title: Proinflammatory cytokines stimulate the expression of nerve growth factor by human intervertebral disc cells.
abstract: METHODS
  In vitro studies of the effects of proinflammatory cytokines on the production of nerve growth factor (NGF) by human intervertebral disc (IVD) cells.
  
  
  OBJECTIVE
  To determine the constitutive expression and production of NGF and the effect of cytokines on the expression of NGF by human IVD cells.
  
  
  BACKGROUND
  NGF may play a role in the collateral sprouting of sensory axons, neural survival, and regulation of nociceptive sensory neurons. NGF is known to be up-regulated by proinflammatory cytokines.
  
  
  METHODS
  The presence of NGF protein was analyzed by immunohistochemistry using human IVD cells obtained from cadaveric human spines with no known disc disease (MRI Thompson grades 2-4). The effects of interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) on NGF production and mRNA expression of NGF by IVD cells were examined. The expression of NGF receptors, trkA and p75, was also assessed immunohistochemically.
  
  
  RESULTS
  Cadaveric anulus fibrosus (AF) and nucleus pulposus (NP) cells cultured in vitro in monolayer and in alginate beads positively stained with an anti-NGF antibody. The constitutive production of NGF protein in IVD cells was low (NP) or not detectable (AF). The expression of NGF mRNA was detectable in both cell types. IL-1beta and TNF-alpha up-regulated the NGF mRNA expression and the secretion of NGF protein into the media. TrkA was immunolocalized in AF and NP cells.
  
  
  CONCLUSIONS
  Our results demonstrate, for the first time, that human AF and NP cells constitutively express NGF protein and mRNA, and that the proinflammatory cytokines IL-1beta and TNF-alpha stimulate the production of NGF. The precise role of NGF produced by IVD cells in the generation of discogenic pain or on the metabolism of IVD cells, especially under certain physiologic conditions in which cytokines are up-regulated, needs to be clarified in future experimentation.
authors.affiliation: Department of Orthopedic Surgery, Rush Medical College at Rush University Medical Center, Chicago IL, USA.
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Abe
authors.forename: Koji
authors.initials: K
authors.lastname: Akeda
authors.forename: Howard S
authors.initials: HS
authors.lastname: An
authors.forename: Yasuchika
authors.initials: Y
authors.lastname: Aoki
authors.forename: Rajeswari
authors.initials: R
authors.lastname: Pichika
authors.forename: Carol
authors.initials: C
authors.lastname: Muehleman
authors.forename: Tomoatsu
authors.initials: T
authors.lastname: Kimura
authors.forename: Koichi
authors.initials: K
authors.lastname: Masuda
mesh_terms: D002102:Cadaver; D018929:Cell Culture Techniques; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007150:Immunohistochemistry; D018836:Inflammation Mediators / Q000378:metabolism; D053583:Interleukin-1beta / Q000378:metabolism; D007403:Intervertebral Disc / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008875:Middle Aged; D020932:Nerve Growth Factor / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis; D020800:Receptor, Nerve Growth Factor / Q000378:metabolism; D020917:Receptor, trkA / Q000378:metabolism; D012016:Reference Values; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D016207:Cytokines; D018836:Inflammation Mediators; D053583:Interleukin-1beta; D012333:RNA, Messenger; D020800:Receptor, Nerve Growth Factor; D014409:Tumor Necrosis Factor-alpha; D020932:Nerve Growth Factor; D020917:Receptor, trkA