MMP12 and pulmonary emphysema: In patients with COPD, representative changes in the pulmonary system include mucous hypersecretion [4], fibrosis [5], and alveolar wall destruction (emphysema) [6]; these changes are related to several factors such as cytokines (TGF-β, TNF-α, IL-1β, and IL-6), chemokines (CCL2, CXCL1, and CCR2), and collagenase/gelatinase (MMP-9 and MMP-12) [15, 32].