TRANSPLANTATION OF CULTURED HUMAN RETINAL-PIGMENT EPITHELIUM INTO RABBIT SUBRETINA

Transplantation of normal retinal pigment epithelium (RPE) into a dise ased eye holds promise for treatment of several blinding disorders. Pr eviuos studies have involved immunosuppression and implantation of fre shly isolated cells. We report here the successful transplantation of cultured human RPE cells into rabbits that were not immunosuppressed. A modified pars plana transvitreal technique was used for RPE transpla ntation. The cultured RPE cells, loaded with carbon as a marker, were transplanted into the denuded Bruch's membrane of albino rabbits. The animals were followed for from 1 week to 3 months. On histologic exami nation at 2 months, no infiltrating lymphocytes were found in the vitr eous cavity or choroid, even though Bruch's membrane was damaged. At a bout 3 months there were some macrophages in the subretina of transpla nted eyes, indicating that an immunoreaction does occur eventually. El ectron microscopy of the transplanted RPE showed apical-basal polarity and gap junctions. Restored function was attested to by the presence of phagosomes and phagocytosed outer segments in the transplanted cell s. Our findings suggest that there is a weak, delayed immunoreaction t o human RPE cells transplanted beneath the retina of the rabbit; howev er, functional recovery of the transplanted cells occurs before this i mmune response develops.