The retinal pigment epithelium (RPE) is derived from the multipotent optic neuroepithelium. It develops in close proximity to the retina, and is indispensible for eye organogenesis and vision. During embryogenesis, RPE cells participate in ciliary body and iris formation, control the closure of the optic fissure, influence retinal neurogenesis and ganglion cell projections, and are implicated in the regulation of the choroidal vasculature.
In the adult, they serve as life-long partners of photoreceptor cells by providing nutritional support, forming a blood/retinal barrier, replenishing 11-cis retinal after its photoisomerization to all-trans retinal, controlling ion flow and oxidative damage, and cleaning up the bits of membrane that accumulate at the apex of the photoreceptors’ outer segments.