Hypoxia-driven histone modification landscape and the role of EZH2 in retinal neovascularization

Enhancer of zeste homolog 2 (EZH2) is a critical histone methyltransferase involved in catalyzing H3K27 trimethylation, regulating cell fate determination, DNA damage repair, cell proliferation, and differentiation. However, its role in retinal neovascularization (RNV) remains unclear. Here, we investigated the effects of EZH2-mediated H3K27me3 in human retinal microvascular endothelial cells (HRMECs) under hypoxic conditions. Hypoxia significantly upregulated various histone modifications in HRMECs, with the most pronounced increase in H3K27me3. Immunofluorescence confirmed increased EZH2 expression in the neo-vessels of the oxygen-induced retinopathy (OIR) model and hypoxia-treated HRMECs. Inhibition of EZH2, through specific inhibitors or siRNA, effectively reduced EZH2 and H3K27me3 levels, leading to decreased HRMEC proliferation, migration, and angiogenesis. Chromatin immunoprecipitation assays indicated that EZH2-mediated H3K27me3 suppresses miR-221 expression. Overexpression of miR-221 reproduced the effects of EZH2 inhibition, and dual-luciferase reporter assays confirmed that miR-221 directly targets KDR. Inhibition of miR-221 counteracted the KDR downregulation caused by EZH2 inhibition. Furthermore, intravitreal administration of the EZH2 inhibitor DZNeP significantly reduced RNV in OIR mice. In conclusion, our findings identify the EZH2-miR-221-KDR axis as a critical regulatory pathway in RNV and suggest that EZH2 inhibition may represent a promising therapeutic strategy for RNV-related diseases.