Bone Morphogenetic Protein-2 Signaling in the Osteogenic Differentiation of Human Bone Marrow Mesenchymal Stem Cells Induced by Pulsed Electromagnetic Fields.

Fernanda Martini,Elisa Mazzoni,Agnese Pellati,Deyanira Contartese,Simona Salati,Gaetano Caruso,Monica De Mattei

doi:10.3390/ijms21062104

Abstract

Pulsed electromagnetic fields (PEMFs) are clinically used with beneficial effects in the treatment of bone fracture healing. This is due to PEMF ability to favor the osteogenic differentiation of mesenchymal stem cells (MSCs). Previous studies suggest that PEMFs enhance the osteogenic activity of bone morphogenetic protein-2 (BMP2) which is used in various therapeutic interventions. This study investigated the molecular events associated to the synergistic activity of PEMFs and BMP2 on osteogenic differentiation. To this aim, human MSCs (hMSCs) were exposed to PEMFs (75 Hz, 1.5 mT) in combination with BMP2, upon detection of the minimal dose able to induce differentiation. Changes in the expression of BMP signaling pathway genes including receptors and ligands, as well as in the phosphorylation of BMP downstream signaling proteins, such as SMAD1/5/8 and MAPK, were analyzed. Results showed the synergistic activity of PEMFs and BMP2 on osteogenic differentiation transcription factors and markers. The PEMF effects were associated to the increase in BMP2, BMP6, and BMP type I receptor gene expression, as well as SMAD1/5/8 and p38 MAPK activation. These results increase knowledge concerning the molecular events involved in PEMF stimulation showing that PEMFs favor hMSCs osteogenic differentiation by the modulation of BMP signaling components.

Highlights

Impaired fracture healing represents a major clinical problem that can lead to serious consequences and patient disability
During osteogenic differentiation of human MSCs (hMSCs) cultured in the presence of pulsed Electromagnetic field (EMF) (PEMFs) and bone morphogenetic protein-2 (BMP2) used alone or in combination, we investigated changes in the gene expression of Bone morphogenetic proteins (BMPs) signaling pathway components including receptors, ligands, and nuclear target genes as well as the earlier events involved in BMP signaling, including activation of SMAD1/5/8 and mitogen-activated protein kinases (MAPKs)
Preliminary experiments were executed to evaluate the lowest dose of BMP2 able to stimulate osteogenic differentiation of hMSCs cultured in osteogenic medium (OM)

Summary

Introduction

Impaired fracture healing represents a major clinical problem that can lead to serious consequences and patient disability. Bone fractures heal by standard clinical practices, approximately 10% patients suffer from delayed unions or non-unions [1]. Electromagnetic field (EMF) exposure represents a safe and efficient non-surgical treatment in promoting bone ununited fracture healing in clinics [2,3,4]. EMFs have been shown to promote the differentiation of MSCs, including human MSCs (hMSCs) derived from different tissues, toward the osteoblastic lineage by increasing osteogenic transcription factor gene expression and the production of bone matrix components [7,8,9,10,11,12]. It has been reported that pulsed EMFs (PEMFs) increase the activity of bone morphogenetic protein-2 (BMP2), an essential growth factor for bone cells [6,7,15]

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