Abstract
Introduction: Alternating and pulsed electromagnetic magnetic fields (AEMF and PEMF) of different amplitudes and frequencies can induce metabolic and proliferative effects in osteoblasts, but there is no clearly directed tendency of these effects. I hypothesize that there are extremely low triggering parameters of alternating electromagnetic field (EMF) intensity, i.e., above the background magnetic field on earth but below the lowest AEMF and PEMF that have been investigated to date (above 0.07 mT and below 0.4 mT) that induce cellular response. Methods: Accordingly, human monolayer explant culture replica were exposed four times in 24-hour intervals to two minutes of 10 kHz AEMF or PEMF (10 Hz pulses at a basic 5 kHz frequency) with a maximal EMF intensity of 0.2 mT for both. Cell proliferation was estimated from microscopic cell counting and cell death by lactate dehydrogenase (LDH) specific activity in culture media (measured using a colorimetric method). The early marker of osteoblast maturation, cellular alkaline phosphatase (AP) specific activity, was measured using a colorimetric method (n=6 for all experiment conditions). Results: No difference was found in cell numbers in the culture samples exposed either to AEMF or PEMF and in the LDH’s specific activity in culture media in comparison to the unexposed controls (p>0.05, for both). The cellular AP’s specific activity increased significantly only in cell cultures exposed to the 10 kHz AEMF (p=0.011). Conclusions: The triggering for human osteoblast activation for maturation by an extremely low AEMF (10 kHz) is at least 0.2 mT, which is distinct and below the previously found triggering range of a PEMF for proliferation induction. Therefore, application of these EMF parameters in a clinical setup by a separate finetuning of osteoblast proliferation and maturation might have a therapeutic value in enhancing damaged bone regeneration.
Highlights
Alternating and pulsed electromagnetic magnetic fields (AEMF and pulsed electromagnetic field (PEMF)) of different amplitudes and frequencies can induce metabolic and proliferative effects in osteoblasts, but there is no clearly directed tendency of these effects
The same maximal magnetic flux of 1.8 Magnetic Flux (mT) causes a decrease in cellular alkaline phosphatase (AP) synthesis when applied in an alternating mode of 30 Hz [10], but has an opposite incremental effect when applied in a pulsed mode (PEMF) of 15 Hz with a basic 4 kHz frequency [7]
The exposure of cells to the 0.2 mT 10 kHz Alternating the EMF (AEMF) and 10 Hz/5 kHz PEMF had no significant effect on cultured human osteoblast-like cell death and proliferation
Summary
Alternating and pulsed electromagnetic magnetic fields (AEMF and PEMF) of different amplitudes and frequencies can induce metabolic and proliferative effects in osteoblasts, but there is no clearly directed tendency of these effects. The exact cellular mechanism of this phenomenon is not known, but there is a clear indication that there are distinct and different ranges and combinations of AEMF and PEMF frequencies and intensities for affecting different cellular responses of proliferation, metabolic activity and cell cycle modulation Recognizing these combinations might provide powerful therapeutic tools for enhancing bone regeneration. Since the control cultures for comparison are exposed only to a background earth magnetic field, which doesn’t exceed 0.07 mT [5], the intriguing question is whether there is intensity lower than 0.4 EMF but higher than the background EMF that might affect human osteoblasts by enhancing proliferation and/or metabolic activity An answer to this question might define the triggering values of EMF that induce cellular response. It should be noted that this EMF intensity and pulsed electromagnetic field (PEMF)
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