Moreover, several studies have linked various MMP family members, including MMP-9, MMP-12, and MMP-15, to COPD through the degradation of the alveolar extracellular matrix (Babusyte et al., 2007; Gharib et al., 2018; Wells et al., 2018; Zhou et al., 2020). Here, MMP9 is linked to chronic obstructive pulmonary disease.