Medical/biological study (experimental study)

Pulsed electromagnetic fields affect phenotype and connexin 43 protein expression in MLO-Y4 osteocyte-like cells and ROS 17/2.8 osteoblast-like cells med./bio.

By: Lohmann CH, Schwartz Z, Liu Y, Li Z, Simon BJ, Sylvia VL, Dean DD, Bonewald LF, Donahue HJ, Boyan BD

Published in: J Orthop Res 2003; 21 (2): 326-334

Aim of study (acc. to author)

To examine long term effects of pulsed electromagnetic fields (PEMFs) on MLO-Y4 osteocyte-like cells and ROS 17/2.8 osteoblast-like cells.

Background/further details

It was examined if MLO-Y4 cells respond to PEMFs with change in connexin 43 protein expression (essential for gap junction intercellular communication) and altered production of agents involved in bone remodeling; if prostaglandin (essential for the increase in gap junction formation) production modulates the effects of PEMFs; and if the response of osteocytes differs from that of osteoblasts.

Endpoint

effects on osteocyte-like cells and osteoblast-like cells (connexin 43 protein expression; production of agents involved in bone remodeling; prostaglandin production)

Exposure

- magnetic field
- low frequency
- signals/pulses

Exposure	Parameters
Exposure 1: 15 Hz Modulation type: pulsed Exposure duration: 8 h/d on day 1	magnetic flux density: 1.6 mT maximum (increased within 200 µs and decreased to 0 within 25 µs.)
Exposure 2: 15 Hz Modulation type: pulsed Exposure duration: 8 h/d for 2 days.	magnetic flux density: 1.6 mT maximum (increased within 200 µs and decreased to 0 within 25 µs.)
Exposure 3: 15 Hz Modulation type: pulsed Exposure duration: 8 h/d for 4 days.	magnetic flux density: 1.6 mT maximum (increased within 200 µs and decreased to 0 within 25 µs.)

Exposure 1

Main characteristics

Frequency	15 Hz
Type	magnetic field
Waveform	pulsed
Exposure duration	8 h/d on day 1

Modulation

Modulation type	pulsed
Rise time	200 µs
Additional info	Burst of 4.5 ms of 20 pulses.

Exposure setup

Exposure source	Helmholtz coils
Chamber	Incubator with plastic shelves

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	1.6 mT	maximum	unspecified	-	increased within 200 µs and decreased to 0 within 25 µs.

Exposure 2

Main characteristics

Frequency	15 Hz
Type	magnetic field
Waveform	pulsed
Exposure duration	8 h/d for 2 days.

Modulation

Modulation type	pulsed
Rise time	200 µs
Additional info	Burst of 4.5 ms of 20 pulses.

Exposure setup

Exposure source	same setup as exposure 1

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	1.6 mT	maximum	unspecified	-	increased within 200 µs and decreased to 0 within 25 µs.

Exposure 3

Main characteristics

Frequency	15 Hz
Type	magnetic field
Waveform	pulsed
Exposure duration	8 h/d for 4 days.

Modulation

Modulation type	pulsed
Rise time	200 µs
Additional info	Burst of 4.5 ms of 20 pulses.

Exposure setup

Exposure source	same setup as exposure 1

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	1.6 mT	maximum	unspecified	-	increased within 200 µs and decreased to 0 within 25 µs.

Reference articles

Guerkov HH et al. (2001): Pulsed electromagnetic fields increase growth factor release by nonunion cells

Exposed system:

intact cell/cell culture
MLO-Y4 (osteocyte-like cells); ROS 17/2.8 (osteoblast-like cells)

Methods Endpoint/measurement parameters/methodology

molecular biosynthesis: level of osteocalcin, osteocalcin mRNA, prostaglandin E₂, connexin 43 protein, NO^2- and transforming growth factor (TGF)-β1
cell function: enzyme activity (cellular and cell layer alkaline phosphatase specific activity)
cell viability/cell division/proliferation: cell growth (cell number)

Investigated system:

isolated bio./chem. substance
DNA/RNA
intact cell/cell culture
lysates of isolated cells or cell layers

Time of investigation:

after exposure

Main outcome of study (acc. to author)

It was shown for the first time that osteocytes respond to pulsed electromagnetic fields (PEMF) stimulation. PEMF affected the release of factors that modulate cell activity via autocrine and paracrine mechansims. PEMFs for 8h/day for one, two or four days increased alkaline phosphatase activity in MLO-Y4 cells but had no effect on cell number or osteocalcin level. Transforming growth factor (TGF)-β1 and prostaglandin E₂ were increased, and NO^2--level was altered. In ROS 17/2.8 cells, PEMFs for 24, 48 or 72h did not affect cell number, osteocalcin mRNA or osteocalcin protein level. PEMFs reduced connexin 43 protein in both cell cultures. Longer exposure decreased connexin mRNA.

Study character:

medical/biological study
experimental study
full/main study

Study funded by

Electro-Biology, Parsippany, New York, USA
Public Health Service (PHS), USA

Zhou J et al. (2011): Effects of 50 Hz sinusoidal electromagnetic fields of different intensities on proliferation, differentiation and mineralization potentials of rat osteoblasts
Sun LY et al. (2009): Effect of pulsed electromagnetic field on the proliferation and differentiation potential of human bone marrow mesenchymal stem cells
Wei Y et al. (2008): Effects of extremely low-frequency-pulsed electromagnetic field on different-derived osteoblast-like cells
Zhao D et al. (2008): Electromagnetic field change the expression of osteogenesis genes in murine bone marrow mesenchymal stem cells
Sontag W et al. (2006): No effect of pulsed electromagnetic fields on PC12 and HL-60 cells
Sul AR et al. (2006): Effects of sinusoidal electromagnetic field on structure and function of different kinds of cell lines
Yamaguchi DT et al. (2002): Inhibition of gap junction intercellular communication by extremely low-frequency electromagnetic fields in osteoblast-like models is dependent on cell differentiation

Pulsed electromagnetic fields affect phenotype and connexin 43 protein expression in MLO-Y4 osteocyte-like cells and ROS 17/2.8 osteoblast-like cells med./bio.

Aim of study (acc. to author)

Background/further details

Endpoint

Exposure

Exposure 1

Main characteristics

Modulation

Exposure setup

Parameters

Exposure 2

Main characteristics

Modulation

Exposure setup

Parameters

Exposure 3

Main characteristics

Modulation

Exposure setup

Parameters

Reference articles

Methods Endpoint/measurement parameters/methodology

Main outcome of study (acc. to author)

Study funded by

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