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: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: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.
Project description:In this study, we used a cardiac-specific, inducible expression system to activate YAP in adult mouse heart. Activation of YAP in adult heart promoted cardiomyocyte proliferation and did not deleteriously affect heart function. Furthermore, YAP activation after myocardial infarction (MI) preserved heart function and reduced infarct size. Using adeno-associated virus subtype 9 (AAV9) as a delivery vector, we expressed human YAP in the murine myocardium immediately after MI. We found that AAV9:hYAP significantly improved cardiac function and mouse survival. AAV9:hYAP did not exert its salutary effects by reducing cardiomyocyte apoptosis. Rather, we found that AAV9:hYAP stimulated adult cardiomyocyte proliferation. Gene expression profiling indicated that AAV9:hYAP stimulated cell cycle gene expression, enhanced TGFβ-signaling, and activated of components of the inflammatory response.Cardiac specific YAP activation after MI mitigated myocardial injury after MI, improved cardiac function and mouse survival. These findings suggest that therapeutic activation of hYAP or its downstream targets, potentially through AAV-mediated gene therapy, may be a strategy to improve outcome after MI. Three groups were involved in this study: sham group, AAV9:Luci+MI group and AAV9-YAP+MI group. Each group contained three biological replicates. The sham group had neither myocardial infarction nor AAV injection. The AAV9:Luci +MI(L for brief) group had myocardial infarction and injected with AAV9:Luic. The AAV9:hYAP+MI(YAP for brief) group had myocardial infarction and injected with AAV9:hYAP. 5 days after MI and AAV injection, the heart apexes were collected and the total RNA were isolated for microarray analysis.
Project description:The molecular mechanism underlying cardiac remodeling following myocardial infarction have been incompletely understood. Until now, most studies have been performed in rodents. We studied cardiac remodeling in the physiologically more relevant animal model, the swine. Microarray analysis was performed on animals that underwent either sham surgery or permanent ligation of the left coronary artery (MI). RNA was isolated from the remote, non-ischemic, regions of the left ventricle. RNA was isolated from 8 sham and 8 MI animals three weeks after surgery. Each group contained 4 males and 4 females. Animals used for the study were 2-3 months old Yorkshire x Landrace swine. Only neutered males entered the study.
Project description:Myocardial infarction (MI) leads to cardiomyocyte death, which triggers an immune response that clears debris and restores tissue integrity. In the adult heart, the immune system facilitates scar formation, which repairs the damaged myocardium but compromises cardiac function. In neonatal mice, the heart can regenerate fully without scarring following MI; however, this regenerative capacity is lost by P7. The signals that govern neonatal heart regeneration are unknown. By comparing the immune response to MI in mice at P1 and P14, we identified differences in the magnitude and kinetics of monocyte and macrophage responses to injury. Using a cell-depletion model, we determined that heart regeneration and neoangiogenesis following MI depends on neonatal macrophages. Neonates depleted of macrophages were unable to regenerate myocardia and formed fibrotic scars, resulting in reduced cardiac function and angiogenesis. Immunophenotyping and gene expression profiling of cardiac macrophages from regenerating and nonregenerating hearts indicated that regenerative macrophages have a unique polarization phenotype and secrete numerous soluble factors that may facilitate the formation of new myocardium. Our findings suggest that macrophages provide necessary signals to drive angiogenesis and regeneration of the neonatal mouse heart. Modulating inflammation may provide a key therapeutic strategy to support heart regeneration. Total RNA was isolated from CD11b+Ly6G- cells sorted from hearts 3 days following ligation of LAD. 6 samples total: Triplicates of cells from P1 mice and from P14 mice
Project description:Male Clock∆19/∆19 and WT C57Bl/6 mice were randomized into 3 groups: i) baseline, ii) short-term post-myocardial infarction (MI; 64h post-MI), iii) long-term post-MI (heart failure, HF; 8 weeks post-MI). Medial prefrontal cortex (mPFC) and hippocampus brain regions were collected at ZT19 (waketime). The microarray approach allows the investigation of transcriptome-wide gene expression changes in brain regions from Clock∆19/∆19 and WT mice at baseline, post-MI, and in HF.