title: Effects of electromagnetic field (PEMF) exposure at different frequency and duration on the peripheral nerve regeneration: in vitro and in vivo study.
abstract: OBJECTIVE
  The purpose was to clarify the influence of frequency and exposure time of pulsed electromagnetic fields (PEMF) on the peripheral nerve regeneration.
  
  
  METHODS
  Immortalized rat Schwann cells (iSCs) (1 × 10(2)/well) were exposed at four different conditions in 1 mT (50 Hz 1 h/d, 50 Hz 12 h/d, 150 Hz 1 h/d and 150 Hz 12h/d). Cell proliferation, mRNA expression of S100 and brain-derived neurotrophic factor (BDNF) were analyzed. Sprague-Dawley rats (200-250 g) were divided into six groups (n = 10 each): control, sham, 50 Hz 1 h/d, 50 Hz 12 h/d, 150 Hz 1 h/d and 150 Hz 12 Hr/d. Mental nerve was crush-injured and exposed at four different conditions in 1 mT (50 Hz 1 Hr/d, 50 Hz 12 Hr/d, 150 Hz 1 h/d and 150 Hz 12 h/d). Nerve regeneration was evaluated with functional test, histomorphometry and retrograde labeling of trigeminal ganglion.
  
  
  RESULTS
  iSCs proliferation with 50 Hz, 1 h/d was increased from fourth to seventh day; mRNA expression of S100 and BDNF was significantly increased at the same condition from first week to third week (p < .05 vs. control); difference score was increased at the second and third week, and gap score was increased at the third under 50 Hz 1 h PEMF compared with control while other conditions showed no statistical meaning. Axon counts and retrograde labeled neurons were significantly increased under PEMF of four different conditions compared with control. Although there was no statistical difference, 50 Hz, 1 h PEMF showed highest regeneration ability than other conditions.
  
  
  CONCLUSIONS
  PEMF enhanced peripheral nerve regeneration, and that it may be due to cell proliferation and increase in BDNF and S100 gene expression.
authors.affiliation: a Department of Oral and Maxillofacial Surgery, School of Dentistry , Seoul National University , Seoul , Korea.
authors.forename: Wei-Hong
authors.initials: WH
authors.lastname: Hei
authors.affiliation: a Department of Oral and Maxillofacial Surgery, School of Dentistry , Seoul National University , Seoul , Korea.
authors.forename: Soo-Hwan
authors.initials: SH
authors.lastname: Byun
authors.affiliation: b Department of Oral and Maxillofacial Surgery, Hallum Medical School , Sacred Kangdong hospital , Seoul , Korea.
authors.forename: Jong-Sik
authors.initials: JS
authors.lastname: Kim
authors.affiliation: c Graduate School of Bio & Information Technology , Hankyong National University , Anseong-si, Kyonggi-do , Seoul , Korea.
authors.forename: Soochan
authors.initials: S
authors.lastname: Kim
authors.affiliation: d Research Institute of Biotechnology , Dongguk University , Seoul , Korea.
authors.forename: Young-Kwon
authors.initials: YK
authors.lastname: Seo
authors.affiliation: e Department of Oral Histology-Developmental Biology, School of Dentistry , Seoul National University , Seoul , Korea.
authors.forename: Joo-Cheol
authors.initials: JC
authors.lastname: Park
authors.affiliation: a Department of Oral and Maxillofacial Surgery, School of Dentistry , Seoul National University , Seoul , Korea.
authors.forename: Soung-Min
authors.initials: SM
authors.lastname: Kim
authors.affiliation: f Dental Research Institute , Seoul National University , Seoul , Korea.
authors.forename: Jeong Won
authors.initials: JW
authors.lastname: Jahng
authors.affiliation: a Department of Oral and Maxillofacial Surgery, School of Dentistry , Seoul National University , Seoul , Korea.|f Dental Research Institute , Seoul National University , Seoul , Korea.
authors.forename: Jong-Ho
authors.initials: JH
authors.lastname: Lee
mesh_terms: D000818:Animals; D018929:Cell Culture Techniques; D055909:Magnetic Field Therapy / Q000379:methods*; D008297:Male; D009416:Nerve Regeneration / Q000502:physiology*; D059348:Peripheral Nerve Injuries / Q000378:metabolism / Q000503:physiopathology / Q000628:therapy*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012583:Schwann Cells / Q000502:physiology*
keywords: S100; brain-derived neurotrophic factor (BDNF); crush nerve injury; immortalized Schwann cells (iSCs); peripheral nerve regeneration; pulsed electromagnetic fields (PEMFs)