title: Cathepsin B and its endogenous inhibitor cystatin C in rheumatoid arthritis synovium.
abstract: OBJECTIVE
  To compare the expression of cathepsin B and its endogenous inhibitor cystatin C in synovial tissue of patients with rheumatoid arthritis (RA) and to determine the cell type expressing cystatin C.
  
  
  METHODS
  The expression of cathepsin B and cystatin C was studied by immunohistochemistry in synovial tissue of 10 patients with RA and compared to healthy controls. Applying double labeling methods, the expression of cathepsin B was compared to that of cystatin C. To determine the cell type expressing cystatin C, double labeling with anti-CD68 (PG-M1) was performed.
  
  
  RESULTS
  Both cystatin C and cathepsin B were strongly expressed in synoviocytes of patients with RA. Furthermore, fibroproliferative tissue at the site of cartilage and bone destruction contained fibroblast-like and macrophage-like cells positive for cystatin C and cathepsin B, whereas normal synovial tissue exhibited only limited expression of these molecules. Osteoclasts revealed positive staining for CD68 and cystatin C, but not for cathepsin B.
  
  
  CONCLUSIONS
  Cystatin C is a product of both macrophage-like and fibroblast-like synoviocytes. The strong expression of both the matrix degrading cysteine proteinase cathepsin B and the cysteine proteinase inhibitor cystatin C in rheumatoid synovium, particularly at the sites of bone and cartilage erosion, suggests that cystatin C--although increased--is not sufficient to prevent matrix degradation by cathepsin B.
authors.affiliation: Institute of Pathology and the Clinic of Orthopedics, University of Mainz, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Hansen
authors.forename: P K
authors.initials: PK
authors.lastname: Petrow
authors.forename: A
authors.initials: A
authors.lastname: Gaumann
authors.forename: G M
authors.initials: GM
authors.lastname: Keyszer
authors.forename: P
authors.initials: P
authors.lastname: Eysel
authors.forename: A
authors.initials: A
authors.lastname: Eckardt
authors.forename: R
authors.initials: R
authors.lastname: Bräuer
authors.forename: J
authors.initials: J
authors.lastname: Kriegsmann
mesh_terms: D000328:Adult; D000368:Aged; D015703:Antigens, CD / Q000032:analysis; D015214:Antigens, Differentiation, Myelomonocytic / Q000032:analysis; D001172:Arthritis, Rheumatoid / Q000378:metabolism* / Q000473:pathology; D002356:Cartilage / Q000737:chemistry / Q000473:pathology; D002401:Cathepsin B / Q000032:analysis*; D055316:Cystatin C; D015891:Cystatins / Q000032:analysis*; D015853:Cysteine Proteinase Inhibitors / Q000032:analysis*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D010006:Osteoblasts / Q000737:chemistry / Q000473:pathology; D010010:Osteoclasts / Q000737:chemistry / Q000473:pathology; D013583:Synovial Membrane / Q000737:chemistry* / Q000473:pathology; D000097382:CD68 Molecule
chemical_list: D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D002401:Cathepsin B; D055316:Cystatin C; D015891:Cystatins; D015853:Cysteine Proteinase Inhibitors; C067980:CD68 antigen, human; D000097382:CD68 Molecule; C525030:CST3 protein, human