Effects Of Pulsed Electromagnetic Fields On Osteoporosis Fracture Healing And Osteoblast Proliferation And Differentiation

Objective: 1.Study the effect of pulsed electromagnetic fields(PEMFs)of different intensities on the proliferation and differentiation of osteoblasts in rats with osteoporosis fracture(OPF),to provide the best intensity parameter of PEMFs for the treatment of OPF healing.2.Study the effect of PEMFs on the fracture healing of OPF rats.Methods: 1.The SD rats of 4 months were treated with bilateral ovariectomy and middle femur osteotomy.After the successful establishment of the models,the osteoblast-like cells were extracted from the femur of the OPF rats and cultured to the third generation in vitro.Then the osteoblasts were identified by alkaline phosphatase(ALP)staining and mineralized nodule alizarin red(ARS)staining.2.Study the effects of different intensity of PEMFs on the proliferation and differentiation of osteoblasts in OPF rats.The third-generation osteoblasts were divided into five groups: A group,B group,C group,D group and control group.The first four groups were received PEMFs intervention of 1m T-50 Hz,2m T-50 Hz,3m T-50 Hz,4m T-50 Hz,respectively.The control group was not treated with PEMFs.The osteoblastic proliferation,differentiation and mineralization were respecticely evaluated using MTT assay,ALP determination of alkaline phosphatase(ALP)activities and alizarin red staining.3.Study the effect of PEMFs on fracture healing in OPF rats.The OPF rat models were divided into two groups: the control group and the treatment group.The control group was not treated with PEMFs intervention,while the treatment group was given PEMFs intervention.The bone mineral density(BMD),fracture healing score and callus morphological score were respectively evaluated using dual energy X-ray absorptiometry,Lane and Sandhu marking system and Huo and associates marking system.Results: 1.Extraction,culture and identification of osteoblasts from OPF rats.The cultured cells were confirmed to be osteoblasts by ALP staining and ARS staining.2.The proliferation and differentiation of osteoblasts were stimulated by PEMFs with different intensities.Although the absorptivity value of 1m T-50 Hz group was not significantly increased(P>0.05),the light absorption value of 2m T-50 Hz,3m T-50 Hz and 4m T-50 Hz group was significantly higher than that of the control group(P<0.05),and the light absorption value of 3m T-50 Hz group was significantly higher than in the control group(P<0.01).Compared with the control group,the ALP activity of the 2m T-50 Hz,3m T-50 Hz and 4m T-50 Hz group increased significantly(P<0.05),but that of the 1m T-50 Hz group was not significantly increased(P>0.05).The results of ARS staining of the mineralized nodules showed that the number of the mineralized nodules in the 2m T-50 Hz,3m T-50 Hz and 4m T-50 Hz group was significantly higher than that in the control group(P<0.05),while that in the 1m T-50 Hz group was not significantly higher than that in the control group(P>0.05).According to the detection of osteoblast proliferation,differentiation and mineralization,it is concluded that 3m T-50 Hz is the best parameter for the proliferation,differentiation and mineralization of osteoblasts stimulated by PEMFs in OPF rats.3.Study the effect of PEMFs on fracture healing in OPF rats.After 4 and 8 weeks of the PEMFs treatment,the BMD in the treated group was significantly higher than that in the control group(P<0.01),which indicated that PEMFs could increase the BMD of OPF,and the Lane and Sandhu fracture healing score in the treated group was significantly higher than that in the control group(P<0.01).The results showed that PEMFs could promote and accelerate the healing of OPF and the Huo and associates score of callus morphology in the treatment group was significantly higher than that in the control group(P<0.01),indicating that PEMFs could promote fracture healing.Conclusion: This study proved that PEMFs with low intensity and low frequency could promote fracture healing in the OPF rats and stimulate the proliferation,differentiation and mineralization of in vitro osteoblasts.We further demonstrated that the effects of PEMFs relied on the selection of intensity and the existence of “intensity window” for PEMFs on osteoblastic activities.