Expression of fibrosis-related factors such as transforming growth factor beta (TGF-β1), matrix metalloproteinase 12 (MMP-12), tissue inhibitor of metalloproteinases-1 (TIMP-1), connective tissue growth factor (CTGF), and fibronectin, have been associated with the development of lung fibrosis. This evidence concerns the gene MMP12 and pulmonary fibrosis.