title: Cartilage oligomeric matrix protein neoepitope in the synovial fluid of horses with acute lameness: A new biomarker for the early stages of osteoarthritis.
abstract: BACKGROUND
  Clinical tools to diagnose the early changes of osteoarthritis (OA) that occur in the articular cartilage are lacking.
  
  
  OBJECTIVE
  We sought to identify and quantify a novel cartilage oligomeric matrix protein (COMP) neoepitope in the synovial fluid from the joints of healthy horses and those with different stages of OA.
  
  
  METHODS
  In vitro quantitative proteomics and assay development with application in synovial fluids samples obtained from biobanks of well-characterised horses.
  
  
  METHODS
  Articular cartilage explants were incubated with or without interleukin-1β for 25 days. Media were analysed via quantitative proteomics. Synovial fluid was obtained from either normal joints (n = 15) or joints causing lameness (n = 17) or with structural OA lesions (n = 7) and analysed for concentrations of the COMP neoepitope using a custom-developed inhibition enzyme-linked immunosorbent assay (ELISA). Explants were immunostained with polyclonal antibodies against COMP and the COMP neoepitopes.
  
  
  RESULTS
  Semitryptic COMP peptides were identified and quantified in cell culture media from cartilage explants. A rabbit polyclonal antibody was raised against the neoepitope of the N-terminal portion of one COMP fragment (sequence SGPTHEGVC). An inhibition ELISA was developed to quantify the COMP neoepitope in synovial fluid. The mean concentration of the COMP neoepitope significantly increased in the synovial fluid from the joints responsible for acute lameness compared with normal joints and the joints of chronically lame horses and in joints with chronic structural OA. Immunolabelling for the COMP neoepitope revealed a pericellular staining in the interleukin-1β-stimulated explants.
  
  
  CONCLUSIONS
  The ELISA is based on polyclonal antisera rather than a monoclonal antibody.
  
  
  CONCLUSIONS
  The increase in the COMP neoepitope in the synovial fluid from horses with acute lameness suggests that this neoepitope has the potential to be a unique candidate biomarker for the early molecular changes in articular cartilage associated with OA.
authors.affiliation: Department of Clinical Chemistry and Transfusion Medicine, Institute of Biomedicine, Sahlgrenska University Hospital, Gothenburg University, Gothenburg, Sweden.|Division of Pathology, Pharmacology and Toxicology, Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences, Uppsala, Sweden.
authors.forename: E
authors.initials: E
authors.lastname: Skiöldebrand
authors.affiliation: Division of Pathology, Pharmacology and Toxicology, Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences, Uppsala, Sweden.
authors.forename: S
authors.initials: S
authors.lastname: Ekman
authors.affiliation: Department of Clinical Chemistry, Sahlgrenska University Hospital, Gothenburg, Sweden.
authors.forename: L
authors.initials: L
authors.lastname: Mattsson Hultén
authors.affiliation: Department of Clinical Chemistry and Transfusion Medicine, Institute of Biomedicine, Sahlgrenska University Hospital, Gothenburg University, Gothenburg, Sweden.|Division of Pathology, Pharmacology and Toxicology, Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences, Uppsala, Sweden.
authors.forename: E
authors.initials: E
authors.lastname: Svala
authors.affiliation: Department of Clinical Chemistry, Sahlgrenska University Hospital, Gothenburg, Sweden.
authors.forename: K
authors.initials: K
authors.lastname: Björkman
authors.affiliation: Department of Clinical Chemistry and Transfusion Medicine, Institute of Biomedicine, Sahlgrenska University Hospital, Gothenburg University, Gothenburg, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Lindahl
authors.affiliation: Department of Clinical Chemistry, Sahlgrenska University Hospital, Gothenburg, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Lundqvist
authors.affiliation: Section for Rheumatology and Molecular Skeletal Biology, Department of Clinical Sciences Lund, Lund University, Lund, Sweden.
authors.forename: P
authors.initials: P
authors.lastname: Önnerfjord
authors.affiliation: Proteomics Core Facility, Sahlgrenska Academy, Gothenburg University, Gothenburg, Sweden.
authors.forename: C
authors.initials: C
authors.lastname: Sihlbom
authors.affiliation: Department of Clinical Chemistry and Transfusion Medicine, Institute of Biomedicine, Sahlgrenska University Hospital, Gothenburg University, Gothenburg, Sweden.
authors.forename: U
authors.initials: U
authors.lastname: Rüetschi
mesh_terms: D000818:Animals; D015415:Biomarkers; D064236:Cartilage Oligomeric Matrix Protein / Q000134:cerebrospinal fluid*; D006023:Glycoproteins; D006734:Horse Diseases / Q000134:cerebrospinal fluid*; D006736:Horses; D007794:Lameness, Animal / Q000134:cerebrospinal fluid*; D064235:Matrilin Proteins; D010003:Osteoarthritis / Q000134:cerebrospinal fluid / Q000662:veterinary*; D013582:Synovial Fluid / Q000378:metabolism
chemical_list: D015415:Biomarkers; D064236:Cartilage Oligomeric Matrix Protein; D006023:Glycoproteins; D064235:Matrilin Proteins
keywords: biomarker; cartilage oligomeric matrix protein neoepitope; horse; lameness; osteoarthritis; synovial fluid