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

Abstract

PurposeIncreasing evidence suggests a role for macrophages in the pathogenesis of age-related macular degeneration (AMD). This study examined choroidal macrophages and their activation in postmortem eyes from subjects with and without AMD.MethodsChoroids were incubated with anti-ionized calcium-binding adapter molecule 1 (anti-IBA1) to label macrophages, anti-human leukocyte antigen-antigen D-related (anti-HLA-DR) as a macrophage activation marker, and Ulex europaeus agglutinin lectin to label blood vessels. Whole mounts were imaged using confocal microscopy. IBA1- and HLA-DR–positive (activated) cells were counted in submacula, paramacula, and nonmacula, and cell volume and sphericity were determined using computer-assisted image analysis.ResultsIn aged control eyes, the mean number of submacular IBA1+ and HLA-DR+ macrophages was 433/mm2 and 152/mm2, respectively. In early AMD eyes, there was a significant increase in IBA1+ and HLA-DR+ cells in submacula compared to those in controls (P = 0.0015 and P = 0.008, respectively). In eyes with neovascular AMD, there were significantly more HLA-DR+ cells associated with submacular choroidal neovascularization (P = 0.001). Mean cell volume was significantly lower (P ≤ 0.02), and sphericity was significantly higher (P ≤ 0.005) in all AMD groups compared to controls.ConclusionsThe average number of IBA1+ macrophages in submacular and paramacular choroid was significantly higher in early/intermediate AMD compared to that in aged controls. HLA-DR+ submacular macrophages were significantly increased in all stages of AMD, and they were significantly more round and smaller in size in the submacular AMD choroid, suggesting their activation. These findings support the concept that AMD is an inflammatory disease.

Macrophage physiology in the eye

“…A similar finding has been recently reported in the normal human choroid [65]. Kumar et al [47] were the first to examine the behavior of macrophages in mouse choroid explants using time lapse confocal microscopy and revealed that their cell bodies were rather sessile however their processes exhibited repeated extension and retraction in multiple directions.…”

Zinc Nutrition and Inflammation in the Aging Retina

“…Macrophages, in particular, seem to play an important role in AMD pathogenesis . In striking similarity to their presence at atherosclerotic blood vessel sites in cardiovascular disease, macrophages are found at the sites of RPE atrophy, breakdown of Bruch's membrane, and choroidal neovascularization .…”

Altered proportion of CCR2+ and CX3CR1+ circulating monocytes in neovascular age‐related macular degeneration and polypoidal choroidal vasculopathy

“…Development of choroidal neovascularizations (CNVs) defines the late stage of neovascular age‐related macular degeneration (AMD). Monocytes play an important role as shown in several studies: tissue specimens of neovascular AMD show macrophages in significantly higher number around the lesion, experimental CNV in mice is attenuated in size upon experimental depletion of circulating monocytes, patients with new‐onset neovascular AMD have increased circulating monocytes and retinal injury leads to chemokine secretion to which circulating monocytes are drawn . These monocytes respond to the injury by secreting vascular endothelial growth factor (VEGF) .…”