Project description:An important event in the pathogenesis of heart failure is the development of pathological cardiac hypertrophy. In cultured cardiac cardiomyocytes, the transcription factor Gata4 is required for agonist-induced cardiomyocyte hypertrophy. We hypothesized that in the intact organism Gata4 is an important regulator of postnatal heart function and of the hypertrophic response of the heart to pathological stress. To test this hypothesis, we studied mice heterozygous for deletion of the second exon of Gata4 (G4D). At baseline, G4D mice had mild systolic and diastolic dysfunction associated with reduced heart weight and decreased cardiomyocyte number. After transverse aortic constriction (TAC), G4D mice developed overt heart failure and eccentric cardiac hypertrophy, associated with significantly increased fibrosis and cardiomyocyte apoptosis. Inhibition of apoptosis by overexpression of the insulin-like growth factor 1 receptor prevented TAC-induced heart failure in G4D mice. Unlike WT-TAC controls, G4D-TAC cardiomyocytes hypertrophied by increasing in length more than width. Gene expression profiling revealed upregulation of genes associated with apoptosis and fibrosis, including members of the TGF? pathway. Our data demonstrate that Gata4 is essential for cardiac function in the postnatal heart. After pressure overload, Gata4 regulates the pattern of cardiomyocyte hypertrophy and protects the heart from load-induced failure. Experiment Overall Design: We reasoned that if Gata4 was a crucial regulator of pathways necessary for cardiac hypertrophy, then modest reductions of Gata4 activity should result in an observable cardiac phenotype. To test this hypothesis, we used gene targeted mice that express reduced levels of Gata4. We characterized these mice at baseline and after pressure Experiment Overall Design: overload.
Project description:An important event in the pathogenesis of heart failure is the development of pathological cardiac hypertrophy. In cultured cardiac cardiomyocytes, the transcription factor Gata4 is required for agonist-induced cardiomyocyte hypertrophy. We hypothesized that in the intact organism Gata4 is an important regulator of postnatal heart function and of the hypertrophic response of the heart to pathological stress. To test this hypothesis, we studied mice heterozygous for deletion of the second exon of Gata4 (G4D). At baseline, G4D mice had mild systolic and diastolic dysfunction associated with reduced heart weight and decreased cardiomyocyte number. After transverse aortic constriction (TAC), G4D mice developed overt heart failure and eccentric cardiac hypertrophy, associated with significantly increased fibrosis and cardiomyocyte apoptosis. Inhibition of apoptosis by overexpression of the insulin-like growth factor 1 receptor prevented TAC-induced heart failure in G4D mice. Unlike WT-TAC controls, G4D-TAC cardiomyocytes hypertrophied by increasing in length more than width. Gene expression profiling revealed upregulation of genes associated with apoptosis and fibrosis, including members of the TGF? pathway. Our data demonstrate that Gata4 is essential for cardiac function in the postnatal heart. After pressure overload, Gata4 regulates the pattern of cardiomyocyte hypertrophy and protects the heart from load-induced failure. Keywords: genetic modification, pressure overload stress response
Project description:Cardiac hypertrophy is regulated by the zinc finger-containing DNA binding factors Gata4 and Gata6, both of which are required to mount a productive growth response of the adult heart. To determine if Gata4 and Gata6 are redundant or have non-overlapping roles, we performed cardiomyocyte-specific conditional gene deletions for Gata4 and Gata6 in conjunction with reciprocal replacement with a transgene encoding either Gata4 or Gata6, during the pressure overload response. We determined that Gata4 and Gata6 play a redundant and dosage-sensitive role in programming the hypertrophic growth response itself following pressure overload stimulation. However, non-redundant functions were identified as functional decompensation induced by either Gata4 or Gata6 deletion was not rescued by the reciprocal transgene, and only Gata4 heart-specific deletion produced a reduction in capillary density after pressure overload. Gene expression profiling from hearts of these gene-deleted mice showed both overlapping and unique transcriptional codes, with Gata4 exhibiting the strongest impact. These results indicate that Gata4 and Gata6 play a dosage-dependent and semi-redundant role in programming cardiac hypertrophy, but that each has a unique role in maintaining cardiac homeostasis and adaptation to injury that cannot be compensated by the other. Microarray-bassed gene expression profiling identified overlapping, distinct, and quantitatively/differentially regulated classes of Gata4 or Gata6 regulated genes. To determine if Gata4 and Gata6 are redundant or have non-overlapping roles in programming cardiac hypertrophic responses and adaptation to stress or injury, we performed cardiomyocyte-specific conditional gene deletions for Gata4 and Gata6 in conjunction with reciprocal replacement with a transgene encoding either Gata4 or Gata6, during the pressure overload response.
Project description:In humans, cardiac hypertrophy is the principal risk factor for the development of overt heart failure and sudden cardiac death from lethal arrhythmias. Although aberrant reactivation of fetal² gene programs is intricately linked to maladaptive hypertrophy of postnatal cardiomyocytes, loss of cardiac function and heart failure, the transcription factors driving these gene programs remain ill defined. We report that the basic helix-loop-helix (bHLH) transcription factor dHAND/Hand2 is re-expressed in the mammalian postnatal myocardium in response to stress signaling. Interestingly, mutant mice overexpressing Hand2 in otherwise healthy ventricular myocytes developed a phenotype of pathological hypertrophy. In contrast, conditional gene-targeted Hand2 mice demonstrated a marked resistance to pressure overload-induced hypertrophy, fibrosis, ventricular dysfunction and induction of a fetal gene program. These data suggest a critical role for the Hand2 transcription factor during hypertrophic remodeling and heart failure. To gain more mechanistically insight in the processes underlying heart failure, we here identified Hand2 target genes by microarray gene expression profiling. RNA samples were collected 4 weeks after sham or TAC surgery (to induce pressure overload) of both tamoxifen-treated Hand2f/f (WT) and MCM-Hand2f/f (KO) mice.
Project description:The 18-kDa mitochondrial translocator protein (TSPO), likely through its interaction with the voltage-dependent anion channel (VDAC), has been shown to modulate mitochondrial function and the cardiac response to pressure overload. We have previously shown that conditional knockout of TSPO limited the development of heart failure in the murine model of transverse aortic constriction (TAC). In this study, we tested the hypothesis that similar protection could be achieved by a ligand of TSPO, Ro5-4864 (Ro5), in in-vivo animal model of pressure-overload induced heart failure. To elucidate mechanisms, we performed proteomic and western blot analysis of cardiac tissue after 8 weeks of TAC in mice treated and untreated with Ro5.
Project description:Heart failure is a complex clinical syndrome characterized by insufficient cardiac function. It has been characterized that heart resident and infiltrated macrophages play important roles in the cardiac remodeling in response to cardiac pressure overload, however, role of T cells has not been well characterized. Here we show that CD8+T cell depletion resulted in the late stage heart protection, but induced cardioprotective hypertrophy at an early stage of heart failure caused by cardiac pressure overload. Single cell RNA sequencing analysis revealed that cardioprotective hypertrophy was characterized by an expression of mitochondrial genes and growth factor receptors genes. CD8+T cells regulated the conversion of cardiac-resident macrophages as well as infiltrated macrophages to cardioprotective macrophages which express growth factor genes including Areg, Osm and Csf1 at the early phase of cardiac pressure overload, which are essential for the myocardial adaptive response. Our results demonstrate a dynamic interplay between cardiac CD8+T cells and macrophages that is necessary for adaptation to cardiac stress, and they highlight the homeostatic functions of tissue macrophages.
Project description:Atherosclerosis and pressure overload are major risk factors for the development of heart failure in patients. Cardiac hypertrophy often precedes the development of heart failure. However, underlying mechanisms are incompletely understood. To investigate pathomechanisms underlying the transition from cardiac hypertrophy to heart failure we used experimental models of atherosclerosis- and pressure overload-induced cardiac hypertrophy and failure, i.e. apolipoprotein E (apoE)-deficient mice, which develop heart failure at an age of 18 months, and non-transgenic C57BL/6J (B6) mice with heart failure triggered by 6 months of pressure overload induced by abdominal aortic constriction (AAC). The development of heart failure was monitored by echocardiography, invasive hemodynamics and histology. The microarray gene expression study of cardiac genes was performed with heart tissue from failing hearts relative to hypertrophic and healthy heart tissue, respectively. The microarray study revealed that the onset of heart failure was accompanied by a strong up-regulation of cardiac lipid metabolism genes involved in fat synthesis, storage and oxidation. Microarray gene expression profiling was performed with heart tissue isolated from (i) 18 month-old apoE-deficient mice relative to age-matched non-transgenic C57BL/6J (B6) mice, (ii) 6 month-old apoE-deficient mice with 2 months of chronic pressure overload induced by abdominal aortic constriction (AAC) relative to sham-operated apoE-deficient mice and nontransgenic B6 mice, (iii) 10 month-old B6 mice with 6 months of AAC relative to sham-operated B6 mice, and (iv) 5 month-old B6 mice with 1 month of AAC relative to age-matched B6 mice.
Project description:Here, we show that adult cardiac fibroblasts express the cardiomyocyte transcription factors GATA-4 and GATA-6 to promote adaptive remodeling in pressure overload induced cardiac hypertrophy. Using a mouse model with specific single or double deletion of Gata4 and Gata6 in stress activated fibroblasts, we found a reduced myocardial capillarization in mice with Gata4/6 double deletion following pressure overload, while single deletion of Gata4 or Gata6 had no effect. Importantly, we confirmed the reduced angiogenic response using an in vitro co-culture system with Gata4/6 deleted cardiac fibroblast and endothelial cells. A comprehensive RNA-sequencing analysis revealed an upregulation of anti-angiogenic genes upon Gata4/6 deletion in fibroblasts, and siRNA mediated downregulation of these genes restored endothelial cell growth. In conclusion, we identified a novel role for the cardiac transcription factors GATA4 and GATA6 in heart fibroblasts, where both proteins act in concert to promote myocardial capillarization and heart function by directing intercellular crosstalk.
Project description:Atherosclerosis and pressure overload are major risk factors for the development of heart failure in patients. Cardiac hypertrophy often precedes the development of heart failure. However, underlying mechanisms are incompletely understood. To investigate pathomechanisms underlying the transition from cardiac hypertrophy to heart failure we used experimental models of atherosclerosis- and pressure overload-induced cardiac hypertrophy and failure, i.e. apolipoprotein E (apoE)-deficient mice, which develop heart failure at an age of 18 months, and non-transgenic C57BL/6J (B6) mice with heart failure triggered by 6 months of pressure overload induced by abdominal aortic constriction (AAC). The development of heart failure was monitored by echocardiography, invasive hemodynamics and histology. The microarray gene expression study of cardiac genes was performed with heart tissue from failing hearts relative to hypertrophic and healthy heart tissue, respectively. The microarray study revealed that the onset of heart failure was accompanied by a strong up-regulation of cardiac lipid metabolism genes involved in fat synthesis, storage and oxidation.
Project description:Cardiac hypertrophy is regulated by the zinc finger-containing DNA binding factors Gata4 and Gata6, both of which are required to mount a productive growth response of the adult heart. To determine if Gata4 and Gata6 are redundant or have non-overlapping roles, we performed cardiomyocyte-specific conditional gene deletions for Gata4 and Gata6 in conjunction with reciprocal replacement with a transgene encoding either Gata4 or Gata6, during the pressure overload response. We determined that Gata4 and Gata6 play a redundant and dosage-sensitive role in programming the hypertrophic growth response itself following pressure overload stimulation. However, non-redundant functions were identified as functional decompensation induced by either Gata4 or Gata6 deletion was not rescued by the reciprocal transgene, and only Gata4 heart-specific deletion produced a reduction in capillary density after pressure overload. Gene expression profiling from hearts of these gene-deleted mice showed both overlapping and unique transcriptional codes, with Gata4 exhibiting the strongest impact. These results indicate that Gata4 and Gata6 play a dosage-dependent and semi-redundant role in programming cardiac hypertrophy, but that each has a unique role in maintaining cardiac homeostasis and adaptation to injury that cannot be compensated by the other. Microarray-bassed gene expression profiling identified overlapping, distinct, and quantitatively/differentially regulated classes of Gata4 or Gata6 regulated genes.