To study the effects of 50 Hz sinusoidal electromagnetic field treatment for different durations and at different intensities on cell proliferation, differentiation and mineralization potentials of rat osteoblasts.
Exposure duration: continuous for 30 min/day for up to 15 days (see add. information)
Exposure duration: continuous for 0, 12, 24, 96 h
|Setup||solenoid consisting of three cascade connected coils with an acrylic tube (inner diameter = 18 cm, height = 21 cm) as a common core; the number of windings of enamel copper wire in the middle coil was less than those in the bilateral coils; field homogeneous within 1% for an area of 30 mm to -30 mm from the horizontal and 20 mm to -20 mm from the vertical axis; solenoid positioned in an incubator at 37°C with 5 % CO2 and 100 % humidity; osteoblasts placed in 60 mm culture dishes inside the solenoid|
|Sham exposure||A sham exposure was conducted.|
|Additional info||t = 30 min/day for 3 days - for MTT assay t = 30 min/day for 3, 6, 9, 12 or 15 days - for alkaline phosphatase (ALP) activity t = 30 min/day for 8 days - for ALP histochemical staining t = 30 min/day for 10 days - for Alizarin red staining t = 30 min/day for 5, 8 or 10 days - for morphology of osteoblasts|
|magnetic flux density||4.8 mT||maximum||-||-||0.9, 1.2, 1.5, 1.8, 2.1, 2.4, 2.7, 3.0, 3.3, 3.6, 3.9, 4.2, 4.5, 4.8 mT|
Compared to untreated control, sinusoidal electromagnetic field exposure inhibited osteoblast proliferation (after exposure for 3 days; no dose-dependent effect), but increased alkaline phosphatase enzyme activity (after exposure for 9 days) from 0.9 mT to 1.8 mT, declined from 1.8 mT until 3 mT, and then increased again from 3 mT to 3.6 mT and decreased once again from 3.6 mT to 4.8 mT. Numbers of colonies stained positive for alkaline phosphatase after 8 days and mineralized nodules after 10 days showed the same bimodal tendency as with the alkaline phosphatase enzyme activity, with two peaks at 1.8 mT and 3.6 mT.
Sinusoidal electromagnetic fields also bimodally increased the different gene expression levels at 12, 24 and 96 h after exposure.
The data indicated that while exposure to 50 Hz sinusoidal electromagnetic fields inhibits the osteoblast proliferation, it significantly promotes differentiation and mineralization potentials of osteoblasts in an intensity-dependent manner with peak activity at 1.8 mT and 3.6 mT.