Indeed, the levels of some of these mediators, including TGF-β1, PDGF, TIMP1, OPN, and MMP12, are significantly elevated in CNT-exposed lungs; meanwhile, TGF-β1, TIMP1, and OPN have been demonstrated to play essential pro-fibrotic roles in CNT-induced lung fibrosis (Dong and Ma, 2016b,2017a,b, 2018b). Here, TGFB1 is linked to pulmonary fibrosis.