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Runx1 in Postn-expressing fibroblasts exacerbates adverse cardiac remodeling post myocardial infarction

ABSTRACT: Runx1 is strongly induced in the heart after acute injury and in chronic disease settings. Its expression negatively correlates with outcomes, and past work has shown a protective effect when Runx1 is inhibited through a variety of experimental means. We sought to establish the cell type(s) responsible for Runx1-dependent adverse remodeling following infarction. Using immunostaining for RUNX1 along with existing single cell RNA sequencing data sets, we established which cell types express Runx1 and prioritized two from this list – cardiomyocytes and fibroblasts. Cre drivers for the respective cell populations were paired with a Runx1 floxed allele to generate inducible, cell-type specific knockout mice. Following myocardial infarction induced by permanent ligation, mice were assessed for functional recovery by echocardiography and histological measurements, including scar size, cardiomyocyte dimension, and cell proliferation. Detailed transcriptomic analysis was used to assess mechanism of action. In contrast to existing literature, we did not observe a measurable impact of cardiomyocyte-specific loss of Runx1 on heart function or histology following myocardial infarction when compared to Cre-positive controls. On the other hand, loss of Runx1 in the Postn-expressing activated fibroblast population resulted in a protective effect on heart function seen as early as 3 days post-infarction and maintained until the 56-day experimental endpoint. These functional benefits were accompanied by smaller scars, reduced cardiomyocyte hypertrophy, and a reduction of activated fibroblasts progressing to an SMA-positive myofibroblast. Overall, we demonstrate Runx1 expression in activated fibroblasts drives adverse remodeling phenotypes following myocardial infarction.

ORGANISM(S): Mus musculus

PROVIDER: GSE306883 | GEO | 2026/01/14

REPOSITORIES: GEO

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Project description:<p>Cardiac fibrosis, characterized by excessive extracellular matrix (ECM) deposition in the myocardium, is a critical target for heart disease treatments. Pw1 (paternally expressed gene 3) is an imprinted gene expressed from the paternally allele, and de novo purine biosynthesis (DNPB) is a crucial pathway for nucleotide synthesis. However, the roles of PW1 and DNPB in ECM production by cardiac fibroblasts during myocardial ischemia are not yet understood. To induce myocardial damage, we performed left anterior descending coronary artery ligation. We generated Pw1CreER-2A-eGFP and Pw12A-CreER knock-in mouse lines to evaluate the expression of the two Pw1 alleles in normal and injured hearts. Bisulfite sequencing was employed to analyze the DNA methylation of the Pw1 imprinting control region. We identified the phosphoribosylformylglycinamidine synthase (Pfas) gene, encoding the DNPB enzyme PFAS, as a direct target of PW1 using chromatin immunoprecipitation sequencing and real-time quantitative polymerase chain reaction. The role of DNPB in ECM production and cardiac fibrosis post-injury was examined in vitro using cultured cardiac fibroblasts and in vivo with Pfas-deficient mice. Our study demonstrates that myocardial infarction reduces DNA methylation at the imprinting control region of the maternally imprinted gene Pw1, triggering a switch from monoallelic imprinting to biallelic expression of Pw1 in cardiac fibroblasts. In activated cardiac fibroblasts, increased Pw1 expression promotes purine biosynthesis and induces ECM production by transcriptionally activating the DNPB factor Pfas. Notably, we identified that DNPB is essential for ECM production in activated fibroblasts and that loss of Pfas in fibroblasts limits cardiac fibrosis and improves heart function after heart injury. This study reveals that post-injury, the imprinting of Pw1 is disrupted, highlighting a novel role for the downstream DNPB pathway in cardiac fibrogenesis. Targeting DNPB presents a promising therapeutic strategy for improving cardiac repair following injury.</p>

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Runx1 in Postn-expressing fibroblasts exacerbates adverse cardiac remodeling post myocardial infarction

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