Study type: Medical/biological study (experimental study)

Inhibition of gap junction intercellular communication by extremely low-frequency electromagnetic fields in osteoblast-like models is dependent on cell differentiation. med./bio.

Published in: J Cell Physiol 2002; 190 (2): 180-188

Aim of study (acc. to author)

To study whether extremely low frequency magnetic fields alter gap junction intercellular communication in a pre-osteoblastic model (MC3T3-E1) and a well-differentiated osteoblastic model (ROS 17/2.8).

Background/further details

Gap junctions occur among bone forming cells (osteoblasts) and have been hypothesized to play a role in bone formation.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 30–120 Hz
Exposure duration: 1 h before injection; 1.5 h during injection
injection method (ROS 17/2.8 cells and MC3T3-E1 cells)
Exposure 2: 60 Hz
Exposure duration: experiment 1 (3 days old MC3T3-E1 cells): continuous for 4 h; experiment 2 (4, 8, 15, 23 days old MC3T3-E1 cells): 1 h pre-exposure of parachuting cells + 16 h exposure of all cells
parachute method
Exposure 3: 60 Hz
Exposure duration: continuous for 3 h
distribution of connexin (MC3T3-E1 cells)
Exposure 4: 30–120 Hz
Exposure duration: continuous for 1 h
assessment of calcium (MC3T3-E1 cells)

General information

Three different, not always for certain assignable exposure setups: i) setup according to Wang 1997: two 1.8 cm long solenoids with a radius of 3.8 cm and a double-layer of 100 turns of wire; for cancellation of the horizontal component of the geomagnetic field: pair of 0.7 cm long coils with a radius of 3.8 cm and 71.4 turns of wire, separated by 7.2 cm ii) setup according to Merrit 1983: four square coils with a sidelenght of 25 cm; upper and lower coils: 40-turn copper magnet wire at a distance of 25 - 37 cm; two middle section coils: 17-turn copper magnet wire at a distance of 6.4 cm iii) Helmholtz coil: exposure system built into a CO2 tissue culture incubator

Exposure 1

Main characteristics
Frequency 30–120 Hz
Type
Waveform
Exposure duration 1 h before injection; 1.5 h during injection
Additional info injection method (ROS 17/2.8 cells and MC3T3-E1 cells)
Additional info 30, 60, 120 Hz
Exposure setup
Exposure source
Setup cells grown on coverslips mounted in a round coverslip holder; in most coverslips 4-5 cells in the central portions of the coverslip were injected
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 1.25 mT maximum measured - application of different magnetic flux densities: 0.01, 0.1, 0.3, 0.6, 1.25 mT

Exposure 2

Main characteristics
Frequency 60 Hz
Type
Waveform
Exposure duration experiment 1 (3 days old MC3T3-E1 cells): continuous for 4 h; experiment 2 (4, 8, 15, 23 days old MC3T3-E1 cells): 1 h pre-exposure of parachuting cells + 16 h exposure of all cells
Additional info parachute method
Exposure setup
Exposure source
Setup cells were plated in plates with 12 wells
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 1.25 mT - measured - -

Exposure 3

Main characteristics
Frequency 60 Hz
Type
Waveform
Exposure duration continuous for 3 h
Additional info distribution of connexin (MC3T3-E1 cells)
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 1.25 mT - measured - -

Exposure 4

Main characteristics
Frequency 30–120 Hz
Type
Waveform
Exposure duration continuous for 1 h
Additional info assessment of calcium (MC3T3-E1 cells)
Exposure setup
Exposure source
Setup cells grown on coverslips mounted in a round coverslip holder
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 0.6 mT - measured - application of different frequencies (30 Hz and 120 Hz) at the same magnetic flux density

Reference articles

  • Wang PK (1997): ELF magnetic field exposure system with feedback-controlled disturbance rejection.

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • after exposure

Main outcome of study (acc. to author)

The data showed that magnetic fields over a frequency range from 30 to 120 Hz and magnetic flux densities up to 1.25 mT dose dependently decreased gap junction intercellular communication in MC3T3-E1 cells during their proliferative phase of development. The total amount of connexin 43 and the distribution of connexin 43 gap junction protein between cytoplasmic and plasma membrane fractions were unaltered by magnetic field exposure. Cytosolic calcium which can inhibit gap junction communication, was not altered by magnetic field exposure.
Identical exposure conditions did not affect gap junction communication in the ROS 17/2.8 cell line and when MC3T3-E1 cells were more differentiated. Thus, extremely low frequency magnetic fields may affect only less differentiated or pre-osteoblasts and not fully differentiated osteoblasts. Consequently, electromagnetic fields may aid in the repair of bone by effects exerted only on osteo-progenitor cells or pre-osteoblasts.

Study character:

Study funded by

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