Bone Morphogenetic Protein‐2 Decreases MicroRNA‐30b and MicroRNA‐30c to Promote Vascular Smooth Muscle Cell Calcification

BACKGROUND Vascular calcification resembles bone formation and involves vascular smooth muscle cell (SMC) transition to an osteoblast-like phenotype to express Runx2, a master osteoblast transcription factor. One possible mechanism by which Runx2 protein expression is induced is downregulation of inhibitory microRNAs (miR). METHODS AND RESULTS Human coronary artery SMCs (CASMCs) treated with bone morphogenetic protein-2 (BMP-2; 100 ng/mL) demonstrated a 1.7-fold (P<0.02) increase in Runx2 protein expression at 24 hours. A miR microarray and target prediction database analysis independently identified miR-30b and miR-30c (miR-30b-c) as miRs that regulate Runx2 expression. Real-time-polymerase chain reaction confirmed that BMP-2 decreased miR-30b and miR-30c expression. A luciferase reporter assay verified that both miR-30b and miR-30c bind to the 3'-untranslated region of Runx2 mRNA to regulate its expression. CASMCs transfected with antagomirs to downregulate miR-30b-c demonstrated significantly increased Runx2, intracellular calcium deposition, and mineralization. Conversely, forced expression of miR-30b-c by transfection with pre-miR-30b-c prevented the increase in Runx2 expression and mineralization of SMCs. Calcified human coronary arteries demonstrated higher levels of BMP-2 and lower levels of miR-30b than did noncalcified donor coronary arteries. CONCLUSIONS BMP-2 downregulates miR-30b and miR-30c to increase Runx2 expression in CASMCs and promote mineralization. Strategies that modulate expression of miR-30b and miR-30c may influence vascular calcification.