Medical/biological study (experimental study)

Different electromagnetic field waveforms have different effects on proliferation, differentiation and mineralization of osteoblasts in vitro med./bio.

By: Zhou J, Wang JQ, Ge BF, Ma XN, Ma HP, Xian CJ, Chen KM

Published in: Bioelectromagnetics 2014; 35 (1): 30-38

Aim of study (acc. to author)

To study the effects of different waveforms on cell proliferation, differentiation and mineralization of rat osteoblasts.

Background/further details

Four different waveforms and an untreated control were examined: sinusoidal, triangular, rectangular and sawtooth.
Osteoblasts (primary cells) were isolated from skull bones of neonatal rats.

Endpoint

cell proliferation, cell differentiation and mineralization potentials of osteoblasts

Exposure

- 50/60 Hz
- magnetic field

Exposure	Parameters
Exposure 1: 50 Hz Exposure duration: 30 min/day for up to 12 days	magnetic flux density: 1.8 mT effective value
Exposure 2: 50 Hz Exposure duration: 30 min/day for up to 12 days triangular	magnetic flux density: 1.8 mT effective value
Exposure 3: 50 Hz Exposure duration: 30 min/day for up to 12 days	magnetic flux density: 1.8 mT effective value
Exposure 4: 50 Hz Exposure duration: 30 min/day for up to 12 days	magnetic flux density: 1.8 mT effective value

Exposure 1

Main characteristics

Frequency	50 Hz
Type	magnetic field
Waveform	sinusoidal
Exposure duration	30 min/day for up to 12 days

Exposure setup

Exposure source	solenoid
Chamber	osteoblasts placed in 60 mm culture dishes inside the solenoid
Setup	solenoid consisting of three series-connected coils and the core cylinder was an acrylic tube (inner diameter = 18 cm, height = 21 cm); solenoid positioned in an incubator at 37°C

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	1.8 mT	effective value	measured	-	-

Exposure 2

Main characteristics

Frequency	50 Hz
Type	magnetic field
Exposure duration	30 min/day for up to 12 days
Additional info	triangular
Additional info	Signal form: triangular

Exposure setup

Exposure source	same setup as exposure 1

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	1.8 mT	effective value	measured	-	-

Exposure 3

Main characteristics

Frequency	50 Hz
Type	magnetic field
Waveform	rectangular
Exposure duration	30 min/day for up to 12 days

Exposure setup

Exposure source	same setup as exposure 1

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	1.8 mT	effective value	measured	-	-

Exposure 4

Main characteristics

Frequency	50 Hz
Type	magnetic field
Waveform	sawtooth-shaped
Exposure duration	30 min/day for up to 12 days

Exposure setup

Exposure source	same setup as exposure 1

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	1.8 mT	effective value	measured	-	-

Exposed system:

intact cell/cell culture
rat osteoblasts

Methods Endpoint/measurement parameters/methodology

molecular biosynthesis: gene expression of different osteogenesis-related genes after 1, 3 and 4 days of exposure (Igf-1, Opg, Runx-2; real-time RT-PCR)
cell viability/cell division/proliferation: cell proliferation after 3 days of exposure (MTT assay)
cell differentiation after 3, 6, 9 and 12 days of exposure: osteoblast mineralization (amount of calcium, numbers and area of calcified nodules; Alizarin red staining), alkaline phosphatase (ALP) enzyme activity (as early marker of osteoblast maturation phase; ALP positive colonies; commercial kit and histochemical staining (after 8 days of exposure)) and gene expression (see "molecular biosynthesis")

Investigated system:

DNA/RNA
intact cell/cell culture

Time of investigation:

after exposure

Main outcome of study (acc. to author)

Compared to the untreated control, sinusoidal magnetic field exposure significantly inhibited osteoblast proliferation while rectangular magnetic field exposure significantly increased the proliferation.
After 9 and 12 days of exposure, the enzyme activity of the alkaline phosphatase was significantly higher in the sinusoidal and triangular waveform exposed cultures compared to the control cultures. The amount of alkaline phosphatase positive colonies was significantly higher in the sinusoidal, triangular and sawtooth waveform exposed cultures than in the control cultures.
Regarding mineralization, after 9 and 12 days of exposure to sinusoidal and triangular waveforms (and amount of calcium also sawtooth after 12 days), the amount of calcium and the number of calcified nodules were significantly higher than in the control cultures.
In comparison to the control cultures, the gene expression of Runx-2 and Opg was significantly upregulated after 1 day of exposure to a sinusoidal, triangular and sawtooth waveform, whereas the gene expression of Igf-1 was significantly increased after 3 and 4 days.
While rectangular magnetic fields increased the proliferation and did not effect the differentiation of osteoblasts, sinusoidal fields inhibited the proliferation but promoted osteogenic differentiation. The authors conclude that the influence of magnetic fields on proliferation, differentiation and mineralization of rat osteoblasts is dependent on the waveform.

Study character:

medical/biological study
experimental study
full/main study

Study funded by

Gansu Research Foundation of Science and Technology, China

Zhou J et al. (2019): Sinusoidal Electromagnetic Fields Increase Peak Bone Mass in Rats by Activating Wnt10b/β-Catenin in Primary Cilia of Osteoblasts
Zhou J et al. (2016): Sinusoidal electromagnetic fields promote bone formation and inhibit bone resorption in rat femoral tissues in vitro
Bique AM et al. (2016): Choice of osteoblast model critical for studying the effects of electromagnetic stimulation on osteogenesis in vitro
Xie YF et al. (2016): Pulsed electromagnetic fields stimulate osteogenic differentiation and maturation of osteoblasts by upregulating the expression of BMPRII localized at the base of primary cilium
Ledda M et al. (2015): Nonpulsed sinusoidal electromagnetic fields as a noninvasive strategy in bone repair: the effect on human mesenchymal stem cell osteogenic differentiation
Yan JL et al. (2015): Pulsed electromagnetic fields promote osteoblast mineralization and maturation needing the existence of primary cilia
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Bilotta TW et al. (1994): Electromagnetic fields in the treatment of postmenopausal osteoporosis: an experimental study conducted by densitometric, dry ash weight and metabolic analysis of bone tissue

Different electromagnetic field waveforms have different effects on proliferation, differentiation and mineralization of osteoblasts in vitro med./bio.

Aim of study (acc. to author)

Background/further details

Endpoint

Exposure

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

Methods Endpoint/measurement parameters/methodology

Main outcome of study (acc. to author)

Study funded by

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