Morphological and Functional Rescue in RCS Rats After RPE Cell Line Transplantation at Later Stage of Degeneration

Abstract

Abstract: : Purpose: The Royal College of Surgeons (RCS) rat undergos a progressive photoreceptor loss due to a retinal pigment epithelium (RPE) cell defect. The degeneration can be limited by transplantation of healthy RPE cells. Here we examined the effect of transplantation on the morphology and function of RCS rats receiving RPE transplantation at later stage of degeneration. Methods: Dystrophic RCS rats (2 month old) received subretinal injection of human RPE cell line, ARPE19 (2x10⁵/2µl/eye). OptoMotor and ERG were conducted 2 months later; tectal threshold responses were recorded a further month later. Retinal sections (10µm) were stained with cresyl violet, cell specific markers (for retinal neurons) and human–specific marker (for donor cells). Control animals were dystrophic RCS rats injected with medium alone (sham injection). All animals were immunosupressed by oral cyclosporine administration. Results: In 2 month old untreated dystrophic RCS rats, photoreceptors were reduced to 3–4 layers; by 5 month of age only a few scattered photoreceptors remained. Later transplantation delayed photoreceptor degeneration: there were 2–3 layers of rescued photoreceptors at 5 month old. Retinal cell specific marker staining showed an orderly array of the inner retinal lamination. The morphology of the second–order neurons was better preserved around the grafted area compared with regions distant from the graft. Sham injection had little effect in rescuing photoreceptors. Grafted rats performed better than untreated animals in a OptoMotor test; ERG showed preserved b–waves in RPE–but not untreated eyes. Tectal recording revealed significantly lower visual threshold responses to stimulation of the treated compared with the untreated eye. In general although rescue was achieved, it was less than after transplantation performed at early stage degeneration. Conclusions: RPE transplants delivered later in degeneration can preserve not only the photoreceptors and inner retinal lamination, but also visual function in RCS rats. However, early intervention does lead to optimal rescue.

Keywords: retinal degenerations: cell biology • transplantation • degenerations/dystrophies