Study type: Medical/biological study (experimental study)

Electromagnetic fields affect transcript levels of apoptosis-related genes in embryonic stem cell-derived neural progenitor cells. med./bio.

Published in: FASEB J 2005; 19 (12): 1686-1688

Aim of study (acc. to editor)

To study different effects (e.g. different transcript levels, genotoxicity, proliferation, apoptosis, cytotoxicity, mitochondrial function) of radiofrequency (1.71 GHz) and extremely low frequency (50 Hz) electromagnetic fields on mouse embryonic stem cells (ES).

Background/further details

For differentiation of neural cells, ES cells were cultivated in "hanging drops" as embryonic bodies (EB). Exposure was performed at a stage when nestin-positive progenitor cells developed (from EBs).

Endpoint

Exposure

Exposure Parameters
Exposure 1: 1.71 GHz
Modulation type: pulsed
Exposure duration: intermittent, 5 min on/30 min off, for 6 h and 48 h
  • SAR: 1.5 W/kg average over time
Exposure 2: 50 Hz–1.25 kHz
Exposure duration: intermittent, 5 min on/30 min off, for 6 h and 48 h

Exposure 1

Main characteristics
Frequency 1.71 GHz
Type
Charakteristic
  • guided field
Exposure duration intermittent, 5 min on/30 min off, for 6 h and 48 h
Additional info Uplink band of GSM 1800 system
Modulation
Modulation type pulsed
Pulse width 0.576 ms
Duty cycle 12.5 %
Repetition frequency 217 Hz
Pulse type rectangular
Exposure setup
Exposure source
Chamber Two R14 waveguide chambers containing field and temperature sensors were placed in a humidified incubator (5% CO2, 37°C). Sensor-monitored fans enforced airflow through the waveguide chamber and kept the temperature difference between sham and EMF exposed cultures below 0.2°C.
Setup The RF signal was directed via computer-controlled RF switch to one of the waveguide chambers (blinded). Petri dishes (60 mm diameter) were positioned in the H-field maximum of a standing wave and exposed in E-polarization.
Sham exposure A sham exposure was conducted.
Additional info EMF exposure was performed under defined conditions with respect to field strengths, polarization, modulation, and temperature [Kuster et al., 2000].
Parameters
Measurand Value Type Method Mass Remarks
SAR 1.5 W/kg average over time measured and calculated - -

Exposure 2

Main characteristics
Frequency 50 Hz–1.25 kHz
Type
Waveform
Exposure duration intermittent, 5 min on/30 min off, for 6 h and 48 h
Additional info Power line signal consisting of a dominant 50 Hz sinusoidal and harmonics up to 1250 Hz. The amplitude distribution of the harmonics was derived from the maximum accepted distortions for power systems by the IEC.
Exposure setup
Exposure source
  • coil(s)
  • see chamber details
Chamber Two magnetically shielded four-coil systems [Schuderer et al., 2004] were placed in an incubator. Accurate Pt 100 probes monitoring the airflow temperature and two fans per exposure chamber ensured that the temperature difference between field and sham chambers was kept below 0.2°C.
Setup The currents in the bifilar coils were randomly switched parallel for field exposure or non-parallel for sham exposure by computer (blinded). The coil current and consequently the magnetic field was quasi-continuously (30 s intervals) recorded and regulated using resistors providing very low temperature sensitivity.
Sham exposure A sham exposure was conducted.
Additional info The estimated acceleration load due to B-field-induced coil vibrations was <1 m/s² (0.1 g) for the exposed Petri dishes. This acceleration is a factor of 20 above the minimal background level for sham Petri dishes.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 2 mT unspecified unspecified - -

Reference articles

  • Schuderer J et al. (2004): In vitro exposure apparatus for ELF magnetic fields.
  • Kuster N et al. (2000): Recommended minimal requirements and development guidelines for exposure setups of bio-experiments addressing the health risk concern of wireless communications.

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • after exposure

Main outcome of study (acc. to author)

The data show that extremely low frequency electromagnetic fields affected transcript level of apoptosis-related genes (bcl2, bax), and of cell cycle regulatory GADD45 genes, whereas mRNA levels of neural-specific genes were not affected. Radiofrequency electromagnetic field exposure of neural progenitor cells resulted in down-regulation of neural-specific Nurr1 and in up-regulation of bax and GADD45 mRNA levels.
Short-term radiofrequency electromagnetic field exposure for 6 h, but not for 48 h, resulted in a low and transient increase of DNA double-strand breaks. No effects of extremely low frequency- and radiofrequency electromagnetic fields on mitochondrial function, nuclear apoptosis, cell proliferation, and chromosomal alterations were revealed.
The data indicate that electromagnetic fields are able to induce changes at the transcript level (related to apoptosis and cell cycle control) in embryonic stem-derived neural progenitor cells, but these responses may not affect cell physiological functions.

Study character:

Study funded by

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