In situ zymographic localisation of type II collagen degrading activity inosteoarthritic human articular cartilage

Objectives-Chondrocytic matrix metalloproteinases (MMPs) are believed to be important in osteoarthritic cartilage degradation. The cartilage lesion of osteoarthritis (uw) Is focal and often progressive. During its development chondrocytes differentially up and down regulate production of mRNA for in dividual MMPs. This observation has potential implications for understandin g the disease processes that lead to progressive cartilage loss in OA and d esigning appropriate targeted treatment. The complex regulation of MMP medi ated effects means there is a pressing need to establish whether visualisat ion of MMP mRNA or protein equates to enzyme activity. The technique of in situ zymography (ISZ) offers a way of examining diseased human tissue for i n vivo production of an excess of degrading enzyme over inhibitor. The prim ary objective of this study was to assess, and if positive follow, collagen II degrading activity in cartilage during development of the OA lesion. A secondary objective was to assess whether there was any correlation between sites of collagen II degrading activity and expression of the collagenase (MMP-13), recently implicated in type II collagen degredation in this lesio n. Methods-Biopsied human normal and osteoarthritic cartilage, showing various degrees of damage, was examined by in situ zymography, with and without en zyme inhibitors, to establish sites of type II collagenase activity. Paired samples were probed for MMP-13 mRNA using S-35-labelled oligonucleotide pr obes. Comparative analyses were performed. Results-In situ zymography showed collagen II degrading activity over chond rocytes only in osteoarthritic cartilage. Distribution and amount varied wi th the extent of cartilage damage and position of chondrocytes, being great est in deep cartilage and in cartilage lesions where fissuring was occurrin g. The enzyme causing the degradation behaved as a matrix metalloproteinase . MMP-13 mRNA expression codistributed with the type II collagenase activit y. Conclusion-In OA, chondrocytes can degrade type II collagen. The type II co llagen degrading activity varies in site and amount as the cartilage lesion progresses and throughout codistributes with MMP-13 mRNA expression.