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Keywords:

  • static magnetic field;
  • magnetic field gradient;
  • osteoblast;
  • cyclooxygenase 2;
  • transcription factor nuclear factor kappa B

Abstract

Exposure to static magnetic fields (SMFs) has been reported to promote osteoblast differentiation in vitro, and increase bone formation in vivo and in clinical studies. Prostaglandins respond early to exogenous mechanical loading, and play an important role in bone formation. In this study, we investigated whether exposure to a strong SMF affects prostaglandin E2 (PGE2) secretion from a mouse osteoblastic cell line, MC3T3-E1. We also investigated the PGE2-synthesizing enzyme, cyclooxygenase 2 (Cox-2), and translocation of the transcription factor nuclear factor kappa B (NF-κB), which is involved in the induction of Cox-2 expression. In the SMF exposures, experiments were performed at the 10 T-exposure position, at which the magnetic flux density was highest, and at the 6 T-exposure position, at which the magnetic field gradient was highest (41.7 T/m). PGE2 secretion was not affected by exposure at the 10 T-exposure position compared to sham-exposure, but was enhanced at the 6 T-exposure position (about 1.5-fold). Similarly, Cox-2 expression and NF-κB translocation were not enhanced at the 10 T-exposure position, but increased at the 6 T-exposure position (about twofold, two- to threefold, respectively). These findings suggested that exposure to a high magnetic field gradient induced secretion of PGE2 and expression of the Cox-2 protein, which was mediated through increased translocation of NF-κB. Bioelectromagnetics 29:277–283, 2008. © 2007 Wiley-Liss, Inc.