MicroRNA-26a targets MAPK6 to inhibit smooth muscle cell proliferation and vein graft neointimal hyperplasia.

Neointima formation is the major reason for vein graft failure. However, the underlying mechanism is unclear. The aim of this study was to determine the role of miR-26a in the development of neointimal hyperplasia of autogenous vein grafts. Using autologous jugular vein grafts in the rat carotid artery as a model, we found that miR-26a was significantly downregulated in grafted veins as well as proliferating vascular smooth muscle cells (VSMCs) stimulated with platelet-derived growth factor-BB (PDGF-BB). Overexpression of miR-26a reduced the proliferation and migration of VSMCs. Further analysis revealed that the effects of miR-26a in VSMCs were mediated by targeting MAPK6 at the mRNA and protein levels. Luciferase assays showed that miR-26a repressed wild type (WT) MAPK6-3'-UTR-luciferase activity but not mutant MAPK6-3'-UTR-luciferease reporter. MAPK6 deficiency reduced proliferation and migration; in contrast, overexpression of MAPK6 enhanced the proliferation and migration of VSMCs. This study confirmed that neointimal hyperplasia in vein grafts was reduced in vivo by up-regulated miR-26a expression. In conclusion, our results showed that miR-26a is an important regulator of VSMC functions and neointimal hyperplasia, suggesting that miR-26a may be a potential therapeutic target for autologous vein graft diseases.