PERSISTENT HIGH SERUM LEVELS OF CARTILAGE OLIGOMERIC MATRIX PROTEIN IN A SUBGROUP OF PATIENTS WITH TRAUMATIC KNEE INJURY

The objective was to assess whether changes of cartilage oligomeric ma trix protein (COMP) serum levels can predict the development of osteoa rthritis following traumatic knee injury. Sera and synovial fluids wer e acquired at surgery (TO) and postoperatively during the first (T1) a nd second (T2) year from 30 knee-injured patients. COMP levels and ant i-COMP autoantibodies were quantified by ELISA. Radiographs and patien t questionnaires were used to assess outcomes. At TO, compared with co ntrols (1.6+/-1.6 mu g/ml), the serum COMP concentration was significa ntly elevated (6.5+/-2.8 mu g/ml) with a tendency to further increase (TO vs. T1, P=0.076) and subsequently decrease (T1 vs. T2, P=0.074). H owever, individual variations are observed, e.g, persistently high (8/ 30) or increasing (TO to T2, 8/30) serum COMP. Ten of these patients h ave elevated COMP at T2 that increased from TO. COMP levels in serum a nd synovial fluid correlated significantly (P=0.012). Interestingly, s ome patients who revealed increasing serum levels of COMP from TO to T 2 displayed anti-COMP autoantibodies, These data suggest that local im mune response could contribute to further joint damage. The subgroup o f 10 patients (33%) with elevated and increasing serum COMP levels and in particular the patients with antibodies against cartilage matrix m olecules appear at increased risk for developing posttraumatic osteoar thritis.