Survival of long-term retinal cell transplants

PURPOSE: If retinal cell transplants are to be used in the management of retinal degeneration, they will need to survive in the eye for long time. This study assesses the fate of neural retinal transplants in the eye after long survival times. METHODS: Fragmented pieces of neural retinas from embryonic day 15 rabbits were transplanted to the subretinal space of adult animals of the same strain. The transplants were allowed to survive for up to 583 days prior to sacrifice and light microscopic examination. RESULTS: In most grafts, both neural and glial cells survived, however, some of the grafts seemed to contain predominantly glial cells. Only when the photoreceptors in the graft were apposed to the host pigmented epithelium did they survive. Otherwise, the neuronal components of the grafts were largely cells typically found in the inner retina. The long-term transplants were much thinner than short-term ones. Even after long survival times, the transplants lacked vascularization. No inflammatory cells were seen in or around the grafts. CONCLUSION: The results suggest that the cells of the inner retina survive for long periods after transplantation, but the photoreceptor cells seem to need the support of the host pigmented epithelium for long-term survival. It may therefore be important to have a transplantation technique where the graft photoreceptors can be placed in apposition with the host pigment epithelium.