title: Pathomechanisms of discogenic low back pain in humans and animal models.
abstract: BACKGROUND
  Although explored in humans and animal models, the pathomechanisms of discogenic low back pain (LBP) remain unknown.
  
  
  OBJECTIVE
  The aim of this study was to review the literature about the pathomechanisms of discogenic LBP.
  
  
  METHODS
  Animal models of discogenic pain and specimens from degenerated human intervertebral discs (IVDs) have provided clues about the pathomechanisms of discogenic LBP. Painful discs are characterized by a confluence of innervation, inflammation, and mechanical hypermobility. These three possible mechanisms are discussed in this review.
  
  
  RESULTS
  Animal models and specimens from humans have revealed sensory innervation of lumbar IVDs and sensory nerve ingrowth into the inner layer of IVDs. Cytokines such as tumor necrosis factor-α and interleukins induce this ingrowth. Nerve growth factor has also been recently identified as an inducer of ingrowth. Finally, disc degeneration induces several collagenases; their action results in hypermobility and pain.
  
  
  CONCLUSIONS
  To treat discogenic LBP, it is important to prevent sensitization of sensory nerve fibers innervating the IVD, to suppress pathogenic increases of cytokines, and to decrease disc hypermobility.
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670, Japan. Electronic address: sohtori@faculty.chiba-u.jp.
authors.forename: Seiji
authors.initials: S
authors.lastname: Ohtori
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670, Japan.
authors.forename: Gen
authors.initials: G
authors.lastname: Inoue
authors.affiliation: Department of Orthopaedic Surgery, Kitasato University, School of Medicine, 1-15-1 Kitasato, Minami, Sagamihara, Kanagawa, 252-0374, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Miyagi
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670, Japan.
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Takahashi
mesh_terms: D000818:Animals; D016207:Cytokines / Q000378:metabolism; D004195:Disease Models, Animal; D006801:Humans; D007403:Intervertebral Disc / Q000378:metabolism / Q000473:pathology*; D055959:Intervertebral Disc Degeneration / Q000150:complications / Q000473:pathology*; D017116:Low Back Pain / Q000209:etiology / Q000473:pathology*; D020932:Nerve Growth Factor / Q000378:metabolism
chemical_list: D016207:Cytokines; D020932:Nerve Growth Factor
keywords: Hypermobility; Inflammation; Intervertebral disc; Pain; Psychosocial factors; Sensory nerve