Cathepsin B activity in unfixed and unrecalcified cryostat sections of normal and arthritic mouse knee joints

The possible involvement of cathepsin B in the destruction of articular cartilage in arthritic lesions was investigated by histochemical means. Unfixed and undecalcifled cryostat sections of normal and antigen-induced arthritic knee joints were used. Sections with good morphology were obtained by attaching adhesive tape to the cutting surface of the tissue blocks. Cathepsin B activity was demonstrated by a post-azo-coupling method. Final reaction product indicating cathepsin B activity was localized in small granules within the cytoplasm of synoviocytes, fibroblasts, chondrocytes and osteoclasts. Leupeptin and E-64 inhibited the formation of final reaction product completely. Induction of arthritis resulted in a vast increase of cathepsin B activity in synoviocytes, fibroblasts and chondrocytes and therefore, cathepsin B could be involved in the destruction of articular cartilage.