Effects of static magnetic fields on characteristics of human osteoblasts differentiation in culture

Abstract

Various treatment modalities to enhance the bone defect healing are introduced such as bone morphogenic protein, growth factors or ultrasound. The aim of this study was to investigate the effects of static magnetic fields (SMFs), as an another modality to achieve this goal, on osteoblastic differentiation, and proliferation using a human osteosarcoma cell line (MG63). The magetic fields showed an average flux of 53mT, 73mT, 180mT, 330mT respectively. Each magnetic fields were set apart, so that the influence of the fields of the adjacent magnets would be excluded. The cells were subjected to continuous SMF exposure. To determine cell proliferation by MTT test, a human osteogenic sarcoma cell line MG63 was plated at a density of 2X104 cells per well in 96 well plates. And, to analyse the bone differentiation markers by RT-PCR, total RNA was extracted from cells by homogenizing with Trizol Rreagent on days 1, 7, and 14 of culture. Four bone differentiation markers, collagen type-1(COL-1), alkaline phosphatase (ALP), osteocalcin (OC), and osteopontin (OPN) were examined by RT-PCR. The response of SMFs on the rate of proliferation of MG63 cell were flux density-dependent. Among the 4 bone differentiation markers examined, two markers of osteoblastic phenotype (ALP and OPN) showed a increase in 330 mT through RT-PCR analysis. The effects of SMFs on ALP mRNA in MG63 cells was twice as high as control in 330 mT at only days 14 exposure after, and the effect on OPN mRNA was 6 times as high as control exceptionally in 330 mT at day 1 exposure after. On the other hand, the expression of COL-1 mRNA almost remained unchanged compared to control, and The expression of OC mRNA showed decreased tendency compared to control, irrespective of magnetic flux densities. Within the limited results, the local regulatory factors produced by SMFs-treated cells were higher than those of the control cultures, especially ALP and OPN. And, author proposes that time course of the SMF-stimulation is very critical, suggesting that events in bone formation may be modulated by SMFs. Although, animal studies and clinical trial are needed to understand the real process in the whole body, SMFs might be a good method as inducer for bone differentiation. In the future, animal studies will be needed to enhance the bone regeneration based on the this experiment.