Although IL-1-induce MMPs are involved in the breakdown of ECM in disease processes, such as arthritis and tumor metastasis [11], [41]–[43], there is no MMP-3 mRNA and MMP-3 under normal physiological conditions because of the absence of the required cytokines to stimulate production of this protein, as shown in Figure 1. This evidence concerns the gene MMP3 and Arthritis.