Characterisation of Changes in Retinal Macrophage Subpopulations That Occur With Age in Wild-Type and Ccl-2-/- Mice

Abstract

Purpose: : Macrophages have been shown to play an important role in driving pathological neovascularisation. The purpose of this study was to identify age-related changes in macrophage subsets in mouse retina and to establish their relative contributions to laser-induced choroidal neovascularisation (CNV) in wild-type and Ccl2-/- mice.

Methods: : We used 5 colour flow cytometry to identify subsets in retina and choroid based on expression levels of the markers CD11b, F4/80, Ly6G, Ly6C and CD11c. Single cell suspensions of retina were obtained from wild-type and Ccl2-/- mice of ages <4 months, 12 months and >18 months. The cellular response 3 days after laser-induced rupture of Bruch’s membrane was determined across study groups and the results compared with the extent of CNV as determined by fundus fluorescein angiography at 1 week.

Results: : We found that normal aging in wild-type mice is associated with a significant increase in the size of laser-induced CNV (161% at 1 week post-laser; p<0.01). We were able to divide CD11b+ F4/80+ macrophage populations into Ly6G+ and Ly6G- subsets and further subdivided these two groups on the basis of Ly6C. Both Ly6G+ and Ly6G- subpopulations were significantly increased in young adult Ccl2-/- mice compared to age-matched wild-types. Despite this initial difference we observed a similar age-related behaviour in macrophage subpopulations with age in both genotypes: a significant rise in numbers of CD11b+ F4/80+ Ly6G- cells in the retina with age was seen whereas Ly6G+ cells showed no change.

Conclusions: : We have demonstrated that macrophages in the retina can be subdivided on the basis of Ly6G and Ly6C and the differential behaviour of these groups with age may explain the increase in CNV lesion size.

Keywords: age-related macular degeneration • choroid: neovascularization • aging