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Janani Singaravelu, Lian Zhao, Robert N Fariss, T Michael Nork, Wai T Wong; Microglia specialization in the primate macula: Changes in distribution and morphology with retinal position and aging. . Invest. Ophthalmol. Vis. Sci. 2016;57(12):2230.
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© ARVO (1962-2015); The Authors (2016-present)
Microglia, the primary resident immune cell in the CNS, has been studied in the retina but predominantly in rodent models that lack a macula. To understand how microglia may demonstrate specializations within the macula and how these specializations may change with aging, we examined the distribution and morphology of microglia at different retinal positions in young and aged primate retina.
Flat-mounted retina tissue from the foveal, outer macular, and extramacular peripheral retina were isolated from young adult (4.2 years) and middle-aged (16.8 years) female Rhesus macaque primates. Immunohistochemistry for Iba1 (microglia), cone arrestin (cones), and isolectin IB4 (vasculature) was performed and imaged with confocal microscopy. Morphological analysis was performed using ImageJ software.
Microglial density and morphology was not constant across the primate retina but demonstrated graded variations according to retinal position. Microglia demonstrated particular specializations in the fovea. Around the foveal avascular zone, microglia in the IPL were arranged in a circular pattern with their long axes tangential to the foveal center. Deeper in the OPL, microglia showed elongated morphologies that were oriented with their long axes in a radial pattern radiating from the foveal center. Further from the fovea, microglia in both outer macular (2.5 mm from foveal center) and peripheral extramacular (9 to 10 mm from foveal center) areas demonstrated more symmetric morphologies that tile the retina uniformly. Interestingly, microglial densities in these areas demonstrated differing changes with aging, with microglial density increasing in macular locations and conversely decreasing in peripheral locations with age.
Retinal microglia were not uniformly distributed across the primate retina with identical morphologies but instead demonstrated multiple regional specializations in morphology and density that vary with aging. These may reflect changes in immune function in the macula occurring with aging that are relevant to age-related macular disease.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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