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Sipa1 Drives the Inflammatory Signature of Cardiac Fibroblasts and Aggravates Wound Healing Response After Myocardial Infarction

ABSTRACT: Signal-induced proliferation-associated gene 1 (Sipa1) is known as a specific Rap1 GTPase-activating protein that negatively regulates Rap1 signaling. Although Sipa1 has been extensively studied in cancer research, its role in the wound healing response after myocardial infarction (MI) remains unexplored. To investigate the role of endogenous Sipa1 in MI, we performed permanent left anterior descending artery ligation in both Sipa1 knockout mice and their control littermates. Bone marrow transplantation, flow cytometry, cell sorting, and transcriptomic analysis were conducted to identify the cellular source of Sipa1 in the infarcted heart. The role of cardiac fibroblast-derived Sipa1 during MI was examined using Sipa1 deletion approaches, specifically in cardiac fibroblasts, in vivo and in vitro. Mice deficient in Sipa1 exhibited improved post-MI survival and cardiac function, along with attenuated expression of inflammatory mediators and diminished accumulation of Ly6Chigh monocytes and CCR2+ macrophages in the infarcted heart. Although Sipa1 was broadly expressed in the heart, cardiac fibroblasts were responsible for the Sipa1-induced deleterious phenotype as demonstrated by cardiac fibroblast-specific Sipa1 conditional knockout mice, which averted excessive inflammation and adverse cardiac remodeling following MI. Mechanistically, Sipa1 promotes the production of CCL2, CCL7 and granulocyte/macrophage colony-stimulating factor in the cardiac fibroblasts early after MI via a non-canonical RasGRP2-Ras-JNK signaling pathway, irrespective of canonical Rap1, thereby facilitating the accumulation and activation of inflammatory monocytes and macrophages. These results identify a previously unknown fibroblast-immune axis characterized by Sipa1, which initiates excessive inflammation and leads to poor outcomes after MI. Targeting Sipa1 offers a potential novel therapeutic strategy to optimize post-MI wound healing response, thereby preventing the development of chronic ischemic heart failure.

ORGANISM(S): Mus musculus

PROVIDER: GSE295755 | GEO | 2025/08/01

REPOSITORIES: GEO

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Project description:Aims and introduction: Cardiac fibrosis is the hallmark of cardiac disease, particularly myocardial infarction (MI), and is one of the most prevalent causes of heart failure. MI is intricately linked to inflammation, extracellular matrix (ECM) remodelling, and cardiac fibrosis, however the mechanisms underpinning these events remain poorly understood. We recently identified that ECM1 has potential to play a key role in cardiac wound healing but the cellular origins in the heart and specific mechanisms of ECM1 in fibrosis remain elusive. Therefore, we investigated the spatiotemporal, cell specific, expression profile of ECM1 in the healthy and diseased mouse and human heart and investigate ECM1 dependent human cardiac fibroblast (HuCFb) cell signalling mechanisms. Methods and results: Western blotting, immunohistochemistry (IHC) and mRNA in-situ hybridisation revealed that ECM1 protein expression was significantly upregulated in human ischaemic and dilated heart failure patients, and predominantly localised interstitially to fibrotic, inflammatory, and peri-vascular areas. ECM1 specific analysis of the Litviňuková et al. (2020) single-cell and -nuclei RNA sequencing (sc/snRNAseq) dataset of healthy human hearts, and the Farbehi et al. (2019) scRNAseq dataset of mouse hearts post-MI demonstrated that ECM1 expression originates from fibroblasts, macrophages, and pericytes/vascular mural cells in the heart. Further, we identify that post-MI ECM1 is expressed in a temporal dynamic flux from unactivated fibroblasts in sham-operated mice, to M1 macrophages (M1MΦ) at day-3, and myofibroblasts and M2MΦ at day-7. Phosphoproteomics of ECM1 treated human cardiac fibroblast cells (HuCFb) alongside ECM1 to HuCFb cell surface protein binding pull-down and mass spectrometry, revealed that ECM1 signalling goes via proteins associated with Rho protein signal transduction, cell-cell adhesion, microtubule dynamics, and cell chemotaxis pathways, potentially initiated by ECM1 to CTNND1 binding on the cell surface. Further mechanistic analyses identified that ECM1 inhibits HuCFb cell migration and stimulates inflammatory (IL-6 and IL-1β mRNA expression), fibrotic (TGF-β1, TGF-β2 and Col1a2 mRNA expression), and non-canonical Wnt signalling pathways (Wnt5a mRNA expression and JNK1/2/3 and MYPT1 phosphorylation). Conclusions: This study demonstrates that ECM1 expression originates from macrophages and fibroblasts in the mouse and human heart. ECM1 has significant effects on HuCFb migration, inflammatory, fibrotic, Rho protein, and Wnt5a/non-canonical Wnt signalling pathways. Together, ECM1 plays an important role in cardiac wound healing and may represent a novel mechanism of inflammation-fibrosis crosstalk and progression post-MI.

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Sipa1 Drives the Inflammatory Signature of Cardiac Fibroblasts and Aggravates Wound Healing Response After Myocardial Infarction

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