title: Choice of osteoblast model critical for studying the effects of electromagnetic stimulation on osteogenesis in 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.
authors.affiliation: a Aalto University Department of Electrical Engineering and Automation , School of Electrical Engineering , Espoo , Finland.
authors.forename: Anna-Maria
authors.initials: AM
authors.lastname: Bique
authors.affiliation: a Aalto University Department of Electrical Engineering and Automation , School of Electrical Engineering , Espoo , Finland.
authors.forename: Emilia
authors.initials: E
authors.lastname: Kaivosoja
authors.affiliation: a Aalto University Department of Electrical Engineering and Automation , School of Electrical Engineering , Espoo , Finland.
authors.forename: Marko
authors.initials: M
authors.lastname: Mikkonen
authors.affiliation: a Aalto University Department of Electrical Engineering and Automation , School of Electrical Engineering , Espoo , Finland.
authors.forename: Mervi
authors.initials: M
authors.lastname: Paulasto-Kröckel
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation / Q000528:radiation effects; D002470:Cell Survival / Q000528:radiation effects; D055590:Electromagnetic Phenomena; D006801:Humans; D051379:Mice; D008903:Minerals / Q000378:metabolism; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*; D010012:Osteogenesis / Q000528:radiation effects*
chemical_list: D008903:Minerals; D000469:Alkaline Phosphatase
keywords: Cell proliferation and differentiation; MC3T3-E1 murine osteoblast-like cell line; SaOS-2 osteosarcoma cell line; extremely low frequency electromagnetic fields; osteoblast mineralization; osteoblast phenotype; pulsed electromagnetic fields