MMP12 and chronic obstructive pulmonary disease: Accordingly, the transcript expression of the matrix metalloproteinase (Mmp) 12 (Mmp12; macrophage elastase) and Mmp9 (gelatinase), which are associated with COPD and expressed by macrophages [34], was significantly increased in NTHi-treated miR449−/− mice (Figure 5h).