Effects of Different Concentrations of Estrogen on Proliferation and Apoptosis of Synthetic Bladder Neck Smooth Muscle Cells

Objective: To investigate the effect of different concentrations of 17β-estradiol(E2) on proliferation and apoptosis of bladder neck smooth muscle cells(BSMCs) and the possible underlying mechanisms.Methods: The synthetic(subcultured for 3-4 passages) rat bladder neck smooth muscle cells were obtained by enzyme-digesting method and exposed to gradient concentrations(0.1-1 00 nmol/L) of E2 for 72 h.The α-smooth muscle actin antibody was used to identify the cells by immunohistochemistry.The progression of cell cycle,the apoptosis and the expressions of CyclinD1 protein were examined by flow cytometry.Bcl-2 and Bax proteins were detected via Western blotting method.Results: E2(0.1-10 nmol/L) promoted BSMC proliferation by accelerating their cell cycle progression from G1 to S phases compared with that of control group(0 nmol/L E2).The rates of the BSMC at S and G2/M phase were significantly increased,while those at G0/G1 phase decreased.This was accompanied by an up-regulation of CyclinD1 expression.However,high dose of E2(10 nmol/L and 100 nmol/L) increased the rate of apoptosis of the cells accompanied by a significant raise of Bax expression and the ratio of Bax/Bcl-2.Conclusion: The effect of E2 on subcultured(synthetic) BSMC is bilateral: it promotes BSMC proliferation by enhancing the expression of CyclinD1 which accelerates G1 to S phase transition,and on the other hand,it induces apoptosis of the cells by up-regulating the expression of Bax.