title: Transient receptor potential vanilloid 1-immunoreactive innervation increases in fractured rat femur.
abstract: OBJECTIVE
  Pain from vertebral or femoral neck fractures is a particularly important problem in clinical orthopaedics. Transient receptor potential vanilloid 1 (TRPV1) is a ligand-gated nonselective cation channel, and there are recent reports on an association between bone pain and TRPV1. However, an increase in TRPV1 activity has not been reported following femoral fracture.
  
  
  METHODS
  We applied a neurotracer [Fluoro-gold (FG)] onto femur to detect dorsal root ganglia (DRGs) innervating the cortex of the femur in 30 Sprague Dawley rats. Seven days after application, a closed mid-diaphyseal fracture of the femur was performed. FG labeled TRPV1-immunoreactive (ir) DRGs innervating the femur were examined in nonfractured controls, and 3 days, 1 week, 2 weeks, and 4 weeks after fracture. We evaluated bone healing of the femur and compared the ratio of TRPV1-ir DRG neurons innervating the femur at the time points.
  
  
  RESULTS
  Four weeks after fracture, complete bone union was observed. There was no significant difference in the ratio of FG labeled DRG neurons to total DRG neurons at each time point. The percentages of TRPV1-ir neurons in DRGs innervating the femur at 3 days and 1 week after fracture were significantly higher than those in control, 2 weeks, and 4 weeks after fracture (p<0.05).
  
  
  CONCLUSIONS
  Fracture induced an increase of TRPV1-ir neurons in DRGs innervating the fractured femur within 3 days, and decreased during bone healing over 4 weeks. These findings show that TRPV1 may play a role in sensory sensation of bone fracture pain.
authors: Department of Orthopaedic Surgery, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670, Japan. sohtori@faculty.chiba-u.jp.
authors: Yuya
authors: Y
authors: Kawarai
authors: Miyako
authors: M
authors: Suzuki
authors: Kensuke
authors: K
authors: Yoshino
authors: Gen
authors: G
authors: Inoue
authors: Sumihisa
authors: S
authors: Orita
authors: Kazuyo
authors: K
authors: Yamauchi
authors: Yasuchika
authors: Y
authors: Aoki
authors: Tetsuhiro
authors: T
authors: Ishikawa
authors: Masayuki
authors: M
authors: Miyagi
authors: Hiroto
authors: H
authors: Kamoda
authors: Go
authors: G
authors: Kubota
authors: Yoshihiro
authors: Y
authors: Sakuma
authors: Yasuhiro
authors: Y
authors: Oikawa
authors: Kazuhide
authors: K
authors: Inage
authors: Takeshi
authors: T
authors: Sainoh
authors: Jun
authors: J
authors: Sato
authors: Junichi
authors: J
authors: Nakamura
authors: Masashi
authors: M
authors: Takaso
authors: Tomoaki
authors: T
authors: Toyone
authors: Kazuhisa
authors: K
authors: Takahashi
authors: Seiji
authors: S
authors: Ohtori
mesh_terms: D000818:Animals; D005260:Female; D005269:Femur / Q000294:innervation* / Q000378:metabolism*; D007150:Immunohistochemistry; D051381:Rats; D017207:Rats, Sprague-Dawley; D050916:TRPV Cation Channels / Q000378:metabolism*
chemical_list: D050916:TRPV Cation Channels; C493922:Trpv1 protein, rat
keywords: Fracture; femur; pain; rat; transient receptor potential vanilloid 1