SELECTIVE NEOVASCULARIZATION OF THE RETINAL PIGMENT EPITHELIUM IN RAT PHOTORECEPTOR DEGENERATION IN VIVO

Photoreceptor cell degeneration in rodents from a variety of causes results in neovascularization of the retinal pigment epithelium as a late stage phenomenon. Even though the vessels within the pigment epithelium arise from the retinal circulation, they can manifest the choroidal endothelial cell phenotype of fenestrated endothelial cells. In order to study the detailed cellular events which result in incorporation of retinal vessels within the retinal pigment epithelium, a morphological and morphometric analysis of the RPE and vasculature was performed in rats. Urethane, given subcutaneously to newborn rats, results in a photoreceptor degeneration but does not affect the RPE, choroid or inner retinal layers. Retinas were studied from rats of 8 to 24 weeks of age, the time period when vascularization of the RPE occurs.Loss of retinal vessels is first seen at 12 weeks, primarily in substantial dropout of vessel profiles in the outer plexiform layer (OPL) vessel bed. There is a gradient of loss from the OP...