Effects of treadmill exercise on retinal vascular morphology, function, and circulating immune factors in a mouse model of retinal degeneration.

Purpose: Exercise is neuroprotective in rodents undergoing retinal degeneration (RD). However, the effects of exercise on retinal vasculature remain unexplored. Here, we investigate whether treadmill exercise influences retinal vascular morphology, function, gene expression, and circulating factors in a light-induced retinal degeneration (LIRD) mouse model. Methods: 6-week-old female BALB/c mice were assigned to inactive+dim, active+dim, inactive+LIRD and active+LIRD groups (n=20 per group). Active mice were treadmill exercised (1hr/d 10m/min) for two weeks, then LIRD was induced (5000 lux/4hrs). Inactive mice were placed on a static treadmill. Retinal neurovascular coupling was measured with functional hyperemia (FH) and vascular morphology using OCT-A. Vascular gene expression was quantified from isolated retinal endothelial cells using ddPCR five days following LIRD. Serum was collected for circulating cytokine and chemokine analyses. Data were analyzed using 2-way ANOVA. Results: Retinal vessel vasodilation was significantly increased in active+LIRD mice compared to inactive+LIRD mice. Superficial and intermediate/deep vascular plexi from inactive+LIRD mice had significantly decreased vessel density and total vessel length, with increased numbers of end points and lacunarity compared to active groups. Isolated retinal endothelial cell gene expression varied among groups. Most notably, Active+LIRD mice had a distinct immune response profile, with increased expression of IL-6, KC, and VEGF-A. Conclusions: Treadmill exercise maintained retinal vascular morphology and function, modestly altered endothelial gene expression, and is associated with a specific circulating immune response profile in a LIRD mouse model. These data indicate therapeutic effects of exercise on retinal vasculature in RD.