Study type: Medical/biological study (experimental study)

Effect of 1 mT Sinusoidal Electromagnetic Fields on Proliferation and Osteogenic Differentiation of Rat Bone Marrow Mesenchymal Stromal Cells. med./bio.

Published in: Bioelectromagnetics 2013; 34 (6): 453-464

Aim of study (acc. to author)

To evaluate the influence of an extremely low frequency magnetic field on the cell viability, proliferation and osteogenic differentiation of rat bone marrow mesenchymal stromal cells.

Background/further details

Electromagnetic and magnetic fields are commonly used in bone regenerative medicine. However, the optimal parameters (for example frequency) are not clear and the cellular mechanisms remain poorly understood.
Latex was used as a positive control for cell death.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 10 Hz
Exposure duration: 6 h cycle (2 h exposure followed by 4 h no exposure) for up to 3 weeks
Exposure 2: 30 Hz
Exposure duration: 6 h cycle (2 h exposure followed by 4 h no exposure) for up to 3 weeks
Exposure 3: 50 Hz
Exposure duration: 6 h cycle (2 h exposure followed by 4 h no exposure) for up to 3 weeks
Exposure 4: 70 Hz
Exposure duration: 6 h cycle (2 h exposure followed by 4 h no exposure) for up to 3 weeks

Exposure 1

Main characteristics
Frequency 10 Hz
Type
Waveform
Exposure duration 6 h cycle (2 h exposure followed by 4 h no exposure) for up to 3 weeks
Exposure setup
Exposure source
Chamber cells were cultured in culture flasks or in six well plates and placed between the coils on a 15 cm high transparent polymethylmethacrylate holder in an incubator
Setup magnetic fields were produced by a pair of Helmholtz coils, 30 cm in diameter and 30 cm apart; Helmholtz coils were positioned in an incubator at 37°C; coils were orientated on the left and right sides of the flasks and plates; magnetic fields were parallel to the bottom of the flasks and plates
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 1 mT peak value - - -
electric field strength 0.09 mV/m maximum calculated - -
current density 0.135 A/m² maximum calculated - -

Exposure 2

Main characteristics
Frequency 30 Hz
Type
Waveform
Exposure duration 6 h cycle (2 h exposure followed by 4 h no exposure) for up to 3 weeks
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 1 mT peak value - - -
electric field strength 0.27 mV/m maximum calculated - -
current density 0.405 A/m² maximum calculated - -

Exposure 3

Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration 6 h cycle (2 h exposure followed by 4 h no exposure) for up to 3 weeks
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 1 mT peak value - - -
electric field strength 0.45 mV/m maximum calculated - -
current density 0.675 A/m² maximum calculated - -

Exposure 4

Main characteristics
Frequency 70 Hz
Type
Waveform
Exposure duration 6 h cycle (2 h exposure followed by 4 h no exposure) for up to 3 weeks
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 1 mT peak value - - -
electric field strength 0.63 mV/m maximum calculated - -
current density 0.945 A/m² maximum calculated - -

Reference articles

  • Bassen H et al. (1992): ELF in vitro exposure systems for inducing uniform electric and magnetic fields in cell culture media.

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • during exposure
  • after exposure

Main outcome of study (acc. to author)

After one and two weeks, the cell viability was decreased in the 50 Hz and 70 Hz samples in comparison to the other samples. However, exposure to 10 Hz, 30 Hz and 50 Hz, but not 70 Hz enhanced the proliferation of the cells compared to the sham exposed sample.
After one week, the protein expression of osteocalcin and bone morphogenetic protein-2 in the culture medium was significantly increased in the exposed samples compared to the values measured after one day. After two weeks, the values remained elevated.
The expression of the alkaline phosphatase and collagen type 1 was significantly increased in the 10 Hz sample after one week compared to all other samples, while after two weeks, these expression values were increased especially in the 50 Hz sample. The expression level of fibroblast growth factor-2 in the 10 Hz sample was significantly increased after two weeks of exposure compared to all other samples, while the expression level of fibroblast growth factor receptor-2 was significantly increased after one and two weeks in the 30 Hz sample.
After 3 weeks, in the 50 Hz sample, the percentage of mineralized areas and the percentage of osteocalcin/bone morphogenetic protein-2 positive cells were significantly higher than in the sham exposure, 10 Hz and 70 Hz samples. Regarding cell morphology, no difference among the samples was observed.
The authors conclude that magnetic field exposure to 10 Hz and 50 Hz may be a promising therapeutic approach in bone regenerative medicine and should be further examined.

Study character:

Study funded by

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