MAPK3 and endothelial dysfunction: Critically, STC1 was identified as a crucial regulator secreted from MSCs, which preserves mitochondrial morphology and functional integrity through inhibiting ERK1/2-Drp1 signaling-mediated mitochondrial fission, thus preventing hyperglycemia-induced oxidative injury, endothelial inflammation and mitochondrial apoptotic cascade, and thereby protecting against endothelial dysfunction.