Fibroblasts are the main source of GPR183 ligand-producing enzymes in the lung. (A) Dot plot showing expression of Ch25h, Cyp7b1, and Hsd3b7 in the indicated non-hematopoietic single-cell RNA-sequencing clusters from SPAM deleter mice as in Fig. 3 E. AT1, alveolar type I cells; AT2, alveolar type II cells. See Fig. S2 C for markers used to annotate the cell clusters. (B) Time course of Ch25h, Cyp7b1, and Hsd3b7 expression in the lung of SPAM deleter mice after DT-induced alveolar macrophage depletion as determined by single-cell RNA sequencing. (C) Feature plots showing Ch25h and Cyp7b1 expression in the SPAM deleter cell clusters from Fig. 3 E. (D) Time course of Ch25h and Cyp7b1 expression in the indicated SPAM deleter cell populations corresponding to the lung clusters in Fig. 3 E. Data in panels A–D are from one single-cell RNA-sequencing experiment with n = 4 mice per time point. (E) Experimental setup for single-cell RNA sequencing of lung niche cells from IM-DTR mice. CD45⁻ non-hematopoietic cells (fibroblasts, epithelial cells, and endothelial cells) were purified from the lungs of IM-DTR mice as described in the Materials and methods. IM, interstitial macrophage. (F) UMAP of lung niche cells at the indicated time points after interstitial lung macrophage depletion with 50 ng intraperitoneal DT. Markers used to annotate lung fibroblasts, epithelial cells, and endothelial cells are shown in Fig. S5 A. (G) Dot plot of Ch25h, Cyp7b1, and Hsd3b7 expression in lung fibroblasts, epithelial cells, and endothelial cells from IM-DTR mice. (H) Time course of Ch25h, Cyp7b1, and Hsd3b7 expression in lung fibroblasts after DT-induced interstitial macrophage depletion. Data in panels F–H are from one single-cell RNA-sequencing experiment with n = 3–4 mice per time point. Panel E was adapted from Servier Medical Art.