title: An explorative study comparing levels of soluble mediators in control and osteoarthritic synovial fluid.
abstract: OBJECTIVE
  Soluble mediators in synovial fluid (SF) are acknowledged as key players in the pathophysiology of osteoarthritis (OA). However, a wide-spectrum screening of such mediators in SF is currently lacking. In this study, the levels of 47 mediators in the SF of control donors and osteoarthritic (OA) patients were compared.
  
  
  METHODS
  SF was collected from control donors (n = 16) and end-stage knee OA patients (n = 18) and analysed for 47 cytokines, chemokines and growth factors using several multiplex enzyme-linked immunosorbent assays (ELISAs). A Mann-Whitney U test was used to determine differences between OA and control controls. A principal component analysis (PCA) was performed to cluster the 47 mediators.
  
  
  RESULTS
  The majority of the mediators could be detected in both control and OA SF. Interleukin (IL)-6, interferon inducible protein (IP)-10, macrophage derived chemokine (MDC), platelet derived growth factor (PDGF)-AA and regulated on activation normal T cell expressed and secreted (RANTES) levels were found to be higher in OA compared to control SF (P < 0.001). Leptin, IL-13, macrophage inflammatory protein (MIP)-1β, soluble CD40 (sCD40L) levels were higher and eotaxin and granulocyte colony-stimulating factor (G-CSF) levels were lower in OA SF than in control SF, albeit borderline significant (P < 0.05). The PCA enabled identification of six clusters of mediators, which explained 76% of the variance.
  
  
  CONCLUSIONS
  The current study provides the first extensive profile of cytokines, chemokines and growth factors present in control and OA SF. Increased levels of mediators such as MDC and IL-6 imply involvement of inflammatory processes and might be associated with the influx of inflammatory cells in OA synovial tissue. Moreover, the performed cluster analysis indicated multiple clusters, which could indicate different pathophysiological pathways in the joint.
authors.affiliation: Department of Orthopaedics, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Beekhuizen
authors.forename: L M
authors.initials: LM
authors.lastname: Gierman
authors.forename: W E
authors.initials: WE
authors.lastname: van Spil
authors.forename: G J V M
authors.initials: GJ
authors.lastname: Van Osch
authors.forename: T W J
authors.initials: TW
authors.lastname: Huizinga
authors.forename: D B F
authors.initials: DB
authors.lastname: Saris
authors.forename: L B
authors.initials: LB
authors.lastname: Creemers
authors.forename: A-M
authors.initials: AM
authors.lastname: Zuurmond
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D018925:Chemokines / Q000032:analysis; D016207:Cytokines / Q000032:analysis; D005260:Female; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000032:analysis; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000378:metabolism*; D025341:Principal Component Analysis; D013582:Synovial Fluid / Q000737:chemistry*
chemical_list: D018925:Chemokines; D016207:Cytokines; D036341:Intercellular Signaling Peptides and Proteins