Long Term Visual Rescue of GMP-Compliant Human ES-Derived RPE Cells Transplanted into RCS Rats

Abstract

Purpose: : Cell based therapies for the prevention of blindness have been shown to be effective in animal models of human disease. We investigated conditions under which highly-characterized human RPE cells derived from embryonic stem cell lines and manufactured under Good Manufacturing Practice (GMP)-compliant conditions could optimally rescue visual function in the RCS rat.

Methods: : GMP-compliant hES-RPE cells from Advanced Cell Technology were injected into the subretinal space of 22 day-old (P22) RCS rats in five different dosage groups: 5x10³/eye (5K), 2x10⁴/eye (20k), 5x10⁴/eye (50K), 7.5x10⁴/eye (75K) and 1x10⁵/eye (100K). With each group of animals, 3-4 eyes received injections of sham alone. The unoperated eye provided further baseline data. All animals were maintained on oral cyclosporine A (CyA) administered in the drinking water. The Optomotor test, a quick and repeatable method of estimating rodent acuity, was conducted from P60-P240. Tectal recordings were made at about P100 and P180. At the end of the testing, animals were sacrificed and eyes were processed for histology.

Results: : The OptoMotor test showed a dose dependent response: 50K, 75K and 100K grafted animals performed significantly better than that of 5K, 20K, shams and untreated animals, at P90; also, the visual acuity of RCS rats with 50K, 75K and 100K treatments showed significant improvement (p<0.05) over control animals, at all time points. Threshold recording from the superior colliculus showed that hES-RPE grafted animals had lower visual thresholds compared with sham injected and untreated groups up to P180. Histological analyses indicated that donor cells survived up to P210, with many integrating into the host RPE cells layer. Substantial photoreceptor rescue was observed in and beyond engrafted regions of the retina. There were no signs of tumor formation or other unwanted pathology.

Conclusions: : This study showed that a GMP-compliant human ES-derived cell line injected into subretinal space of RCS rat can preserve photoreceptors and visual functions in a dose-dependent manner. The mechanism underlying this morphological and functional rescue may be neuroprotective factor-release or phagocytosis of photoreceptor outer segments by donor cells. Our data suggest that hES-RPE may provide an effective donor cell source to rescue photoreceptors in conditions such as AMD where RPE function is compromised.

Keywords: transplantation • retinal degenerations: cell biology • retinal pigment epithelium