Cryopreservation and transplantation of immature rat retina into adult rat retina.

A bank of freeze-stored donor retinas would free transplantation research from dependence on availability of fresh donor tissue. Donor retinas from E13, E16, E19 and E22 (P1) rat embryos were cryoprotected and stored in liquid nitrogen for up to 8 months. Cryopreserved and fresh donor retinas were grafted to adult rat retina. After 4 weeks survival, transplants were evaluated according to a scoring protocol for the criteria of size, viability, lamination and integration. All donor ages of fresh and cryopreserved retina resulted in successful transplants, with the exception of cryopreserved E13. Cryopreserved grafts were significantly less laminated than grafts of fresh tissue. The best lamination scores of cryopreserved transplants were achieved with donor age E16. Surviving transplants were found in the epiretinal and/or subretinal space. Subretinal transplants had higher viability scores than did epiretinal grafts; the difference was more pronounced with transplants of cryopreserved than with fresh tissue. Fresh subretinal transplants were also significantly better laminated than fresh epiretinal transplants. This study shows that (1) cryopreserved retinal donor tissue can successfully be transplanted to rat retina; and (2) the subretinal space appears to be more favorable than the epiretinal space for retinal transplants.