Purpose: Age-related macular degeneration (AMD) is the most common cause of irreversible vision loss in the elderly. Increased understanding of the pathogenesis is necessary. Amyloid-beta (Abeta), a major extracellular deposit in Alzheimer's disease plaques, has recently been found in drusen, the hallmark extracellular deposit in AMD. The goal of this study was to characterize the distribution and frequency of Abeta deposits in drusen from AMD and normal post mortem human retinas to gain additional insight about the potential role of Abeta in AMD patho genesis.
Methods: Immunocytochemistry was performed with three Abeta antibodies on sections from 9 normal and 9 AMD (3 early, 3 geographic atrophy, 3 exudative AMD) retinas. Five sections from each eye were evaluated. Abeta positive deposits in drusen were identified using epifluorescence and confocal microscopy. Antibodies were pre-adsorbed with Abeta peptide to verify specificity. Some sections were stained with PAS-hematoxylin to aid in evaluation of morphology.
Results: To test and optimize immunocytochemistry, Abeta was detected in amyloid plaques from Alzheimer's brains. Abeta label was blocked by pre-adsorption of antibody with Abeta peptide, verifying specificity. Four of the 9 AMD retinas and none of the 9 normal retinas had Abeta positive drusen. Two of the early AMD eyes had a few A[beta] positive drusen, each with a few Abeta-containing vesicles, and 2 of the geographic atrophy (GA) eyes had many Abeta positive drusen with many Abeta containing vesicles.
Conclusions: Abeta was present in 4 of 9 AMD eyes. Within these eyes, Abeta localized to a subset of drusen. None of the 9 normal eyes surveyed, some of which had small drusen, were A beta positive. Abetapositive vesicles were most numerous in GA eyes at the edges of atrophy, the region at risk for further degeneration. These results suggest that Abeta in drusen correlates with the location of degenerating photoreceptors and retinal pigment epithelium (RPE) cells. Further work will be necessary to determine whether Abeta deposition in drusen may contribute to or result from retinal degeneration.