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Differentiation of Osteoprogenitor Cells is Accelerated by a Novel Delivery System of High-Frequency Pulsed Electromagnetic Fields
Chad M. Teven, B.S.1, Matthew Greives, MD2, Ryan B. Natale, M.Sc3, Daniel Kwan, M.D.2, Lisa Spiguel, M.D.2, Hue H. Luu, M.D.2, Rex Haydon, M.D., Ph.D.2, Tong-Chuan He, M.D., Ph.D.2, Russell R. Reid, M.D., Ph.D.2.
1University of Chicago Pritzker School of Medicine, Chicago, IL, USA, 2University of Chicago Medical Center, Chicago, IL, USA, 3Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA.
The major limitation in the repair of craniofacial defects lies in the finite supply of autologous tissue (i.e., bone) available. As such, other methods to produce bony healing must be explored. The delivery of low-frequency, pulsed electromagnetic fields (PEMFs) has been shown to stimulate osteogenic differentiation of progenitor cells; however this biophysical stimulus requires co-stimulants in order to achieve complete osteogenesis. The ActiPatch™ is a high-frequency, PEMF-emitting device currently utilized to ameliorate soft tissue inflammation postoperatively. We have used the ActiPatch™ as a novel PEMF delivery system to induce osteogenic differentiation in osteoprogenitor cells.
C3H10T1/2, C2C12, and mouse embryonic fibroblasts (MEFs), osteoprogenitor cells lines generally considered to be at different stages within the osteogenic hierarchy, were stimulated by the ActiPatch™ for 21 days (24 h/day). The nominal carrier frequency delivered by the ActiPatch™ is 27.1 MHz. Markers of early, intermediate and terminal osteogenic differentiation were measured and compared to unstimulated controls.
PEMF-stimulated C3H10T1/2 expressed an alkaline phosphatase (ALP) activity level 230% higher than its unstimulated counterpart on day 12 of stimulation (p<0.01). Stimulated C2C12 showed a 220% increase in its ALP activity compared to unstimulated C2C12 on day 7 (p<0.05). Stimulated MEF cells expressed slightly higher ALP activities. These elevations in early ALP rise correlated with appropriate gene upregulation, as stimulated C3H10T1/2 expressed increased mRNA levels of osteocalcin, osteopontin, Runx2, osterix, BMP-2, BMP-7, and BMP-9 by day 14 post PEMF treatment. Stimulated C3H10T1/2 also showed significantly increased bone nodule formation on day 21, while stimulated C2C12 failed to form bone nodules above baseline.
PEMFs can accelerate osteogenic differentiation in osteoprogenitor cell lines; however this induction depends on the cell type. Given that the PEMF-emitting device used in the current study is already in clinical use, our findings evoke future experiments to address the cell-specific response to this form of biophysical stimulation, the mechanism underlying high-frequency PEMF stimulation, and the potential role of this device for in vivo models of bone formation.
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