MicroRNA-125b Affects Vascular Smooth Muscle Cell Function by Targeting Serum Response Factor.

BACKGROUND/AIMS: Increasing evidence links microRNAs to the pathogenesis of peripheral vascular disease. We recently found microRNA-125b (miR-125b) to be one of the most significantly down­regulated microRNAs in human arteries with arteriosclerosis obliterans (ASO) of the lower extremities. However, its function in the process of ASO remains unclear. This study aimed to investigate the expression, regulatory mechanisms, and functions of miR-125b in the process of ASO. METHODS: Using the tissue explants adherent method, vascular smooth muscle cells (VSMCs) were prepared for this study. A rat carotid artery balloon injury model was constructed to simulate the development of vascular neointima, and a lentiviral transduction system was used to overexpress serum response factor (SRF) or miR-125b. Quantitative real­time PCR (qRT­PCR) was used to detect the expression levels of miR­125b and SRF mRNA. Western blotting was performed to determine the expression levels of SRF and Ki67. In situ hybridization analysis was used to analyze the location and expression levels of miR-125b. CCK-8 and EdU assays were used to assess cell proliferation, and transwell and wound closure assays were performed to measure cell migration. Flow cytometry was used to evaluate cell apoptosis, and a dual-luciferase reporter assay was conducted to examine the effects of miR­125b on SRF. Immunohistochemistry and immunofluorescence analyses were performed to analyze the location and expression levels of SRF and Ki67. RESULTS: miR-125b expression was decreased in ASO arteries and platelet-derived growth factor (PDGF)-BB-stimulated VSMCs. miR-125b suppressed VSMC proliferation and migration but promoted VSMC apoptosis. SRF was determined to be a direct target of miR-125b. Exogenous miR-125b expression modulated SRF expression and inhibited vascular neointimal formation in balloon-injured rat carotid arteries. CONCLUSIONS: These findings demonstrate a specific role of the miR-125b/SRF pathway in regulating VSMC function and suggest that modulating miR-125b levels might be a novel approach for treating ASO.