title: The active form of MMP-3 is a marker of synovial inflammation and cartilage turnover in inflammatory joint diseases.
abstract: BACKGROUND
  Matrix metalloproteinase-3 (MMP-3) plays an important role in the pathology of rheumatoid arthritis (RA) and ankylosing spondylitis (AS). Measurement of active MMP-3 in clinical samples could provide information about progression of rheumatoid diseases, and potentially response to treatment. Hence, we aimed to develop a sensitive assay specifically measuring the active form of MMP-3 (act-MMP-3) both in ex vivo models and in human sera.
  
  
  METHODS
  A monoclonal antibody against the first 6 amino acids of act-MMP-3 was developed, and the specificity was carefully tested by comparing total and active MMP-3. A technically robust act-MMP-3 ELISA was produced. For biological validation, human synovial membrane and human cartilage explant (HEX) culture models were measured and compared by ELISA and immunoblots. For clinical relevance, the serum levels of act-MMP-3 in AS and RA patients before and after anti-TNF-α treatment were evaluated.
  
  
  RESULTS
  A highly specific and technically robust ELISA detecting act-MMP-3 in serum was developed. The lower limit of detection was 33.7 pg/mL. The dilution and spiking recovery of human serum was within 100 ± 20%. The average intra- and inter-assay variations were 3.1% and 13.5% respectively.High levels of act-MMP-3 expression were observed in human synovial membrane culture and oncostatin M and TNF-α stimulated human cartilage. In a cross-sectional study of both AS and RA patients, serum act-MMP-3 level was correlated with C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR). In addition, in patients receiving anti-TNF-α treatment, the serum level of act-MMP-3 was significantly reduced compared to baseline level reflecting the anti-inflammatory effects of the treatment.
  
  
  CONCLUSIONS
  We have successfully developed an assay measuring act-MMP-3 in human serum showing correlation to inflammatory markers. Further studies are required to clarify, whether act-MMP-3 can serve as a predictive marker for outcome in chronic rheumatoid disorders.
authors.affiliation: Nordic Bioscience Biomarkers and Research, Herlev, Denmark. ssu@nordicbioscience.com.
authors.forename: Shu
authors.initials: S
authors.lastname: Sun
authors.forename: Anne-Christine
authors.initials: AC
authors.lastname: Bay-Jensen
authors.forename: Morten A
authors.initials: MA
authors.lastname: Karsdal
authors.forename: Anne Sofie
authors.initials: AS
authors.lastname: Siebuhr
authors.forename: Qinlong
authors.initials: Q
authors.lastname: Zheng
authors.forename: Walter P
authors.initials: WP
authors.lastname: Maksymowych
authors.forename: Thorbjørn G
authors.initials: TG
authors.lastname: Christiansen
authors.forename: Kim
authors.initials: K
authors.lastname: Henriksen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D018501:Antirheumatic Agents / Q000627:therapeutic use; D001172:Arthritis, Rheumatoid / Q000097:blood* / Q000188:drug therapy / Q000201:enzymology; D015415:Biomarkers; D002097:C-Reactive Protein / Q000032:analysis; D002356:Cartilage / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D004789:Enzyme Activation; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007249:Inflammation; D008297:Male; D019278:Matrix Metalloproteinase 3 / Q000097:blood* / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D053683:Oncostatin M / Q000494:pharmacology; D009924:Organ Culture Techniques; D020370:Osteoarthritis, Knee / Q000473:pathology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D013047:Specific Pathogen-Free Organisms; D013167:Spondylitis, Ankylosing / Q000097:blood* / Q000188:drug therapy / Q000201:enzymology; D013583:Synovial Membrane / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D016896:Treatment Outcome; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors / Q000494:pharmacology
chemical_list: D000911:Antibodies, Monoclonal; D018501:Antirheumatic Agents; D015415:Biomarkers; D014409:Tumor Necrosis Factor-alpha; D053683:Oncostatin M; D002097:C-Reactive Protein; D019278:Matrix Metalloproteinase 3