Article Abstract:
Cathepsin B appears to play a role in the pathological degeneration of joint cartilage in osteoarthritis. Cathepsin B is an enzyme that can digest cartilage. Cartilage samples were taken from the head of the thigh bone in patients having hip replacement surgery. Cartilage cells were isolated from the underlying matrix. Cathepsin B was stained and the cells were examined under the microscope. Cartilage cells from normal appearing cartilage in OA patients contained few lysosomes, which are small sacs of digestive enzymes, and only a few cells were cathepsin B positive. Cells from severely degraded cartilage appeared similar to normal cartilage cells. By contrast, most cartilage cells from areas of active degeneration and especially from sites of cartilage repair contained a high number of lysosomes, and the lysosomes contained a high level of cathepsin B in its active form. Cathepsin B appears to sustain and perpetuate cartilage degradation rather than initiate it.
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Article Abstract:
Cathepsin B appears to play a role in the pathological degeneration of joint cartilage in osteoarthritis (OA). Cathepsin B is an enzyme that can digest cartilage. Cylinders of the full thickness of cartilage down to the underlying bone were taken from the head of the thigh bone in patients having hip replacement surgery and from cadavers free of OA at postmortem. Sections were made parallel to the joint surface and assayed for cathepsin B content. Cathepsin B levels in OA patients in areas of normal cartilage and where cartilage was severely degraded were similar to control sample levels. In areas of active disease, cathepsin B levels were substantially higher. Its distribution correlated specifically with localized areas of tissue degeneration. At sites where cartilage regeneration was in progress, capthepsin B levels approached 20 times that of controls. Capthepsin B appears to play a role in the progress of disease and as an antagonist of healing.
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Article Abstract:
Secretion of cathepsin B may be a later development in the osteoarthritic degenerative process. Cathepsin B is a protein dissolving enzyme that can break down cartilage. Experiments with artificially induced osteoarthritis in rabbits revealed that inflammation promoting substances stimulate production of cathepsin B within cartilage cells, but cathepsin B is not secreted until the cartilage material surrounding the cells has been partially destroyed. Cells in the joint lining appear to secrete cathepsin B first followed by the cartilage cells as degeneration continues.
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