title: Matrix metalloproteinase 17 is necessary for cartilage aggrecan degradation in an inflammatory environment.
abstract: OBJECTIVE
  Aggrecan is a critical component of cartilage extracellular matrix. Several members of the 'a disintegrin and metalloproteinase with thrombospondin motifs' (ADAMTS) family have been characterised as aggrecanases by their ability to generate fragments containing the NITEGE neoepitope from aggrecan. Increased NITEGE fragments in synovial fluid and articular cartilage are a hallmark of osteoarthritis (OA) and it is hypothesised that the enhanced rate of aggrecan degradation is critical for cartilage destruction in OA. Recently, matrix metalloproteinase 17 (MMP17, also known as MT4-MMP) has been implicated in the activation of one of the key aggrecanases: ADAMTS4. In the present work, the hypothesis that MMP17 mediates the interleukin 1β (IL-1β) induced release of NITEGE neoepitope from human and murine articular cartilage is investigated.
  
  
  METHODS
  MMP17 was quantified at the protein and RNA level and NITEGE neoepitope generation by immunohistochemistry. Human postmortem articular cartilage explants were treated with recombinant MMP17, or IL-1β in the presence or absence of an MMP17 inhibitor. Glycosaminoglycan (GAG) loss into the media was quantified using the 1,9-dimethylmethylene blue (DMMB) assay. Intra-articular injection (IAI) of IL-1β or meniscotibial ligament transaction was carried out in MMP17 null mice.
  
  
  RESULTS
  The data reveal an association between increased MMP17 protein and NITEGE staining in areas of OA cartilage damage. Ex vivo treatment of normal human cartilage with recombinant MMP17 protein increased NITEGE generation in the cartilage and GAG loss into the media. In addition, IL-1β mediated cartilage GAG loss, and increased NITEGE neoepitope expression, were attenuated with an MMP17 inhibitor. IAI of IL-1β into C57BL6/Jax mice resulted in increased MMP17 expression in articular cartilage and increased GAG content in the synovial fluid. MMP17 null mice were protected against this increase. However, aggrecan loss driven by mechanical stress following medial meniscotibial ligament transection was not dependent on MMP17.
  
  
  CONCLUSIONS
  These data further implicate MMP17 in the control of articular cartilage extracellular matrix aggrecan integrity in an inflammatory environment.
authors.affiliation: AstraZeneca R&D Charnwood, RIRA Bioscience Building 21, Bakewell Road, Loughborough, Leicestershire LE11 5RH, UK. kristen.clements@astrazeneca.com
authors.forename: Kristen M
authors.initials: KM
authors.lastname: Clements
authors.forename: Jo K
authors.initials: JK
authors.lastname: Flannelly
authors.forename: Jonathan
authors.initials: J
authors.lastname: Tart
authors.forename: Sarah M V
authors.initials: SM
authors.lastname: Brockbank
authors.forename: John
authors.initials: J
authors.lastname: Wardale
authors.forename: Jim
authors.initials: J
authors.lastname: Freeth
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Parker
authors.forename: Peter
authors.initials: P
authors.lastname: Newham
mesh_terms: D053674:Aggrecans / Q000378:metabolism*; D000818:Animals; D002358:Cartilage, Articular / Q000187:drug effects / Q000378:metabolism*; D010450:Endopeptidases / Q000378:metabolism; D006025:Glycosaminoglycans / Q000378:metabolism; D006801:Humans; D053515:Matrix Metalloproteinase 17 / Q000494:pharmacology / Q000502:physiology*; D061965:Matrix Metalloproteinase Inhibitors; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011480:Protease Inhibitors / Q000494:pharmacology; D011994:Recombinant Proteins / Q000494:pharmacology; D046509:Tissue Culture Techniques
chemical_list: D053674:Aggrecans; D006025:Glycosaminoglycans; D061965:Matrix Metalloproteinase Inhibitors; D011480:Protease Inhibitors; D011994:Recombinant Proteins; D010450:Endopeptidases; D053515:Matrix Metalloproteinase 17; C083641:aggrecanase