A. Baici et al., CATHEPSIN-B IN OSTEOARTHRITIS - ZONAL VARIATION OF ENZYME-ACTIVITY INHUMAN FEMORAL-HEAD CARTILAGE, Annals of the Rheumatic Diseases, 54(4), 1995, pp. 281-288
Objectives-To determine the quantitative topographical distribution of
cathepsin B in human femoral head cartilage by measuring the zonal va
riation of enzyme activity in specimens taken from various anatomical
regions of normal and osteoarthritic (OA) tissues, and to correlate th
is parameter with the severity of the OA lesions. Methods-OA articular
cartilage was obtained at surgery for total hip replacement and contr
ol cartilage obtained at postmortem. Cylinders of full thickness carti
lage with underlying bone were retrieved with a biopsy trephine. Secti
ons of cartilage were produced by cryocutting the tissue as slices par
allel to the articular surface and assayed for cathepsin B with a spec
ific, highly sensitive fluorogenic substrate. The severity of the OA l
esions was graded according to the histopathological-histochemical met
hod of Mankin. Results-Zonal cathepsin B activity of normal cartilage
was uniform and low in all regions of the femoral head. In apparently
intact OA cartilage and in severely degraded tissue the zonal distribu
tion and the amounts of enzyme were similar to control values. At site
s with active disease, cathepsin B activity was much greater than in c
ontrols and its irregular zonal distribution correlated with tissue de
generation, hypercellularity, or cloning of chondrocytes as determined
histochemically. Particularly high enzyme levels were observed at sit
es with regenerating cartilage, where some zonal peaks attained 20-fol
d activity with respect to controls. Conclusion-Cathepsin B may play a
role in sustaining the chronicity of OA, not as an initiator, but rat
her as a perpetuator of the disease and as an antagonist of regenerati
on.