Choice of osteoblast model critical for studying the effects of electromagnetic stimulation on osteogenesisin vitro

Abstract

The clinical benefits of electromagnetic field (EMF) therapy in enhancing osteogenesis have been acknowledged for decades, but agreement regarding the underlying mechanisms continues to be sought. Studies have shown EMFs to promote osteoblast-like cell proliferation, or contrarily, to induce differentiation and enhance mineralization. Typically these disparities have been attributed to methodological differences. The present paper argues the possibility that the chosen osteoblast model impacts stimulation outcome. Phenotypically immature cells, particularly at low seeding densities, appear to be prone to EMF-amplified proliferation. Conversely, mature cells at higher densities seem to be predisposed to earlier onset differentiation and mineralization. This suggests that EMFs augment ongoing processes in cell populations. To test this hypothesis, mature SaOS-2 cells and immature MC3T3-E1 cells at various densities, with or without osteo-induction, were exposed to sinusoidal 50 Hz EMF. The exposure stimulated the proliferation of MC3T3-E1 and inhibited the proliferation of SaOS-2 cells. Baseline alkaline phosphatase (ALP) expression of SaOS-2 cells was high and rapidly further increased with EMF exposure, whereas ALP effects in MC3T3-E1 cells were not seen until the second week. Thus both cell types responded differently to EMF stimulation, corroborating the hypothesis that the phenotypic maturity and culture stage of cells influence stimulation outcome.

Translational Insights into Extremely Low Frequency Pulsed Electromagnetic Fields (ELF-PEMFs) for Bone Regeneration after Trauma and Orthopedic Surgery

“…In line with this, Wei et al showed that exposure to f = 48 Hz ELF-PEMF promoted proliferation (increased number of cells in S and G(2)M phase) of primary rat calvaria cells but not of MC3T3-E1 cells [33], suggesting that the observed effect is strongly dependent on the differentiation status of the cells. Bique et al observed similar effects in strongly differentiated SaOs-2 cells and less differentiated MC3T3-E1 cells exposed to f = 50 Hz ELF-PEMF [34]. This finding is supported by the work of Kaivosoja et al, which showed stimulatory effects of f = 15 Hz ELF-PEMF on proliferation being more pronounced in SaOs-2 cells when compared with less differentiated mesenchymal stem cells [35].…”

Novel lactone‐layered double hydroxide ionomer powders for bone tissue repair

“…Due to such high ion release levels, the materials synthesized need to be treated with PBS for 24 hr prior to being used with the cells in order to avoid high ion concentrations and sudden pH increases. The authors have chosen to use three osteogenic supplements with Saos‐2 in this study as have many other researchers who study the effect of different stimulus on osteogenesis and matrix production in vitro (Bique, Kaivosoja, Mikkonen, & Paulasto‐Kröckel, 2016). However, the authors have ensured that the concentration of dexamethasone was the same value for both the control and experimental groups.…”

Short Exposures to an Extremely Low-Frequency Magnetic Field (ELF MF) Enhance Protein but not mRNA Alkaline Phosphatase Expression in Human Osteosarcoma Cells

“…In the present study, we show the effects of short exposures to an Extremely Low Frequency Magnetic Field (ELF MF) on human osteosarcoma cell line SaOS-2, which is an effective and widely used in vitro model of human bone tissue [ 26 ]. SaOS-2 is a kind of osteoblast-like cell and widely used in the study of osteogenesis, expecially to analyze the effect of electromagnetic signals [ 38 , 39 ]. The wave was generated by a device recently introduced among clinical treatments of fractures or other bone diseases.…”