Medical/biological study (experimental study)

Effects of Electromagnetic Field (PEMF) Exposure at Different Frequency and Duration on the Peripheral Nerve Regeneration: in Vitro and in Vivo Study med./bio.

By: Hei WH, Byun SH, Kim JS, Kim S, Seo YK, Park JC, Kim SM, Jahng JW, Lee JH

Published in: Int J Neurosci 2016; 126 (8): 739-748

Aim of study (acc. to author)

The effects of exposure to pulsed extremely low frequency magnetic fields of different frequencies and durations on the peripheral nerve regeneration in rats and cell proliferation in Schwann cells should be investigated.

Background/further details

The study comprised in vitro tests with immortalized Schwann cells of rats and in vivo tests with rats.
For the in vitro tests, cells were divided into 5 groups: exposure to a pulsed magnetic field of 1) 50 Hz for 1 hour/day, 2) 50 Hz for 12 hours/day, 3) 150 Hz for 1 hour/day, 4) 150 Hz for 12 hours/day and 5) control group.
For the in vivo tests, chin nerves of rats were crush injured between lip area and mental foramen (except in the sham group) and the animals were divided into 6 groups (n=10 each): exposure to a pulsed magnetic field of 6) 50 Hz for 1 hour/day, 7) 50 Hz for 12 hours/day, 8) 150 Hz for 1 hour/day, 9), 150 Hz for 12 hours/day, 10) control group, 11) sham group without injury and magnetic field exposure.

Endpoint

cell viability/cell division/proliferation: cell proliferation in Schwann cells
effects on the neurological system: peripheral nerve regeneration in rats

Exposure

- 50–150 Hz
- 50/60 Hz
- magnetic field
- low frequency
- signals/pulses

Exposure	Parameters
Exposure 1: 50 Hz Exposure duration: 1 hour/day for up to 3 weeks in vitro exposure	magnetic flux density: 1 mT
Exposure 2: 50 Hz Exposure duration: 12 hours/day for up to 3 weeks in vitro exposure	magnetic flux density: 1 mT
Exposure 3: 150 Hz Exposure duration: 1 hour/day for up to 3 weeks in vitro exposure	magnetic flux density: 1 mT
Exposure 4: 150 Hz Exposure duration: 12 hours/day for up to 3 weeks in vitro exposure	magnetic flux density: 1 mT
Exposure 5: 50 Hz Exposure duration: 1 hour/day for 3 weeks in vivo exposure	magnetic flux density: 1 mT
Exposure 6: 50 Hz Exposure duration: 12 hours/day for 3 weeks in vivo exposure	magnetic flux density: 1 mT
Exposure 7: 150 Hz Exposure duration: 1 hour/day for 3 weeks in vivo exposure	magnetic flux density: 1 mT
Exposure 8: 150 Hz Exposure duration: 12 hours/day for 3 weeks in vivo exposure	magnetic flux density: 1 mT

General information

no details given on pulse repetition rate and pulse width

Exposure 1

Main characteristics

Frequency	50 Hz
Type	magnetic field
Waveform	pulsed
Exposure duration	1 hour/day for up to 3 weeks
Additional info	in vitro exposure

Exposure setup

Exposure source	Helmholtz coils
Chamber	coils in incubator
Setup	two identical Helmholtz coils of 30 cm diameter, 7 cm width and 15 cm distance; vertical field

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	1 mT	-	-	-	-

Exposure 2

Main characteristics

Frequency	50 Hz
Type	magnetic field
Waveform	pulsed
Exposure duration	12 hours/day for up to 3 weeks
Additional info	in vitro exposure

Exposure setup

Exposure source	same setup as exposure 1

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	1 mT	-	-	-	-

Exposure 3

Main characteristics

Frequency	150 Hz
Type	magnetic field
Waveform	pulsed
Exposure duration	1 hour/day for up to 3 weeks
Additional info	in vitro exposure

Exposure setup

Exposure source	same setup as exposure 1

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	1 mT	-	-	-	-

Exposure 4

Main characteristics

Frequency	150 Hz
Type	magnetic field
Waveform	pulsed
Exposure duration	12 hours/day for up to 3 weeks
Additional info	in vitro exposure

Exposure setup

Exposure source	same setup as exposure 1

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	1 mT	-	-	-	-

Exposure 5

Main characteristics

Frequency	50 Hz
Type	magnetic field
Waveform	pulsed
Exposure duration	1 hour/day for 3 weeks
Additional info	in vivo exposure

Exposure setup

Exposure source	Helmholtz coils
Setup	a pair of Helmholtz coils of 60 cm diameter and a distance of 30 cm

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	1 mT	-	-	-	-

Exposure 6

Main characteristics

Frequency	50 Hz
Type	magnetic field
Waveform	pulsed
Exposure duration	12 hours/day for 3 weeks
Additional info	in vivo exposure

Exposure setup

Exposure source	same setup as in E5

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	1 mT	-	-	-	-

Exposure 7

Main characteristics

Frequency	150 Hz
Type	magnetic field
Waveform	pulsed
Exposure duration	1 hour/day for 3 weeks
Additional info	in vivo exposure

Exposure setup

Exposure source	same steup as in E5

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	1 mT	-	-	-	-

Exposure 8

Main characteristics

Frequency	150 Hz
Type	magnetic field
Waveform	pulsed
Exposure duration	12 hours/day for 3 weeks
Additional info	in vivo exposure

Exposure setup

Exposure source	same setup as in E5

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	1 mT	-	-	-	-

Reference articles

Kim YT et al. (2015): Co-treatment Effect of Pulsed Electromagnetic Field (PEMF) with Human Dental Pulp Stromal Cells and FK506 on the Regeneration of Crush Injured Rat Sciatic Nerve

Exposed system:

Methods Endpoint/measurement parameters/methodology

cell viability/cell division/proliferation: cell proliferation (after 1-7 days, MTT assay), gene expression of cell proliferation markers BDNF and S100 (prior to exposure and after 1, 2 and 3 weeks, quantitative real-time PCR)
effects on the neurological system: functional recovery of injured nerve (prior to exposure and after 1, 2 and 3 weeks, difference in sensory test with mechanical stimulus between innervated area of injured mental nerve and healthy contralateral side (difference score) and between lip area and mental foramen on ipsilateral side (gap score)), histology of crush injury site (after 3 weeks, myelinated axon count; toluidine blue stain, light microscopy), quantification of trigeminal ganglion sensory neurons (after 3 weeks, cut of mental nerve distally to the crush injury site and retrograde labeling, i.e., tracing of neurons from their synapses to the cell bodies, with Dil; confocal microscopy)

Investigated system:

DNA/RNA
intact cell/cell culture
tissue slices
cell homogenates, nerve tissue
investigation on living organism

Investigated organ system:

sense organs

Time of investigation:

before exposure
during exposure
after exposure

Main outcome of study (acc. to author)

In the in vitro tests, group 1 (50 Hz exposure for 1 hour/day) showed a significantly increased cell proliferation after 4-7 days and a significantly increased gene expression of S100 and BDNF after 1-3 weeks compared to the control group.
In the in vivo tests, the difference score was significantly decreased after 2 and 3 weeks and the gap score was significantly decreased after 3 weeks in group 6 (50 Hz exposure for 1 hour/day) compared to the control group (group 10), indicating an improved sensory function.
A significantly increased number of axons and retrograde labeled neurons was found in all exposure groups (groups 6-9) compared to the control group, with the highest values found in group 6.
The authors conclude that exposure to a pulsed 50 Hz magnetic field for 1 hour/day might be beneficial in peripheral nerve regeneration via increase in cell proliferation and BDNF and S100 gene expression. Hence, these could also be suitable exposure conditions in clinical applications.

Study character:

medical/biological study
experimental study
full/main study

Study funded by

Ministry of Trade, Industry and Energy (MOTIE), Korea

Hei WH et al. (2016): Schwann-like cells differentiated from human dental pulp stem cells combined with a pulsed electromagnetic field can improve peripheral nerve regeneration
Kim YT et al. (2015): Co-treatment Effect of Pulsed Electromagnetic Field (PEMF) with Human Dental Pulp Stromal Cells and FK506 on the Regeneration of Crush Injured Rat Sciatic Nerve
Beck-Broichsitter BE et al. (2014): Does pulsed magnetic field therapy influence nerve regeneration in the median nerve model of the rat?
Li Y et al. (2014): Pulsed electromagnetic field enhances brain-derived neurotrophic factor expression through L-type voltage-gated calcium channel- and Erk-dependent signaling pathways in neonatal rat dorsal root ganglion neurons
Suszynski K et al. (2014): Variable spatial magnetic field influences peripheral nerves regeneration in rats
Gunay I et al. (2011): Pulsed magnetic fields enhance the rate of recovery of damaged nerve excitability
Baptista AF et al. (2009): PEMF fails to enhance nerve regeneration after sciatic nerve crush lesion
Mert T et al. (2006): Regenerative effects of pulsed magnetic field on injured peripheral nerves
Guven M et al. (2005): Effect of pulsed magnetic field on regenerating rat sciatic nerve: an in-vitro electrophysiologic study
Bervar M (2005): Effect of weak, interrupted sinusoidal low frequency magnetic field on neural regeneration in rats: functional evaluation
De Pedro JA et al. (2005): Pulsed electromagnetic fields induce peripheral nerve regeneration and endplate enzymatic changes
Shah JP et al. (2001): Growth and differentiation of PC6 cells: the effects of pulsed electromagnetic fields (PEMF)
Macias MY et al. (2000): Directed and enhanced neurite growth with pulsed magnetic field stimulation
Longo FM et al. (1999): Electromagnetic fields influence NGF activity and levels following sciatic nerve transection
Kanje M et al. (1993): Pretreatment of rats with pulsed electromagnetic fields enhances regeneration of the sciatic nerve
Rusovan A et al. (1992): Magnetic fields stimulate peripheral nerve regeneration in hypophysectiomized rats
Rusovan A et al. (1992): The stimulatory effect of magnetic fields on regeneration of the rat sciatic nerve is frequency dependent
Sisken BF et al. (1989): Stimulation of rat sciatic nerve regeneration with pulsed electromagnetic fields
Ito H et al. (1983): Effect of weak, pulsing electromagnetic fields on neural regeneration in the rat
Raji AR et al. (1982): Effects of high peak pulsed electromagnetic fields on degeneration and regeneration of the common peroneal nerve in rate
Wilson DH et al. (1974): The effects of pulsed electromagnetic energy on peripheral nerve regeneration

Effects of Electromagnetic Field (PEMF) Exposure at Different Frequency and Duration on the Peripheral Nerve Regeneration: in Vitro and in Vivo Study med./bio.

Aim of study (acc. to author)

Background/further details

Endpoint

Exposure

General information

Exposure 1

Main characteristics

Exposure setup

Parameters

Exposure 2

Main characteristics

Exposure setup

Parameters

Exposure 3

Main characteristics

Exposure setup

Parameters

Exposure 4

Main characteristics

Exposure setup

Parameters

Exposure 5

Main characteristics

Exposure setup

Parameters

Exposure 6

Main characteristics

Exposure setup

Parameters

Exposure 7

Main characteristics

Exposure setup

Parameters

Exposure 8

Main characteristics

Exposure setup

Parameters

Reference articles

Methods Endpoint/measurement parameters/methodology

Main outcome of study (acc. to author)

Study funded by

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