FIGURE 6.

Monocyte-derived alveolar macrophages (Mo-AMs) express Pdgfa which is required for fibroblast proliferation. UMAP: uniform manifold approximation and projection; t-SNE: t-distributed stochastic neighbour embedding; TR-AM: tissue-resident AM; IM: interstitial macrophage. a, b) UMAP and t-SNE plots showing expression of Pdgfa in AMs after a) asbestos and b) bleomycin exposure. c) Bar plot showing expression of Pdgfa in flow-sorted AMs during the course of bleomycin-induced pulmonary fibrosis. Data from Misharin et al. [9]. Box plot centre lines are median, box limits are upper and lower quartiles, and whiskers are minimal and maximal values. One-way ANOVA with Bonferroni correction for multiple comparisons. ***: p<0.001; ****: p<0.0001. d) In situ RNA hybridisation confirms expression of Pdgfa in AMs during pulmonary fibrosis. Analysis performed on day 28 after TiO₂ or asbestos exposure. Macrophages were identified as Mrc1⁺ cells and fibroblasts were identified as Pdgfra⁺ cells. Short arrows indicate Mrc1⁺Pdgfa⁺ macrophages and long arrows indicate Pdgfra⁺ fibroblasts adjacent to Mrc1⁺Pdgfa⁺ macrophages. Scale bar: 50 µm. e) The percentage of Mrc1⁺Pdgfa⁺ AMs is increased after asbestos exposure. Data are from three mice per condition. Mean±sd. Mann–Whitney test.