Objective〖WTBZ〗To investigate the effects of pulsed electromagnetic fields on the proliferation of rat marrow mesenchymal stem cells induced by 5-azacytidine.  Methods Rat marrow mesenchymal stem cells induced for 7 d with 5-azacytidine were exposed or unexposed to 50 Hz pulsed electromagnetic fields and then randomly divided into A

B

C groups and 1

2

3

4 subgroups according to different inductance intensity and different exposed time. Unexposed under pulsed electromagnetic fields was control groups . Prolifera

tion capacity of rat marrow mesenchymal stem cells induced was examined by MTT method. Cell cycle was detected by flow cytometry.  Results Under 0.5 mT and 1 mT inductance intensity for 20-30 min rat marrow mesenchymal stem cells induced by 5-azacytidine were proliferated significantly in comparison with control groups

while restrained significantly proliferation cell under 0.5 mT and 1 mT inductance intensity for 30-60 min compared with control groups. Cell cycle at S+G

2

was increased under 0.5 mT and 1 mT inductance intensity for 20-30 min and decreased under 3 kinds inductance intensity for 60 min and 5 mT over 30 min versus control groups.  Conclusion 50 Hz pulsed electromagnetic field at 0.5 mT and 1 mT inductance intensity for 20-30 min can promote the proliferation of mesenchymal stem cells by increasing cells at S and G

2

stage.