ALKBH5-mediated m6A modification of ID2 mRNA promotes choroidal neovascularization and subretinal fibrosis

Choroidal neovascularization (CNV) and subretinal fibrosis are pivotal in the pathogenesis of wet age-related macular degeneration (wAMD) and contribute significantly to blindness. The role of N6-methyladenosine (m6A) modifications in the progression of wAMD remains unclear. This study identifies a significant upregulation of the RNA demethylase A-ketoglutarate dioxygenase ALKB homolog 5 (ALKBH5) in macular samples of wAMD donors. Mechanistically, ALKBH5 enhances retinal microvascular endothelial cell (RMEC) migration, angiogenesis, and endothelial-mesenchymal transition (EndMT) by upregulating DNA binding/differentiation protein 2 (ID2). Further analysis reveals that ALKBH5 interacts with the YTHDF2 binding domain of the m6A reader, which recognizes the m6A sequence on ID2 mRNA. This interaction stabilizes ID2 mRNA and modulates its m6A methylation, thereby influencing the epigenetic network in wAMD. In laser-induced CNV mouse models, ALKBH5 knockdown significantly inhibits CNV and subretinal fibrosis while protecting the retinal photoreceptor layer, thus preserving visual function. This study highlights the ALKBH5-YTHDF2-ID2 axis as a critical regulator in wAMD and suggests it as a novel therapeutic target for subretinal fibrosis in wAMD.脉络膜新生血管（Choroidal neovascularization, CNV）与视网膜下纤维化是湿性年龄相关性黄斑变性（wet age-related macular degeneration, wAMD）发病机制的核心环节，亦是导致视力丧失的重要因素。目前，N6-甲基腺嘌呤（N6-methyladenosine, m6A）修饰在wAMD进展中的作用仍未明确。本研究在wAMD供体的黄斑组织样本中，发现RNA去甲基化酶α-酮戊二酸双加氧酶ALKB同源物5（A-ketoglutarate dioxygenase ALKB homolog 5, ALKBH5）的表达水平显著上调。机制研究表明，ALKBH5通过上调DNA结合/分化蛋白2（DNA binding/differentiation protein 2, ID2），增强视网膜微血管内皮细胞（retinal microvascular endothelial cell, RMEC）的迁移能力、血管生成活性及内皮-间质转化（endothelial-mesenchymal transition, EndMT）过程。进一步分析显示，ALKBH5可与识别ID2 mRNA上m6A序列的m6A阅读蛋白YTHDF2的结合域相互作用。该相互作用可稳定ID2 mRNA并调控其m6A甲基化水平，进而影响wAMD中的表观遗传调控网络。在激光诱导的CNV小鼠模型中，敲低ALKBH5可显著抑制CNV形成与视网膜下纤维化，同时对视网膜感光细胞层起到保护作用，进而维持视觉功能。本研究阐明了ALKBH5-YTHDF2-ID2轴作为wAMD的关键调控通路，并提示其可作为wAMD相关性视网膜下纤维化的新型治疗靶点。