INTACT SHEETS OF FETAL RETINA TRANSPLANTED TO RESTORE DAMAGED RAT RETINAS

PURPOSE. The aim of this study was to establish a model for morphologi c retinal reconstruction after destruction of photoreceptors. METHODS. Rat embryos were prelabeled by injection of bromodeoxyuridine (BrdU) into timed pregnant rats on 2 to 6 consecutive days. Pieces of fetal r etinas (embryonic day [E] 17 to E22) were embedded in growth factor-re duced matrigel for protection and stored in medium on ice. With the us e of a custom-made implantation tool, trimmed embedded pieces were pla ced into the subretinal space of albino rats whose photoreceptors had been damaged by continuous exposure to blue light for 3 to 4 days. RES ULTS. Donor cells were unequivocally identified by the BrdU label. App roximately 25% of transplants in the subretinal space developed parall el layers,with photoreceptor outer segments facing the host pigment ep ithelium. Transplants developed rosettes if host pigment epithelium ha d been damaged, if trauma to the donor tissue occurred during preparat ion or transplantation, and if the donor tissue was misplaced into the choroid or into the epiretinal space on top of the host retina. If th e surgery was performed more than 4 weeks after the light damage, cont inued degeneration of the host retina caused secondary pigment epithel ium damage, and transplants did not develop parallel layers of photore ceptor outer segments. CONCLUSIONS. After transplantation to the subre tinal space of a degenerated retina, gel-protected fetal retina can de velop parallel layers and photoreceptor outer segments in contact with host pigment epithelium. Transplants call develop good fusion with th e inner retina of a photoreceptor-deficient recipient.