CDH18 is an epicardial biomarker regulating epicardial specification and differentiation towards vascular smooth muscle cells
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ABSTRACT: The epicardium is a mesothelial layer covering the myocardium and contributes to different cardiac lineage descendants during cardiogenesis. Fine-tuned balanced signaling defines epicardial specification and regulates cell plasticity and cell-fate decisions of epicardial-derived cells (EPCDs) by epicardial-to-mesenchymal transition (EMT). However, powerful tools to investigate epicardial cell function, including markers with pivotal roles in developmental signaling, are still lacking. Here, we recapitulated embryonic epicardiogenesis using human induced pluripotent stem cells (hiPSCs) and identified type II classical cadherin CDH18 as a novel biomarker defining lineage specification in human developing epicardium. The loss of CDH18 led to the onset of EMT and specific differentiation towards cardiac smooth muscle cells. Furthermore, GATA4 regulated epicardial CDH18 expression. These results demonstrate the production and enrichment of hiPSC-derived epicardial cells via the tracing of CDH18 expression, providing a model for investigating epicardial function in human development and disease and enabling new possibilities for regenerative medicine.
Project description:Cardiac fibrosis is a detrimental pathophysiological state involved in a number of cardiovascular diseases. Myofibroblasts mediate fibrosis by excessive remodeling of the extracellular matrix, which ultimately leads to tissue stiffness and impaired heart performance. Recently, it was shown that a substantial fraction of cardiac myofibroblasts may originate from the epicardium through Epithelial-to-Mesenchymal Transition (EMT). We have developed a cellular model of EMT in which adult murine epicardium-derived cells are differentiated into myofibroblast-like cells in the presence of Interleukin-1beta, Tumor Necrosis Factor-alpha, or Transforming Growth Factor-beta. Using this model of EMT, the microRNAome was assessed by microRNA (miRNA) arrays. Subsequently, expression levels of differentially expressed miRNAs were validated by qPCR. These miRNAs were targeted by transfecting epicardium-derived cells with anti- or pre-miRs prior to EMT initiation. The ability of the anti- or pre-miRs to inhibit EMT was assessed on a number of phenotypic markers. In this study we have identified a number of miRNAs that potentially play an intrinsic role in cardiac EMT. We speculate that by targeting those miRNA, the onset and long-term progression of cardiac fibrosis can be substantially reduced. Epicardial mesothelial cells were isolated and expanded from the epicardium of adult rats (8-10 weeks). Epithelial-to-mesenchymal Transition was induced by 10 ng/mL Interleukin-1beta, Tumor Necrosis Factor-alpha, or Transforming Growth Factor-beta1 for 48h. The assocciated differential microRNA expressions relative to a control treatment was computed by microRNA arrays. The experiment was conducted on biological quadruplicates for the control treatment and biological triplicates for cytokine treatments.
Project description:Re-activating quiescent adult epicardium represents a potential therapeutic approach for human cardiac regeneration. However, the exact molecular differences between inactive adult and active foetal epicardium are not known. Here, we combined foetal and adult human hearts for the first time using single-cell and single-nuclei RNA sequencing, and compared epicardial cells from both stages. We found a migratory fibroblast-like epicardial population only in the foetal heart and foetal epicardium expressed angiogenic gene programs, while the adult epicardium was solely mesothelial and immune-responsive. Furthermore, we predicted that adult hearts may still receive foetal epicardial paracrine communication, including WNT-signalling with endocardium, reinforcing the validity of regenerative strategies that administer or reactivate epicardial cells in situ. Finally, we explained graft efficacy of our human embryonic stem-cell derived epicardium model, by noting its similarity to human foetal epicardium. Overall, our study defines epicardial programs of regenerative angiogenesis absent in adult hearts, contextualises animal studies, and defines epicardial states required for effective human heart regeneration.
Project description:Identification of epicardium-enriched genes in the embryonic heart. The epicardium encapsulates the heart and functions as a source of multipotent progenitor cells and paracrine factors essential for cardiac development and repair. Injury of the adult heart results in re-activation of a developmental gene program in the epicardium, but the transcriptional basis of epicardial gene expression has not been delineated. We established a mouse embryonic heart organ culture and gene expression system that facilitated the identification of epicardial enhancers activated during heart development and injury. Epicardial activation of these enhancers depends on a combinatorial transcriptional code centered on CCAAT/enhancer binding protein (C/EBP) transcription factors. Disruption of C/EBP signaling in the adult epicardium reduced injury-induced neutrophil infiltration and improved cardiac function. These findings reveal a transcriptional basis for epicardial activation and heart injury, providing a platform for enhancing cardiac regeneration. Total RNA obtained from lacZ-positive epicardial cells isolated from the E11.5 Tcf21lacZ hearts compared to total dissociated heart cells
Project description:Cardiovascular disease (CVD) is one of the leading causes of mortality worldwide, and frequently leads to massive heart injury and the loss of billions of cardiac muscle cells and associated vasculature. Critical work in the last two decades demonstrated that these lost cells can be partially regenerated by the epicardium, the outermost mesothelial layer of the heart, in a process that highly recapitulates its role in heart development. Upon cardiac injury, mature epicardial cells activate and undergo an epithelial-mesenchymal transition (EMT) to form epicardial-derived progenitor cells (EpiPCs), multipotent progenitors that can differentiate into several important cardiac lineages, including cardiomyocytes and vascular cells. In mammals, this process alone is insufficient for significant regeneration, but it may be possible to prime it by administering specific reprogramming factors, leading to enhanced EpiPC function. Here, we compared changes in gene expression induced by oxytocin in epicardial cells to determine potential pro-regenerative effects.
Project description:In the adult heart, the epicardium becomes activated after injury, contributing to cardiac healing by secretion of paracrine factors. Here we analyzed by single-cell RNA sequencing combined with RNA in situ hybridization and lineage tracing of WT1+ cells the cellular composition, location, and hierarchy of epicardial stromal cells (EpiSC) in comparison to activated myocardial fibroblasts/stromal cells in infarcted mouse hearts. We identified 11 transcriptionally distinct EpiSC populations, that can be classified in three groups each containing a cluster of proliferating cells. Two groups expressed cardiac specification makers and sarcomeric proteins suggestive of cardiomyogenic potential. Transcripts of HIF-1α and HIF-responsive genes were enriched in EpiSC consistent with the epicardium being a hypoxic niche. Expression of paracrine factors was not limited to WT1+ cells but was a general feature of activated cardiac stromal cells. Our findings provide the cellular framework by which myocardial ischemia may trigger in EpiSC the formation of cardioprotective/regenerative responses.
Project description:This study is associated with the GEO accession GSE216019. Abstract from article: Re-activating quiescent adult epicardium represents a potential therapeutic approach for human cardiac regeneration. However, the exact molecular differences between inactive adult and active foetal epicardium are not known. Here, we combined foetal and adult human hearts for the first time using single-cell and single-nuclei RNA sequencing, and compared epicardial cells from both stages. We found a migratory fibroblast-like epicardial population only in the foetal heart and foetal epicardium expressed angiogenic gene programs, while the adult epicardium was solely mesothelial and immune-responsive. Furthermore, we predicted that adult hearts may still receive foetal epicardial paracrine communication, including WNT-signalling with endocardium, reinforcing the validity of regenerative strategies that administer or reactivate epicardial cells in situ. Finally, we explained graft efficacy of our human embryonic stem-cell derived epicardium model, by noting its similarity to human foetal epicardium. Overall, our study defines epicardial programs of regenerative angiogenesis absent in adult hearts, contextualises animal studies, and defines epicardial endpoints required for effective human heart regeneration.
Project description:Identification of epicardium-enriched genes in the embryonic heart. The epicardium encapsulates the heart and functions as a source of multipotent progenitor cells and paracrine factors essential for cardiac development and repair. Injury of the adult heart results in re-activation of a developmental gene program in the epicardium, but the transcriptional basis of epicardial gene expression has not been delineated. We established a mouse embryonic heart organ culture and gene expression system that facilitated the identification of epicardial enhancers activated during heart development and injury. Epicardial activation of these enhancers depends on a combinatorial transcriptional code centered on CCAAT/enhancer binding protein (C/EBP) transcription factors. Disruption of C/EBP signaling in the adult epicardium reduced injury-induced neutrophil infiltration and improved cardiac function. These findings reveal a transcriptional basis for epicardial activation and heart injury, providing a platform for enhancing cardiac regeneration.
Project description:By contrast with mammals, adult zebrafish have a high capacity to regenerate damaged or lost myocardium through proliferation of spared cardiomyocytes. The epicardial sheet covering the heart is activated by injury and aids muscle regeneration through paracrine effects and as a multipotent cell source, and has received recent attention as a target in cardiac repair strategies. While it is recognized that epicardium is required for muscle regeneration and itself has high regenerative potential, the extent of cellular heterogeneity within epicardial tissue is largely unexplored. In this study, we performed transcriptome analysis on dozens of epicardial lineage cells purified from zebrafish harboring a transgenic reporter for the pan-epicardial gene tcf21. Hierarchical clustering analysis suggested the presence of at least three epicardial cell subsets defined by expression signatures. We validated many new pan-epicardial and epicardial markers by alternative expression assays. Additionally, we explored the function of the scaffolding protein and main component of caveolae, caveolin-1 (cav1), which was present in each epicardial subset. In BAC transgenic zebrafish, cav1 regulatory sequences drove strong expression in ostensibly all epicardial cells and in coronary vascular endothelial cells. Moreover, cav1 mutant zebrafish generated by genome editing showed grossly normal heart development and adult cardiac anatomy, but displayed profound defects in injury-induced cardiomyocyte proliferation and heart regeneration. Our study defines a new platform for the discovery of epicardial lineage markers, genetic tools, and mechanisms of heart regeneration. Deep sequencing of isolated single epicardial cells
Project description:Epicardial cells undergo an epithelial-to-mesenchymal transtion (EMT) to generate coronary vascular smooth muscle cells (VSMC) and cardiac fibroblasts. Little is known about the mechanisms regulating EMT or the in vivo signals directing epicardial-derived cell (EPDC) fate. Here, we show that loss of PDGF signaling leads to a disruption in Sox9 expression, and when Sox9 expression was restored in mutant hearts, the EMT defect was rescued. Interestingly, mutants lacking only one of the PDGF genes exhibited a lineage specific requirement for the individual receptors. Loss of PDGFRα resulted in a deficit in cardiac fibroblast formation, while cVSMC development was unperturbed. Conversely, PDGFRβ was required for cVSMC development but not cardiac fibroblast development. Combined, our data demonstrate a novel role for PDGF receptors in epicardial EMT and EPDC development. GSM671723-GSM671724: Total RNA was isolated from E12.5 control and PDGF receptor epicardial knockout hearts using the Trizol reagent. RNA was processed as per manufacturer's instructions (Illumina Gene expression array, Illumina, inc. San Diego, CA, USA) GSM671877-GSM671882: Total RNA was isolated from E12.5 control and PDGF receptor epicardial knockout primary epicardial cultures using the Trizol reagent. RNA was processed as per manufacturer's instructions (Illumina Gene expression array, Illumina, inc. San Diego, CA, USA)
Project description:Adult zebrafish regenerate heart muscle after severe cardiac damage without significant scarring. The epicardium, a mesothelial cell sheet covering the vetebrate heart, is activated by injury and supports muscle regeneration through paracrine effects and as a source of multipotent cells. The understudied cellular heterogeneity of the adult epicardium during heart regeneration has constrained the effort in mobilizing the epicardium for heart repair. To dissect epicardial cell states and the underlying mechanisms that lead to successful heart regeneration in zebrafish, we performed single-cell RNA-sequencing of isolated epicardial cells from the regenerating adult heart and revealed their dynamic cellular heterogeneity. We defined the epithelial and mesenchymal layers of the epicardium and identified a transiently activated epicardial progenitor cell (aEPC) subpopulation that expresses aldh1a2, ptx3a, col12a1b and marcksb. Upon heart amputation injury, aEPCs emerge from the existing epicardial cells, migrate to enclose the wound, and disappear as regeneration progresses. Genetic lineage tracing combined with modified RNA labelling confirmed an epithelial-mesenchymal transition (EMT) process of aEPCs and their differentiations to pdgfrb+ mural cells and pdgfra+hapln1a+ mesenchymal fibroblast-like cells that support heart regeneration. Genetic ablation of aEPCs blocked wound closure of the injured ventricle, suppressed cardiomyocyte proliferation, and disrupted heart regeneration. Our findings define a transient progenitor state of the adult epicardium that is an indispensable driver of zebrafish heart regeneration and identified ptx3a as a regeneration-specific non-ontogenetic regulator of the epicardium.