| Objectives: To investigate the effect of all-trans retinoic acid on the apoptosis of vascular smooth muscle cells(VSMC) ,which cultured with or without serum ,and the expressions of Bcl-2 and Bax genes, and to explore the possible underlying mechanism of its role.Methods : Sprague-Dawley(SD) rats'thoracic aorta VSMC were primarily cultured in vitro , using 5-8 passage cells, and application MTT assay selected all-trans retinoic acid inhibited VSMC rate of 30% (for 24 hours) of the drug concentration of 1.0×10-5mol/L. Confluent VSMC population were synchronize G0 period in DMEM without FBS for 24 hours, then the SMC were randomly divided into four groups: Group A (control group, VSMC were cultured in normal DMEM medium without any interference factors for 24 hours); Group B (FBS group , cultured in normal DMEM medium with 20% FBS for 24 hours); Group C (Static group, the medium without FBS adding 1.0×10-5mol/L ATRA after 24 hours incubation) and Group D (Experimental Group, training to join 20% FBS and ATRA 1.0×10-5mol / L at the same time for 24 hours). Collecting these cells, the rate of apoptosis was examined by flow-cytometry. The expression of Bax and Bcl-2 genes were detected by RT-PCR, and we can see the VSMCS'apoptosis forms by using scanning electron microscopy.Results: (1) Without fetal bovine serum, 1.0×10-5mol/L all-trans retinoic acid could not improve the apoptosis of VSMC (apoptosis rate of the two groups had no significant difference, P = 0.423), and also apoptosis gene Bax, and Bcl-2 expression was not significantly different (The P values were respectively 0.190,0.760) , So Bax / Bcl-2 ratio unchanged(P=0.20). (2) Under the conditions of fetal bovine serum, 1.0×10-5mol / L all-trans retinoic acid can significantly promote the VSMC apoptosis (apoptosis rate of the two groups had significant difference, P <0.05), the expression of Bax increased (P <0.05), and Bcl-2 expression was not significantly different (P = 0.960). Therefore, Bax / Bcl-2 ratio increased(P<0.05).Conclusion:(1) ATRA can significantly promote the apoptosis rote of proliferation of secretory phenotype smooth muscle cells, but it has not obvious role in the smooth muscle cells quiescent.(2) ATRA could significantly promote smooth muscle apoptosis, which may be related to increased ratio of Bax / Bcl-2.
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