title: Proteomic analysis of synovial fluid: insight into the pathogenesis of knee osteoarthritis.
abstract: OBJECTIVE
  We conducted a proteomic analysis of synovial fluid (SF) to identify differentially expressed proteins and analyse their correlation with osteoarthritis (OA) severity. Our primary purpose was to gain insight into the pathogenesis of OA.
  
  
  METHODS
  SF samples were acquired from 12 knee OA patients and 12 non-OA controls (ten had a meniscus injury, two had a discoid meniscus and all exhibited intact articular cartilage) and sequentially subjected to two-dimensional electrophoresis (2-DE). The radiographic grading of knee OA was performed using the Kellgren-Lawrence criteria. Differentially expressed proteins were identified by matrix-assisted laser desorption/ionisation time-of-flight/time-of-flight mass spectrometry (MALDI-TOF/TOF MS). Proteins of interest identified from SF were detected using an enzyme-linked immunosorbent assay (ELISA).
  
  
  RESULTS
  A total of 31 protein spots showed significant differences (p < 0.05) between the sample groups; 25 of the 31 spots (80.6 %) were identified as proteins of interest. Among them 20 corresponded to up-regulation and five to down-regulation in OA samples. HLA-DR was one of the proteins up-regulated, which was confirmed by ELISA.
  
  
  CONCLUSIONS
  These observations have implications in delineating the protein expression underlying the pathogenesis of OA and facilitate further elucidation of molecular mechanisms involved in disease progression. Substantial alterations of the protein profile in SF may be associated with OA severity.
authors.affiliation: Department of Orthopaedics, General Hospital of PLA, No. 28 Fuxing Road, Haidian District, Beijing, People's Republic of China.
authors.forename: Weixiong
authors.initials: W
authors.lastname: Liao
authors.forename: Zhongli
authors.initials: Z
authors.lastname: Li
authors.forename: Hongli
authors.initials: H
authors.lastname: Wang
authors.forename: Jie
authors.initials: J
authors.lastname: Wang
authors.forename: Yangmu
authors.initials: Y
authors.lastname: Fu
authors.forename: Xiaowei
authors.initials: X
authors.lastname: Bai
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000378:metabolism; D016022:Case-Control Studies; D018450:Disease Progression; D015180:Electrophoresis, Gel, Two-Dimensional; D005260:Female; D006684:HLA-DR Antigens / Q000378:metabolism; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000209:etiology* / Q000378:metabolism*; D040901:Proteomics; D011859:Radiography; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013582:Synovial Fluid / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D006684:HLA-DR Antigens