The quantitation of a native chondroitin sulfate epitope in synovial fluid lavages and articular cartilage from canine experimental osteoarthritis and disuse atrophy

Objective. Previous studies have shown the presence of a native chondroitin sulfate epitope in articular cartilage proteoglycans from canine knee joints with experimental early osteoarthritis (OA), but not in normal cartilage. The objective of this study was to quantitate the native epitope recognized by monoclonal antibody 3‐B‐3 in synovial fluids and articular cartilage of diseased joints. Methods. An immunoassay with monoclonal antibody 3‐B‐3, which recognizes a native chondroitin‐6‐sulfate structure, was developed and used to analyze synovial fluid lavage material and extracts of articular cartilage from canine knee joints with early experimental OA or with mild disuse atrophy, and from control animals. Results. The concentration of epitope in the OA fluids was elevated 33–35‐fold, and in the OA articular cartilage extracts it was elevated > 200‐fold, compared with samples from the control group. No significant difference was detected in the levels of 3‐B‐3 epitope in the synovial fluid lavage material or cartilage extracts from the joints of the disuse group versus the control group. Conclusion. The native 3‐B‐3 epitope in articular cartilage and synovial fluids may be a specific marker of ongoing anabolic events in early degenerative joint disease.