Long-Term Efficacy of GMP Grade Xeno-Free hESC-Derived RPE Cells Following Transplantation.

PURPOSE: Retinal pigment epithelium (RPE) dysfunction underlies the retinal degenerative process in age-related macular degeneration (AMD), and thus RPE cell replacement provides an optimal treatment target. We characterized longitudinally the efficacy of RPE cells derived under xeno-free conditions from clinical and xeno-free grade human embryonic stem cells (OpRegen) following transplantation into the subretinal space of Royal College of Surgeons (RCS) rats. METHODS: Postnatal (P) day 20 to 25 RCS rats (n = 242) received a single subretinal injection of 25,000 (low)-, 100,000 (mid)-, or 200,000 (high)-dose xeno-free RPE cells. BSS+ (balanced salt solution) (vehicle) and unoperated eyes served as controls. Optomotor tracking (OKT) behavior was used to quantify functional efficacy. Histology and immunohistochemistry were used to evaluate photoreceptor rescue and transplanted cell survival at 60, 100, 150, and 200 days of age. RESULTS: OKT was rescued in a dose-dependent manner. Outer nuclear layer (ONL) was significantly thicker in cell-treated eyes than controls up to P150. Transplanted RPE cells were identified in both the subretinal space and integrated into the host RPE monolayer in animals of all age groups, and often contained internalized photoreceptor outer segments. No pathology was observed. CONCLUSIONS: OpRegen RPE cells survived, rescued visual function, preserved rod and cone photoreceptors long-term in the RCS rat. Thus, these data support the use of OpRegen RPE cells for the treatment of human RPE cell disorders including AMD. TRANSLATIONAL RELEVANCE: Our novel xeno-free RPE cells minimize concerns of animal derived contaminants while providing a promising prospective therapy to the diseased retina.

Standardization of the teratoma assay for analysis of pluripotency of human ES cells and biosafety of their differentiated progeny.

Teratoma tumor formation is an essential criterion in determining the pluripotency of human pluripotent stem cells. However, currently there is no consistent protocol for assessment of teratoma forming ability. Here we present detailed characterization of a teratoma assay that is based on subcutaneous co-transplantation of defined numbers of undifferentiated human embryonic stem cells (hESCs) with mitotically inactivated feeder cells and Matrigel into immunodeficient mice. The assay was highly reproducible and 100% efficient when 100,000 hESCs were transplanted. It was sensitive, promoting teratoma formation after transplantation of 100 hESCs, though larger numbers of animals and longer follow-up were required. The assay could detect residual teratoma forming cells within differentiated hESC populations however its sensitivity was decreased in the presence of differentiated cells. Our data lay the foundation, for standardization of a teratoma assay for pluripotency analysis. The assay can also be used for bio-safety analysis of pluripotent stem cell-derived differentiated progeny.

Directed differentiation of human embryonic stem cells into functional retinal pigment epithelium cells.

Dysfunction and loss of retinal pigment epithelium (RPE) leads to degeneration of photoreceptors in age-related macular degeneration and subtypes of retinitis pigmentosa. Human embryonic stem cells (hESCs) may serve as an unlimited source of RPE cells for transplantation in these blinding conditions. Here we show the directed differentiation of hESCs toward an RPE fate under defined culture conditions. We demonstrate that nicotinamide promotes the differentiation of hESCs to neural and subsequently to RPE fate. In the presence of nicotinamide, factors from the TGF-beta superfamily, which presumably pattern RPE development during embryogenesis, further direct RPE differentiation. The hESC-derived pigmented cells exhibit the morphology, marker expression, and function of authentic RPE and rescue retinal structure and function after transplantation to an animal model of retinal degeneration caused by RPE dysfunction. These results are an important step toward the future use of hESCs to replenish RPE in blinding diseases.