Pulsed electromagnetic fields increase osteogenetic commitment of MSCs via the mTOR pathway in TNF-alpha mediated inflammatory conditions: an in-vitro study

Pulsed electromagnetic fields (PEMFs) have been considered a potential treatment modality for fracture healing, however, the mechanism of their action remains unclear. Mammalian target of rapamycin (mTOR) signaling may affect osteoblast proliferation and differentiation. This study aimed to assess the osteogenic differentiation of mesenchymal stem cells (MSCs) under PEMF stimulation and the potential involvement of mTOR signaling pathway in this process. PEMFs were generated by a novel miniaturized electromagnetic device. Potential changes in the expression of mTOR pathway components, including receptors, ligands and nuclear target genes, and their correlation with osteogenic markers and transcription factors were analyzed. Involvement of the mTOR pathway in osteogenesis was also studied in the presence of proinflammatory mediators. PEMF exposure increased cell proliferation and adhesion and the osteogenic commitment of MSCs even in inflammatory conditions. Osteogenic-related genes were over-expressed following PEMF treatment. Our results confirm that PEMFs contribute to activation of the mTOR pathway via upregulation of the proteins AKT, MAPP kinase, and RRAGA, suggesting that activation of the mTOR pathway is required for PEMF-stimulated osteogenic differentiation. Our findings provide insights into how PEMFs influence osteogenic differentiation in normal and inflammatory environments.