MMP1 and rheumatoid arthritis: Interestingly, MMP-1 (or collagenase-1) and/or MMP-13 (or collagenase-3) are among the enzymes expressed by human chondrocytes in degenerative pathologies of cartilage, namely osteoarthritis and rheumatoid arthritis [41] and are thus thought to play a critical role in cartilage destruction.