Mettl3‐Mediated m6A Methylation of Pdgfrb Regulates the Angiogenesis‐Dependent Bone Formation

ABSTRACT CD31 hi EMCN hi (type H) vessels orchestrate the bone metabolic microenvironment, yet the epigenetic control of their endothelial identity remains unclear. N6‐methyladenosine (m6A), catalyzed by Mettl3, is essential for mRNA fate and emerging as a regulator of skeletal homeostasis. After isolating and validating type H bone microvascular endothelial cells (H‐BMECs) from mouse femora, we used lentiviral shRNA and endothelial‐specific Cdh5‐Cre;Mettl3 fl/fl mice to silence Mettl3 in vitro and in vivo. m6A‐seq and RNA‐seq pinpointed downstream targets; qPCR, Western blot, MeRIP‐qPCR, RNA stability, migration, and tube formation assays dissected mechanisms. Local platelet‐derived growth factor‐BB (PDGF‐BB) administration was employed to rescue Mettl3 ‐null phenotypes. Mettl3 expression and global m6A levels were reduced in ovariectomy‐induced osteoporosis. Knock‐down or genetic deletion of Mettl3 decreased m6A methylation within the 3′UTR of Pdgfrb , accelerated Pdgfrb mRNA decay, blunted PI3K/AKt signaling and impaired H‐BMEC proliferation, migration and tube formation. Consequently, type H vessels and trabecular bone mass were markedly diminished. PDGF‐BB ligand delivery restored Pdgfrb abundance, reactivated PI3K/AKt, and fully reversed vascular and skeletal defects in Mettl3 ‐null mice. Mettl3‐mediated m6A methylation preserves Pdgfrb mRNA stability in bone endothelial cells and is associated with the maintenance of type H vessels, thereby coupling angiogenesis to bone formation. Targeting the Mettl3‐m6A‐Pdgfrb/PI3K‐AKt axis may represent a potential therapeutic strategy for estrogen‐deficiency‐induced bone loss.