MMP3 and rheumatoid arthritis: Except for soft tissue and bone lesions, RA synovial fibroblasts can spontaneously secrete numerous proinflammatory cytokines such as interleukin-6 (IL-6) and IL-8 and matrix metalloproteinases (MMPs) including MMP-1 and MMP-3, which result in infiltration of inflammatory cells and play a critical role in progressive destruction of articular cartilage and bone [5–7].