Abundance of infiltrating CD163+ cells in the retina of postmortem eyes with dry and neovascular age-related macular degeneration

Abstract

Purpose: Prior research in animal models has suggested that retinal macrophages play an important role in age-related macular degeneration (AMD), but studies have insufficiently characterized the distribution of retinal macrophages in various stages of human AMD.

Methods: In this case series, we analyzed H&E, periodic acid-Schiff, and CD163 and CD68 immunostained slides from 56 formaldehyde-fixed, paraffin-embedded autopsy eyes of patients over age 75: 11 age-matched, normal eyes, and 45 AMD eyes.

Results: Qualitative analysis of the macula and retinal periphery revealed that all eyes contained a significant number of CD163+ cells but a negligible number of CD68+ cells. In normal eyes and eyes with thin or infrequent basal laminar deposits, CD163+ cells were restricted to the inner retina. In contrast, in AMD eyes with thick basal deposits, choroidal neovascular membranes, and geographic atrophy, qualitatively there was a marked increase in the number and size of the CD163+ cells in the outer retina, sub-retinal, and sub-retinal pigment epithelium space in the macula.

Conclusions: The changes in number and localization of retinal CD163+ cells in eyes with intermediate-severe AMD support a key role for macrophages in the pathogenesis and progression of the disease. A larger, quantitative study evaluating the distribution of macrophage subpopulations in postmortem AMD eyes is warranted.

Keywords: Age related-macular degeneration; Histopathology; Inflammation; Macrophages; Postmortem eyes.

Fig 1

Eyes stained with hematoxylin and eosin illustrating histopathology in normal eyes and AMD eyes with various disease severities according to the Sarks classification system [7]. a Normal, age-matched control eye with normal RPE and absence of basal deposits (group I). b AMD eye with a few discrete, discontinuous sub-RPE basal laminar deposits, and mild RPE irregularity (group II). c AMD eye with thin, eosinophilic and finely granular, continuous basal deposits, and irregular RPE (consistent with group III); inset depicts the continuous sub-RPE basal deposits. d AMD eye with thick, continuous basal deposits, irregular RPE with indistinct cell borders and photoreceptors with foci of retraction, distortion, and occasional degeneration (group IV). e AMD eye with thick deposits, areas of RPE loss (geographic atrophy), RPE hyperplasia at the edges of atrophy, and photoreceptor loss (group V). f AMD eye with a disciform scar, RPE, and photoreceptor loss (group VI). Scale bar = 100 μm; insets are enlarged 4-fold. Please note that the white line in panels a and b is a break between two separate images, which were obtained due to the presence of a postmortem sensory retinal detachment

Fig 2

Immunohistochemical localization of CD163+ and CD68+ cells in normal, age-matched control eyes and eyes with AMD of various severity grades. CD163+ and CD68+ cells were detected using a red alkaline phosphatase polymer system. The tissue was counterstained with hematoxylin and the nuclei are blue. CD163+ cells are present solely in the inner retina in normal, age-matched eyes (a) and AMD eyes groups II and III (b, c), but were present in the outer retina and subretinal space in eyes with thick subretinal deposits in AMD group IV (d), geographic atrophy in group V (e), and disciform scar in group VI (f). In contrast, a negligible number of CD68+ cells were detected in the retina of control, age-matched eyes (g) and only a small number were in eyes with severe AMD (h group VI, disciform scar, same eye as in f). Insets in a: In normal eyes, CD163+ cells in the nerve fiber layer and ganglion cell layer had a dendritic, microglioid phenotype with a small soma and long processes. In the inner plexiform layer and inner nuclear layer, some of the CD163+ cells had a dendritic morphology and others were characterized by a more rounded, epithelioid conformation. Insets in d and f In eyes from groups IV-VI, CD163+ cells in the outer retina and subretinal space had a rounded morphology with large cell bodies and small processes. Insets in e In eyes with geographic atrophy (group V), the CD163+ cells had a larger soma and shorter processes, consistent with an activated macrophage morphology. The edges of geographic atrophy expressed the marker CD163 in cells filled with melanin granules. Inset in h In the negative controls, there was a complete absence of cellular staining with red chromogen. Scale bar = 100 μm; insets in a-f are enlarged fourfold and the inset in h is at the same magnification as images a-h. Arrow heads: CD163+ macrophages in the outer retina; arrows: subretinal CD163+ cells; *: sub-RPE CD163+ cells. The white line in panels a, b, d and g is the break between two separate photomicrographs taken due to postmortem sensory retinal detachment separating photoreceptors from RPE