Abstract

Arterial calcification is a key pathologic component of vascular diseases such as atherosclerosis, coronary artery disease and peripheral vascular disease. A hallmark of this pathological process is the phenotypic transition of vascular smooth muscle cells (VSMCs) to osteoblast-like cells. Several studies have demonstrated that microRNAs (miRNAs) regulate osteoblast differentiation, but it is unclear whether miRNAs also regulate VSMC-mediated arterial calcification. In the present study, we sought to characterize the role of miR-133a in regulating VSMC-mediated arterial calcification. Northern blotting analysis of VSMCs treated with ß-glycerophosphate demonstrated that miR-133a was significantly decreased during osteogenic differentiation. Overexpression of miR-133a inhibited VSMC transdifferentiation into osteoblast-like cells as evidenced by a decrease in alkaline phosphatase activity, osteocalcin secretion, Runx2 expression and mineralized nodule formation. Conversely, the knockdown of miR-133a using a miR-133a inhibitor promoted osteogenic differentiation of VSMCs by increasing alkaline phosphatase activity, osteocalcin secretion and Runx2 expression. Runx2 was identified as a direct target of miR-133a by co-transfection experiment in VSMCs with luciferase reporter plasmids containing wild-type or mutant 3`-UTR sequences of Runx2. Furthermore, the pro-osteogenic effects of miR-133a inhibitor were abrogated in Runx2 knockdown cells, and the inhibition of osteogenic differentiation by pre-miR-133a was reversed by overexpression of Runx2, providing functional evidence that the effects of miR-133a in osteogenic differentiation were mediated by targeting Runx2. These results demonstrate that miR-133a is a key negative regulator of the osteogenic differentiation of VSMCs.

View details for DOI 10.1210/en.2012-2236

View details for PubMedID 23798596