SFRP2 and idiopathic pulmonary fibrosis: demonstrated that in idiopathic pulmonary fibrosis (IPF), TGF‐β1 activates fibroblasts to secrete secreted frizzled‐related protein 2 (sFRP2), a noncanonical Wnt ligand, which in turn drives epithelial metaplasia through Frizzled 5 (Fzd5)‐mediated activation of nuclear NFATc3 [109].