Lipid mediators control macrophage and fibroblast phenotype, and support regeneration in the alveolar niche

Macrophage-derived lipid mediators play pivotal autocrine/paracrine roles in resolution and repair. In the alveolar niche, “regenerative fibroblasts” produce vital growth factors (FGF7/10) for alveolar stem cells to regenerate damaged epithelia, however the signals controlling fibroblast phenotype are yet to be defined. <bold>Aim:</bold> To investigate the role of macrophage-derived PGE₂, specialized pro-resolving mediators (SPMs) and growth factors in controlling interstitial fibroblast phenotype during regeneration of alveolar injury. IPF myofibroblasts were treated with PGE₂ and studied by RNAseq. IPF BAL macrophages were treated with PGE₂ and analysed in a fibrosis and resolution-focused QuantiGene assay. Further, to investigate the regenerative potential of lipid mediators in the macrophage-fibroblast-epithelial cell axis, we are developing 3D co-culture systems integrating macrophage signals, fibroblasts and lung progenitors. <bold>Results:</bold> PGE₂ reverted myofibroblast phenotype, re-activated expression of FGF7/10, and upregulated markers of lipofibroblasts and matrix fibroblasts (TCF21 and COL14A1), while reducing myofibroblast genes (ACTA2, COL1A1 and SERPINE1) and genes involved in the Serine - Glycine synthesis pathway (PHGDH, PSAT1, PSPH and SHMT2). Similarly, PGE₂ inhibited pro-fibrotic signals such as SERPINE1 and CCL24 from IPF BAL macrophages and enhanced expression of THBS1, AREG and VEGFA known to increase efferocytotic capacity, drive fibroblasts FGF7/10 and to support vascular regeneration, respectively. Our data support a model where macrophage signals controlling fibroblast phenotype have the potential to restrict fibrosis in IPF and activate regeneration of the alveolar niche.