Abstract 212: MicroRNA-663 is a Novel Regulator of Human Vascular Smooth Muscle Cell Phenotypic Switch in vitro and Neointimal Formation in vivo

Abstract

Background Abnormal phenotypic switch of vascular smooth muscle cell (VSMC) is a hallmark of vascular disorders such as atherosclerosis and restenosis after angioplasty. Recently, microRNAs (miRNAs) emerge as critical regulators for vascular smooth muscle cell (VSMC) function. Our initial study identified miR-663 as one of the most sharply downregulated miRNAs in human proliferative aortic smooth muscle cells. Hypothesis MiR-663 is implicated in human VSMC phenotypic switch and the development of neointima formation. Methods and Results By using quantitative real-time PCR (qRT-PCR), we found that microRNA-663 (miR-663) was significantly downregulated in cultured human aortic VSMCs upon platelet-derived growth factor (PDGF) treatment, whereas its expression was markedly increased during VSMC differentiation as induced by either retinoid acid or SMC differentiation medium, a condition which induces SMC differentiation and inhibits cell proliferation. Furthermore, we demonstrated that overexpression of miR-663 significantly increased the expression of VSMC differentiation marker genes, such as SM22α, SM α-action, calponin, and SM myosin heavy chain, suggesting that miR-663 is a novel modulator implicated in human VSMC phenotypic switch. Moreover, miR-663 potently inhibited PDGF induced VSMC proliferation and migration. Mechanistically, we identified JunB as a downstream target of miR-663 in human VSMCs. Indeed, overexpression of miR-663 markedly inhibited the expression of the transcription factor JunB as well as its downstream molecules including matrix metallopeptidase-9 (MMP-9) and myosin light chain-9 (Myl9), thus inhibiting VSMC proliferation and migration. Finally, we showed that adeno-miR-663 markedly suppressed the neointimal lesion formation by approximately 50% in mice after vascular injury induced by carotid artery ligation, specifically via decreased JunB expression. Conclusion These results indicate that miR-663 is a novel modulator implicated in human VSMC phenotypic switch through targeting JunB expression and suggest that specific modulation of miR-663 in human VSMCs may represent a novel and attractive approach for the treatment of vascular proliferative diseases.