Project description:Cardiac fibroblasts stay relatively quiescent under normal condition. These cells differentiate to myofibroblasts after myocardial infarction (MI), characterized by the expression of contractile proteins and secretion of elevated levels of extracellular matrix proteins, leading to cardiac remodeling. The differentiated myofiroblasts gradually lose most myofibroblast phenotypes but still persist in the infarct area to maintain the tissue structural integrity. We used microarrays to reveal the change in cardiac fibroblast gene expression profile after MI.
Project description:Despite recent advances in pre-clinical research on cardiac remodeling following myocardial infarction (MI), the precise molecular pathways remain poorly understood, and effective therapies for heart failure are still delayed in development. The use of young animal models fails to mirror the clinical scenario of aged human patients, as aging is associated to less well-defined cellular identities that can alter the overall picture of cardiac repair. Here, we explore the active role of cardiac fibroblasts in post-MI ventricular remodeling, aiming to identify fibroblast-specific pathways through the lens of aging that enhance translational relevance. Cardiac fibroblasts were isolated from mice with MI through 5 day-culture of total interstitial population of cardiac cells under fibroblast-favoring conditions. The expression profiling of these cells was conducted as the initial approach to depict fibroblasts-specific changes that are common to young and old animals. For a translational perspective of the study, a group of young animals that endured MSC therapy after MI surgery was also included, to help identify the molecular changes that are amenable for therapeutic modulation. This analysis revealed GLIPR1 as being activated in cardiac fibroblasts within the infarct zone during the maturation phase post-MI, thus suggesting a role in the fibrotic process. Further investigations indicated that the inflammatory environment post-MI induced the upregulation of GLIPR1 in the myofibroblast subpopulation of infarcted cardiac fibroblasts, which promoted matrix reorganization by increase in TIMP3 expression. Our study shows a key role of GLIPR1 in modulating the matrix remodeling during cardiac repair post-MI. The data presented here provide a fundamental cellular and molecular knowledge that paves the way for further exploration of GLIPR1 as a potential therapeutic target to reduce cardiac fibrosis.
Project description:Cardiac fibrosis is a common feature of ischemic heart disease and cardiac fibroblasts (CF) are key players in cardiac remodeling of the injured heart after myocardial infarction (MI). Fibrosis increases myocardial stiffness, thereby impairing cardiac function, which ultimately progresses to end-stage heart failure. Little is known, however, on the secretome of CF and cell-to-cell communication of CF is only incompletely understood. Here, we in vivo labeled secreted proteins by expressing TurboID under control of the POSTN promotor in cardiac fibroblasts of mouse with myocardial infarction, enriched biotinylated proteins and analyzed them using LC-MS.
Project description:Heart failure (HF) is a leading cause of morbidity and mortality. As adult cardiomyocytes (CMs) have little regenerative capacity, after myocardial infarction (MI), resident cardiac fibroblasts (CFs) synthesize extracellular matrix to form scar tissues, resulting in myocardial remodeling and HF. Thus, both cardiac regeneration and fibrosis are therapeutic targets for chronic MI. We previously reported that fibroblasts were directly reprogrammed into induced CMs (iCMs) by overexpression of cardiogenic transcription factors in acute and chronic MI. Here we show that in vivo cardiac reprogramming improved cardiac function, and reversed cardiac remodeling in chronic MI using a novel transgenic mouse system. Transcriptome analysis revealed that in vivo cardiac reprogramming suppressed signs of fibrosis and inflammation. Thus, in vivo cardiac reprogramming may be a promising approach for chronic HF.
Project description:In response to myocardial infarction (MI), quiescent cardiac fibroblasts differentiate into myofibroblasts mediating tissue repair in the infarcted area. One of the most widely accepted markers of myofibroblast differentiation is the expression of Acta2 which encodes smooth muscle alpha-actin (SMαA) that is assembled into stress fibers. However, the requirement of Acta2/ SMαA in the myofibroblast differentiation of cardiac fibroblasts and its role in post-MI cardiac repair remained largely unknown. To answer these questions, we generated a tamoxifen-inducible cardiac fibroblast-specific Acta2 knockout mouse line. Surprisingly, mice that lacked Acta2 in cardiac fibroblasts had a normal survival rate after MI. Moreover, Acta2 deletion did not affect the function or overall histology of infarcted hearts. No difference was detected in the proliferation, migration, or contractility between WT and Acta2-null cardiac myofibroblasts. It was identified that Acta2-null cardiac myofibroblasts had a normal total filamentous actin level and total actin level. Acta2 deletion caused a significant compensatory increase in the transcription level of non- Acta2 actin isoforms, especially Actg2 and Acta1, 2 other muscle actin isoforms. Moreover, in myofibroblasts the transcription levels of cytoplasmic actin isoforms were significantly higher than those of muscle actin isoforms. In addition, we found that myocardin-related transcription factor-A is critical for myofibroblast differentiation but is not required for the compensatory effects of non-Acta2 isoforms. In conclusion, the deletion of Acta2 does not prevent the myofibroblast differentiation of cardiac fibroblasts or affect the post-MI cardiac repair, and the increased expression and stress fiber formation of non-SMαA actin isoforms and the functional redundancy between actin isoforms are able to compensate for the loss of Acta2 in cardiac myofibroblasts.
Project description: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.
Project description:Immune cell infiltration in response to myocyte death contributes to extracellular matrix (ECM) remodeling and scar formation after myocardial infarction (MI). Caspase-recruitment domain protein 9 (CARD9) which belongs to CARD family acts as an adapter that mediate the transduction of proinflammatory signaling cascades in innate immunity. To investigate the role of CARD9 in cardiac injury and repair post ischemia, we subjected Card9 knockout mice to myocardial infarction (MI) , and then performed RNA-seq and gene expression profiling analysis using the ischemic cardiac tissues at 3 days post-MI, to identify key genes and pathways regulated by CARD9.