The overall goal is to develop a technique to transplant freshly biopsied retinal pigment epithelium (RPE) onto abnormal Bruch's membrane such that the RPE will survive and rescue overlying photoreceptors. Age related macular degeneration (AMD) is the most common cause of blindness in the US among persons over age 55 years. Ninety percent of cases of severe visual loss in AMD are due to the growth of choroidal neovascular membranes (CNVs) under the RPE and retina with secondary retinal degeneration. Laser photocoagulation is the only proven effective treatment for CNV but is useful only in a minority of patients. Surgical techniques exist for complete CNV excision, however, postoperative visual improvement usually is minimal. We hypothesize that: (1) RPE removal at surgery is a major factor limiting visual recovery after CNV excision in AMD patients; (2) RPE transplantation will improve visual outcome following CNV excision in AMD patients; (3) the abnormal surface of the dissection bed plays a major role in limiting RPE attachment to Bruch's membrane and RPE transplant survival in AMD patients; and (4) the use of freshly isolated syngeneic RPE transplants will not be associated with transplant rejection.
Specific aims are: I: Reconstitute Bruch's membrane, from which native RPE have been abrasively debrided, in vitro such that freshly biopsied RPE sheets will adhere to the surface and survive. The ability of (1) serum and (2) heparin + bFGF+laminin to improve RPE adhesion and growth on Bruch s membrane in vitro will be assessed. II: Develop manufacturing techniques that permit delivery of sheets of freshly biopsied RPE into the subretinal space. We will determine: (1) the maximal in vitro storage time of gelatin-embedded RPE sheets, and (2) the effect of Bruch s membrane attachment-promoting substances with this preparation in vitro and in vivo. III: Improve techniques to identify syngeneic RPE transplants in vivo. We will assess: (1) dye retention and dilution using CM-DiI-and Fluorogold-labeled RPE in vitro, and (2) the specificity of dye label in vivo. IV: Assess long-term viability of syngeneic RPE sheet transplants onto damaged Bruch's membrane using a published in vivo RPE debridement model.
