title: Synovial fluid proteins differentiate between the subtypes of juvenile idiopathic arthritis.
abstract: OBJECTIVE
  Juvenile idiopathic arthritis (JIA) is a heterogeneous group of inflammatory diseases, and no clinically useful prognostic markers to predict disease outcome in children with JIA are currently available. Synovial fluid likely reflects the proteins present in the inflamed synovium. The purpose of this study was to delineate the synovial fluid proteome and determine whether protein expression differs in the different subtypes of JIA.
  
  
  METHODS
  Synovial fluid samples obtained from children with oligoarticular JIA, polyarticular JIA, or systemic JIA were compared. Two-dimensional gel electrophoresis for protein separation and matrix-assisted laser desorption ionization-time-of-flight mass spectrometry and quadripole time-of-flight mass spectrometry for protein identification were used for this study. Synovial fluid cells were analyzed by polymerase chain reaction (PCR) for the presence of haptoglobin messenger RNA (mRNA).
  
  
  RESULTS
  The synovial fluid proteome of the samples was delineated. The majority of proteins showed overexpression in JIA synovial fluid as compared with noninflammatory control samples. There were 24 statistically significantly differentially expressed spots (>2-fold change; P < 0.05) between the subtypes of JIA. PCR analysis revealed haptoglobin mRNA, suggesting that haptoglobin is locally produced in an inflamed joint in JIA.
  
  
  CONCLUSIONS
  Despite the similar histologic appearance of inflamed joints in patients with different subtypes of JIA, there are differences in protein expression according to the subtype of JIA. Haptoglobin is differentially expressed between the subtypes of JIA and is locally produced in an inflamed joint in JIA. Haptoglobin and other differentially expressed proteins may be potential biomarkers in JIA.
authors.affiliation: Children's Hospital of Pittsburgh, Division of Rheumatology, Pittsburgh, Pennsylvania 15213, USA. margalit.rosenkranz@chp.edu
authors.forename: Margalit E
authors.initials: ME
authors.lastname: Rosenkranz
authors.forename: David C
authors.initials: DC
authors.lastname: Wilson
authors.forename: Anthony D
authors.initials: AD
authors.lastname: Marinov
authors.forename: Alisha
authors.initials: A
authors.lastname: Decewicz
authors.forename: Patrick
authors.initials: P
authors.lastname: Grof-Tisza
authors.forename: David
authors.initials: D
authors.lastname: Kirchner
authors.forename: Brendan
authors.initials: B
authors.lastname: Giles
authors.forename: Paul R
authors.initials: PR
authors.lastname: Reynolds
authors.forename: Michael N
authors.initials: MN
authors.lastname: Liebman
authors.forename: V S Kumar
authors.initials: VS
authors.lastname: Kolli
authors.forename: Susan D
authors.initials: SD
authors.lastname: Thompson
authors.forename: Raphael
authors.initials: R
authors.lastname: Hirsch
mesh_terms: D000293:Adolescent; D001171:Arthritis, Juvenile / Q000145:classification / Q000378:metabolism*; D002648:Child; D002675:Child, Preschool; D015180:Electrophoresis, Gel, Two-Dimensional; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D020543:Proteome / Q000378:metabolism*; D040901:Proteomics; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013582:Synovial Fluid / Q000378:metabolism*
chemical_list: D020543:Proteome; D012333:RNA, Messenger