Age-related Macular Degeneration (AMD) is the leading cause of blindness in persons over age 55 in the United States and Western Europe. In 80- 90% of cases, severe visual loss is caused by the growth of choroidal neovascular membranes (CNVs) under the RPE and retina. While laser therapy is the only proven treatment for CNVs a minority of patients are candidates for treatment, which is complicated by relatively poor visual outcome and a high rate of recurrent disease. Our desire to carry our RPE debridement, RPE transplantation, and growth factor treatment studies arises from the development of a new surgical technique (subretinal dissection and excision of CNVs) to treat the exudative complications of AMD. Excised CNVs are associated with overlying RPE and Bruch's membrane fragments. Thus, a large area of RPE is debrided as a consequence of CNV removal. We believe removal of RPE limits photoreceptor (and visual) recovery. We will model CNV-associated RPE removal by mechanically debriding RPE from Bruch's membrane. We will determine whether RPE transplantation and/or growth factor therapy reverses these changes. These experiments may establish a basis for RPE transplantation in humans following surgical removal of CNVs. The effect of varying the surface area of debridement on photoreceptor survival centrally will be described. The time course of retinal degeneration following debridement will be described. The ability of proliferating RPE to migrate from the edge into the center of the debrided area and to rescue overlying and/or adjacent photoreceptors will be assessed. For growth factor studies, the ability of basic fibroblast growth factor to prevent retinal degeneration induced by RPE debridement will be assessed. For RPE transplantation, a suspension of cultured cells is then transplanted over the tapetum. Transplanted RPE are identified by their pigmentation, and, in some cases, by fluorescent labels or by a marker gene (pSV GAL). We will evaluate different vehicles for RPE delivery, determine the number of RPE cells needed to repopulate a debrided surface, and evaluate homologous (and perhaps autologous) transplants. The viability of transplants, the ability of transplants to rescue overlying/neighboring photoreceptors, and the possibility of transplant proliferation, rejection or the development of proliferative vitreoretinopathy will be assessed with light and electron microscopy.
