CORNEAL ELECTRORETINOGRAPHIC FUNCTION RESCUED BY NORMAL RETINAL-PIGMENT EPITHELIAL GRAFTS IN RETINAL DEGENERATIVE ROYAL-COLLEGE OF SURGEONSRATS

Purpose. This study was designed to examine whether retinal function c an be rescued by allogeneic normal retinal pigment epithelial (RPE) gr afts in Royal College of Surgeons (RCS) with retinal degeneration and, if so, whether this rescued function can be measured and followed by recording the corneal electroretinogram (ERG). Methods. RPE donors wer e RCS-Long Evans crossbred F1 rats with phenotypically normal retinas. Half an RPE sheet was implanted in the subretinal space of RCS rats a t postnatal day 20. The fundi of the recipients' eyes were examined, a nd the corneal ERGs were recorded, The eyes were also examined histolo gically. Results. The RPE grafts were identified by fundus examination in all 21 recipients. No clinical or histologic evidence of inflammat ion was detected in the media or the retina of the host eye. Eighteen of 21 (86%) recipients showed rescued corneal ERG function. In nine re cipients, the PIII response in the grafted eye was significantly great er than in the nongrafted eye. In the other nine recipients, the ERG i n the grafted eye showed a b-wave and an a-wave, whereas no b-wave was detected in the nongrafted eye. Recipients of the sham operation (n = 13) revealed no ERG function rescue. To determine long-term corneal E RG function in RPE recipients, 8 of 18 animals in which ERG function w as rescued were randomly selected for continued observation. These rec ipients sustained rescued ERG function for 16 to 17 weeks, at which ti me the experiment ended. Conclusion. Results indicate that retinal fun ction of degenerative RCS rats, as measured by corneal ERG, can be res cued by implantation of allogeneic normal RPE into the subretinal spac e of the eye, Furthermore, this rescued function can be followed up ov er a relatively long period of time, thus providing a useful model for studying the functional changes of RPE allografts resulting from eith er immunologic or neurobiologic influences.