NAD-dependent redox control enables endothelial quiescence and vascular stabilization during angiogenesis

Angiogenesis requires endothelial cells (ECs) to toggle between quiescence versus proliferation, migration, and invasion. While activation from quiescence is well characterized, mechanisms governing the return from proliferation to quiescence (PtoQ) remain unclear. We show here that metabolic rewiring during PtoQ renders ECs sensitive to oxidative stress, requiring nicotinamide adenine dinucleotide (NAD) turnover for protection. Limiting EC NAD does not affect proliferation or migration but prevents cell-cell contact formation and quiescence acquisition during PtoQ. In vivo and ex vivo, limiting EC NAD permits initial sprouting but impairs vascular stabilization and plexus formation. Mechanistically, NAD suppresses mitochondria-derived hydrogen peroxide (H₂O₂) during PtoQ. Exogenous H₂O₂ mimics NAD deficiency, whereas its removal rescues PtoQ. In pathological settings, inhibiting NAD synthesis limits exuberant angiogenesis of retinopathy and tumors. In summary, we unveil metabolic events critical for PtoQ, a poorly studied component of angiogenesis, and point to new ways to suppress pathological angiogenesis.