YKL-40: a potential biomarker for osteoarthritis.

Current pharmacotherapy for osteoarthritis (OA) alleviates pain and inflammation but does not protect the articular cartilage from further damage or affect disease progression. Biological markers such as YKL-40 may provide a snapshot of current events in joint tissues, allowing rapid assessment of treatments. This review discusses recent data regarding YKL-40, with an emphasis on the relationship between YKL-40 and OA. The presence of YKL-40 in cartilage and synovium in OA patients correlates with histopathological changes and may reflect local disease activity. In addition, the levels of YKL-40 in serum and synovial fluid also seem to correlate with disease severity. The functional role of YKL-40 is not yet clear, but its production as part of the inflammatory response in articular chondrocytes may modulate the cellular response to proinflammatory cytokines, acting to limit connective tissue degradation. Further elucidation of its roles and relationships may enable YKL-40 to act as a useful biomarker in the development of therapies for OA.