Although downregulation of Tgfb in lungs of BLM‐induced pulmonary fibrosis is considered to be an important mechanism (Figure 5), TGF‐β1/Smad signaling pathway includes both positive and negative regulatory ones in each constituent cell such as fibroblasts, endothelial cells, and EndMT cells. Here, TGFB1 is linked to pulmonary fibrosis.