Long–Term Preservation of Photoreceptors in RCS Rats by Transplantation of Homologous and Heterologous IPE Cells

Abstract

Abstract: : Purpose: The aim of this study was to examine whether IPE cells transplanted to the subretinal space of Royal College of Surgeons (RCS) rats would rescue the photoreceptors that would deteriorate following the degeneration of the RPE in these animals. Methods: Freshly isolated Long Evans rat iris pigment epithelial (rIPE) or cultured human IPE (hIPE) cells were transplanted transsclerally into the subretinal space of 17 23–day–old RCS rats using a Hamilton syringe. Sham injection of medium and transplantation of human ARPE cells into the subretinal space served as controls. Animals were immunosupressed throughout the study period. After 12 weeks eyes from experimental and control rats as well as from age–matched RCS rats without surgical treatment were evaluated for photoreceptor survival by morphometric measurement of photoreceptors in semithin sections of the retina and by morphological examination by light and electron microscopy. Results: The IPE cells transplanted into the subretinal space were localized between the host RPE and neural retina. Morphometric analysis showed that photoreceptor rescue occurred in all transplanted and sham injected animals (Number of photoreceptors/300 µm retina ± sd: rIPE = 41.67 ± 28; hIPE 29.50 ± 16; ARPE = 36.12 ± 21; Sham = 16.56 ± 6) but was not evident in age–matched control rats (Number of photoreceptors/300 µm retina = 9.71 ± 4). Photoreceptor rescue was prominent in IPE–transplanted rats and was statistically significantly different from sham–injected eyes (p=0,02 for rIPE and p=0,04 for hIPE). Conclusions: IPE cells transplanted to the subretinal space have the ability to rescue photoreceptors from the deterioration that follows RPE cell degeneration in the RCS rat.

Keywords: transplantation • retinal pigment epithelium • age-related macular degeneration