In the present study, exogenous administration of Gal-9 in an emphysema animal model reduced the levels of MMP-9, MMP-2 and TIMP-1 in BALF (Fig 3A–3C), and these MMPs levels correlated significantly with the number of neutrophils in BALF (Fig 4A–4C). Here, MMP2 is linked to pulmonary emphysema.