Juvenile human RPE graft rescues photoreceptor cells in dystrophic RCS rats

Purpose: To investigate the utility of non-fetal human RPE for subretinal transplantation in dystrophic RCS rats. Methods: Two eyes from a 10 year old female donor were obtained through the Rochester Eye and Human Parts Bank. The eyes were held in Optisol for less than 24 hrs. The RPE was isolated by enzymatic treatment of the choroid-RPE with 2% dispase for 30 min. at 37°C (Castillo et al. 1995 Curr. Eye Res 1:677). Mechanically dissociated RPE was injected into the subretinal space of P21 dystrophic RCS rats at the superior equatorial (SE) region using the transcleral technique of del Cerro et al. (1992 J. Neurosci. Meth. 43:157). Rats receiving vehicle injection served as sham controls. The animals were immunosuppresed with daily cyclosporine injections (10 mg/kg). At 4 wks post-transplantation, the fundi were examined and the eyes were enucleated for histologic evaluation and morphometric analysis of PRC survival. Results: Fundoscopic examination revealed survival of the juvenile RPE graft which varied from large dense focal collections to small scattered islands of pigmented cells. Histologically, the grafted eyes exhibited greater number of surviving photoreceptor cells. Morphometric analysis of 1 μm thick sections demonstrated a 6 fold increase in PRC density at the SE region of grafted eyes (62.10 ± 29.3) compared to the same region of sham controls (10.75 ± 2.2) (p<0.005). In addition, a decrease in debris zone thickness was observed at the SE region of grafted eyes (13.75 ± 9.2 μm) compared to sham controls (23.65 ± 1.9 μm). Conclusion: Juvenile human RPE survive transplantation into the subretinal space and rescue PRC of dystrophic RCS rats. This study demonstrates that human RPE transplantation is not limited to use of fetal tissue.