| Summary: | 碩士 === 中原大學 === 醫學工程研究所 === 91 === Burst pulsed electromagnetic flied (bPEMF) has been shown to have a significant impact in the healing of recalcitrant bone fractures in clinical trials and animal models. It has also demonstrated that bPEMF exposure accelerated bone defect healing and induced osteogenesis in vitro. However, the mechanism involved is still unclear. In this research, we studied the dosimetry effects of bPEMF on osteoblast-like cells proliferation in vitro, and investigated the biochemical pathways of that by some inhibitors.
We found that the optimum parameters of specific 15 Hz bPEMF were exposure time 8 hours (h), magnetic field 1 gauss, exposure duration 1 day with osteoblast seeding density of 5 × 104 cells/cm2. We exposed bPEMF on rat osteoblasts in the presence of various inhibitors of signal transduction, with or without bPEMF stimulation, and evaluated the stimulation effects on the cell growth by colorimetric tetrazolium (MTT) assay, and the secretion of prostaglandin E2 (PGE2) by enzyme-linked immunosorbent assay (ELISA). Six signal transduction inhibitors were used： W-7, a calmodulin antagonist; H-7, an inhibitor of cyclic nucleotide dependent protein kinase (PKA and PKG) and protein kinase C; KT5720, a specific, cell-permeable inhibitor of protein kinase A (PKA); KT5823, a selective inhibitor of protein kinase G (PKG); Indomethacin, which inhibits prostaglandin synthesis in the cell membrane; or Bromophenacyl bromide (BPB), which inhibits phospholipase A2 in the cell membrane.
bPEMF stimulations produced a significant increase in optical density (O.D.) of MTT assay and reduced PGE2 production compared with that in the control group. KT5720, KT5823 and BPB inhibitors prevented the PGE2 secretion of osteoblasts. It means that PGE2 production probably are mediated by PKA (block by KT5720), PKG (block by KT5823) and PLA2 (block by BPB) pathway activation. The stimulation effect of cell proliferation was inhibited significantly prevented increased cellular proliferation caused by stimulation. It means that PKG pathway (block by KT5823 and H7) probably are one of the important pathways of osteoblast proliferation promotion by PEMF exposure.
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