Ythdf2 loss in microglia aggravates ischemic retinopathy by increasing microglia activation and microvascular anomalies

• The expression of microglial Ythdf2 is reduced in retinal vasculopathy. • Microglia-specific knockout of Ythdf2 triggers microglial activation under both physiological and pathological conditions. • Loss of microglial Ythdf2 disrupts physiological angiogenesis and exacerbates pathological angiogenesis. • Ythdf2 directly regulates the mRNA stability of Ace and Bmp4 as an m 6 A reader. • Targeting the Ythdf2-Ace/Bmp4 network holds therapeutic potential for retinal vasculopathy. Microvascular dysfunction is a key contributor to life-threatening diseases, with retinal microvascular diseases being a leading cause of blindness. Aberrant microglia activation is critical in microvasculopathies, but the underlying molecular mechanisms remain unclear. Post-transcriptional modifications, such as N 6 -methyladenosine (m 6 A) modification, are key in these processes, yet their role in retinal vasculopathy is unexplored. We aimed to investigate the role of the m 6 A reader, YTH domain-containing family protein 2 (Ythdf2), in microglia and its involvement in retinal vasculopathy, and to uncover its underlying regulatory mechanisms. We assessed the expression of microglial Ythdf2 in the retinas of oxygen-induced retinopathy (OIR) mice using single-cell RNA sequencing (scRNA-seq). To investigate its function, we generated a microglia-specific Ythdf2 knockout mouse model and analyzed retinal microglial and vascular phenotypes under both physiological and pathological conditions. Additionally, RNA-seq and selective inhibitors were employed to explore the underlying signaling pathways. Down-regulation of Ythdf2 was observed in microglia from mice with microvascular diseases. Microglial Ythdf2 knockout in developing retinas caused aberrant microglial activation, disrupting capillary function, delaying sprouting, and accelerating vascular remodeling, thereby affecting physiological angiogenesis. In OIR retinas, Microglial Ythdf2 knockout intensified microglial activation and aggravated pathological angiogenesis. Mechanistically, Ythdf2 directly regulated the mRNA stability of Ace and Bmp4 as an m 6 A reader. Captopril (an Ace inhibitor) or noggin (a Bmp4 antagonist) alleviated microvascular retinopathy exacerbated by Ythdf2 insufficiency. Loss of Ythdf2 in retinal microglia increased their activation and caused microvascular anomalies through Ace and Bmp4, providing insights into microvascular development and disease mechanisms. These findings suggest potential therapeutic approaches targeting the Ythdf2-Ace/Bmp4 network for microvascular diseases.