title: Type X collagen levels are elevated in serum from human osteoarthritis patients and associated with biomarkers of cartilage degradation and inflammation.
abstract: BACKGROUND
  Osteoarthritis (OA) is the most common degenerative joint disease, of which the pathogenesis is inadequately understood. Hypertrophy-like changes have been observed as part of the progression of OA. The aim of the study was to develop and characterize a novel biomarker of chondrocytes hypertrophy and investigate how this marker was associated with cartilage degradation and inflammation in patients with various degrees of OA.
  
  
  METHODS
  A competitive ELISA, C-Col10, applying a well-characterized monoclonal antibody was developed as a biomarker of chondrocyte hypertrophy through measurement of type X collagen (ColX). The levels of C-Col10, C2M (matrix metalloproteinase-derived fragments of type II collagen) and hsCRP (high sensitive C-reactive protein) were quantified by ELISAs in serum of 271 OA patients stratified by Kellgren-Lawrence (KL) score 0-4. Associations between serum levels of the three biomarkers (log transformed) were analyzed by Pearson's correlation and differences in C-Col10 levels between patients with high and low levels of inflammation measured by hsCRP were analyzed by ANOVA.
  
  
  RESULTS
  We developed a C-Col10 assay measuring the C-terminus of ColX. We found significantly higher levels of ColX in patients with KL score 2 compared to patients with no radiographic evidence of OA (KL0) (p = 0.04). Levels of ColX were significantly elevated in OA patients with above normal hsCRP levels (p < 0.0001), as well as significantly correlated with levels of C2M (r = 0.55, p < 0.0001), which suggested that chondrocyte hypertrophy was associated with inflammation and cartilage degradation. There was no correlation between C2M and hsCRP. Age and BMI adjustment didn't change the results. Immuno-staining revealed that ColX was predominately located around the hypertrophic chondrocytes and the clustered chondrocytes indicating that C-Col10 measures may be linked to cartilage hypertrophic changes.
  
  
  CONCLUSIONS
  We developed a novel assay, C-Col10, for measurement of chondrocyte hypertrophy and found its levels significantly elevated in OA patients with KL score of 2, and also in OA patients with above normal hsCRP levels. Concentration of C-Col10 strongly correlated with levels of C2M, a marker of cartilage destruction. The data suggest that chondrocyte hypertrophy and subsequent collagen X fragmentation seem to be increased in a subset of patients with inflammatory OA.
authors.forename: Yi
authors.initials: Y
authors.lastname: He
authors.forename: Anne Sofie
authors.initials: AS
authors.lastname: Siebuhr
authors.forename: Niels Ulrik
authors.initials: NU
authors.lastname: Brandt-Hansen
authors.forename: Jianxia
authors.initials: J
authors.lastname: Wang
authors.forename: Di
authors.initials: D
authors.lastname: Su
authors.forename: Qinlong
authors.initials: Q
authors.lastname: Zheng
authors.forename: Ole
authors.initials: O
authors.lastname: Simonsen
authors.forename: Kristian Kjær
authors.initials: KK
authors.lastname: Petersen
authors.forename: Lars
authors.initials: L
authors.lastname: Arendt-Nielsen
authors.forename: Thomas
authors.initials: T
authors.lastname: Eskehave
authors.forename: Hans Christian
authors.initials: HC
authors.lastname: Hoeck
authors.forename: Morten Asser
authors.initials: MA
authors.lastname: Karsdal
authors.affiliation: Nordic Bioscience, Herlev Hovedgade 207, DK-2730 Herlev, Denmark. acbj@nordicbioscience.com.
authors.forename: Anne C
authors.initials: AC
authors.lastname: Bay-Jensen
mesh_terms: D015415:Biomarkers / Q000097:blood; D002357:Cartilage Diseases / Q000097:blood* / Q000175:diagnosis*; D045744:Cell Line, Tumor; D015331:Cohort Studies; D024121:Collagen Type X / Q000097:blood*; D005260:Female; D006801:Humans; D007249:Inflammation / Q000097:blood / Q000175:diagnosis; D008297:Male; D020370:Osteoarthritis, Knee / Q000097:blood* / Q000175:diagnosis*
chemical_list: D015415:Biomarkers; D024121:Collagen Type X