Identification of transplanted retinal pigment epithelium with a novel chromosomal marker

Purpose. To demonstrate the ability of a novel chromosomal marker to identify retinal pigment epithelium (RPE) after xenotransplantation, and determine the short-term correlation between pigment and this nuclear marker. Methods. Primary pigmented RPE harvested from third trimester fetal pigs were transplanted as microaggregates into the subretinal space of 3 albino rabbits. We then used an in situ probe for a repetitive segment of the porcine chromosome to identify the transplanted RPE. Results. Pigmented cells were visible in the subretinal space 2 weeks after transplantation. Approximately 70% of pigment-containing cells were also labeled with the porcine chromosomal marker. Labeled cells were predominantly flatter in morphology and close to Bruch’s membrane whereas unlabeled cells were rounder and further from Bruch’s membrane. The outer nuclear layer thickness was normal above the pigmented monolayer but was decreased over areas containing multiple layers of pigmented cells. Conclusions. Fetal porcine RPE xenografts can be identified with a nuclear marker for a repetitive segment of the porcine chromosome. The presence of pigment within unlabelled cells suggests that pigment is not a robust marker for transplanted RPE.