The exposure to Static Magnetic Field (SMF) increased progressively during the last decades, impacting our everyday life. In the context of bone, the Pulsed ElectroMagnetic Field (PEMF) is largely used to promote the fracture healing and bone formation. Nevertheless, this approach presents some limitations associated with the fact that the devices generating PEMF require electrical power and patients can benefit of this system only for a limited period of time. For these reasons, researchers started to investigate the effect of the static low Magnetic Fields (MFs) on bone. In this regard, the low MFs have been implicated in the osseus fusion, osteoblasts differentiation and orientation of the bone matrix, with mechanisms that are not yet fully understood.
In this paper, Okada and colleagues studied the effect of low Magnetic Fields (MFs) on osteoblast differentiation, bone formation and cell orientation in the bone matrix. They employed two different models: an in vitro model using Bone Marrow-Derived stromal Cells (BMDCs), and an in vivo model of ectopic bone formation induced by human recombinant Bone Morphogenic Protein 2 (hrBMP2). Overall, they demonstrated that the low MFs stimulate osteoblast differentiation in vitro by inducing an upregulation of the Runx2 and Alp mRNA expression along with an increased cytochemical Alp activity. In line with this, in vivo data demonstrated that the exposure to low MFs enhanced the ectopic bone formation, improving the bone mineralization and quality. Finally, they also demonstrated, for the first time, that the low MFs influence the orientation of the BMDCs in a way that they are aligned parallel to the magnetic field. Even if further studies are required to elucidate the mechanisms mediating the effect of the of low MFs on the bone and to clarify the limits of the MFs intensity, this study demonstrated that the exposure to low MFs could be applied in the clinical practice to induce early bone regeneration with mechanical strength.