The long-term stimulation of hyperglycemia greatly increases the incidence of vascular restenosis (RS) after angioplasty. Neointimal hyperplasia after vascular injury is the pathological cause of RS, but its mechanism has not been elucidated. MicroRNA-24 (miR-24) has low expression in the injured carotid arteries of diabetic rats. However, the role of miR-24 in the vascular system is unknown. In this study, we explore whether over-expression of miR-24 could attenuate neointimal formation in streptozotocin (STZ)-induced diabetic rats. Adenovirus (Ad-miR-24-GFP) was used to deliver the miR-24 gene to injured carotid arteries in diabetic rats. The level of neointimal hyperplasia was examined by hematoxylin-eosin (HE) staining. Vascular smooth muscle cell (VSMC) proliferation in the neointima was evaluated by immunostaining for proliferating cell nuclear antigen (PCNA). The mRNA levels of miR-24, PCNA, wingless-type MMTV integration site family member 4 (Wnt4), disheveled-1 (Dvl-1), β-catenin and cell cycle-associated molecules (Cyclin D1, p21) were determined by Quantitative Real-Time PCR (qRT-PCR). PCNA, Wnt4, Dvl-1, β-catenin, Cyclin D1 and p21 protein levels were measured by Western blotting analysis. STZ administration decreased plasma insulin and increased fasting blood glucose in Sprague-Dawley (SD) rats. The expression of miR-24 was decreased in the carotid artery after a balloon injury in diabetic rats, and adenoviral transfection (Ad-miR-24-GFP) increased the expression of miR-24. Over-expression of miR-24 suppressed VSMC proliferation and neointimal hyperplasia in diabetic rats at 14 days. Furthermore, compared with Sham group, the mRNA and protein levels of PCNA, Wnt4, Dvl-1, β-catenin, and Cyclin D1 were strikingly up-regulated in the carotid arteries of diabetic rats after a balloon injury. Interestingly, up-regulation of miR-24 significantly reduced the mRNA and protein levels of these above molecules. In contrast, the change trend in p21 mRNA and protein levels was opposite after a balloon injury. However, over-expression of miR-24 after gene delivery increased the mRNA and protein levels of p21. We conclude that over-expression of miR-24 could attenuate VSMC proliferation and neointimal hyperplasia after vascular injuries in diabetic rats. This result is possibly related to the regulation of the expression of Cyclin D1 and p21 through the Wnt4/Dvl-1/β-catenin signaling pathway.
Keywords: carotid artery balloon injury; hyperglycemia; microRNA-24; neointimal hyperplasia; vascular restenosis; vascular smooth muscle cells.