Background Ascending aortic dissection (AD) is a lethal vascular disease with a high mortality.Smooth muscle cell is an important component of aortic medial wall and therefore its role in the pathogenesis of aortic dissection has been emphasized.Upregulation of microRNA-145 has been reported to been involved in vessel remodeling.The present study aimed to investigate the role of miRNA-145 in aortic medial wall remodeling and the pathogenesis of AD.Methods Between August 2014 and November 2016,58 patients with aortic dissection and 58 healthy controls were enrolled in the study.Serum levels of miRNA-145 had been measured by qRTPCR.In in vitro studies,vascular smooth muscular cells were transfected with miRNA-145 mimic or negative control,respectively.The expressions of osteopontin and type Ⅲ collagen were measured by weste blot.Results Serum levels of miRNA-145 was significantly higher in patients with aortic dissection as compared with healthy controls (P ＜ 0.001).Furthermore,the expression of osteopontin and type Ⅲ collagen increased significantly in vascular smooth muscular cells transfected with miRNA-145 mimic than negative controls.Conclusion MiRNA-145 could be participating in the the pathogenesis of aortic dissection through influencing subtype transformation of smooth vascular cells and expression of collagen,indicating a novel target for intervention of aortic dissection.