To study the possibility that a sinusoidal 50 Hz magnetic field could induce cell damage and variations in the invasive properties of MG-63 cells (a human osteosarcoma cell line) when these cells are organized in a manner that simulate in vivo tumors.
The use of three-dimensional multicellular tumor spheroids, which mimic tumors in vivo, are more realistic experimental model than monolayer cell cultures to study many aspects of tumor biology.
Invasion chambers were used to study the invasive properties of tumor cells by providing a chamber with an in vitro basement membrane, which blocks non-invasive cells from migrating through it (in contrast, invasive cells are able to invade).
| Exposure | Parameters |
|---|---|
|
Exposure 1:
50 Hz
Exposure duration:
continuous for 2 days
|
|
| Frequency | 50 Hz |
|---|---|
| Type | |
| Waveform | |
| Exposure duration | continuous for 2 days |
| Exposure source |
|
|---|---|
| Chamber | The exposure system was located inside an incubator (Model 3028, Forma Scientific, Marietta, OH) and maintained at 37 ± 0.5 °C in a 5% CO2 atmosphere. |
| Setup | It consisted of a pair of coaxial circular Helmholtz coils. They each had the same diameter (30 cm) and the same number of turns (100) and were connected in series. The distance between the two coils was 15 cm. The generated magnetic field was horizontal with respect to gravity (and to the tissue culture plates). A uniformity of the magnetic field within ±5% over the exposure area of 12.5 x 8 x 2 cm was achieved. |
| Additional info | "Sham" samples were kept in the same incubator as exposed ones but inside a cylinder of Mumetal with a horizontal axis so as to be shielded from the magnetic field produced by the Helmholtz coils as well as from the terrestrial static field. The Mumetal cylinder used was 30 cm in length and 23.5 cm in diameter and was open at both ends in order to allow air circulation. The alternating magnetic field measured inside the Mumetal cylinder was close to zero (0.84 µT), measured with an accuracy of ±3%. In addition, the static component was found to be 2.2 ± 0.5% µT. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 1 mT | peak value | measured | - | - |
The data revealed no induction of cell damage by extremely low frequency magnetic fields while invasion chamber assays demonstrated a significant increase in the invasive potential of exposed spheroids.
Although both the fibronectin and CD44 (hyaluronan) receptors play an important role in cell adhesion and invasion, these two molecules do not appear to be directly involved in the variations in invasiveness observed.
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