Biochemical and Ultrastructural Observations in Normal and Degenerative Canine Articular Cartilage

SUMMARY Metabolic, histochemical, and ultrastructural patterns were studied in normal and degenerative articular cartilage from hip joints of 6-month-old dogs. Degenerative cartilage had lower glycosaminoglycan (gag) content than did normal cartilage. Soluble collagen concentrations were higher in arthritic cartilage than in normal cartilage. Deoxyribonucleic acid (dna) and noncollagen protein remained essentially constant, but the percentage of water increased approximately 7% in the degenerative cartilage. Ultrastructural examination of cartilage zone II indicated a different orientation and degeneration of the extracellular cartilage matrix, whereas chondrocytes seemed relatively unchanged in the osteoarthritic cartilage. In vitro incubation of both normal and degenerative cartilage slices with radioactive precursors of dna, proteins, and gag resulted in greatly reduced overall synthesis of the macromolecular constituents in degenerative cartilage. Specific activities indicated that the turnover rate of gag was high in degenerative cartilage, whereas the rates of synthesis of dna and protein were diminished. Results indicated that cartilage in its early stages of degeneration had altered metabolic and degradative activities.