration and Stargardt disease have been completed successfully, and 18 clinical trials of cell-based therapy for retinal degenerative disease are currently underway.