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

Purpose The purpose was to clarify the influence of frequency and exposure time of PEMF on the peripheral nerve regeneration. Materials and methods Immortalized rat Schwann cells (iSCs) (1×102/well) were exposed at 4 different conditions in 1mT (50Hz 1Hr/day, 50Hz 12Hr/day, 150Hz 1Hr/day and 150Hz 12Hr/day). Cell proliferation, mRNA expression of S100 and brain-derived neurotrophic factor (BDNF) were analyzed. Sprague-Dawley rats (200-250g) were divided into 6 groups (n = 10 each): control, sham, 50Hz 1Hr/day, 50Hz 12Hr/day, 150Hz 1Hr/day and 150Hz 12Hr/day. Mental nerve was crush-injured and exposed at 4 different conditions in 1mT (50Hz 1Hr/day, 50Hz 12Hr/day, 150Hz 1Hr/day and 150Hz 12Hr/day). Nerve regeneration was evaluated with functional test, histomorphometry and retrograde labeling of trigeminal ganglion. Results iSCs proliferation with 50Hz, 1Hr/day was increased from 4th to 7th day; mRNA expression of S100 and BDNF was significantly increased at the same condition from 1st week to 3rd week (p<.05, vs. control); Difference score was increased at the 2nd and 3rd week, and Gap score was increased at the 3rd under 50Hz 1Hr PEMF compared with control while other conditions showed no statistical meaning. Axon counts and retrograde labeled neurons were significantly increased under PEMF of 4 different conditions compared with control. Although there was no statistical difference, 50 Hz, 1Hr PEMF showed highest regeneration ability than other conditions. Conclusion PEMF enhanced peripheral nerve regeneration, and that it may be due to cell proliferation and increase in BDNF and S100 gene expression.
KEYWORDS:
Pulsed electromagnetic fields (PEMF); S100; brain-derived neurotrophic factor (BDNF); crush nerve injury; immortalized Schwann cells (iSCs); peripheral nerve regeneration
PMID: 26010211