Regulation of osteogenic differentiation of human adipose-derived stem cells by controlling electromagnetic field conditions

Many studies have reported that an electromagnetic field can promote osteogenic differentiation of mesenchymal stem cells. However, experimental results have differed depending on the experimental and environmental conditions. Optimization of electromagnetic field conditions in a single, identified system can compensate for these differences. Here we demonstrated that specific electromagnetic field conditions (that is, frequency and magnetic flux density) significantly regulate osteogenic differentiation of adipose-derived stem cells (ASCs) in vitro. Before inducing osteogenic differentiation, we determined ASC stemness and confirmed that the electromagnetic field was uniform at the solenoid coil center. Then, we selected positive (30/45 Hz, 1 mT) and negative (7.5 Hz, 1 mT) osteogenic differentiation conditions by quantifying alkaline phosphate (ALP) mRNA expression. Osteogenic marker (for example, runt-related transcription factor 2) expression was higher in the 30/45 Hz condition and lower in the 7.5 Hz condition as compared with the nonstimulated group. Both positive and negative regulation of ALP activity and mineralized nodule formation supported these responses. Our data indicate that the effects of the electromagnetic fields on osteogenic differentiation differ depending on the electromagnetic field conditions. This study provides a framework for future work on controlling stem cell differentiation. Researchers in Korea have determined the frequencies that optimize and inhibit bone healing using electromagnetic fields. For close to 40 years doctors have applied electromagnetic fields at the sites of bone fractures to accelerate healing, yet the mechanism by which this technique promotes bone growth remains elusive. Part of the uncertainty rests with the variability among experimental setups in common use, leading to widely uneven results. In an effort to standardize techniques, a team led by Young Hun Jeong from Korea Polytechnic University and Dong-Woo Cho from Pohang University of Science and Technology studied the effects of a wide range of electromagnetic field conditions on the bone-forming potential of adipose-derived stem cells. Among various exposures, they found that frequencies from 30 to 45 Hertz had positive effects on ossification, whereas 7.5 Hertz had an inhibitory effect.