Downregulation of miR-542-3p promotes osteogenic transition of vascular smooth muscle cells in the aging rat by targeting BMP7.

Background: Aging is believed to have a close association with cardiovascular diseases, resulting in various pathological alterations in blood vessels, including vascular cell phenotypic shifts. In aging vessels, the microRNA(miRNA)-mediated mechanism regulating the vascular smooth muscle cell (VSMC) phenotype remains unclarified. MiRNA microarray was used to compare the expressions of miRNAs in VSMCs from old rats (oVSMCs) and young rats (yVSMCs). Quantitative reverse transcription real-time PCR (qRT-PCR) and small RNA transfection were used to explore the miR-542-3p expression in oVSMCs and yVSMCs in vitro. Calcification induction of yVSMCs was conducted by the treatment of β-glycerophosphate (β-GP). Alizarin red staining was used to detect calcium deposition. Western blot and qRT-PCR were used to investigate the expression of the smooth muscle markers, smooth muscle 22α (SM22α) and calponin, and the osteogenic markers, osteopontin (OPN), and runt-related transcription factor 2 (Runx2). Lentivirus was used to overexpress miR-542-3p and bone morphogenetic protein 7 (BMP7) in yVMSCs. Luciferase reporter assay was conducted to identify the target of miR-542-3p.

Results: Compared with yVSMCs, 28 downregulated and 34 upregulated miRNAs were identified in oVSMCs. It was confirmed by qRT-PCR that oVSMC expressed four times lower miR-542-3p than yVSMCs. Overexpressing miR-542-3p in yVSMCs suppressed the osteogenic differentiation induced by β-GP. Moreover, miR-542-3p targets BMP7 and overexpressing BMP7 in miR-542-3p-expressing yVSMCs reverses miR-542-3p's inhibition of osteogenic differentiation.

Conclusions: miR-542-3p regulates osteogenic differentiation of VSMCs through targeting BMP7, suggesting that the downregulation of miR-542-3p in oVSMCs plays a crucial role in osteogenic transition in the aging rat.