Impaired RPE survival on aged submacular human Bruch's membrane

Resurfacing of diseased or iatrogenically damaged Bruch's membrane with healthy retinal pigment epithelium (RPE) has been proposed as adjunctive treatment for age-related macular degeneration (AMD). The purpose of this study was to determine whether cultured fetal human RPE cells can attach and differentiate on aged submacular human Bruch's membrane. Bruch's membrane was debrided to expose native RPE basement membrane, the superficial inner collagenous layer directly below the RPE basement membrane, or the deep inner collagenous layer. These are three surfaces that transplanted RPE cells will encounter in situ. Approximately 3146 cultured fetal RPE cells mm−2 were seeded onto these three surfaces and grown in organ culture for 1, 7, or 14 days. Explants were bisected and examined histologically or analyzed with a scanning electron microscope. RPE nuclear density was measured on stained sections. Morphology and cell density were compared to cells seeded onto bovine corneal endothelial cell-extracellular matrix (BCE-ECM). In situ submacular RPE nuclear density was also measured in tissue sections of donor eyes ranging from 18 weeks gestation to 88 years of age to determine the effect of age on RPE density. Compared to cells seeded onto BCE-ECM at similar density, RPE cell coverage and cellular morphology on aged submacular human Bruch's membrane was poor at all time points. In contrast to cells on BCE-ECM, RPE cell density on Bruch's membrane decreased with time. In general, cell morphology on all three Bruch's membrane surfaces worsened by day-7 compared to day-1. Although some cells were more pigmented on RPE basement membrane and the deep inner collagenous layer at day-7, poor cellular morphology indicated the remaining cells were not well differentiated. At day-14, the cells were uniform and cuboidal on BCE-ECM, with cell density similar to that at day-7 and similar to in situ density of young donors (