Repopulation of different layers of host human Bruch's membrane by retinal pigment epithelial cell grafts.

PURPOSE To determine the morphology of human retinal pigment epithelium (RPE) after reattachment to different ultrastructural layers of human Bruch's membrane (BM). METHODS Bruch's membrane explants were prepared from eyes of 23 human donors (age range, 11-89 years). The basal lamina of the RPE, inner collagenous layer, and elastin layer were removed sequentially by mechanical and enzymatic techniques. First-passage cells of human RPE (15,000 cells/6 mm explant) from three donors (ages, 52, 64, and 80 years) were plated onto different layers of human BM, and the explants were examined by scanning and transmission electron microscopy up to 21 days later. RESULTS RPE flattened and extended footplates 6 hours after plating onto basal lamina. Cells remained round 6 and 24 hours after plating onto the inner collagenous, elastin, or outer collagenous layer. The RPE cells became confluent 14 days after plating onto basal lamina but did not become confluent up to 21 days after plating onto the inner collagenous or elastin layer. Sparse round cells were observed 21 days after plating onto deeper layers, suggesting extensive loss of RPE. CONCLUSIONS The morphology and subsequent behavior of the RPE reattached to BM depends on the anatomic layer of BM available for cell reattachment. The results suggest that the ability of transplanted RPE to repopulate BM in age-related macular degeneration and other disorders may depend on the layer of BM available to serve as a substrate for cell reattachment.