Cartilage oligomeric matrix protein neoepitope in the synovial fluid of horses with acute lameness: A new biomarker for the early stages of osteoarthritis

Clinical tools to diagnose the early changes of osteoarthritis (OA) that occur in the articular cartilage are lacking. Objectives: We sought to identify and quantify a novel cartilage oligomeric matrix protein (COMP) neo-epitope in the synovial fluid from the joints of healthy horses and those with different stages of OA. Study design: 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 (IL)-1β for 25 days. Media were analysed via quantitative proteomics. Synovial fluid were obtained from the 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 neo-epitope using a custom developed inhibition enzyme-linked immunosorbent assay (ELISA). Explants were immunostained with polyclonal antibodies against COMP and the COMP neo-epitopes. Results: Semi-tryptic COMP peptides were identified and quantified in cell culture media from cartilage explants. A rabbit polyclonal antibody was raised against the neo-epitope of the N-terminal portion of one COMP fragment (sequence SGPTHEGVC). An inhibition This article is protected by copyright. All rights reserved.