The effects of exposure of human mesenchymal stem cells to a combined static and 50 Hz magnetic field on osteogenesis and differentiation towards a bone phenotype should be investigated.
The combined static and 50 Hz magnetic field was used to generate a Ca2+-ion cyclotron resonance frequency, which was found to have biological effects in former studies by the authors (Ledda et al. (2013), De Carlo et al. (2012), Gaetani et al. (2009)).
Dexamethasone, a glucocorticoid, was used as a positive control and in a co-exposure, as it induces the osteogenic differentiation of human mesenchymal stem cells.
Cells were divided into the following groups: 1) combined magnetic field, 2) dexamethasone (100 nM), 3) combined magnetic field and dexamethasone and 4) untreated control group.
Cells were exposed after 3, 4 and 5 weeks of cultivation for 3 and 5 days, respectively, and were analyzed thereafter. Additionally, cells were examined 3 days after termination of exposure.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
0–50 Hz
Exposure duration:
continuous for 3 or 5 days
|
| Frequency | 0–50 Hz |
|---|---|
| Type | |
| Waveform | |
| Exposure duration | continuous for 3 or 5 days |
| Exposure source | |
|---|---|
| Chamber | mu-metal shielded room |
| Setup | exposure system consisted of a cellular incubator made of polymethyl methacrylate with 37°C ± 0.1°C and 5% CO2 and a solenoid (5-mm-thick polyvinyl chloride cylinder with 3.3 m length and 33 cm diameter made of 3300 turns of 1 mm diameter copper wire) |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 66 µT | - | - | - | static magnetic field |
| magnetic flux density | 1 mT | effective value | - | - | 50 Hz magnetic field |
Cell proliferation was significantly reduced in the magnetic field exposure group (group 1) and MF/dexamethasone co-exposure group (group 3) compared to the control group and dexamethasone exposure group (group 2), respectively, in 3- and 4-week-old cell cultures. After 5 weeks, however, proliferation was significantly increased in group 1 compared to the control group.
Morphologically, groups 1 and 2 showed distinct differences which had larger, polygonal-shaped cells and a widespread actin network compared to the control group with elongated spindle-shaped cells and peripheral actin filaments. In group 3, this appearance was even more pronounced.
The gene expressions of several osteogenic markers, except for osteoprotegerin, were significantly upregulated in group 1 (MF alone) and group 3 (co-exposure) compared to the control group and group 2 (dexamethasone alone), respectively (remark EMF-Portal: results in text and figure are contradictory and not clear). The gene expression of osteoprotegerin was significantly reduced in groups (co-)exposed to dexamethasone (2 and 3) and significantly increased in group 2 compared to the control group.
The protein expressions of alkaline phosphatase and osteopontin were significantly upregulated in all exposure groups 1-3 compared to the control group.
The authors conclude that exposure of human mesenchymal stem cells to a combined static and 50 Hz magnetic field could induce a differentiation towards a bone phenotype and a sustainable stimulation of osteogenesis, what might be of therapeutic use.
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