SMALL FRAGMENTS OF CARTILAGE OLIGOMERIC MATRIX PROTEIN IN SYNOVIAL-FLUID AND SERUM AS MARKERS FOR CARTILAGE DEGRADATION

We determined the tissue distribution of cartilage oligomeric matrix p rotein (COMP) in man and evaluated COMP in synovial fluid (SF) and ser um. COMP was purified from human articular cartilage. Polyclonal antib odies were used to detect COMP in tissue cryosections an. protein extr acts. COMP was determined quantitatively and qualitatively in SF and s erum by competitive enzyme-linked immunosorbent assay and immunoblotti ng, Knee joint SF was taken from nine cadaveric and six living control s, 52 patients with osteoarthritis (OA), 85 patients with rheumatoid a rthritis (RA! and GO patients with other forms of inflammatory arthrit is. The degradative potential of SF on native COMP was tested in vitro . The highest concentrations of COMP were measured in articular cartil age and meniscus, the lowest in rib and trachea. Compared with control s, the concentrations of COMP in SF and serum were elevated in 36 and 50% of the patients. A total of 84% of patients with RA and 60% of pat ients with other forms of inflammatory arthritis showed significant am ounts of low-molecular-weight COMP fragments (50-70 kDa) in SF. In con trast, SF fragments were present in only 21% of the OA patients. Furth ermore, 13% of SF taken from patients with RA or other forms of inflam matory arthritis were able to degrade COMP in vitro. Using inhibitors, the involvement of serine proteinases could be demonstrated in only 8 % of the cases. Based on these results, the absolute levels of COMP in SF and serum, and its fragmentation pattern in SF, seem to be promisi ng as markers of joint tissue metabolism.