title: Enhanced local production of osteopontin in rheumatoid joints.
abstract: OBJECTIVE
  To investigate the involvement of osteopontin (OPN) in the pathogenesis of rheumatoid arthritis (RA), localization and production of OPN were examined in patients with RA.
  
  
  METHODS
  Localization of OPN in the rheumatoid synovium was examined by immunohistochemistry. In vitro OPN production by cultured synovial cells from patients with RA (n = 5) and with osteoarthritis (OA) (n = 5) was assessed by ELISA. OPN concentrations in plasma and synovium were quantified in patients with RA (n = 23) by 2 distinct ELISA systems to measure both thrombin cleaved and non-cleaved OPN. The same experiments were done in patients with OA (n = 15) and healthy volunteers (n = 10) as a control.
  
  
  RESULTS
  OPN was highly detected by immunohistochemistry predominantly in the RA synovial lining cells, while less and scattered OPN was detected in OA synovial tissues. ELISA revealed that cultured RA synovial cells secreted significantly more OPN than OA cells. ELISA also showed a marked increase of OPN levels in synovial fluid (SF) of patients with RA and with OA compared to the control plasma OPN levels, although OPN levels were not increased in RA and OA plasma compared to healthy controls. SF OPN levels of patients with RA were significantly higher than those of patients with OA, and correlated with serum C-reactive protein levels. The ratios of thrombin cleaved versus non-cleaved OPN were significantly increased in RA plasma and SF compared with OA plasma and SF and plasma from healthy controls.
  
  
  CONCLUSIONS
  Our results revealed enhanced local production of OPN in rheumatoid joints, suggesting involvement of OPN in the pathogenesis of RA.
authors.affiliation: Department of Molecular Medicine, Osaka University Medical School, Osaka, Japan.
authors.forename: Shiro
authors.initials: S
authors.lastname: Ohshima
authors.forename: Norihiko
authors.initials: N
authors.lastname: Yamaguchi
authors.forename: Katsuhiro
authors.initials: K
authors.lastname: Nishioka
authors.forename: Toru
authors.initials: T
authors.lastname: Mima
authors.forename: Taeko
authors.initials: T
authors.lastname: Ishii
authors.forename: Mitsuko
authors.initials: M
authors.lastname: Umeshita-Sasai
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Kobayashi
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Shimizu
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Katada
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Wakitani
authors.forename: Norikazu
authors.initials: N
authors.lastname: Murata
authors.forename: Shintaro
authors.initials: S
authors.lastname: Nomura
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Matsuno
authors.forename: Rie
authors.initials: R
authors.lastname: Katayama
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Kon
authors.forename: Manabu
authors.initials: M
authors.lastname: Inobe
authors.forename: Toshimitsu
authors.initials: T
authors.lastname: Uede
authors.forename: Ichiro
authors.initials: I
authors.lastname: Kawase
authors.forename: Yukihiko
authors.initials: Y
authors.lastname: Saeki
mesh_terms: D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000378:metabolism / Q000473:pathology; D053495:Osteopontin; D012795:Sialoglycoproteins / Q000276:immunology / Q000378:metabolism*; D013583:Synovial Membrane / Q000378:metabolism* / Q000473:pathology
chemical_list: C506895:SPP1 protein, human; D012795:Sialoglycoproteins; D053495:Osteopontin