MMP13 and pulmonary fibrosis: Drawn against this background and the recently shown involvement of MMP-13 in bone remodeling defects in skeletal diseases [29], in mediating collagen breakdown in atherosclerotic plaques [30], and in the reduction of liver fibrosis after CCl4 injury [15], we hypothesized that MMP-13 might also play a significant role in the pathogenesis of pulmonary fibrosis.