CCN2 and pulmonary fibrosis: Many profibrotic factors, such as the connective tissue growth factor (CTGF), transforming growth factor 1 (TGF-β1), and fibroblast growth factor (FGF), can cause the excessive secretion of collagen and then deposition in the lung interstitium, constantly forming “scars” in the lung, resulting in pulmonary fibrosis [53,54].