microRNA-18a-5p promotes vascular smooth muscle cell phenotypic switch by targeting Notch2 as therapeutic targets in vein grafts restenosis

Vascular smooth muscle cells (VSMCs) phenotype switching plays a crucial role in vein graft restenosis following coronary artery bypass grafting (CABG) surgery. To discover novel clinically relevant therapeutic targets for vein graft restenosis after CABG, we therefore investigated whether miRNA-18a-5p mediated phenotype switching plays a critical role in the development of vein graft restenosis. We studied miRNA-18a-5p expression in plasma samples of patients with or without vein graft restenosis at 1, 3 and 5 years after coronary artery bypass graft surgery, and in normal vs. atherosclerotic human femoral artery samples, to prove its role in VSMC phenotype switching. We found that the expression of miRNA-18a-5p significantly increased in vein grafts restenosis rat model after bypass surgery at 7, 14, 28 days and human blood specimens with vein grafts failure after grafting surgery. Through gain- and loss-of-function approaches, we determined that miRNA-18a-5p affects VSMC proliferation, migration, differentiation, and contractility. Notch2 was found to be a direct target of miRNA-18a-5p, which is critical for VSMC phenotype switching. Finally, miRNA-18a-5p knockdown used miRNA sponge via AAV6 locally delivery in vivo, miRNA-18a-5p sponge gene transfer therapy reduced the neointimal area, neointimal thickness, and intimal/media area ratio in vein grafts compared with the controls and improved vein graft hemodynamics. miRNA-18a-5p is a critical modulator of VSMC phenotypic switch during development of vein graft restenosis by downregulating Notch2, therefore targeting miRNA-18a-5p may be a helpful strategy for the treatment of vein grafts restenosis or failure after CABG surgery.