Effects of stromelysin activity on proteoglycan degradation of canine articular cartilage explants

We investigated whether stromelysin activity in the medium of canine articular cartilage explants is associated with proteoglycan degradation in these explants. Cartilage explants were treated with recombinant human interleukin 1 alpha (rh-IL-1 alpha), lipopolysaccharide, or canine monocyte-conditioned medium. Proteoglycan synthesis and degradation were measured. Metalloproteinase activity (inhibitable by tissue inhibitor of metalloproteinase 2) in the culture medium was measured by use of fluorimetry with a quenched fluorescent substrate. Western blots of the medium were probed with polyclonal antibodies to human stromelysin, collagenase, and gelatinase. Neither metalloproteinase activity nor proteoglycan degradation were inducible in canine cartilage explants treated with rh-IL-1 alpha. However, proteoglycan synthesis was significantly (P < 0.05) decreased by concentrations of 10 and 100 ng of rh-IL-1 alpha/ml. Metalloproteinase activity in the medium accompanied proteoglycan degradation of cartilage treated with lipopolysaccharide and monocyte-conditioned medium. The metalloproteinase released into the medium was identified as prostromelysin by results of western blotting.