TGFB1 and pulmonary fibrosis: At the same time, the alveolar epithelium is the main cell population responsible for the production of platelet growth factor (PDGF), transforming growth factor beta (TGF-β), and tumor necrosis factor alpha (TNF-α), which are key orchestrators in the system of intercellular interaction and the subsequent development of pulmonary fibrosis [42].