Evaluation of the Effects of a Moderate Intensity Static Magnetic Field Application on Human Osteoblast-Like Cells

There is a general interest in the effects of magnetic fields on human tissue, for biomedical imaging, cancer therapy or tissue engineering applications. In particular the orthopaedic field may greatly benefit from magnetic scaffolds, magnetic fixation and magnetic delivery techniques. In this study, MG-63 osteoblast-like cells were analysed in vitro after exposure to a 320mT static magnetic field (SMF), either continuously or applied for 1h at any 24-hour interval. Results demonstrate that SMF causes a reduction in cell number after 7 days of exposure, as demonstrated by the MTT assay. This reduction in proliferation is not associated to an increase in Lactate Dehydrogenase production, a marker of cellular stress and/or disruption of membrane integrity. Osteocalcin secretion increased at day 3 for the condition 1h/day exposure and this effect was reversed after 7 days. Instead, the continuous application of a SMF resulted in a significantly decreased osteocalcin release at day 7. Cell distribution, morphology and cytoskeleton organization were unaltered, with the typical osteoblastic morphology maintained and normal distribution of cytoplasmic actin fibrils, as demonstrated by phalloidin staining. Gene expression analysis of COL1A1, ALPL and RUNX2 show no alterations respect to control. These results suggest that such a moderate intensity static magnetic field has a detrimental effect on cell proliferation and osteocalcin secretion, while maintaining morphological features and gene expression unaltered. The in vitro effects of magnetic fields depend on cell type, magnetic field intensity and modality of application. This study gives a contribution to understand moderate strength static magnetic field effects on human tissue, with particular importance for the orthopaedic field.