Study type: Medical/biological study (experimental study)

Egr1 mediated the neuronal differentiation induced by extremely low-frequency electromagnetic fields. med./bio.

Published in: Life Sci 2014; 102 (1): 16-27

Aim of study (acc. to author)

The effect of exposure of different stem cells types to extremely low frequency magnetic fields on neuronal differentiation in relation to gene expression should be investigated.

Background/further details

The study was conducted in the view of a possible therapeutic use for transplantations to treat neurodegenerative diseases.
Human bone marrow-derived mesenchymal stem cells and mouse neural stem cells were either exposed to different magnetic fields (0-200 Hz; exposure groups) or not exposed (control groups). Additionally, tests were conducted with Egr1-knockdown and Egr1-overexpressing human bone marrow-mesenchymal stem cells as Egr1 was supposed to play a crucial role in magnetic field mediated neuronal differentiation.
Finally, tests were conducted with mice, in which the loss of dopaminergic neurons in Parkinson's disease was simulated by the administration of 6-hydroxy-dopamine (6-OHDA). The mice were divided into the following groups: 1) only administration of 6-OHDA, 2) 6-OHDA and sham transplantation, 3) 6-OHDA and transplantation of human bone marrow-mesenchymal stem cells, 4) 6-OHDA and transplantation of Egr1-overexpressing human bone marrow-mesenchymal stem cells, 5) 6-OHDA, transplantation of Egr1-overexpressing human bone marrow-mesenchymal stem cells and subsequent exposure to the magnetic field, 6) 6-OHDA and transplantation of embryonic midbrain cells (positive control). Stem cell transplantations were conducted 4 weeks after injection of 6-OHDA and mice were exposed afterwards.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 0–200 Hz
Exposure duration: continuous for 8 days with 0, 50, 100 or 200 Hz
pretest (with human stem cells)
Exposure 2: 50 Hz
Exposure duration: continuous for 8 days
Exposure 3: 50 Hz
Exposure duration: continuous for 6 days
mouse stem cells
Exposure 4: 50 Hz
Exposure duration: continuous for 1 day every other day for 4 weeks
mice

Exposure 1

Main characteristics
Frequency 0–200 Hz
Type
Waveform
Exposure duration continuous for 8 days with 0, 50, 100 or 200 Hz
Additional info pretest (with human stem cells)
Exposure setup
Exposure source
Setup cells were exposed in 35 mm cell culture plates in a system formed by two Helmholtz coils (15 cm inner diameter), which produced a vertical magnetic field in a cell culture incubator with 5% CO2 at 37°C
Additional info control cultures were grown in a separate incubator without Helmholtz coils
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 1 mT - measured - -

Exposure 2

Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration continuous for 8 days
Additional info human stem cells
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 1 mT - measured - -

Exposure 3

Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration continuous for 6 days
Additional info mouse stem cells
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 1 mT - measured - -

Exposure 4

Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration continuous for 1 day every other day for 4 weeks
Additional info mice
Exposure setup
Exposure source
Setup mice were exposed in 2 plastic cages in a system formed by two Helmholtz coils, which produced a horizontal magnetic field
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 2 mT - measured - -

Reference articles

  • Cho H et al. (2012): Neural stimulation on human bone marrow-derived mesenchymal stem cells by extremely low frequency electromagnetic fields.

Exposed system:

Methods Endpoint/measurement parameters/methodology

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

Main outcome of study (acc. to author)

In the pretest (field 1), a significant increase of TuJ1 was observed in cells exposed to the 50 Hz magnetic field compared to cells exposed to the other magnetic fields.
Human stem cells (field 2) showed a significant increase of TuJ1 and NeuroD1 compared to the control group and moreover, these cells showed a neuronal morphology. Additionally, these cells showed electrophysiological properties after exposure comparable to those of primary neurons.
In exposed mouse stem cells (field 3), a significant increase of the TuJ1 and TH protein expression as well as a neuronal morphology were observed compared to the control.
A total of 57 genes were up-regulated in exposed human and mouse stem cells (fields 2+3) compared to the control groups with Egr1 showing the highest up-regulation in both cell types. Egr1-overexpressing cells showed a high degree of neuronal differentiation after exposure to the magnetic field (field 2) with significant increases of the expression of neuronal marker genes compared to the control group, whereas the Egr1-knockdown cells did not show neuronal differentiation and no significant increase of the expression of neuronal marker genes compared to the control.
The apomorphine-induced turning behavior of mice was significantly reduced in group 5 after exposure to the magnetic field (field 4) compared to mice without transplantation (group 1+2) or without exposure (groups 3+4), indicating a replacement of destroyed neurons and neuronal differentiation of injected cells in vivo, which was confirmed by immunofluorescence.
The authors conclude that Egr1 could induce a 50 Hz magnetic field mediated neuronal differentiation of stem cells.

Study character:

Study funded by

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