Experimental Study On The Effects Of High Static Magnetic Field On Biological Behavior And Iron Metabolism In Bone Tissue

Static magnetic field(SMF)is a magnetic field which the direction and intensity of magnetic field do not change with time.SMF can be divided into three classes based on magnetic field strength,including hypomagnetic field(<5 ?T),weak magnetic field(5 ?T-1 m T),moderate magnetic field(1 m T-1T)and high magnetic field(>1 T).With the rapid development of industrial technology and biomedical science,human beings have more and more opportunities to be exposed to SMF with higher-intensity.The most common high static magnetic field(Hi SMF)is the MRI scanner in hospitals.For the biological effects of Hi SMF,there are only some short-term exposure reports,and they focus on the study of brain,heart and blood.There are few studies pay attention to the effects of Hi SMF on the skeletal system.Although magnetic fields and iron have a natural connection,there are few studies involve the regulation of cellular or the body's iron metabolism by magnetic fields.Furthermore,iron is an essential element to maintain the balance of normal bone remodeling.A large number of studies have shown that iron overload or iron deficiency can affect the biological functions of osteoblasts and osteoclasts,eventually causing osteoporosis.Therefore,how does a Hi SMF affect the biological behavior of bone tissue,including bone cells and bone? How does a Hi SMF affect the iron metabolism of bone tissue? Is the effect of Hi SMF on the biological behavior of bone tissue related to changes in bone iron metabolism?In this study,the changes of biological behavior and cellular iron metabolism in osteoblasts(MC3T3-E1),osteoclasts(Raw264.7)and ostecytes(MLO-Y4)were studied using a 16 T Hi SMF.The effects of Hi SMF on bone structure and function,bone tissue cells and bone iron metabolism in normal mice were studied by using the Hi SMF of 2-4 T,6-8 T and 10-12 T.The effects of Hi SMF on bone structure and function and bone iron content were studied in osteoporosis mice induced by hindlimb unloading(HLU).The results of cell experiments showed that 16 T Hi SMF promoted the proliferation of osteoblasts and increased the cellular iron content,and facilitated osteoblast differentiation while reduced iron levels in osteoblasts.Hi SMF significantly inhibited osteoclast differentiation and bone resorption ability,and decreased iron content and oxidative stress levels in osteoclasts.Hi SMF promoted cell activity,reduced cell apoptosis,and increased fractal dimension of cytoskeleton in osteocytes.The level of iron content in osteocytes was elevated by Hi SMF.These results suggest that Hi SMF affect the biological behavior of bone cells in vitro,and the potential mechanism may be the regulation of cellular iron metabolism by Hi SMF.Animal experiment showed that Hi SMF of 2-4 T significantly improved the microstructure and mechanical properties of femur in normal mice,and reduced iron levels in femur.Hi SMF of 6-8 T and 10-12 T destroyed the microstructure and mechanical properties of femur,and had a tendency to increase femoral iron levels.The iron content of the lumbar vertebrae was increased in Hi SMF of 10-12 T.In the mice of osteoporosis induced by HLU,compared with the geomagnetic field(GMF),Hi SMF of 2-4 T enhanced the recovery of the damaged femoral microstructure and mechanical properties,and significantly decreased iron levels of femur in osteoporotic mice.Hi SMF of 6-8 T and 10-12 T inhibited the recovery of damaged microstructure of femur,and increased iron content was not restored in osteoporotic mice.These results suggest that the structure and mechanical properties of bone are promoted by 2?4T Hi SMF,and are inhibited by 6-8 T and 10-12 T Hi SMF,and the potential mechanism is that bone iron metabolism is affected by Hi SMF.In summary,these findings suggested that the effects of Hi SMF on bone iron metabolism were involved in the regulation of Hi SMF on biological behavior of bone tissue.These findings contribute to understanding the biological function and potential mechanism of Hi SMF on bone cells and skeletal system,and providing a theoretical basis to develope the magnetic therapy equipment which is used for adjuvant therapy on osteoporosis in the future.