title: Mechanical destabilization induced by controlled annular incision of the intervertebral disc dysregulates metalloproteinase expression and induces disc degeneration.
abstract: METHODS
  An investigation of mechanical destabilization of the lumbar ovine intervertebral disc (IVD) inducing IVD degeneration (IVDD) as determined by multiparameter outcome measures (magnetic resonance imaging [MRI], IVD composition, biomechanical testing, gene profiling, immunohistochemistry, and immunoblotting).
  
  
  OBJECTIVE
  To assess the effect of IVD mechanical destabilization on matrix protein and metalloproteinase gene expression to investigate the pathophysiological mechanisms of lumbar IVDD.
  
  
  BACKGROUND
  Several earlier studies have used annular transection to induce IVDD in sheep, but none have optimized or validated the most appropriate lesion size.
  
  
  METHODS
  The annulus fibrosus (AF) incision inducing maximal change in IVD biomechanics was applied to L1-L2, L3-L4, and L5-L6 discs in vivo to compare with a sham procedure at 3 months post operation. IVDs were evaluated by MRI, biomechanics, histopathology, proteoglycan and collagen content, gene expression, and aggrecan proteolysis by Western blotting.
  
  
  RESULTS
  Significant changes were observed in lesion (6 × 20 mm(2)) compared with sham IVDs at 3 months post operation: reduced disc height on MRI; increased neutral zone in biomechanical testing; depleted proteoglycan and collagen content in the nucleus pulposus (NP) and lesion half of the AF but not in the contralateral AF; increased messenger RNA for collagen I and II, aggrecan, versican, perlecan, matrix metalloproteinase (MMP)-1 & 13, and ADAMTS-5, in the lesion-site AF and NP but not in the contralateral AF. ADAMTS-4 messenger RNA was increased in the lesion-site AF but decreased in the NP. Despite an upregulation in MMPs, there was no change in MMP- or ADAMTS-generated aggrecan neoepitopes in any region of the IVD in lesion or sham discs.
  
  
  CONCLUSIONS
  Lumbar IVDD was reproducibly induced with a 6 × 20 mm(2) annular lesion, with focal dysregulation of MMP gene expression, cell cloning in the inner AF, loss of NP aggrecan, and disc height. Loss of aggrecan from the NP was not attributable to increased proteolysis in the interglobular domain by MMPs or ADAMTS.
authors.affiliation: Raymond Purves Bone and Joint Research Laboratories, Kolling Institute of Medical Research, Institute of Bone and Joint Research, University of Sydney, The Royal North Shore Hospital of Sydney, St Leonards, New South Wales, Australia. jmelrose@med.usyd.edu.au
authors.forename: James
authors.initials: J
authors.lastname: Melrose
authors.forename: Cindy
authors.initials: C
authors.lastname: Shu
authors.forename: Cara
authors.initials: C
authors.lastname: Young
authors.forename: Ronald
authors.initials: R
authors.lastname: Ho
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Smith
authors.forename: Allan A
authors.initials: AA
authors.lastname: Young
authors.forename: Susan S
authors.initials: SS
authors.lastname: Smith
authors.forename: Ben
authors.initials: B
authors.lastname: Gooden
authors.forename: Andrew
authors.initials: A
authors.lastname: Dart
authors.forename: Juan
authors.initials: J
authors.lastname: Podadera
authors.forename: Richard C
authors.initials: RC
authors.lastname: Appleyard
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Little
mesh_terms: D051722:ADAM Proteins / Q000235:genetics / Q000378:metabolism; D000071121:ADAMTS4 Protein; D000818:Animals; D003094:Collagen / Q000235:genetics / Q000378:metabolism; D004195:Disease Models, Animal; D015870:Gene Expression; D020869:Gene Expression Profiling; D007403:Intervertebral Disc / Q000293:injuries / Q000378:metabolism* / Q000473:pathology; D055959:Intervertebral Disc Degeneration / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D008159:Lumbar Vertebrae / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D008279:Magnetic Resonance Imaging; D008297:Male; D045726:Metalloproteases / Q000235:genetics / Q000378:metabolism*; D009919:Orchiectomy; D011348:Procollagen N-Endopeptidase / Q000235:genetics / Q000378:metabolism; D011509:Proteoglycans / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012756:Sheep; D013314:Stress, Mechanical
chemical_list: D011509:Proteoglycans; D012333:RNA, Messenger; D003094:Collagen; D045726:Metalloproteases; D051722:ADAM Proteins; D011348:Procollagen N-Endopeptidase; D000071121:ADAMTS4 Protein