Objective   To investigate the effect of pulsed electromagnetic fields (PEMFs) on the osteoblast differentiation of mouse embryonic stem cells.    Methods   The cells isolated from 4-day embryoid bodies (EBs) derived from mouse embryonic stem cells (mESCs) were inoculated into each well of cell culture plate at 5×10

4

/ml in DMEM and then cultured. During the period from 14 to 21 d after the EBs-derived single cells attachment

the cells was divided into 4 groups: control (group A)

PEMFs (group B

50 Hz

1.1 mT

twice per day

30 min per time

in an interval of 12 h)

chemical inductor (group C

50 μg/ml Vitami

n C

10 mmol/L β-glycerophosphate and 1 μmol/L  dexamethasone   in the culture medium)

B+C (group D). Histochemical staining for Alizarin Red

immunocytochemical staining for osteoclacin expression and PCR for Osterix and Cbfa-1/Runx-2 were applied to measure the osteoblast differentiation.     Results   Alizarin Red staining revealed that compared with group A

the surface area of bone nodule colonies of group B

C and D were increased respectively by 123%

229% and 262% (P0.01). The surface area of bone nodule colonies of group D was raised by 62% compared with that of group B (P0.01) and by 10% with that of group C (P0.05). Immunocytochemical staining for osteoclacin revealed that the expression of osteoclacin were the most in group D. PCR revealed that the expression of Osterix and Cbfa-1/Runx-2 of group B

C and D were more than that of group A.     Conclusion   PEMF accelerates the differentiation of mESCs to osteoblasts. Combining PEMFs and chemical inducers together have synergistic effect.