title: Differential expression pattern of membrane-type matrix metalloproteinases in rheumatoid arthritis.
abstract: OBJECTIVE
  To study the expression of messenger RNA (mRNA) for different membrane-type matrix metalloproteinases (MT-MMPs) and compare their expression pattern in rheumatoid arthritis (RA) and normal synovium.
  
  
  METHODS
  Polymerase chain reaction (PCR) with specific primers was performed to analyze the presence of MT1-, MT2-, MT3-, and MT4-MMP in synovial tissue and synovial fibroblasts from 10 patients with RA and 4 subjects without arthritis. In addition, in situ hybridization with digoxigenin-labeled RNA probes was used to investigate the expression pattern of MT-MMPs in the synovium of these subjects. MT-MMP-expressing cells were characterized by immunohistochemical double labeling with anti-CD68 monoclonal antibodies.
  
  
  RESULTS
  Reverse transcription-PCR revealed the expression of MT1-, MT2-, MT3-, and MT4-MMP mRNA in all tissues and cell cultures examined. However, in situ hybridization showed considerable differences in the expression pattern of the different MT-MMPs in RA synovium. MT1- and MT3-MMP mRNA were highly expressed in both the lining and the sublining layer, with more intense staining in the lining. Immunohistochemical double labeling demonstrated the presence of mRNA for MT1-MMP in fibroblasts and macrophages, as well as in osteoclast-like cells at sites of bone resorption. Expression of MT3-MMP mRNA was seen in fibroblasts and some macrophages. Expression of MT2- and MT4-MMP was characterized by staining of only a few CD68-negative fibroblasts, and no differences could be found between the lining and sublining. Normal synovial samples showed only limited staining for all MT-MMPs.
  
  
  CONCLUSIONS
  Our results indicate a role for MT1-MMP not only in the matrix degradation by fibroblasts, but also in osteoclast-mediated bone resorption in RA. Given the ability of MT1-MMP to activate MMP-2 and MMP-13, the findings also point to a cooperation between fibroblasts and macrophages in degrading cartilage and bone. While MT3-MMP is also intensely expressed in RA synovium, MT2- and MT4-MMP appear not to be involved in rheumatoid joint destruction.
authors.affiliation: WHO Collaborating Center for Molecular Biology and Novel Therapeutic Strategies for Rheumatic Diseases, University Hospital, Zurich, Switzerland.
authors.forename: T
authors.initials: T
authors.lastname: Pap
authors.forename: Y
authors.initials: Y
authors.lastname: Shigeyama
authors.forename: S
authors.initials: S
authors.lastname: Kuchen
authors.forename: J K
authors.initials: JK
authors.lastname: Fernihough
authors.forename: B
authors.initials: B
authors.lastname: Simmen
authors.forename: R E
authors.initials: RE
authors.lastname: Gay
authors.forename: M
authors.initials: M
authors.lastname: Billingham
authors.forename: S
authors.initials: S
authors.lastname: Gay
mesh_terms: D001172:Arthritis, Rheumatoid / Q000201:enzymology* / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D020782:Matrix Metalloproteinases / Q000235:genetics / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012016:Reference Values; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013583:Synovial Membrane / Q000378:metabolism
chemical_list: D020033:Protein Isoforms; D012333:RNA, Messenger; D020782:Matrix Metalloproteinases