| Although electric, pulsed electromagnetic, and magnetic fields have been used in attempts to accelerate bone repair in animal models and in clinical studies, the underlying cellular/molecular mechanisms responsible for new bone formation under these conditions are still not fully understood. Motivated by this need, the present in vitro study designed, assembled, and used novel laboratory systems to examine, and compare, the effects of alternating current, pulsed electromagnetic fields, and magnetic fields on select functions of osteoblasts (the bone-forming cells) pertinent to bone formation.; The three biophysical stimuli tested affected various functions of osteoblasts differently. For example, osteoblast adhesion was dependent on serum proteins. Both cell proliferation and calcium content in the extracellular matrix increased under alternating current (10 μA at 10 Hz), decreased under pulsed electromagnetic (270 μT at 15 Hz), and remained unchanged under static magnetic (700 G) stimulation for 6 hours daily for 21 consecutive days. In addition, the present study provided the first molecular-level evidence that gene expression for collagen type I (the major structural protein of the organic phase of bone) was upregulated under alternating current (10 μA at 10 Hz), downregulated under pulsed electromagnetic (270 μT at 15 Hz), and remained unchanged under static magnetic (700 G) stimulation for 6 hours daily for 21 consecutive days.; In addition to contributions to cellular physiology, the present study provided the first evidence that the electric, magnetic, and pulsed electromagnetic stimuli tested affected osteoblast functions pertinent to the composition of both the organic and inorganic phases of bone. These results provide cellular/molecular-level explanation(s) of the events that take place during bone repair under biophysical stimulation in animal models and clinical studies. Furthermore, application(s) of the knowledge of the mechanisms underlying the effects of biophysical stimuli on the cellular/molecular responses of osteoblasts could be valuable in optimizing bone-related tissue engineering strategies as well as developing alternative therapeutic techniques for accelerating bone repair, healing, and regeneration. |
