Project description:Myocardial interstitial fibrosis is a common thread in multiple cardiovascular diseases including heart failure, atrial fibrillation, conduction disease and sudden cardiac death. To investigate the biologic pathways that underlie interstitial fibrosis in the human heart, we developed a machine learning model to measure myocardial T1 time, a marker of myocardial interstitial fibrosis, in 41,505 UK Biobank participants. Greater T1 time was associated with diabetes mellitus, renal disease, aortic stenosis, cardiomyopathy, heart failure, atrial fibrillation, conduction disease and rheumatoid arthritis. Mendelian randomization analysis supported a potential causal role for diabetes mellitus type 1 in myocardial interstitial fibrosis. In genome-wide association analysis, we identified 11 independent loci associated with native myocardial T1 time. The identified loci implicated genes involved in glucose transport (SLC2A12), iron homeostasis (HFE, TMPRSS6), tissue repair (ADAMTSL1, VEGFC), oxidative stress (SOD2), cardiac hypertrophy (MYH7B) and calcium signaling (CAMK2D). Transcriptome-wide association studies highlighted the role of expression of ADAMTSL1 and SLC2A12 in human cardiac tissue in modulating myocardial interstitial fibrosis. Using a TGFβ1-mediated cardiac fibroblast activation assay, we found that 9 out of the 11 genome-wide significant loci comprised genes that exhibited temporal changes in expression and/or open chromatin conformation supporting the biological relevance of these loci to myocardial fibrosis and myofibroblast cell state acquisition. Harnessing machine learning to perform large-scale phenotyping of interstitial fibrosis in the human heart, our results yield novel insights into biologically relevant pathways to myocardial fibrosis and prioritize a number of pathways for further investigation.
Project description:Heart failure (HF) and cardiac arrhythmias share overlapping pathological mechanisms that act cooperatively to accelerate disease pathogenesis. Cardiac fibrosis is associated with both pathological conditions. Our previous work identified a link between phytosterol accumulation, cardiac fibrosis and death in a mouse model of phytosterolemia, a rare disorder characterized by elevated circulating phytosterols and increased cardiovascular disease risk. Here, we uncover a previously unknown pathological link between phytosterols and cardiac arrhythmias in the same animal model. Phytosterolemia resulted in inflammatory pathway induction, premature ventricular contractions (PVC) and ventricular tachycardia (VT). Both pharmacological and genetic inhibition of phytosterol absorption prevented the induction of both pathways. Inhibition of phytosterol absorption reduced inflammation and cardiac fibrosis, improved cardiac function, reduced the incidence of arrhythmias and increased survival in a mouse model of phytosterolemia. Collectively, this work identified a pathological mechanism whereby elevated phytosterols result in inflammation and cardiac fibrosis leading to impaired cardiac function, arrhythmias and sudden death. These phytosterolemia-associated comorbidities provide novel insight into the underlying pathophysiological mechanism that predispose these patients to increased risk of sudden cardiac death.
Project description:Prolonged electrocardiographic indices reflecting myocardial impulse conduction and repolarization are risk factors for sudden cardiac death and drug-induced arrhythmia. The PR-interval, QRS-duration and QT-interval are heritable traits influenced by multiple genetic and environmental factors. The genetic underpinnings of these traits are still largely unknown. In this study, we leveraged the variability in cardiac gene expression and the variation in PR-, QRS- and QT-intervals among F2 mice harboring the cardiac sodium ion-channel mutation Scn5a-1798insD/+ derived from the 129P2-Scn5a1798insD/+ and FVB/NJ-Scn5a1798insD/+ cross, to isolate novel genes and biological pathways impacting on cardiac conduction and repolarization. Cardiac left-ventricle total RNA from 120 F2-(129P2xFVBN/J)-Scn5a-1798insD/+ mice at 12 to 14 weeks old.
Project description:Rationale. Sickle cell cardiomyopathy is characterized by prolonged QTc, myocardial fibrosis, diastolic dysfunction, and vulnerability to ventricular tachycardia (VT). Based on previous reports, IL-18 mediates cardiac fibrosis and its promoter SNPs are associated with sudden cardiac death in a non-sickle population. We, therefore, hypothesized that IL-18 may mediate cardiomyopathy and VT in sickle cell disease. Findings. Sickle cell patients with evidence of myocardial fibrosis demonstrated greater IL18 expression. Patients with higher IL18 gene expression levels also exhibited increased QTc intervals and overall mortality. A novel SNP within IL-18, rs5744285, was associated with both QTc and IL-18 expression levels. Similar to sickle cell patients, sickle mice demonstrated increased cardiac fibrosis and prolonged action potential duration (APD) associated with higher VT inducibility. Administration of exogenous IL-18 acutely ex vivo to hearts resulted in increased triggered activity and VTs while inhibition of IL-18 resulted in reduced cardiac NFkB expression, fibrosis, and dysfunction in sickle mice. Conclusions. IL-18 is associated with prolonged QTc, myocardial fibrosis, and mortality in sickle cell patients, and prolonged APD associated with heightened VT susceptibility in sickle mice. Inhibition of IL-18 improves cardiac function, in part, via NFκB. Inflammatory cytokines contribute to the development of sickle cardiomyopathy and inducible VT.
Project description:Prolonged electrocardiographic indices reflecting myocardial impulse conduction and repolarization are risk factors for sudden cardiac death and drug-induced arrhythmia. The PR-interval, QRS-duration and QT-interval are heritable traits influenced by multiple genetic and environmental factors. The genetic underpinnings of these traits are still largely unknown. In this study, we leveraged the variability in cardiac gene expression and the variation in PR-, QRS- and QT-intervals among F2 mice harboring the cardiac sodium ion-channel mutation Scn5a-1798insD/+ derived from the 129P2-Scn5a1798insD/+ and FVB/NJ-Scn5a1798insD/+ cross, to isolate novel genes and biological pathways impacting on cardiac conduction and repolarization.
2012-12-01 | GSE27236 | GEO
Project description:Genetic variants in sudden cardiac death victims with coronary artery disease and LV hypertrophy
Project description:Sudden cardiac death is the number one cause of death worldwide. Major causes of sudden cardiac death include myocardial infarction and cardiomyopathies. To develop novel therapeutic strategies, we need to identify key factors that are required for proper cardiac function and are dysregulated in the diseased heart. Under this notion, we found T-box 5 (TBX5), a transcription factor regarded solely in the context of congenital heart disease, to be downregulated in human diseased left ventricles. To investigate the effects of TBX5 loss in the adult heart, we generated an inducible ventricular cardiomyocyte specific knock-out mouse model (vTbx5KO). We performed integrative genome-wide chromatin occupancy and transcriptomic analysis and identified 47 downregulated transcripts in vTbx5KO that contain TBX5 active enhancers. The TBX5 targets in the ventricle included genes implicated in cardiac conduction and contraction (Gja1, Kcnj5, Kcng2, Cacna1g, Chrm2), cytoskeleton organization (Fstl4, Pdlim4, Emilin2, Cmya5) as well as cardiac protection upon stress (Fhl2, Gpr22, Fgf16). In line with this analysis, vTbx5KO mice presented cardiac conduction defects and arrhythmias at baseline as well as exacerbated cardiac remodeling upon Angiotensin II-induced hypertrophy. In conclusion, this study uncovers a novel protective role of TBX5 upon cardiac remodeling and renders TBX5 as an interesting therapeutic target.
Project description:Deletion of Lmna, encoding nuclear membrane protein LMNA, specifically in mouse cardiac myocytes activates BRD4 and leads to heart failure, arrhythmias, myocardial fibrosis, apoptosis, and premature death, which were partially rescued upon inhibition of BRD4.
Project description:Early reperfusion of ischemic cardiac tissue remains the most effective intervention for improving clinical outcome following myocardial infarction. However, abrupt increases in intracellular Ca2+ during myocardial reperfusion cause cardiomyocyte death and consequent loss of cardiac function, referred to as ischemia/reperfusion (IR) injury. Cardiac IR is accompanied by dynamic changes in expression of microRNAs (miRNAs), which inhibit specific mRNA targets. miR-214 is up-regulated during ischemic injury and heart failure in mice and humans, but its potential role in these processes is unknown. We show that genetic deletion of miR-214 in mice causes loss of cardiac contractility, increased apoptosis, and excessive fibrosis in response to IR injury. The microarray contains 6 samples, each containing cDNA pooled from 3 mice per group. There are no replicates. The array was designed to make 3 different pairwise comparisons between the following: P14 WT and miR-214 KO hearts; adult WT and miR-214 KO skeletal muscle; adult WT and miR-214 KO hearts