ObjectiveTo study the effects of tacrolimus on intimal hyperplasia in autogenous vein grafts of rats. Methods(1) After jugular vein-to-artery bypass grafting surgery，28 male SD rats were randomly divided into the treatment group and control group, treatment group received intramuscular injections of tacrolimus 0.2 mg/(kg·d)，while the control group received saline. The vein grafts were harvested after 2 or 4 weeks of operation. HE staining was performed for histological changes of grafted vein intimal membranes; the expression level of cyclin-dependent kinase inhibitor p27 in the vein grafts was detected by western blot, the expression level of p27 was compared between two groups. (2) Human saphenous vein smooth muscle cells were treated with tacrolimus (treatment group, including four subgroups depends on the concentration gradient of tacrolimus) or PBS(control group ). Cell proliferation was assayed by MTT and migration was observed by Transwell chamber. Results(1) After 2 and 4weeks of intervention, intimal thickness in treatment group was decreased significantly in treatment group compared to control group (P＜0.05), and the decrease was more significant after 4 weeks of intervention (P＜0.01). The expression level of p27 in the treatment group was significantly higher than that in control group in treatment group (P＜0.05 or 0.01).(2) Difference concentration of tacrolimus can inhibit cell proliferation, and had the dose-dependent effect on inhibiting the cell proliferation (P＜0.01). 50% inhibiting concentration (IC50) was 390 nmol·L-1. Tacrolimus can markedly depress the migration of cells, the depression was more significant, when the concentration of tacrolimus was higher, and almost no cell was observed at the level of 2 000 nmol·L-1. ConclusionsTacrolimus can obviously inhibit hyperplasia of intimal thickness after venous transplantation, which may be related to the up-regulated expression of p27 and inhibition of smooth muscle cell proliferation and migration.

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