title: Correlation analyses of clinical and molecular findings identify candidate biological pathways in systemic juvenile idiopathic arthritis.
abstract: BACKGROUND
  Clinicians have long appreciated the distinct phenotype of systemic juvenile idiopathic arthritis (SJIA) compared to polyarticular juvenile idiopathic arthritis (POLY). We hypothesized that gene expression profiles of peripheral blood mononuclear cells (PBMC) from children with each disease would reveal distinct biological pathways when analyzed for significant associations with elevations in two markers of JIA activity, erythrocyte sedimentation rate (ESR) and number of affected joints (joint count, JC).
  
  
  METHODS
  PBMC RNA from SJIA and POLY patients was profiled by kinetic PCR to analyze expression of 181 genes, selected for relevance to immune response pathways. Pearson correlation and Student's t-test analyses were performed to identify transcripts significantly associated with clinical parameters (ESR and JC) in SJIA or POLY samples. These transcripts were used to find related biological pathways.
  
  
  RESULTS
  Combining Pearson and t-test analyses, we found 91 ESR-related and 92 JC-related genes in SJIA. For POLY, 20 ESR-related and 0 JC-related genes were found. Using Ingenuity Systems Pathways Analysis, we identified SJIA ESR-related and JC-related pathways. The two sets of pathways are strongly correlated. In contrast, there is a weaker correlation between SJIA and POLY ESR-related pathways. Notably, distinct biological processes were found to correlate with JC in samples from the earlier systemic plus arthritic phase (SAF) of SJIA compared to samples from the later arthritis-predominant phase (AF). Within the SJIA SAF group, IL-10 expression was related to JC, whereas lack of IL-4 appeared to characterize the chronic arthritis (AF) subgroup.
  
  
  CONCLUSIONS
  The strong correlation between pathways implicated in elevations of both ESR and JC in SJIA argues that the systemic and arthritic components of the disease are related mechanistically. Inflammatory pathways in SJIA are distinct from those in POLY course JIA, consistent with differences in clinically appreciated target organs. The limited number of ESR-related SJIA genes that also are associated with elevations of ESR in POLY implies that the SJIA associations are specific for SJIA, at least to some degree. The distinct pathways associated with arthritis in early and late SJIA raise the possibility that different immunobiology underlies arthritis over the course of SJIA.
authors.affiliation: Program in Immunology, Department of Pediatrics, Stanford University, Stanford, CA 94305, USA.
authors.forename: Xuefeng B
authors.initials: XB
authors.lastname: Ling
authors.forename: Claudia
authors.initials: C
authors.lastname: Macaubas
authors.forename: Heather C
authors.initials: HC
authors.lastname: Alexander
authors.forename: Qiaojun
authors.initials: Q
authors.lastname: Wen
authors.forename: Edward
authors.initials: E
authors.lastname: Chen
authors.forename: Sihua
authors.initials: S
authors.lastname: Peng
authors.forename: Yue
authors.initials: Y
authors.lastname: Sun
authors.forename: Chetan
authors.initials: C
authors.lastname: Deshpande
authors.forename: Kuang-Hung
authors.initials: KH
authors.lastname: Pan
authors.forename: Richard
authors.initials: R
authors.lastname: Lin
authors.forename: Chih-Jian
authors.initials: CJ
authors.lastname: Lih
authors.forename: Sheng-Yung P
authors.initials: SY
authors.lastname: Chang
authors.forename: Tzielan
authors.initials: T
authors.lastname: Lee
authors.forename: Christy
authors.initials: C
authors.lastname: Sandborg
authors.forename: Ann B
authors.initials: AB
authors.lastname: Begovich
authors.forename: Stanley N
authors.initials: SN
authors.lastname: Cohen
authors.forename: Elizabeth D
authors.initials: ED
authors.lastname: Mellins
mesh_terms: D001171:Arthritis, Juvenile / Q000473:pathology*; D001799:Blood Sedimentation; D002648:Child; D002675:Child, Preschool; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D007596:Joints / Q000473:pathology; D007963:Leukocytes, Mononuclear / Q000276:immunology; D008297:Male; D057089:Pathology, Molecular