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- Author or Editor: Jeff P. Holt x
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Objective—To determine effects of interleukin (IL)-1β and glucocorticoids on total glycosaminoglycan (GAG) loss and aggrecanase-mediated matrix degradation in equine cartilage.
Sample Population—Cartilage from 24 equine cadavers free of sepsis and musculoskeletal disease.
Procedures—Effects of IL-1β, IL-1β with glucocorticoids (dexamethasone and triamcinolone, 10−6 and 10−7M), and glucocorticoids alone on degradation of equine articular and nasal cartilage explants were assessed by measuring GAG release in media and GAG content in cartilage. Aggrecanase-mediated cleavage within the interglobular domain at Glu373-Ala374 was evaluated via western blot analysis and ELISAs. Steady-state mRNA concentrations of matrix metalloproteinase (MMP)-3, MMP-13, a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)4, and ADAMTS5 were assessed by use of real-time reverse transcriptase PCR assay (cartilage explants) and northern blot analysis (cell culture).
Results—IL-1β increased GAG release and aggrecanase activity (11-fold). The MMP-3, MMP-13, and ADAMTS4 mRNA were upregulated with IL-1β, whereas ADAMTS5 mRNA was increased (13-fold), but significantly less than ADAMTS4 mRNA (27-fold), suggesting a role for both ADAMTS4 and ADAMTS5 in degradation of cytokine-stimulated cartilage. Despite downregulation of MMP-3 and MMP-13 mRNA, glucocorticoids did not alter GAG degradation. A further increase in aggrecanase activity was detected with ELISAs and western blot analysis, whereas ADAMTS4 mRNA was downregulated and ADAMTS5 mRNA was maintained or upregulated.
Conclusions and Clinical Relevance—MMP-3, MMP-13, and ADAMTS4 were regulated differently than ADAMTS5. Glucocorticoids increased aggrecanase activity despite down-regulation of ADAMTS4 mRNA, suggesting a major role of ADAMTS5. Effects of glucocorticoids on aggrecanase activity have important implications in terms of treatment.