Exacerbating role of angiopoietin-2 in cardiac hypoxia and inflammation after myocardial infarction
ABSTRACT: To unveil the role of Angiopoietin-2 in regulating vascular remodeling after myocardial infarction Overall design: Infarct border zone endothelial cells were sorted from myocardial infarction model mice deleting Angiopoietin-2 or Wild-type control.
Project description:Emerging evidence indicates that angiopoietin-2 (Angpt2), a well-recognized vascular destabilizing factor, is a biomarker of poor outcome in ischemic heart disease. However, its precise role in postischemic cardiovascular remodeling is poorly understood. Here, we show that Angpt2 plays multifaceted roles in the exacerbation of cardiac hypoxia and inflammation after myocardial ischemia. Angpt2 was highly expressed in endothelial cells at the infarct border zone after myocardial infarction (MI) or ischemia/reperfusion injury in mice. In the acute phase of MI, endothelial-derived Angpt2 antagonized Angpt1/Tie2 signaling, which was greatly involved in pericyte detachment, vascular leakage, increased adhesion molecular expression, degradation of the glycocalyx and extracellular matrix, and enhanced neutrophil infiltration and hypoxia in the infarct border area. In the chronic remodeling phase after MI, endothelial- and macrophage-derived Angpt2 continuously promoted abnormal vascular remodeling and proinflammatory macrophage polarization through integrin ?5?1 signaling, worsening cardiac hypoxia and inflammation. Accordingly, inhibition of Angpt2 either by gene deletion or using an anti-Angpt2 blocking antibody substantially alleviated these pathological findings and ameliorated postischemic cardiovascular remodeling. Blockade of Angpt2 thus has potential as a therapeutic option for ischemic heart failure.
Project description:VEGF and angiopoietin-1 (Ang1) are two major angiogenic factors being investigated for the treatment of myocardial infarction (MI). Targeting VEGF and Ang1 expression in the ischemic myocardium can increase their local therapeutic effects and reduce possible adverse effects. Adeno-associated viral vectors (AAVs) expressing cardiac-specific and hypoxia-inducible VEGF [AAV-myosin light chain-2v (MLC)VEGF] and Ang1 (AAV-MLCAng1) were coinjected (VEGF/Ang1 group) into six different sites of the porcine myocardium at the peri-infarct zone immediately after ligating the left descending coronary artery. An identical dose of AAV-Cytomegalovirus (CMV)LacZ or saline was injected into control animals. AAV genomes were detected in the liver in addition to the heart. RT-PCR, Western blotting, and ELISA analyses showed that VEGF and Ang1 were predominantly expressed in the myocardium in the infarct core and border of the infarct heart. Gated single-photon emission computed tomography analyses showed that the VEGF/Ang1 group had better cardiac function and myocardial perfusion at 8 wk than at 2 wk after vector injection. Compared with the saline and LacZ controls, the VEGF/Ang1 group expressed higher phosphorylated Akt and Bcl-xL, less Caspase-3 and Bad, and had higher vascular density, more proliferating cardiomyocytes, and less apoptotic cells in the infarct and peri-infarct zones. Thus, cardiac-specific and hypoxia-induced coexpression of VEGF and Ang1 improves the perfusion and function of porcine MI heart through the induction of angiogenesis and cardiomyocyte proliferation, activation of prosurvival pathways, and reduction of cell apoptosis.
Project description:Stress-response gene activity replaces cardiomyocyte lineage-specific program in a transcriptionally discrete infarct border zone Overall design: RNA-seq & ATAC-seq on left ventricular remote and border zone tissues at 3, 7 and 14 days after myocardial infarction
Project description:Myocardial infarction causes sympathetic activation and parasympathetic dysfunction, which increase risk of sudden death due to ventricular arrhythmias. Mechanisms underlying parasympathetic dysfunction are unclear. The aim of this study was to delineate consequences of myocardial infarction on parasympathetic myocardial neurotransmitter levels and the function of parasympathetic cardiac ganglia neurons, and to assess electrophysiological effects of vagal nerve stimulation on ventricular arrhythmias in a chronic porcine infarct model. While norepinephrine levels decreased, cardiac acetylcholine levels remained preserved in border zones and viable myocardium of infarcted hearts. In vivo neuronal recordings demonstrated abnormalities in firing frequency of parasympathetic neurons of infarcted animals. Neurons that were activated by parasympathetic stimulation had low basal firing frequency, while neurons that were suppressed by left vagal nerve stimulation had abnormally high basal activity. Myocardial infarction increased sympathetic inputs to parasympathetic convergent neurons. However, the underlying parasympathetic cardiac neuronal network remained intact. Augmenting parasympathetic drive with vagal nerve stimulation reduced ventricular arrhythmia inducibility by decreasing ventricular excitability and heterogeneity of repolarization of infarct border zones, an area with known proarrhythmic potential. Preserved acetylcholine levels and intact parasympathetic neuronal pathways can explain the electrical stabilization of infarct border zones with vagal nerve stimulation, providing insight into its antiarrhythmic benefit.
Project description:Myocardial infarction (MI) is a highly prevalent cardiac emergency, which results in adverse left ventricular remodeling exacerbating progressive heart failure. Inflammation in post-MI is necessary for myocyte repair and wound healing. However, it is also a key component of subsequent heart failure pathology. Myoblasts transplantation after MI have been fulfilled a good effect on cardiac repair, but the occasion, complications of transplantation, and the underlying mechanisms have not been fully elucidated. Here, we found that myoblast transplantation decreased the expression of many pro-inflammatory genes and the activation of inflammation-related signal pathway in heart tissue of pig post MI, which mainly contributed to the improved heart function and attenuated damage of myocardial cells. Overall design: We constructed a minipig surgical model of myocardial infarction. Myoblasts were intramyocardially injected into the infarct and border zone of heart. The infarct and border zone heart tissues from minipigs treated with myoblast transplantation or untreated control (one sample for every group) were submitted for gene expression array analysis.
Project description:Comparison of both LncRNAs and mRNAs expression in the border zone of the myocardial infarction rats and the sham operation rats Border zone (BZ) of the myocardial infarction is critical to patients. Current treatments of myocardial infarction are primarily aimed to save the dying myocardial cell in the border zone. During myocardial infarction, certain changes in BZ, e.g, apoptosis, fibrosis, inflammation, etc, played an important role in deciding the survival. Impairment and recovery of BZ has been linked to gene expression changes. The aim of our study was to obtain a global expression profile of lncRNAs and mRNAs of the border zone in Wistar rats myocardial infarction, and identify the changes during myocardial infarction. Overall design: 3 male rats were used to set up myocardial infarction model by ligation of LAD, and 3 rats were sham-operated. Border zone tissue of myocardial infarction was determined by TTC&EB double stain, then was send to further microarry analysis.
Project description:Diabetes is a risk factor for myocardial infarction, and outcomes after myocardial infarction are worse among diabetics compared with nondiabetics. Diabetes is associated with impaired Heme clearance. Here, we determined whether heme toxicity and impaired heme clearance contribute to diabetic myocardial infarction injury and assessed IL-10 as a therapeutic agent for diabetic myocardial infarction. Plasma-free hemoglobin was significantly elevated in diabetic mice compared with nondiabetic mice after myocardial infarction. Infarct size had strong correlation to the level of plasma-free hemoglobin. Hemoglobin and reactive iron deposition within the infarct zone were also demonstrated in diabetic MI. IL-10 significantly reduced infarct size and improved cardiac function in diabetic mice. Moreover, IL-10 improved capillary density, reduced apoptosis, and decreased inflammation in the border zone of the infarcted hearts, findings that were partially inhibited by Tin protoporphyrin (a heme oxygenase-1 inhibitor). IL-10 upregulated CD163, the hemoglobin:haptoglobin scavenger receptor, and heme oxygenase-1 in THP-1-derived and primary human CD14+ macrophages. IL-10 significantly protected against ischemic injury when HL-1 cardiomyocytes were cotreated with hemoglobin. Together, our findings indicate that IL-10 is cardioprotective in diabetic myocardial infarction via upregulation of heme clearance pathways. These findings implicate heme clearance as a potentially novel therapeutic direction for diabetic myocardial infarction.
Project description:BACKGROUND: In humans, myocardial infarction is characterized by irreversible loss of heart tissue, which becomes replaced with a fibrous scar. By contrast, teleost fish and urodele amphibians are capable of heart regeneration after a partial amputation. However, due to the lack of a suitable infarct model, it is not known how these animals respond to myocardial infarction. RESULTS: Here, we have established a heart infarct model in zebrafish using cryoinjury. In contrast to the common method of partial resection, cryoinjury results in massive cell death within 20% of the ventricular wall, similar to that observed in mammalian infarcts. As in mammals, the initial stages of the injury response include thrombosis, accumulation of fibroblasts and collagen deposition. However, at later stages, cardiac cells can enter the cell cycle and invade the infarct area in zebrafish. In the subsequent two months, fibrotic scar tissue is progressively eliminated by cell apoptosis and becomes replaced with a new myocardium, resulting in scarless regeneration. We show that tissue remodeling at the myocardial-infarct border zone is associated with accumulation of Vimentin-positive fibroblasts and with expression of an extracellular matrix protein Tenascin-C. Electrocardiogram analysis demonstrated that the reconstitution of the cardiac muscle leads to the restoration of the heart function. CONCLUSIONS: We developed a new cryoinjury model to induce myocardial infarction in zebrafish. Although the initial stages following cryoinjury resemble typical healing in mammals, the zebrafish heart is capable of structural and functional regeneration. Understanding the key healing processes after myocardial infarction in zebrafish may result in identification of the barriers to efficient cardiac regeneration in mammals.
Project description:Ventricular tachycardia is a common and lethal complication after myocardial infarction. Here we show that focal transfer of a gene encoding a dominant-negative version of the KCNH2 potassium channel (KCNH2-G628S) to the infarct scar border eliminated all ventricular arrhythmias in a porcine model. No proarrhythmia or other negative effects were discernable. Our results demonstrate the potential viability of gene therapy for ablation of ventricular arrhythmias.
Project description:The aim of this study was to evaluate the links between connexin43 (Cx43) expression, myocardial conduction velocity, and ventricular tachycardia in a model of healed myocardial infarction.Post-infarction ventricular arrhythmias frequently cause sudden death. Impaired myocardial conduction has previously been linked to ventricular arrhythmias. Altered connexin expression is a potential source of conduction slowing identified in healed scar border tissues. The functional effect of increasing border-zone Cx43 has not been previously evaluated.Twenty-five Yorkshire pigs underwent anterior infarction by transient left anterior descending coronary artery occlusion, followed by weekly testing for arrhythmia inducibility. Twenty animals with reproducibly inducible sustained monomorphic ventricular tachycardia were randomized 2:1:1 to receive AdCx43, Ad?gal, or no gene transfer. One week later, animals underwent follow-up electrophysiologic study and tissue assessment for several functional and molecular measures.Animals receiving AdCx43 had less electrogram fractionation and faster conduction velocity in the anterior-septal border zone. Only 40% of AdCx43 animals remained inducible for ventricular tachycardia, while 100% of controls were inducible after gene transfer. AdCx43 animals had 2-fold higher Cx43 protein levels in the anterior-septal infarct border, with similar percents of phosphorylated and intercalated disk-localized Cx43 compared with controls.These data mechanistically link Cx43 expression to slow conduction and arrhythmia susceptibility in the healed scar border zone. Targeted manipulation of Cx43 levels improved conduction velocity and reduced ventricular tachycardia susceptibility. Cx43 gene transfer represents a novel treatment strategy for post-infarction arrhythmias.