MicroRNA-204 Targets Runx2 to Attenuate BMP-2-induced Osteoblast Differentiation of Human Aortic Valve Interstitial Cells

Osteoblast differentiation of valve interstitial cells (VICs) is a key step in valve calcification, but the molecular mechanisms involved are not fully understood. In this study, we aimed to investigate whether microRNA (miR)-204-regulated VICs differentiation through modulation of runt-related transcription factor 2 (Runx2), a key transcription factor for osteogenesis. Our data demonstrated that miR-204 was markedly downregulated in both human calcified aortic valves and bone morphogenetic protein (BMP)-2-stimulated aortic VICs. In vitro experiments showed that miR-204 acted as a negative regulator of osteogenic differentiation by repressing Runx2 and thereby inhibiting expression of osteoblast-related genes, including alkaline phosphatase and osteocalcin, which were all induced by BMP-2. Luciferase reporter assays validated Runx2 as the direct target of miR-204. Furthermore, increased alkaline phosphatase activity and osteocalcin expression after miR-204 inhibition were abolished by small interfering RNA-mediated silencing of Runx2. Overall, these data suggested miR-204 as a possible molecular switch inhibiting osteoblastic transdifferentiation of human aortic VICs and targeting miR-204 may have therapeutic potential for human aortic valve calcification.