Despite their discovery in 1998, only 2 groups, to our knowledge, have published findings on clinical trials using human embryonic stem cells. We and another group have reported results following the subretinal transplant of human embryonic stem cell–derived retinal pigment epithelial cells (hES-RPE).1- 3 Subretinal pigmentation developed in the area of hES-RPE injection in 13 of 18 patients in the US trial2 and in 3 of 4 patients in the Korean trial.3 These reports presumed that the pigmentation resulted from the engraftment of hES-RPE. However, these trials have no confirmative measurements of engraftment because performing a biopsy causes a defect in the retina and the injected cells were not labeled.
Shim SH, Kim G, Lee DR, Lee JE, Kwon HJ, Song WK. Survival of Transplanted Human Embryonic Stem Cell–Derived Retinal Pigment Epithelial Cells in a Human Recipient for 22 Months. JAMA Ophthalmol. Published online February 09, 2017. doi:10.1001/jamaophthalmol.2016.5824