Purpose

Many retinal diseases, such as macular degeneration, affect both retinal pigment epithelium (RPE) and photoreceptors. Therefore, retinal repair may require transplantation of both tissues together as a cograft.

Methods

As recipients of retina-RPE cografts, 7- to 10-week-old albino Royal College of Surgeons rats that lose their photoreceptors because of a pigment epithelium defect were used. Freshly harvested intact sheets of RPE with neural retina from pigmented normal rat fetuses were gel embedded for protection and transplanted into the subretinal space.

Results

After 6 to 7 weeks, with the support of the cografted RPE sheet, transplanted photoreceptors developed fully in organized parallel layers in the subretinal space. Immunohistochemistry for rhodopsin, rod alpha-transducin, and S-antigen and peanut agglutinin labeling for cone interphotoreceptor matrix domains suggested that the photoreceptors in the graft were capable of normal function.

Conclusions

Freshly harvested intact sheets of fetal RPE and retina, transplanted together into the subretinal space, can develop a normal morphology. Such transplants have the potential to benefit retinal diseases with dysfunctional RPE and photoreceptors.

The aim was to demonstrate functional properties of transplanted histologically normal photoreceptors. Subretinal intact-sheet transplants of fetal E17-E20 rat retinas to light-damaged albino rat eyes were fixed in light or dark, 2 to 42 weeks after transplantation, and stained immunohistochemically for certain phototransduction proteins. In light adapted transplants, transducin was predominantly found in inner segments of parallel-organized photoreceptors. Transducin shifted to the outer segments with dark-adaptation. S-antigen distribution was opposite to transducin. Rhodopsin distribution did not change. The shift of signal transduction proteins correlated to the light conditions indicates that normal phototransduction processes were established in photoreceptors of transplanted retinal sheets.