Abstract 2285: miR-133 Controls Vascular Smooth Muscle Cell Growth in vitro and in vivo
MicroRNAs (miRNAs) are an emerging class of highly conserved, non-coding small RNAs that regulate gene expression at the post-transcriptional level. Recent findings have shown that miR-1 and miR-133 play a critical role in cardiogenesis and cardiomyocyte hypertrophy. However, the role of miR-1 and miR-133 in vascular disease is currently unknown. Thus, the aim of the present study was to evaluate the role, if any, of miR-1 and miR-133 in vascular smooth muscle cell (VSMC) growth in vitro and in vivo. miR-1 and miR-133 transcripts were evaluated by quantitative real-time polymerase chain reaction (qRT-PCR) in quiescent vs. proliferating VSMCs in vitro and in vivo. VSMC were transfected in culture dishes with adenoviral vector constructs carrying miR-1 or miR133. VSMC proliferation was measured by Brdu incorporation. VSMC apoptosis was induced by H2O2 and measured by a Tdt assay. In the in vivo protocol, balloon injury of the right carotid was produced in male Wistar rats. Straight after the vascular injury, the balloon-dilated arteries were randomly transfected with adenoviral vector constructs carrying miR-133 or green fluorescent protein (GFP). An empty adenoviral vector was transfected as additional control. qRT-PCR revealed that mi-133 levels rapidly decrease as VSMCs enter the cell cycle in vitro. Overexpression of miR-133 by an adenoviral vector transfection resulted in decreased VSMC proliferation and apoptosis in vitro. Adeno-miR-1 transfection did not affect VSMC proliferation neither apoptosis in vitro. Using microarray analysis, we identified specific targets of miR-133 regulating vascular smooth muscle cell proliferation and apoptosis in vitro. Northern blot and qRT-PCR demonstrated that miR-133 is down-regulated in the balloon-dilated vascular walls 2 days after vascular injury. Importantly, the in vivo transfection of adeno-miR-133, but not adeno-miR-1, significantly reduced neointimal formation after balloon injury. In conclusions, our data show that miR-133 is a key regulator of vascular smooth muscle cell growth in vitro and in vivo, suggesting its potential therapeutic application for restenosis after percutaneous coronary interventions.