Histologic correlation of human neural retinal transplantation

PURPOSE. TO describe the histologic findings of the transplanted eye of a 9 4-year-old man with neovascular age-related macular degeneration, who 3 yea rs earlier underwent subretinal transplantation of both a fetal neural reti nal sheet and a retinal microaggregrate suspension. METHODS. Serial sections of the posterior segment of the eye and the transp lanted areas were processed and studied by routine histologic techniques, i ncluding both light and transmission electron microscopy (TEM). Transplante d areas were also examined for the presence of glial, neuronal, and photore ceptor cell markers by standard immunohistochemical methods. RESULTS. After transplantation in this patient, there was no visual improve ment. Light microscopic examination disclosed survival of the transplanted cells in the subretinal space with no evidence of inflammation or rejection . The neural retinal sheet transplant developed a layered configuration. Th e retinal pigment epithelium (RPE) was absent over much of the posterior po le, including the area of transplantation. TEM examination and immunohistoc hemical analysis disclosed the presence of neuronal and glial cells within the transplant. A few transplant neuronal cell processes overlying a focus of residual RPE cells were positive for S-antigen, but well-developed photo receptor outer segments were not present. CONCLUSIONS. Long-term survival of transplanted neural retinal tissue can b e achieved in human patients without immunosuppression. The lack of photore ceptor development in this patient may be the result of absent or dysfuncti onal RPE. Nonetheless, the long-term survival of grafted tissue in the huma n subretinal space in the absence of immunosuppressive treatment is promisi ng for future efforts in the field of neural retinal transplantation.