Quantification and Distribution of Choroidal Macrophages in Human Eyes with Age-Related Macular Degeneration

Abstract

Purpose : Increasing evidence suggests a role for macrophages in the pathogenesis of age-related macular degeneration (AMD). It is unclear whether they participate in early AMD, geographic atrophy (GA), and/or exudative AMD. In this study, we examined choroidal macrophages in postmortem eyes from aged control subjects and in eyes with early and late stage AMD and evaluated the characteristics of activation: HLA-DR expression and shape change.

Methods : Choroids from postmortem human eyes with clinically documented AMD were incubated with a cocktail of antibodies against IBA-1 to label macrophages and HLA-DR as a macrophage activation marker as well as with UEA lectin to label blood vessels. Whole mounts were imaged using confocal microscopy. IBA-1 and HLA-DR positive cells were counted in three areas (submacula, paramacula, and nonmacula) using computer-assisted image analysis and cell volume and sphericity were determined with Imaris software.

Results : In aged control eyes, the mean number of submacular IBA-1⁺ and HLA-DR⁺ choroidal macrophages was 444/mm² and 153/mm² respectively. The number was not statistically significantly different in paramacular and nonmacular regions. In early AMD, there was a significant increase in IBA-1⁺ (p=0.03) in submacula; however, the increase in HLA-DR⁺ macrophages was not significant compared to controls. In eyes with GA, the number of IBA-1⁺ and HLA-DR⁺ cells was not significantly different than controls in most regions; however, HLA-DR⁺ cells were slightly increased in areas of RPE atrophy. In eyes with exudative AMD, there was a significant increase in HLA-DR⁺ cells associated with choroidal neovascularization (CNV)(p=0.004). Also, cell volume decreased significantly (p≤0.02) and sphericity increased significantly (p≤0.005) in all AMD groups compared to controls.

Conclusions : Our results demonstrate that the number of macrophages in AMD choroid is not significantly different compared to aged controls but increased activated (HLA-DR⁺) macrophages were associated with CNV. Macrophage shape became significantly more round and their size decreased significantly in the submacular choroid of all AMD groups.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.