MMP dysregulation has been associated with many acute and chronic inflammatory respiratory diseases such as acute respiratory distress syndrome (ARDS) [10], idiopathic pulmonary fibrosis (IPF) [11], chronic obstructive pulmonary disease (COPD) [12], and lung cancer [13], with upregulation of the gelatinases (MMP-2 and MMP-9) often found in IPF [9, 14] and associated with a more aggressive disease phenotype [15]. Here, MMP9 is linked to acute respiratory distress syndrome.