Stimulation of osteogenic differentiation in human osteoprogenitor cells by pulsed electromagnetic fields: an in vitro study

Abstract

BackgroundAlthough pulsed electromagnetic field (PEMF) stimulation may be clinically beneficial during fracture healing and for a wide range of bone disorders, there is still debate on its working mechanism. Mesenchymal stem cells are likely mediators facilitating the observed clinical effects of PEMF. Here, we performed in vitro experiments to investigate the effect of PEMF stimulation on human bone marrow-derived stromal cell (BMSC) metabolism and, specifically, whether PEMF can stimulate their osteogenic differentiation.MethodsBMSCs derived from four different donors were cultured in osteogenic medium, with the PEMF treated group being continuously exposed to a 15 Hz, 1 Gauss EM field, consisting of 5-millisecond bursts with 5-microsecond pulses. On culture day 1, 5, 9, and 14, cells were collected for biochemical analysis (DNA amount, alkaline phosphatase activity, calcium deposition), expression of various osteoblast-relevant genes and activation of extracellular signal-regulated kinase (ERK) signaling. Differences between treated and control groups were analyzed using the Wilcoxon signed rank test, and considered significant when p < 0.05.ResultsBiochemical analysis revealed significant, differentiation stage-dependent, PEMF-induced differences: PEMF increased mineralization at day 9 and 14, without altering alkaline phosphatase activity. Cell proliferation, as measured by DNA amounts, was not affected by PEMF until day 14. Here, DNA content stagnated in PEMF treated group, resulting in less DNA compared to control.Quantitative RT-PCR revealed that during early culture, up to day 9, PEMF treatment increased mRNA levels of bone morphogenetic protein 2, transforming growth factor-beta 1, osteoprotegerin, matrix metalloproteinase-1 and -3, osteocalcin, and bone sialoprotein. In contrast, receptor activator of NF-κB ligand expression was primarily stimulated on day 14. ERK1/2 phosphorylation was not affected by PEMF stimulation.ConclusionsPEMF exposure of differentiating human BMSCs enhanced mineralization and seemed to induce differentiation at the expense of proliferation. The osteogenic stimulus of PEMF was confirmed by the up-regulation of several osteogenic marker genes in the PEMF treated group, which preceded the deposition of mineral itself. These findings indicate that PEMF can directly stimulate osteoprogenitor cells towards osteogenic differentiation. This supports the theory that PEMF treatment may recruit these cells to facilitate an osteogenic response in vivo.

Bone Morphogenic Protein--mRNA upregulation after exposure to low frequency electric field

“…This observation was confirmed by Jansen et al [23] who showed, using a pulsed electromagnetic field, an enhanced mineralisation on bone marrow derived stromal cells in parallel with the increase of the mRNA levels of BMP-2 measured by real time rtPCR. They also concluded that there was an induction of differentiation at the expense of proliferation.…”

Harnessing magnetic-mechano actuation in regenerative medicine and tissue engineering

“…Magnetically induced cytoskeletal rearrangements can activate different mechanosensors embedded in the plasma membrane, such as stretch-activated ion channels and integrins [51], as well as signalling pathways such as the p38/MAPK pathway ( Figure 1A) [52]. Such changes can also improve cell survival and viability, decrease the amount of apoptotic molecules (e.g., caspases), increase the amount of antiapoptotic molecules (e.g., bcl-2), diminish the expression of pluripotent genes [53], or accelerate osteoblast differentiation, bone regeneration, and mineralisation [52,54]. Although these cellular events are mediated by the Rho/ROCK and MAPK mechanotransduction signalling pathways, other pathways such as the AKT/PI3K pathway, which is linked to the regulation of the cell cycle and directly related to cell proliferation, can play an important role.…”

Magnetic responsive hydroxyapatite composite scaffolds construction for bone defect reparation

“…Research has indicated that magnetic fields may stimulate the proliferation and differentiation of osteoblasts, promote the expression of growth factors such as bone morphological protein, increase osteointegration, and accelerate new bone formation. [1][2][3][4] Magnetic fields were also found to be beneficial in promoting the integration of bone and implants, increasing bone density and calcium content, and accelerating the healing of bone fractures. [5][6][7][8] Among the magnetic materials usually used in the biomedical field, magnetic nanoparticles (MNPs) have drawn great interest owing to their unique magnetic properties, including the fact that they become superparamagnetic at diameters of ,20 nm.…”