By using single cell RNA sequence analysis, we reveal that TGF-β1 induces MMT in bone marrow-derive macrophages via the Smad3-Src-POU4F1 pathway as Smad3 can bind Src and POU4F1 promoters to induce MMT and targeting this pathway can block MMT and renal fibrosis in vitro and in vivo30, 33. Here, SMAD3 is linked to renal fibrosis.