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Leukocyte-Dependent Regulation of Cardiac Fibrosis.

ABSTRACT: Cardiac fibrosis begins as an intrinsic response to injury or ageing that functions to preserve the tissue from further damage. Fibrosis results from activated cardiac myofibroblasts, which secrete extracellular matrix (ECM) proteins in an effort to replace damaged tissue; however, excessive ECM deposition leads to pathological fibrotic remodeling. At this extent, fibrosis gravely disturbs myocardial compliance, and ultimately leads to adverse outcomes like heart failure with heightened mortality. As such, understanding the complexity behind fibrotic remodeling has been a focal point of cardiac research in recent years. Resident cardiac fibroblasts and activated myofibroblasts have been proven integral to the fibrotic response; however, several findings point to additional cell types that may contribute to the development of pathological fibrosis. For one, leukocytes expand in number after injury and exhibit high plasticity, thus their distinct role(s) in cardiac fibrosis is an ongoing and controversial field of study. This review summarizes current findings, focusing on both direct and indirect leukocyte-mediated mechanisms of fibrosis, which may provide novel targeted strategies against fibrotic remodeling.

SUBMITTER: Okyere AD

PROVIDER: S-EPMC7156539 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Leukocyte-Dependent Regulation of Cardiac Fibrosis.

Okyere Ama Dedo AD Tilley Douglas G DG

Frontiers in physiology 20200408

Cardiac fibrosis begins as an intrinsic response to injury or ageing that functions to preserve the tissue from further damage. Fibrosis results from activated cardiac myofibroblasts, which secrete extracellular matrix (ECM) proteins in an effort to replace damaged tissue; however, excessive ECM deposition leads to pathological fibrotic remodeling. At this extent, fibrosis gravely disturbs myocardial compliance, and ultimately leads to adverse outcomes like heart failure with heightened mortalit ...[more]

PMID: 32322219

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Project description:BACKGROUND:Genetic diversity and the heterogeneous nature of cardiac fibroblasts (CFbs) have hindered characterization of the molecular mechanisms that regulate cardiac fibrosis. The Hybrid Mouse Diversity Panel offers a valuable tool to examine genetically diverse cardiac fibroblasts and their role in fibrosis. METHODS:Three strains of mice (C57BL/6J, C3H/HeJ, and KK/HlJ) were selected from the Hybrid Mouse Diversity Panel and treated with either isoproterenol (ISO) or saline by an intraperitoneally implanted osmotic pump. After 21 days, cardiac function and levels of fibrosis were measured by echocardiography and trichrome staining, respectively. Activation and proliferation of CFbs were measured by in vitro and in vivo assays under normal and injury conditions. RNA sequencing was done on isolated CFbs from each strain. Results were analyzed by Ingenuity Pathway Analysis and validated by reverse transcription-qPCR, immunohistochemistry, and ELISA. RESULTS:ISO treatment in C57BL/6J, C3H/HeJ, and KK/HlJ mice resulted in minimal, moderate, and extensive levels of fibrosis, respectively (n=7-8 hearts per condition). Isolated CFbs treated with ISO exhibited strain-specific increases in the levels of activation but showed comparable levels of proliferation. Similar results were found in vivo, with fibroblast activation, and not proliferation, correlating with the differential levels of cardiac fibrosis after ISO treatment. RNA sequencing revealed that CFbs from each strain exhibit unique gene expression changes in response to ISO. We identified Ltbp2 as a commonly upregulated gene after ISO treatment. Expression of LTBP2 was elevated and specifically localized in the fibrotic regions of the myocardium after injury in mice and in human heart failure patients. CONCLUSIONS:This study highlights the importance of genetic variation in cardiac fibrosis by using multiple inbred mouse strains to characterize CFbs and their response to ISO treatment. Our data suggest that, although fibroblast activation is a response that parallels the extent of scar formation, proliferation may not necessarily correlate with levels of fibrosis. In addition, by comparing CFbs from multiple strains, we identified pathways as potential therapeutic targets and LTBP2 as a marker for fibrosis, with relevance to patients with underlying myocardial fibrosis.

Project description:Conversion of cardiospheres derived primitive cardiac stromal cells into myofibroblasts is typically associated with hypoxia conditions, metabolic insults, and/or inflammation, all of which are predisposing factors to cardiac fibrosis and heart failure. We hypothesized that this conversion could be also mediated by response of these cells to mechanical cues through activation of the Hippo transcriptional pathway. The objective of the present study was to assess the role of cellular/nuclear straining forces acting in myofibroblast differentiation of cardiospheres derived primitive cardiac stromal cells under the control of YAP transcription factor and to validate this finding using a pharmacological agent that interferes with the interactions of the YAP/TAZ complex with their cognate transcription factors TEADs, under high-strain and pro-fibrotic stimulation. We employed high content imaging, 2D/3D culture, atomic force microscopy mapping and molecular methods to prove the role of cell/nuclear straining in YAP-dependent fibrotic programming in a mouse model of ischemia-dependent cardiac fibrosis and in human-derived primitive cardiospheres derived primitive cardiac stromal cells . We also tested treatment of cells with Verteporfin, a drug known to prevent the association of the YAP/TAZ complex with their cognate transcription factors TEADs. Results suggested that pharmacologically targeting the YAP-dependent pathway overrides the pro-fibrotic activation of cardiospheres derived primitive cardiac stromal cells by mechanical cues in vitro, and that this occurs even in the presence of pro-fibrotic signaling mediated by TGF-β1. In vivo administration of Verteporfin in mice with permanent cardiac ischemia reduced significantly fibrosis and morphometric remodeling but did not improve cardiac performance. Our study indicates that preventing molecular translation of mechanical cues in cardiospheres derived primitive cardiac stromal cells reduces the impact of cardiac maladaptive remodeling with a positive effect on fibrosis.

Dataset Information

Leukocyte-Dependent Regulation of Cardiac Fibrosis.

Publications

Leukocyte-Dependent Regulation of Cardiac Fibrosis.

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