Upregulation of miR‐146a‐5p is associated with increased proliferation and migration of vascular smooth muscle cells in aortic dissection

BACKGROUND: This study aimed to investigate whether miR‐146a‐5p was involved in the pathogenesis of thoracic aortic dissection (AD) via regulating the biological function of vascular smooth muscle cells (VSMCs). METHODS: Circulating miR‐146a‐5p level was measured by quantitative polymerase chain reaction (qPCR) in AD patients and healthy controls. Human dissected aortic samples were obtained from patients with thoracic AD Stanford type A undergoing surgical repair, and normal control samples were from organ donors who died from nonvascular diseases. The expression level of miR‐146a‐5p was detected using qPCR in each sample. The expression of SMAD4, which is involved in the TGF‐β pathway and indicated as the target gene of miR‐146a‐5p, was measured by qPCR and Western blot analysis at the mRNA level and protein level, respectively. Subsequently, VSMCs were transfected with miR‐146a‐5p mimics or inhibitors in vitro. VSMC proliferation and migration were detected using 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide and Transwell assay, respectively. Flow cytometry was used to identify apoptosis. The expression of SMAD4 in VSMCs was determined using qPCR and Western blot analysis. RESULTS: Plasma level of miR‐146a‐5p is significantly higher in the AD group as compared with the control group. The expression of miR‐146a‐5p was significantly upregulated in dissected aorta compared with controls (P < 0.05). The overexpression of miR‐146a‐5p significantly induced VSMC proliferation and migration in vitro. CONCLUSIONS: The expression of SMAD4 was modulated by miR‐146a‐5p. miR‐146a‐5p induced VSMC proliferation and migration through targeting SMAD4 and hence might be potentially involved in the development of AD.