Human cartilage chitinase 3-like protein 2: cloning, expression, and production of polyclonal and monoclonal antibodies for osteoarthritis detection and identification of potential binding partners.

Human cartilage chitinase 3-like protein 2 (CHI3L2 or YKL-39) is a member of family-18 glycosyl hydrolases that lacks chitinase activity. YKL-39 is known as a potential marker for the activation of chondrocytes and the progression of osteoarthritis. In this study, we cloned and expressed a functional form of human YKL-39 in the bacterial system. The Escherichia coli expressed YKL-30 was used as immugen for production of anti YKL-39 polyclonal and monoclonal antibodies. Both antibody types were highly selective, reacting only with YKL-39. Isotype mapping identified two hybridoma clones (so called clones 6H11 and 8H3) to be IgM isotype. Dot blot assay showed that the monoclonal antibody was strongly active with the synovial fluid of an osteoarthritis patient, human monocyte, and T lymphocyte cell lines. Database search for protein binding partners gave high hits with several glycoproteins that play particular roles in cartilage tissue scaffolding, connective tissue formation, and cell-cell interactions. In conclusion, anti YKL-39 polyclonal and monoclonal antibodies were raised and tested to be suitable for immunological applications, such as the investigation of the YKL-39 regulating pathway and the development of an immunosensing tool for sensitive detection of cartilage tissue destruction.