EFFECTS OF STROMELYSIN ACTIVITY ON PROTEOGLYCAN DEGRADATION OF CANINEARTICULAR-CARTILAGE EXPLANTS

We investigated whether stromelysin activity in the medium of canine a rticular cartilage explants is associated with proteoglycan degradatio n in these explants. Cartilage explants were treated with recombinant human interleukin 1 alpha (rh-IL-1 alpha), lipopolysaccharide, or cani ne monocyte-conditioned medium. Proteoglycan synthesis and degradation were measured. Metalloproteinase activity (inhibitable by tissue inhi bitor of metalloproteinase 2) in the culture medium was measured by us e of fluorimetry with a quenched fluorescent substrate. Western blots of the medium were probed with polyclonal antibodies to human stromely sin, collagenase, and gelatinase. Neither metalloproteinase activity n or proteoglycan degradation were inducible in canine cartilage explant s treated with rh-IL-1 alpha. However, proteoglycan synthesis was sign ificantly (P < 0.05) decreased by concentrations of 10 and 100 ng of r h-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 t he medium was identified as prostromelysin by results of western blott ing.