RORα Regulates Experimental Choroidal Neovascularization

Abstract

Purpose : Age-related macular degeneration (AMD) is a leading cause of visual impairment in the elderly. Choroidal neovascularization (CNV) leads to the majority of AMD-related blindness. Dysregulation of lipid-cholesterol metabolic pathways is implicated in CNV formation. Retinoic acid receptor-related orphan receptor alpha (RORα), a lipid-sensing nuclear receptor, is linked with AMD genetically. RORα functions as a ligand (cholesterol derivatives)-dependent transcriptional regulator and mediates gene expression in many physiological processes, including lipid metabolism and immunity. Here we investigated the role of RORα in the regulation of CNV using a laser-induced mouse model.

Methods : Laser photocoagulation was performed to induce CNV in mice with spontaneous RORα deficiency (Rora^Sg/Sg), the littermate wild type (WT) controls, macrophage-specific RORα knockout (LysM^Cre; Rora^f/f), and Rora^f/f. CNV lesion size and leakage were analyzed with in vivo fluorescein fundus angiography (FFA) evaluation and in isolated choroid complex flat mounts and cross-sections from enucleated eyes stained with vascular markers. Expression levels of Rora and relevant angiogenic, metabolic and inflammatory genes were analyzed in retinas and RPE/choroid complexes from mouse eyes with induced CNV.

Results : RORα is expressed in both retinas and RPE/choroid complexes in WT eyes, with specific staining in macrophages. Genetic deficiency of RORα significantly increases CNV lesion size in RPE/choroidal flat mounts, with increased recruitment of macrophages to CNV lesions. CNV vessel leakage is also worsened with RORα deficiency as analyzed by FFA imaging. Moreover, macrophage-specific knockout of RORa (LysM^Cre; Rora^f/f) leads to significantly larger CNV lesion areas, suggesting a negative role of RORα in regulating macrophage activity and CNV formation. Upregulation of pro-angiogenic, pro-inflammatory, and other immune-related genes are found in RORα deficient choroidal complex with induced CNV, consistent with increased CNV lesion size in the absence of RORα.

Conclusions : Our findings suggest that both systemic and macrophage deficiency of RORα worsens CNV, and indicate that RORα may be a new molecular target for inhibiting CNV in neovascular AMD.

This is a 2020 ARVO Annual Meeting abstract.