Abnormal Basement Membrane of Human Retinal Pigment Epithelium with and without Age-related Macular Degeneration: An Electron Microscopic Study

Abstract

Abstract: : Purpose: Abnormal thickenings of the basement membrane of retinal pigment epithelium (RPE), called also basal laminar deposits (BLD),are frequently observed in eye affected by age-related macular degeneration (ADM). Here we present comparative ultrastructural studies on the basement membrane alterations of human RPE affect either by AMD or by other eye-disease. Methods: Twenty-eight surgically removed human eyes (aged from 1 to 85 years) were studied by standard transmission electron microscopic technique. Diagnosis of AMD was established either by ophthalmoscopy before surgery.Presence of soft drusen and/or pigment irregularieties were considered as sign of early AMD, while RPE atrophy or subretinal exudative/hemorragic alterations were considered to be signs of dry or wet form of advanced AMD, respectively. Results: Basament membrane of RPE from normal eyes showed homogeneous appearance with uniform thickness in both central and peripheral retina.In AMD focal and/or diffuse thickening of basement membrane were constant finding in both central and peripheral retina.In contrast to the normal basement membrane, these thickenings showed fibrillary structures and focal electron-densities. In several places these structure were observed in the extracellular lacuna of basal infoldings formed by basal cell membrane of RPE. Moreover, they may be found deeply in these invaginations apparently non connected to the basement membrane.Suprinsingly, we observed similar alteration in case of retinoblastome, long-lasting retinal detachment, and particulary in eyes affected by chronic uveitis. Conclusions: These observation showed that abnormal basement membrane of RPE seen in AMD may be found in some other eye-disease associated with chronic inflammation.A hypothesis on local cellular origin of basement membrane alterations due to pro-inflammatory stimuli will be presented.

Keywords: age-related macular degeneration • Bruch's membrane • pathology: human