title: The transcriptional response of normal and rheumatoid arthritis synovial fibroblasts to hypoxia.
abstract: OBJECTIVE
  Hypoxia is a prominent feature in rheumatoid arthritis (RA) synovium. However, its contribution to the pathogenesis of RA remains unclear. We undertook this study to systematically characterize the changes in gene expression induced by hypoxia in synovial fibroblasts.
  
  
  METHODS
  We used microarray expression profiling in paired normoxic and hypoxic cultures of healthy synovial fibroblasts (HSFs) and RA synovial fibroblasts (RASFs). We used Student's paired t-test with Benjamini and Hochberg multiple testing correction to determine statistical significance. Validation of microarray data was performed by quantitative real-time reverse transcription-polymerase chain reaction analysis of selected genes. Biologic pathways differentially modulated by hypoxia in RASFs or HSFs were identified using unsupervised Ingenuity Pathways Analysis.
  
  
  RESULTS
  Hypoxia induced significant changes in the expression of a large group of genes in both HSFs and RASFs. In RASFs, we observed a lower number of hypoxia-regulated genes and partial differences in their functional categories. The number of differentially expressed genes in RASFs compared with HSFs was significantly increased by hypoxia. Multiple gene sets involved in energy metabolism, intracellular signal transduction, angiogenesis, and immune and inflammatory pathways were significantly modified, the last in both proinflammatory and antiinflammatory directions.
  
  
  CONCLUSIONS
  These data demonstrate that hypoxia induces significant changes in gene expression in HSFs and RASFs and identify differences between RASF and HSF profiles. The hypoxia-induced gene expression program in synovial fibroblasts identifies new factors and pathways relevant to understanding their contribution to the pathogenesis of chronic arthritis.
authors.affiliation: Instituto de Investigación Hospital 12 de Octubre, Madrid, Spain.
authors.forename: Manuel J
authors.initials: MJ
authors.lastname: Del Rey
authors.forename: Elena
authors.initials: E
authors.lastname: Izquierdo
authors.forename: Alicia
authors.initials: A
authors.lastname: Usategui
authors.forename: Elena
authors.initials: E
authors.lastname: Gonzalo
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Blanco
authors.forename: Francesco
authors.initials: F
authors.lastname: Acquadro
authors.forename: José L
authors.initials: JL
authors.lastname: Pablos
mesh_terms: D000263:Adenylate Kinase / Q000235:genetics / Q000378:metabolism; D001172:Arthritis, Rheumatoid / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D015687:Cell Hypoxia / Q000235:genetics / Q000502:physiology*; D002478:Cells, Cultured; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism; D004734:Energy Metabolism / Q000235:genetics / Q000502:physiology; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism* / Q000473:pathology; D020869:Gene Expression Profiling; D006801:Humans; D051793:Hypoxia-Inducible Factor 1 / Q000235:genetics / Q000378:metabolism; D007109:Immunity / Q000235:genetics / Q000502:physiology; D007249:Inflammation / Q000235:genetics / Q000503:physiopathology; D046228:Microarray Analysis; D018919:Neovascularization, Physiologic / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D013583:Synovial Membrane / Q000166:cytology / Q000378:metabolism* / Q000473:pathology; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism
chemical_list: D051793:Hypoxia-Inducible Factor 1; D042461:Vascular Endothelial Growth Factor A; D051546:Cyclooxygenase 2; D000263:Adenylate Kinase