Disruption of Prostaglandin F2a Receptor Signaling Attenuates Fibrotic Remodeling and Alters Fibroblast Population Dynamics in A Preclinical Murine Model of Idiopathic Pulmonary Fibrosis
Idiopathic Pulmonary Fibrosis (IPF) is a chronic, progressive, and diffuse parenchymal lung disease characterized by repetitive alveolar cell injury, myofibroblast proliferation, and excessive extracellular matrix deposition resulting in progressive loss of lung function.  Despite approved treatment options, unmet need persists for effective IPF therapeutics. The bioactive eicosanoid, prostaglandin F2a, and its cognate receptor FPr (Ptfgr) are implicated as a TGFb1 independent signaling hub for IPF. To further assess this signaling in IPF, we leveraged our published murine PF model (IER-SftpcI73T) expressing an inducible disease associated missense mutation in the SFTPC gene (I73T). Tamoxifen induction of IER-SftpcI73T mice resulted in an early multiphasic alveolitis and transition to spontaneous fibrotic remodeling by 28 days.  IER-SftpcI73T mice were crossed to a Ptgfr null (FPr-/-) line and resulted in attenuated weight loss and reductions in fibrotic endpoints. Through single cell RNA sequencing, pseudotime analysis, and in-vitro assays we demonstrated expression of Ptgfr predominantly within adventitial fibroblasts whichwere reprogrammed to an “inflammatory/transitional” cell state population in a PGF2a / FPr dependent manner..   Collectively, the findings provide added evidence a role for PGF2a signaling in IPF, mechanistically identify a susceptible fibroblast subpopulation, and establish a benchmark effect size for disruption of this pathway in mitigating fibrotic lung disease. Overall design: To capture representative proportions of all major parenchymal and immune cell populations, we profiled IER-SftpcI73T/ Ptgfr+/+ and IER-SftpcI73T/ Ptgfr-/- animals with oral TAM and harvested the lungs at 14 and 28 days (n=2 per genotype per time point). Controls (n= 4) consisted of one mouse each of uninduced IER-SftpcI73T/ Ptgfr+/+, IER-SftpcI73T/ Ptgfr-/-, SftpcWT/ Ptgfr+/+, and SftpcWT/ Ptgfr-/- genotypes. Single cell suspension prepared by physical and enzymatic dissociation followed by MACS sorting by LS columns with CD45+ cell removal using CD45 micobeads followed by followed by “spike-back” of immune cells (~20% of final suspensions) with biological replicates for each timepoint loaded onto individual GemCodes