Synovial macrophages produce both catabolic and anabolic factors that
contribute to degradation and new formation of cartilage.
Major catabolic factors produced by activated macrophages are alarmins or
damage associated molecular patterns (DAMPs) S100A8 andS100A9.
These are found in large amounts in the serum and synovium of OA patients and we recently showed that S100A8/A9 predict development of cartilage destruction in the Dutch CHECK cohort of
early symptomatic OA patients and have catabolic effects on OA chondrocytes via Toll-like receptor (TLR)-4