title: Rat tail static compression model mimics extracellular matrix metabolic imbalances of matrix metalloproteinases, aggrecanases, and tissue inhibitors of metalloproteinases in intervertebral disc degeneration.
abstract: BACKGROUND
  The longitudinal degradation mechanism of extracellular matrix (ECM) in the interbertebral disc remains unclear. Our objective was to elucidate catabolic and anabolic gene expression profiles and their balances in intervertebral disc degeneration using a static compression model.
  
  
  METHODS
  Forty-eight 12-week-old male Sprague-Dawley rat tails were instrumented with an Ilizarov-type device with springs and loaded statically at 1.3 MPa for up to 56 days. Experimental loaded and distal-unloaded control discs were harvested and analyzed by real-time reverse transcription-polymerase chain reaction (PCR) messenger RNA quantification for catabolic genes [matrix metalloproteinase (MMP)-1a, MMP-2, MMP-3, MMP-7, MMP-9, MMP-13, a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4, and ADAMTS-5], anti-catabolic genes [tissue inhibitor of metalloproteinases (TIMP)-1, TIMP-2, and TIMP-3], ECM genes [aggrecan-1, collagen type 1-α1, and collagen type 2-α1], and pro-inflammatory cytokine genes [tumor necrosis factor (TNF)-α, interleukin (IL)-1α, IL-1β, and IL-6]. Immunohistochemistry for MMP-3, ADAMTS-4, ADAMTS-5, TIMP-1, TIMP-2, and TIMP-3 was performed to assess their protein expression level and distribution. The presence of MMP- and aggrecanase-cleaved aggrecan neoepitopes was similarly investigated to evaluate aggrecanolytic activity.
  
  
  RESULTS
  Quantitative PCR demonstrated up-regulation of all MMPs and ADAMTS-4 but not ADAMTS-5. TIMP-1 and TIMP-2 were almost unchanged while TIMP-3 was down-regulated. Down-regulation of aggrecan-1 and collagen type 2-α1 and up-regulation of collagen type 1-α1 were observed. Despite TNF-α elevation, ILs developed little to no up-regulation. Immunohistochemistry showed, in the nucleus pulposus, the percentage of immunopositive cells of MMP-cleaved aggrecan neoepitope increased from 7 through 56 days with increased MMP-3 and decreased TIMP-1 and TIMP-2 immunopositivity. The percentage of immunopositive cells of aggrecanase-cleaved aggrecan neoepitope increased at 7 and 28 days only with decreased TIMP-3 immunopositivity. In the annulus fibrosus, MMP-cleaved aggrecan neoepitope presented much the same expression pattern. Aggrecanase-cleaved aggrecan neoepitope increased at 7 and 28 days only with increased ADAMTS-4 and ADAMTS-5 immunopositivity.
  
  
  CONCLUSIONS
  This rat tail sustained static compression model mimics ECM metabolic imbalances of MMPs, aggrecanases, and TIMPs in human degenerative discs. A dominant imbalance of MMP-3/TIMP-1 and TIMP-2 relative to ADAMTS-4 and ADAMTS-5/TIMP-3 signifies an advanced stage of intervertebral disc degeneration.
authors.affiliation: Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Kobe, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Yurube
authors.forename: Toru
authors.initials: T
authors.lastname: Takada
authors.forename: Teppei
authors.initials: T
authors.lastname: Suzuki
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Kakutani
authors.forename: Koichiro
authors.initials: K
authors.lastname: Maeno
authors.forename: Minoru
authors.initials: M
authors.lastname: Doita
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kurosaka
authors.forename: Kotaro
authors.initials: K
authors.lastname: Nishida
mesh_terms: D053674:Aggrecans / Q000378:metabolism*; D000818:Animals; D004195:Disease Models, Animal; D005109:Extracellular Matrix / Q000378:metabolism*; D055959:Intervertebral Disc Degeneration / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D008297:Male; D020782:Matrix Metalloproteinases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013117:Spinal Cord Compression / Q000378:metabolism* / Q000473:pathology; D013623:Tail / Q000378:metabolism / Q000473:pathology; D019714:Tissue Inhibitor of Metalloproteinases / Q000378:metabolism*
chemical_list: C508321:Acan protein, rat; D053674:Aggrecans; D019714:Tissue Inhibitor of Metalloproteinases; D020782:Matrix Metalloproteinases