title: Increased serum YKL-40 in patients with pulmonary sarcoidosis--a potential marker of disease activity?
abstract: BACKGROUND
  YKL-40, a growth factor for fibroblasts and vascular endothelial cells, is secreted by macrophages and neutrophils. Elevated serum YKL-40 is found in patients with diseases characterized by inflammation, tissue remodelling and ongoing fibrosis. The aim was to evaluate whether macrophages and giant cells in the granulomatous sarcoid lesions of patients with pulmonary sarcoidosis produce YKL-40 and to determine whether serum YKL-40 in these patients were associated with disease activity.
  
  
  METHODS
  Serum YKL-40 was determined by radioimmunoassay in 27 patients with a histological diagnosis of pulmonal sarcoidosis. Immunohistochemical staining for YKL-40 antigen was performed in five biopsies with pulmonary sarcoid lesions. Serum YKL-40 was likewise measured in 173 healthy age-matched control subjects.
  
  
  RESULTS
  Mononuclear cells/macrophages and giant cells in pulmonary sarcoid granulomas expressed YKL-40 protein. Serum YKL-40 was higher in patients with pulmonary sarcoidosis compared to controls (P<0.001) and 63% had elevated serum YKL-40. There was a positive correlation between serum YKL-40 and serum angiotensin converting enzyme (rho=0.55, P=0.0053). Patients with serum YKL-40>median value in the patient group had lower carbon monoxide diffusion capacity corrected for alveolar volume (DLCO/VA) than patients with serum YKL-40 the median value (P=0.015).
  
  
  CONCLUSIONS
  Serum YKL-40 may be a novel biomarker of sarcoid disease activity and ongoing fibrosis in patients with pulmonary sarcoidosis.
authors.affiliation: Department of Rheumatology, Herlev Hospital, University of Copenhagen, Denmark. julia.johansen@post3.tele.dk
authors.forename: Julia S
authors.initials: JS
authors.lastname: Johansen
authors.forename: Nils
authors.initials: N
authors.lastname: Milman
authors.forename: Michael
authors.initials: M
authors.lastname: Hansen
authors.forename: Charly
authors.initials: C
authors.lastname: Garbarsch
authors.forename: Paul A
authors.initials: PA
authors.lastname: Price
authors.forename: Niels
authors.initials: N
authors.lastname: Graudal
mesh_terms: D054392:Adipokines; D000328:Adult; D015415:Biomarkers / Q000097:blood; D000071451:Chitinase-3-Like Protein 1; D005260:Female; D015726:Giant Cells / Q000378:metabolism; D006023:Glycoproteins / Q000097:blood*; D006801:Humans; D037102:Lectins; D008264:Macrophages / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D011863:Radioimmunoassay / Q000379:methods; D012129:Respiratory Function Tests; D012189:Retrospective Studies; D017565:Sarcoidosis, Pulmonary / Q000175:diagnosis*; D018709:Statistics, Nonparametric
chemical_list: D054392:Adipokines; D015415:Biomarkers; C084533:CHI3L1 protein, human; D000071451:Chitinase-3-Like Protein 1; D006023:Glycoproteins; D037102:Lectins