| Objective: The aim of this study is to explore the effect of pulsed electromagnetic field on autophagy of bone marrow mesenchymal stem cells and osteoporosis in ovariectomized rats.Methods: Twenty-four 3-month-old female Sprague-Dawley rats weighting 250g-300 g were assigned randomly into sham operation group(Sham group),ovariectomized model group(OVX group),ovariectomized model + pulse electromagnetic field group(PEMF group),8 rats in each group.The bilateral ovariectomized was used to construct an animal model of osteoporosis animal models in OVX group and PEMF group.The same volume of adipose tissue beside the ovaries were cut of the rats in the Sham group.Rats in the PEMF group were exposed to PEMF(whole body;3.8m T,8 Hz,40 min/day,5 days/week,for 12 weeks).The rats of Sham group and OVX group were administered as in the PEMF group,but without activating the “on” switch.After the 12-week intervention,blood was taken from the orbit of rats in each group,E2 and BALP were detected by ELISA.The left tibia was stained with HE,the right tibia was scanned by MicroCT and quantitative analyzed of bone microstructure,the left femur and the fifth lumbar vertebrae were measured by the bone density,RT-PCR was used to detect the m RNA levels of Beclin1,LC3 B,P62 and Runx-2 of bone marrow mesenchymal stem cells,and the relative expression of Beclin 1,LC3Ⅱ/Ⅰ,P62 and Runx-2 were detected by Western blot.Results:1.Serological analysis: Compared with the Sham group,serum E2 and BALP levels in the OVX group decreased significantly(P<0.001,P<0.001).Compared with the OVX group,serum E2 and BALP levels in the PEMF group increased significantly(P<0.001,P<0.001).2.Pathological section: For the Sham group,the structure of trabecular bones was complete.For the OVX group,the bone trabeculae was sparsely broken.For the PEMF group,the trabecular bone arrangement of structure is regular and connected to each other.3.Bone Mineral Density: Compared with the Sham group,the bone mineral density of the left femur and the 5th lumbar vertebra decreased significantly in the OVX group(P<0.01,P<0.01).Compared with the OVX group,the BMD of the left femur and the 5th lumbar vertebra of the PEMF group were significantly increased(P<0.05,P<0.05).4.Quantitative analysis of bone microstructure: Compared with the Sham group,Tb.N and BV/TV of the OVX group were significantly reduced(P<0.001,P<0.05),and Tb.Sp increased significantly(P<0.001)in the OVX group,while Tb.Th decreased,but it was no statistical difference(P>0.05).Compared with the OVX group,Tb.N and BV/TV in the PEMF group were increased(P<0.05,P<0.05),Tb.Sp decreased significantly(P<0.05),Tb.Th increased,but it was no statistical significance(P>0.05).5.m RNA level: For the OVX group,the m RNA levels of Beclin 1,LC3 B,and P62 were significantly increased compared with the Sham group(P<0.001,P<0.001,P<0.001),and the m RNA level of Runx-2 decreased(P<0.001).Compared with the OVX group,the m RNA levels of Beclin1,LC3 B,and P62 in the PEMF group were significantly lower(P<0.001,P<0.001,P<0.01),the m RNA level of Runx-2increased significantly(P<0.001).6.Protein expression level: The protein expression levels of Beclin1,LC3II/I and P62 in the OVX group were significantly higher than those in the Sham group(P<0.001,P<0.01,P<0.001),the protein expression level of Runx-2 decreased(P<0.001).Compared with the OVX group,the protein expression levels of Beclin1,LC3II/I,and P62 in the PEMF group were significantly decreased(P<0.01,P<0.05,P<0.01),and the protein expression level of Runx-2 increased significantly(P<0.05).Conclusion:Pulsed electromagnetic fields may be through inhibiting the autophagy of bone marrow mesenchymal stem cells,to promote bone formation,thus inhibit osteoporosis. |
