Sub-retinal injection of human induced pluripotent stem cell-derived RPE cells: Six-month safety and integration in a rat model

Abstract

Purpose : To report the 6-month safety and integration of human induced pluripotent stem cell-derived RPE cells in a dystrophic rat model

Methods : The study was carried out in Royal College of Surgeon (RCS) rats that undergo gradual retinal degeneration over a period of 6-8 months. The rats were anesthetized by a trained veterinarian by following the ARVO guidelines for ethical handling of animals. Human induced pluripotent stem cell-derived RPE cells preparedunder standardized GMP controlled conditions were injected into the sub-retinal space of one eye of 4 weeks old RCS rats (N=10). Sub-retinal injections are done by a trained vitreoretinal surgeon by making an incision just behind the limbus. About 0.5-1x10⁵ cells in 3-5 µL volumes were injected using a 28G blunt tipped needle, fitted to a 5-10 µL Hamilton syringe. Prior to injection and post injection, the rats were maintained under immunosuppression by oral cyclosporine administration in the drinking water. The rats were followed up at regular intervals. At 6-month follow up, fundus examination under anesthesia revealed visible patches of pigmented RPE cells, which were well positioned within the sub-retinal space. The animals were sacrificed and the enucleated eye balls were subjected to histological evaluations and immunostaining.

Results : Fundus evaluation of the live albino RCS rats revealed the presence of pigmented cells in the retina. Further IHC evaluations and H&E staining confirmed that the pigmented cells were well positioned within the sub-retinal space, either as diffuse cell clusters or as multi-cellular clumps. They neither showed abnormal proliferation nor formed any visible tumors. Further immunostaining using anti-PAX6 and anti-Human mitochondrial antibodies confirmed that the pigmented cells are of human origin. None of the animals showed any signs of local or systemic inflammation or adverse events

Conclusions : Human induced pluripotent stem cell-derived RPE cells transplanted into RCS rat eyes survived for upto 6 month post transplantation, without any significant risk of inflammation or tumor growth

This is a 2020 ARVO Annual Meeting abstract.