CCN2 and pulmonary fibrosis: Profibrotic responses of fibroblasts are also enhanced by the release of growth factors from injured alveolar epithelium, such as PDGF, a potent mitogen for lung fibroblast and CTGF (connective tissue growth factor), which stimulates fibroblast proliferation and increases collagen production, further contributing to the development and progression of pulmonary fibrosis [76].