Objective:To investigate the effects of major vault protein (MVP)on the proliferation of vascular smooth muscle cells(VSMCs). Methods:The wild-type mouse VSMCs were isolated,and cultured,and the human aortic smooth muscle cells(HAoSMCs)were used. Western blot analysis was used to determine the MVP,α-SMA and SM22α. Expression of MVP stimulated by platelet-derived growth factor (PDGF-BB)or 15% fetal bovine serum (FBS) was measured. MVP siRNA was used to downregulate the MVP expression in HAoSMCs. Cell proliferation CCK-8 assay was conducted to detect the proliferation ability of VSMCs in the case of MVP deficiency or downregulation. Results:After the treatment of PDGF-BB or 15% FBS,the MVP expression of VSMCs was downregulated in a time-dependent and dose-dependent manner. Compared with wild-type mouse VSMCs,the proliferation of MVP in knockout mouse VSMCs was suppressed. MVP siRNAs inhibited FBS-induced HAoVSMCs proliferation. Conclusion:MVP may played crucial effects in the proliferation of the VSMCs.