Cysteine proteases as cathepsins K and L as well as matrix metalloproteases are considered to be basically involved in collagen turnover. Degenerative joint diseases such as gonarthrosis are characterised by massive cartilage degradation mediated by increased activities of these proteases. These enzymes are, therefore, interesting targets for the treatment of painful arthritic joint diseases. The aim of these studies was to reconsider the hypothesis that cathepsin activities are enhanced in patients suffering from osteoarthritis.
We report on a 69-year-old female suffering from severe pain due to predominant retropatellar arthrosis. The clinical symptoms of this patient did not significantly differ from that of 30 other patients who were involved in this study. All patients undergone an endoprosthetic knee joint replacement. During the operation we harvested cartilage probes and isolated the chondrocytes from the joint cartilage for determination of the mRNA and the activities of cathepsins B, H, K and L. Compared to chondrocytes isolated from the control patients we found the activity of cysteine proteases to be extremely enhanced in chondrocytes of this patient. Moreover, the concentration of cystatin c, an endogenous inhibitor of cathepsins, was not detectable.
The results raise doubts on the predominant role of cysteine proteases in severe cartilage destruction.