To elucidate the mechanisms by which NiO NPs induced pulmonary fibrosis, Tian et al. investigated the roles of TGF-β1, the MAPK pathway, and the balance between matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in NiO NPs-induced lung fibrosis [120]. Here, TGFB1 is linked to pulmonary fibrosis.