Abstract
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.
Highlights
Low-frequency, low-energy, electromagnetic fields are commonly used to promote bone fracture healing.[1,2] These electromagnetic fields enhance osteogenesis, decrease osteoporosis[3,4,5,6] and regulate diverse osteoblastic responses for osteogenesis in vitro
Electromagnetic field identification Before evaluating the effects of the electromagnetic field on adipose-derived stem cells (ASCs), we characterized the electromagnetic field generated by the solenoid coil (Figure 1a)
Here, we demonstrated that osteogenic differentiation of ASCs could be regulated by controlling the conditions of an electromagnetic field in vitro
Summary
Low-frequency, low-energy, electromagnetic fields are commonly used to promote bone fracture healing.[1,2] These electromagnetic fields enhance osteogenesis, decrease osteoporosis[3,4,5,6] and regulate diverse osteoblastic responses for osteogenesis in vitro. Two parameters primarily characterize electromagnetic field properties: frequency and magnetic flux density. The magnetic flux density used in most previous studies to induce osteogenesis varied from 0.1 to 3 mT.[6,8,9,11,12,13] Such studies have shown that a low-frequency electromagnetic field is more effective than a static field in causing biological effects.[14,15] Frequencies used for osteogenesis varied from 7.5 to 75 Hz.[5,6,7,8,11,16,17] Unlike bio-mimetic stimuli (for example, cyclic strain and shear stress), this time-varying electromagnetic field does not have logical cues for each stimulation parameter. Studies aimed at identifying optimal parameters, at least within the ranges of previous investigations, are required
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