Abstract: Objective: To explore the effects of the Yishenhuoxue Capsule(YSHXC) on the proliferation of vascular smooth muscle cells (VSMCs) induced by HCY in rabbits. Methods: VSMCs were cultured by tissue explants in vitro and were induced proliferation by HCY. Cells were divided into four groups: the control group, the HCY group, the Yishenhuoxue group and the folic acid group. The proliferation of cells, the expression of PCNA and cell cycles were determined by MTT, immunohistochemistry and flow cytometric technique respectively. Results: After separately incubated with Yishenhuoxue and folic acid, the expression of PCNA was effectively reduced（P<0.01）　and that was especially in the Yishenhuoxue group（P<0.05）. Cell cycles were also homologously changed. Compared with the HCY group, the cell number of the Yishenhuoxue group in the G0/G1 period was increased while in the S period was decreased, which showed that the cell number in the synthesis period of DNA remarkably went down（P<0.01）. Conclusion: Yishenhuoxue can significantly inhibit the proliferation of cells induced by HCY and bring down the level of PCNA, which may be related to the change of cell cycle. Therefore Yishenhuoxue Capsule can delay the process of atheroscleorsis in the earlier period.

Key words: Yishenhuoxue Capsule, Vascular smooth muscle cells, Proliferation, Cell cycle, Proliferating cell nuclear antigen