title: Elevated synovial expression of triggering receptor expressed on myeloid cells 1 in patients with septic arthritis or rheumatoid arthritis.
abstract: OBJECTIVE
  To determine whether synovial expression of triggering receptor expressed on myeloid cells 1 (TREM-1) is upregulated in patients with distinct types of inflammatory or non-inflammatory arthritis.
  
  
  METHODS
  Synovial fluid (SF) samples were analysed for levels of soluble TREM-1 (sTREM; n = 132), tumour necrosis factor alpha (TNFalpha, n = 78) and leucocyte TREM-1 messenger RNA (n = 48). Synovial tissue from four rheumatoid arthritis (RA) patients, two patients with Crohn's-associated arthritis, one patient with ankylosing spondylitis and one patient with osteoarthritis were examined for TREM-1 expression by immunohistology, and three of the RA samples were also analysed by Western blotting.
  
  
  RESULTS
  Synovial fluid sTREM-1 levels in septic arthritis and RA were similar to each other and were each greater than those in gouty arthritis, non-septic/non-RA inflammatory arthritis and non-inflammatory arthritis. Synovial fluid TNFalpha and sTREM-1 levels correlated with each other, and sTREM-1 and leucocyte TREM-1 mRNA levels each correlated with SF leucocyte counts. TREM-1 in RA was expressed in situ in synovial tissue by cells of myelomonocytic lineage but was not detectably expressed in control osteoarthritis synovial tissue.
  
  
  CONCLUSIONS
  Synovial TREM-1 expression is increased in septic arthritis and RA. In patients with acute inflammatory arthritis, elevated SF sTREM-1 levels may point the clinician to a diagnosis of septic arthritis or RA. In RA patients, targeting TREM-1 may have therapeutic benefits by reducing local proinflammatory cytokine and chemokine release.
authors.affiliation: Division of Rheumatology, University of Southern California Keck School of Medicine, Los Angeles, CA 90033, USA.
authors.forename: C E
authors.initials: CE
authors.lastname: Collins
authors.forename: D T
authors.initials: DT
authors.lastname: La
authors.forename: H-T
authors.initials: HT
authors.lastname: Yang
authors.forename: F
authors.initials: F
authors.lastname: Massin
authors.forename: S
authors.initials: S
authors.lastname: Gibot
authors.forename: G
authors.initials: G
authors.lastname: Faure
authors.forename: W
authors.initials: W
authors.lastname: Stohl
mesh_terms: D000328:Adult; D001170:Arthritis, Infectious / Q000378:metabolism*; D001172:Arthritis, Rheumatoid / Q000378:metabolism* / Q000473:pathology; D015415:Biomarkers / Q000378:metabolism; D005260:Female; D006801:Humans; D007958:Leukocyte Count; D007962:Leukocytes / Q000378:metabolism; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D008875:Middle Aged; D012333:RNA, Messenger / Q000235:genetics; D011971:Receptors, Immunologic / Q000235:genetics / Q000378:metabolism*; D013582:Synovial Fluid / Q000166:cytology / Q000378:metabolism*; D013583:Synovial Membrane / Q000378:metabolism; D000073871:Triggering Receptor Expressed on Myeloid Cells-1; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D015415:Biomarkers; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D011971:Receptors, Immunologic; C408842:TREM1 protein, human; D000073871:Triggering Receptor Expressed on Myeloid Cells-1; D014409:Tumor Necrosis Factor-alpha