DIFFERENTIAL LEVELS OF SYNOVIAL-FLUID AGGRECAN AGGREGATE COMPONENTS IN EXPERIMENTAL OSTEOARTHRITIS AND JOINT DISUSE

The levels of proteoglycan aggregate components (link protein, keratan sulfate epitope, and total sulfated glycosaminoglycan) were determine d in the synovial fluid lavages of dogs with experimental osteoarthrit is or disuse atrophy. A model of experimental osteoarthritis was creat ed by transection of the anterior cruciate ligament of the sight knee; studies were carried out 6 and 12 weeks after surgery. Joint disuse w as studied at 4 and 8 weeks after initiation of the disuse. Recovery a fter disuse also was studied in joints that had 3 weeks of remobilizat ion after 4 or 8 weeks of disuse. Synovial fluid lavages from the righ t knee joints of untreated animals were used as controls. The concentr ations of keratan sulfate epitope, sulfated glycosaminoglycan, and lin k protein in the synovial fluid lavages at 6 and 12 weeks after transe ction of the anterior cruciate were elevated compared with the control values. Similar analysis of the fluid after disuse showed that the le vels of keratan sulfate epitope and sulfated glycosaminoglycan were in creased compared with the control levels and the levels after transect ion. However, the concentration of link protein,in the fluid after dis use was not significantly different from the control level. The levels of keratan sulfate epitope and sulfated glycosaminoglycan in the syno vial fluid lavages after disuse with recovery were high, but the level s of link protein remained low. The results indicate that the cataboli sm of proteoglycan aggregates in articular cartilage during early oste oarthritis and disuse is different. The determination of keratan sulfa te epitope in synovial fluid lavages appears to provide a relatively g eneral indication of proteoglycan catabolism, whereas increased levels of link protein may be more indicative of cartilage degeneration.