In vivo and in vitro experiments demonstrated that fibrosis-associated macrophages promoted mesangial-to-myofibroblast differentiation by activating the TGF-β1/Smad2/3/YAP signal axis and collagen, and increased α-SMA expression, which further slowed DKD fibrosis progression. The gene discussed is TGFB1; the disease is diabetic kidney disease.