MMP-9 breaks down ECM proteins; TIMP-1 inhibits MMP-9.Sputum MMP-9 and TIMP-1 concentrations are higher in asthmatics compared to controls; The MMP-9/TIMP-1 ratio is lower in patients with asthma and chronic bronchitis, and positively correlates with FEV1 (101).MMP-9 is required for angiogenesis in mice (102). This evidence concerns the gene TIMP1 and chronic bronchitis.