Matrix metalloproteinase (MMP)‐12, also known as macrophage elastase, is required for the development of cigarette smoke‐induced emphysema in mice (Hautamaki, Kobayashi, Senior, & Shapiro, 1997), and the inhibition of macrophage recruitment or induction of apoptosis in alveolar macrophages was found to suppress alveolar collapse in an elastase‐induced emphysema model (Houghton et al., 2006; Ueno et al., 2015). This evidence concerns the gene MMP12 and pulmonary emphysema.