Effect of 3.6-mT sinusoidal electromagnetic fields on proliferation and differentiation of osteoblasts in vitro.

Objective: To investigated the effect of 50-Hz 3.6-mT sinusoidal electromagnetic fields (SEMFs) on the proliferation and differentiation of osteoblasts in vitro.
Methods: The newborn rat calvarial osteoblasts were isolated by enzyme digestion and randomly divided into 6 groups after one passage. The treatment groups under 50-Hz 3.6-mT SEMFs and controls without SEMFs treatment. The cells were exposed in the SEMFs for 0.5 h, 1.0 h, 1.5 h, 2.0 h, and 2.5 h. They were observed under the contrast phase microscope each day. The calcified nodules were stained by alizarin red. The SEMFs were arranged in spiral appearance after 3 to 5 days.
Results: The SEMFs showed characteristic distribution 3 to 5 days after SEMFs treatment. On the 9(th) day after treatment, the activity of alkaline phosphatase (ALP) significantly increased in the 0.5-h group, whereas the ALP histochemical straining results and the area of calcified nodules were consistent with ALP activity. In the 48-h and 96-h groups, the genetic expression levels of osteoprotegerin and collagen-1 were significantly higher than that in the control group; particularly, the mRNA expression increased in the 0.5-h group.
Conclusion: The SEMFs at 50-Hz 3.6-mT could suppress the proliferation of osteoblasts maturation but stimulate the differentiation and maturation of osteoblasts in vitro.