The presence of a molecular clock maintaining a circadian rhythm in cells is known. This intracellular clock is regulated by so-called "clock genes". The set of clock genes investigated in this study is inactive under nutrient defiency conditions, but the circadian gene expression can be induced by the addition of nutrients ("serum shock stimulation"). However, also other stimuli, such as magnetic fields, could affect this intracellular clock.
Cells were divided into the following groups: 1) exposure of nutrient-limited cells to the magnetic field for 1 h and afterwards observation for 47 h, 2) induction of circadian gene expression by serum shock stimulation and afterwards exposure to the magnetic field and observation for 48 h. For each group, a corresponding sham exposure was conducted.
Each experiment was repeated three times with 3 replicates, respectively.
|Exposure duration||continuous for 1 hour|
|Setup||the coil consisted of a ferromagnetic core with a cross section of 4 x 5 cm2 equipped with two windings (550 turns each) connected in series, which were inserted around the lateral columns; in the middle of the central column, there was a 4 cm air gap for the culture flasks; magnetic flux orientation was orthogonal to the culture flask; exposure unit was positioned into a water-jacked temperature and atmosphere regulated incubator (37.0 ± 0.1°C and 5% CO2)|
|Sham exposure||A sham exposure was conducted.|
|Additional info||electric resistors in sham exposure incubator produced an average magnetic flux density of 5 µT|
|Exposure duration||continuous for up to 48 hours|
A significant circadian gene expression pattern with a robust 24 h oscillation in all genes investigated could be induced in nutrient-limited cells exposed to the magnetic field (group 1) in contrast to the corresponding sham exposed cells.
Both, cells exposed after serum shock (group 2) and the corresponding sham exposed cells showed a circadian, oscillating gene expression pattern in all genes investigated after serum shock, but cells exposed to the magnetic field showed a significant up-regulation of the gene expression rates of all genes over time in comparison to the corresponding sham exposed cells. However, the oscillation in principle pattern was not altered by the magnetic field.
The authors conclude that exposure of human dermal fibroblasts to a 50 Hz magnetic field could induce a circadian gene expression and modulate an existing circadian gene expression pattern.