Collagen I has a triple helix structure that arises from two α-1 and one α-2 chains, which are the products of the COL1A1 and COL1A2 genes, respectively; down-regulation of COL1A1 alleviates the accumulation of ECM and then inhibits pulmonary fibrosis [52–54]. The gene discussed is COL1A2; the disease is pulmonary fibrosis.