COL1A1 and idiopathic pulmonary fibrosis: Recent scRNA-Seq analysis of whole lung derived from bleomycin-treated Col1a1-GFP+ transgenic mice, as well analysis of IPF lungs, identified a distinct high collagen–expressing fibroblast population defined by the expression of the fibroblast gene markers Cthrc1, Postn, and Col3a1 (7).