MMP9 and idiopathic pulmonary fibrosis: MMPs are known to cleave secreted proteins such as collagen and elastin fibers of the extracellular matrix [60], are essential for extracellular matrix remodeling, wound healing, and angiogenesis, and some of them, including MMP-1 and MMP-9, have been implicated in the pathogenesis of IPF [23,51,61,62,63] and other diseases [34].