To investigate the effects of exposure to 50 Hz-magnetic fields on bone mesenchymal stem cells or osteoblasts alone, respectively and in combination (co-culture system).
Two experiments were performed. In the first experiment, bone mesenchymal stem cells or osteoblasts alone, respectively were exposed to a magnetic field. Different groups were examined: 1 a) sham exposure group, 1 b) 2 hours magnetic field-exposure, 1 c) 4 hours magnetic field-exposure and 1 d) 8 hours magnetic field-exposure.
In the second experiment, bone mesenchymal stem cells were co-cultured with osteoblasts and exposed to magnetic fields in the same way.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
50 Hz
Exposure duration:
2, 4 or 8 hours/day for up to 14 days
|
|
| Frequency | 50 Hz |
|---|---|
| Type | |
| Waveform | |
| Exposure duration | 2, 4 or 8 hours/day for up to 14 days |
| Exposure source | |
|---|---|
| Setup | pair of Helmholtz coils (diameter 30 cm) was placed in CO2 incubator; coil was connected to the power generator outside the incubator; plexiglas shelf was placed in the center of the coils for holding culture dishes |
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 1 mT | - | - | - | - |
From the 3. to the 7. day, cell proliferation was significantly increased in 2 hours-exposed cell cultures of bone mesenchymal stem cells and osteoblasts (alone, respectively) compared to the control group, while no significant changes were observed in the 4 or 8 hours-exposed groups.
In 4 and 8 hours-exposed bone mesenchymal stem cells, the number of alkaline phosphatase positive cells and the mineralization was significantly increased compared to the control group, while in osteoblasts, the number of alkaline phosphatase positive cells was significantly decreased in all exposure groups. In exposed (2, 4 and 8 hours) co-cultured cells, alkaline phosphatase-positive cells and mineralization were significantly increased in comparison to the sham exposed cell culture and compared to the single-cultured groups.
In exposed osteoblasts, most of the differentiation related gene expression was significantly increased in comparison to the sham exposed control, while the expression of Bmp2 and ALP was significantly decreased. In bone mesenchymal stem cells, exposure led to significant decreases in the expression of Runx2, Sp7, Col1a2, Bglap and partially to significant increases regarding Bmp2 expression. In co-cultured cell cultures, gene expression of the differentiation related genes was significantly increased after exposure when compared to the unexposed co-cultured control and mostly to the single-cultured cell cultures.
The data indicate that exposure to 50 Hz-magnetic fields could promote the differentiation of bone mesenchymal stem cells especially in combination with osteoblasts via a Bmp2-mediated cellular interaction. The authors suggest that the study might provide helpful information for the clinical application of magnetic fields in the treatment of bone diseases.
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