Proteinases and their inhibitors in normal and osteoarthritic articular cartilage

Specimens of human articular cartilage obtained at replacement surgery was divided into three groups, i.e. weight-bearing and non-weight-bearing portions of normal control cartilage, and osteoarthritic cartilage. Fractions of 2 M guanidine hydrochloride-cartilage extracts obtained by Sephadex G-75 chromatography contained serine proteinases which had the ability to degrade gelatin and proteoglycan aggregate. The serine proteinase activity of the weight-bearing control cartilage was two times higher than that of the non-weight-bearing control cartilage. Moreover, the activity of osteoarthritic cartilage was about 80 times higher than that of non-weight-bearing control cartilage. fractions of control cartilage extracts on Sephadex G-75 chromatography contained inhibitory activity against trypsin and collagenase with M(r) of 14,000 and 36,000, respectively. The trypsin inhibitory level in osteoarthritic cartilage was lower than in control cartilage. The level of collagenase inhibitor in control cartilage was higher in non-weight-bearing portions than in weight-bearing portions. However, no significant collagenase inhibitor activity was observed in osteoarthritic cartilage. On sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) followed by zymography, the cartilage serine proteinases had M(r) of 67,000 and 22,000. The data suggest that the increased level of destructive proteinases acting in the presence of the decreased level of inhibitors may lead to the extracellular matrix degradation in osteoarthritic cartilage.