Clinical significance of different effects of static and pulsed electromagnetic fields on human osteoclast cultures

Electromagnetic fields are known to affect the bone metabolism by modifying some relevant physiologic cell parameters of cells, even though the underlying mechanisms are still unclear. The aim of our study was to evaluate the effect of both static magnetic fields (SMFs) of the same intensity of the one generated by spinal metal devices and pulsed electromagnetic fields (PEMFs) of the same intensity used for the management of nonunion on human osteoclasts cell culture. Primary osteoclast cells were isolated from primary human osteoclast precursors and were exposed to SMFs and to PEMFs. Morphology and tartrate-resistant acid phosphatase (TRAP) activity were evaluated in the osteoclast cultures after 7, 10, and 14 days of exposure. The SMF-exposed cells show a more differentiated phenotype and a significantly higher TRAP activity after 7 and 10 days of treatment with respect to a sham control. PEMF-exposed cells have a less-differentiated phenotype after 7 days of exposure compared with the relative sham control, while the TRAP activity shows no statistically significant differences between exposed and control cells at any observation time. Our results indicate that SMFs of the same intensity of the one generated around spinal devices can affect osteoclast differentiation and activity. Aseptic loosening around titanium implants might be due in part to an increased osteoclast activity and differentiation. PEMFs of the same intensity than the one used for the management of nonunions can affect osteoclasts phenotype after 7 days of exposure, while osteoclasts TRAP activity is not affected by this kind of electromagnetic fields.