Down‐regulation of CYTL1 attenuates bleomycin‐induced pulmonary fibrosis in mice by inhibiting M2 macrophage polarization via the TGF‐β/CCN2 axis

haematopoietic cells. However, its possible effects on IPF progression remain unclear. This study investigated the role of CYTL1 in IPF progression in a bleomycin-induced lung injury and fibrosis model. In bleomycin-induced mice, CYTL1 is highly expressed. Moreover, CYTL1 ablation alleviates lung injury and fibrosis in vivo. Further, downregulating CYTL1 reduces macrophage M2 polarization. Mechanically, CYTL1 regulates transforming growth factor β (TGF-β)/connective tissue growth factor (CCN2) axis and inhibition of TGF-β pathway alleviates bleomycin-induced lung injury and fibrosis. In conclusion, highly expressed CYTL1 inhibits macrophage M2 polarization by regulating TGF-β/CCN2 expression, alleviating bleomycin-induced lung injury and fibrosis. CYTL1 could, therefore, serve as a promising IPF target.