CHANGES IN CARTILAGE COMPOSITION AND PHYSICAL-PROPERTIES DUE TO STROMELYSIN DEGRADATION

Objective. To determine the effects of stromelysin treatment on biochemical, histologic, and swelling characteristics of intact cartilage explants and to correlate these effects with changes in the functional physical properties of the tissue. Methods. Bovine articular cartilage explants were cultured for up to 3 days in the presence or absence of recombinant human stromelysin (SLN). Damage to matrix proteoglycans and collagens was assessed and characterized by N-terminal sequencing and Western blot analysis, respectively. Explants were mechanically tested to assess the ability of the tissue to withstand cyclic and static compressive loads. Results. Treatment with SLN resulted in a time- and dose-dependent loss of proteoglycans from cartilage explants, with significant loss seen after 3 days of exposure to 20 nM SLN. Histology indicated that initial loss of proteoglycans occurred in regions near the tissue surface and proceeded inward with increasing time of SLN exposure. SLN treatment resulted in degradation of matrix collagen types IX and II, and a concomitant increase in tissue swelling. This matrix degradation resulted in severe alterations in functional physical properties of the tissue, including compressive stiffness. The initial, focal loss of proteoglycans that resulted from SLN treatment was most accurately detected with high-frequency streaming potential measurements. Conclusion. Exposure of intact cartilage to SLN caused specific, molecular-level degradation of matrix molecules, which resulted in changes in the swelling behavior and marked deterioration of functional physical properties of the tissue.