The matrix metalloproteinases (MMPs) are a family of peptidase pathway responsible for the degradation of extracellular matrix components, including collagen, gelatin, fibronectin, laminin and proteoglycan. Transcription of MMP genes is is differentially activated by phorbol ester, lipopolysaccharide (LPS) or staphylococcal enterotoxin MMP-9 (also designated 92 kDa type IV collagenase or gelatinase B) has been shown to degrade bone collagens in concert with MMP-1 (also specified interstitial collagenase, fibroblast collagenase or Collagenase-1), and cysteine proteases and may play a role in bone osteoclastic resorption. MMP-1 is downregulated by p53, and abnormality of p53 expression can contribute to joint degradation in rheumatoid arthritis by regulating MMP-1 expression.