RETINAL-PIGMENT EPITHELIAL TRANSPLANTS AND RETINAL FUNCTION IN RCS RATS

Purpose. To determine if retinal pigment epithelium (RPE) transplantat ion maintains visual function in Royal College of Surgeons (RCS) strai n of rats. Methods. Twelve RCS rats received RPE transplants at 16 to 20 days after birth. The retinas were studied electrophysiologically a nd histologically from 3 to 10 months after transplantation and compar ed with 11 RCS controls and 11 normal rats of comparable ages. A micro electrode was guided to the transplant site visible by its pigmentatio n in the albinotic RCS retina to detect responses. Results. Spontaneou s ganglion cell activity was present in all retinas. Ganglion cell res ponses to light were detected in 9 of the 12 transplant eyes but not i n any of the 11 controls. 96, 44, 140 units were encountered and 30%, 0%, 97% were driven by light respectively in transplant, control, and normal retinas. In transplants 36%, 29%, and 28% were driven at 3 to 4 , 6 to 7, and 10 months after transplantation, respectively. Intrareti nal ERGs with both a- and b-waves were recorded in 5 of the 8 transpla nts studied. None of the RCS controls studied had an IERG. The average IERG was 2.5 muV (SD = 1.9) in transplants and 59 muV (SD = 19) in no rmal retinas. The electrode track was traced to the transplant site in six of the seven retinas that were responsive to light and examined h istologically. Conclusion. RPE transplants to RCS rats maintain retina l function in the transplant site for long periods of time.