A novel rabbit model for studying RPE transplantation

PURPOSE. The goal of this project was to develop a model of retinal pigment epithelium (RPE) transplantation that permits extensive and reliable analysis of the transplants. METHODS. Cultures of newborn rabbit RPE were evaluated by morphology, electrophysiology, and the expression of zonula occludens-1, cytokeratin, and the melanocyte marker S-100. Cells labeled with 5,6-carboxyfluorescein diacetate succinimidyl ester (CFDA-SE) were transplanted into the subretinal space of rabbits with a 30-gauge needle without making a conjunctival flap or sclerotomy. The transplants were examined by fundus photography, confocal scanning laser ophthalmoscopy (cSLO), optical coherence tomography (OCT), and angiography. At 2 months, the retina was examined histochemically. RESULTS. A 1-minute incubation at 37 C with 20 mu M CFDA-SE did not affect morphology or the expression of marker proteins. In coculture, the labeled cells integrated into monolayers that developed a normal transepithelial electrical resistance of 400 to 450 Omega center dot cm(-2). Dye was not transferred from labeled to nonlabeled RPE cells. Transplanted RPE was detectable for at least 2 months. Angiography demonstrated an intact blood retinal barrier. The normal morphology of the retina and lack of debris in the subretinal space suggested that the transplanted RPE was functional. CONCLUSIONS. Primary cultures of newborn rabbit RPE were highly differentiated, even when labeled with CFDA-SE. Labeled cells were observed long-term in vitro and in vivo. This model can be used to examine how culture and transplantation protocols affect the reformation of a functional RPE monolayer. The similar size of rabbit and human eyes will facilitate the translation of these protocols to the bedside.