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 degrees C with 20 muM 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 . 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.