In 1979, FDA approved the usage of pulsed electromagnetic fields for the treatment of delayed or non-healing fractures. However, the underlying mechanisms at a cellular level are still not completely understood. Both in vitro and vivo, research findings have revealed that certain electromagnetic fields, can enhance bone fracture healing and bone formation by bone marrow derived osteoblasts. Researchers also found that electromagnetic fields can either accelerate apoptosis, enhance cell proliferation or suppress cell proliferation of osteoclasts depending on the strength and frequency of the field. This indicates that electromagnetic fields could be a function generator which manipulates bone cells by different combinations of its physical parameters. If so, can we program bone cells by electromagnetic fields, such as switching the mode of osteoblasts from proliferation to apoptosis and then back to proliferation?
We developed a system to generate electromagnetic fields within an incubator. This system is capable of switching from static electromagnetic fields to pulsed electromagnetic fields and monitoring the induced magnetic field’s intensity and frequency. We studied osteoblasts and osteoclasts separately under different combinations of induced magnetic field intensity and frequency, as well as osteoblasts and osteoclasts co-culture. Based on the experiment data, we built several mathematical models trying to explain the underlying mechanism of bone cells at cellular level in an explicit formulation.
We found that exposure time of electromagnetic fields on bone cells showed no statistically significant differences. The influence of induced magnetic strength on osteoblast proliferation can be formulated with two postulated parameters of osteoblasts: (1) Adhesive coefficient and; (2) Diffusion coefficient. Alteration of these two parameters by changing induced magnetic intensity, direction and frequency can switch the mode of osteoblasts between proliferation and apoptosis. The osteoclasts have a more complicated mechanism than osteoblasts in electromagnetic fields and future research will attempt to find a targeted parameter to control.