Osteoarthritis in cynomolgus macaques II. Detection of modulated proteoglycan epitopes in cartilage and synovial fluid

Abstract

The purpose of the present study was to determine the usefulness of the monoclonal antibodies 7-D-4 and 3-B-3 as biomarkers of severity of naturally occurring osteoarthritis in the knee joints of adult cynomolgus macaques. The antibodies were used to immunolocate chondroitin sulfate proteoglycan epitopes in articular cartilage or synovial fluid from knee joints with a range in severity of osteoarthritis. The joints were examined radiographically, grossly, microradiographically, and histologically to characterize the severity of disease, and the results of three different methods of proteoglycan analysis (immunohistochemistry, enzyme-linked immunosorbent assay, and Western blot analysis) were compared. Subjectively, the degree of positive immunostaining for 7-D-4 was minimal in normal sites and increased as damage to articular cartilage increased. The scores for 7-D-4 immunostaining in the medial tibial plateau (the site most severely involved in this model) were correlated significantly with severity of damage to articular cartilage (p < 0.05, r2 = 0.50), thus supporting the subjective observations. The ratio of 7-D-4 to sulfated glycosaminoglycans in synovial fluid also was correlated with the score for 7-D-4 immunostaining in the medial tibial plateau (p < 0.05, r2 = 0.54) and with the score for 3-B-3 immunostaining in the medial femoral condyle (p < 0.05, r2 = 0.65). There were no significant correlations among scores for 3-B-3 immunostaining, severity scores, and the ratios of 3-B-3 to sulfated glycosaminoglycans in the synovial fluid. By Western blot analysis, both epitopes were sensitive markers of early cartilage damage in young adult monkeys but were less sensitive in older monkeys. This work provides evidence that measurement of the epitope recognized by 7-D-4 in synovial fluid or, by immunohistochemical or Western blot methods, in articular cartilage has potential use as a marker of severity of naturally occurring osteoarthritis.

Chemical and Immunological Assay of the Nonreducing Terminal Residues of Chondroitin Sulfate from Human Aggrecan

“…Specifically, concentration and presentation of the CS chains are important factors that need to be considered in the interpretation of 3B3(Ϫ) immunochemical assays. It may be particularly important to consider when comparing aggrecans by immunohistochemistry (21,23,38) or Western blotting after agarose acrylamide composite gels (15,20,22,24). For example, we have demonstrated that in nitrocellulose-based assays (Fig.…”

Effects of chronic growth hormone and insulin‐like growth factor 1 deficiency on osteoarthritis severity in rat knee joints

“…Additionally, although the data are not included in this study, sections of 13 knee joints were immunostained using the monoclonal antibody 7-D-4, which binds a chondroitin sulfate proteoglycan epitope that is a sensitive marker for early to mild lesions of OA in tissues from monkeys, dogs, and humans (21,34,35). Although these sections revealed focally increased 7-D-4 binding in areas of chondrocyte death and matrix degeneration, large numbers of chondrocytes in morphologically normal areas also exhibited positive staining, indicating that this technique would not be useful for identifying early articular cartilage lesions in this model.…”

Degradation of the cartilage collagen matrix associated with changes in chondrocytes in osteoarthrosis. Assessment by loss of background fluorescence and immunodetection of matrix components

“…Like changes in background fluorescence, collagen denaturation products were first detected in the upper mid region of the cartilage and The association of the proteoglycan epitopes 7D4 and 3B3-with activation of an immature chondrocyte phenotype in OA cartilage has been controversial. The immunodetection of these proteoglycan epitopes has been shown to be enhanced in immature articular cartilage [14] and growth cartilage [6,14] and also in OA articular cartilage [29] and in animal models of OA [7,30]. However, a recent chemical analysis of the 3B3-epitope failed to detect any substantial change in OA cartilage [26] and suggested instead that immunodetection of the 3B3-epitope is influenced by clustering or unmasking of existing proteoglycan structures.…”