INCREASED SECRETION AND ACTIVITY OF MATRIX METALLOPROTEINASE-3 IN SYNOVIAL TISSUES AND CHONDROCYTES FROM EXPERIMENTAL OSTEOARTHRITIS

Objective: The aim of this study was to define the relative regulation of matrix metalloproteinase-3 (MMP-3), and tissue inhibitor of metall oproteinases-1 (TIMP-1), in chondrocytes and synovium in experimental osteoarthritis (EOA). Methods: Partial-meniscectomized (PM) rabbits, s urgical sham controls (SH), and normal non-surgical controls (N) were killed at times corresponding to early degenerative lesions (4 weeks) and increasingly progressive stages of EOA at 8 and 12 weeks post-PM. MMP-3 activity was measured in conditioned media from chondrocytes and synovium using a peptide cleavage assay with substance P (SP) as the substrate. TIMP-1 was quantitated using an enzyme-linked immunosorbent assay (ELISA). Results: Early degenerative lesions (4 weeks post-PM) were characterized by inflammatory responses in the synovium accompani ed by a significant rise of MMP-3 activity in synovial cultures (P < 0 .05). At 8 weeks there was no discernible inflammation, and MMP-3 acti vity in EOA synovial cultures was comparable to that in the controls; this was followed by a second increase in MMP-3 activity in EOA sample s at 12 weeks. MMP-3 activity was significantly elevated in EOA chondr ocyte cultures at 8 weeks post-PM relative to N controls, correspondin g to the most destructive phase of EGA, but not in the early phase (4 weeks) or 'late' degenerative phase (12 weeks). Medium derived from ch ondrocytes contained little or no TIMP-1. Synovia secreted relatively higher amounts of TIMP-1, and this was elevated at 8 weeks post-PM rel ative to the SH controls. The majority (approximately 90%) of MMP-3 ac tivity could be inhibited using recombinant TIMP-1 or a hydroxamate MM P inhibitor. Complete inhibition was achieved with EDTA or 1,10 phenan throline. Conclusion: Together, these data indicate that in EOA, MMP-3 is initially upregulated in the synovium which may play a pivotal rol e in the pathogenesis of cartilage lesions. In contrast, chondrocyte-d erived MMP-3 is upregulated in the later phases of EGA, contributing f urther to progression of cartilage lesions.