Aldosterone Exposure Causes Increased Retinal Edema and Severe Retinopathy Following Laser-Induced Retinal Vein Occlusion in Mice.

Purpose: To determine the effects of aldosterone exposure on retinal edema and retinopathy in a mouse model of retinal vein occlusion (RVO).
Methods: RVO was induced immediately following intravenous injection of Rose bengal (66 mg/kg) using a 532-nm wavelength laser to place three to seven applications at 80 mW and 50-μm spot size directed at the superior retinal vein one disc diameter away from the nerve. Negative control consisted of placing an equal number of laser spots without targeting the vein. Male and female C57BL/6J mice aged 7 to 9 months with confirmed absence of Crb1rd8 were used. Aldosterone pellets releasing a daily dose of 0.83 μg/day were implanted subcutaneously 4 weeks prior to RVO. Retinal imaging by optical coherence tomography (OCT) was performed using a Micron IV rodent imaging system. Retinas were analyzed by immunohistochemistry using standard techniques. Retinal imaging and tissue analysis were performed 2, 4, and 7 days following RVO. Comparisons were made using Student's t-test, ANOVA, and Pearson's χ2.
Results: RVO caused retinal edema in the form of cystic spaces and retinal thickening detectable by both OCT and histology. RVO also caused Müller glia (MG) dysfunction manifest as upregulated glial fibrillary acidic protein (GFAP) and altered localization of aquaporin 4 (AQP4) and Kir4.1. Treatment with aldosterone caused a significant increase in retinal edema and more severe retinopathy manifest as retinal whitening and extensive intraretinal hemorrhage. MG dysfunction was more severe and persistent in aldosterone-treated mice. Finally, aldosterone greatly increased the number of infiltrating mononuclear phagocytes following RVO.
Conclusions: Systemic aldosterone exposure causes a more severe RVO phenotype manifest as increased severity and duration of retinal edema and more severe retinopathy. The effects of aldosterone may be mediated by MG dysfunction and increased infiltration of mononuclear phagocytes. This suggests that small increases in aldosterone levels may be a risk factor for severe RVO.