Retinal Pigment Epithelium Wound Healing in Human Bruch's Membrane Explants
Investigative Ophthalmology and Visual Science
PURPOSE. To compare retinal pigment epithelium (RPE) resurfacing on the RPE basement membrane and inner collagenous layer (ICL) in human submacular Bruch's membrane explants. METHODS. Debridements were created in RPE-choroid-sclera explants (mean donor age 71.91 Ϯ 7.76 years) to create defects exposing the RPE basement membrane (RPEbm(ϩ) defects), the ICL immediately below the RPE basement membrane (superficial ICL, [SICL]) or deeper layers of the ICL (DICL). Eleven pairs of eyes-four pairs
... eyes-four pairs with one eye having an RPEbm(ϩ) defect and the fellow eye having an SICL defect and seven pairs with corresponding RPEbm(ϩ) and DICL defects-were observed for 10 days by visualizing RPE ingrowth with 4Ј,6Јdiamino-2-phenylindole (DAPI) filters. At day 10, specimens were processed for scanning electron microscopy. RESULTS. Resurfacing of localized RPE defects occurred to some degree in all 11 pairs of eyes. No significant difference in the percentage of resurfacing of RPEbm(ϩ) defects (67.35% Ϯ 18.82%) and SICL defects (64.26% Ϯ 16.07%) was observed although healing of the SICL showed more variability in the morphology of RPE cells migrating into the defect. Significant differences in healing were observed between pairs with RPEbm(ϩ) defects versus DICL defects (84.07% Ϯ 15.35% and 54.00% Ϯ 14.54% resurfacing, respectively). RPE ingrowth into DICL defects exhibited the greatest morphologic variability. CONCLUSIONS. RPE basement membrane supports RPE resurfacing of localized RPE defects. The deeper portion of the ICL of aged submacular human Bruch's membrane does not support RPE resurfacing to the same extent as does the RPE basement membrane. The poor RPE resurfacing observed in DICL defects mimics the histopathological findings in patients with agerelated macular degeneration after excision of choroidal new vessels. (Invest Ophthalmol Vis Sci. * D-E, time between death of the donor and enucleation; D-Ex, time between death of the donor and processing for experiment. † RPEbm(ϩ), RPE defect with the RPE basement membrane intact. SICL, RPE defect after removal of RPE basement membrane, exposing the surface of the ICL that lies directly under the RPE basement membrane. DICL, RPE defect with basement membrane and part of the ICL removed, exposing more disrupted, less densely packed collagen fibrils composing the ICL.