scholarly journals Zebrafish cardiac regeneration—looking beyond cardiomyocytes to a complex microenvironment

2020 ◽  
Author(s):  
Rebecca Ryan ◽  
Bethany R. Moyse ◽  
Rebecca J. Richardson
Keyword(s):  
Cardiac Injury ◽  
Cell Communication ◽  
Cardiac Regeneration ◽  
Cell Types ◽  
Regenerative Process ◽  
Heart Regeneration ◽  
Cardiomyocyte Proliferation ◽  
Underlying Mechanisms ◽  
Different Cell Types

Abstract The study of heart repair post-myocardial infarction has historically focused on the importance of cardiomyocyte proliferation as the major factor limiting adult mammalian heart regeneration. However, there is mounting evidence that a narrow focus on this one cell type discounts the importance of a complex cascade of cell–cell communication involving a whole host of different cell types. A major difficulty in the study of heart regeneration is the rarity of this process in adult animals, meaning a mammalian template for how this can be achieved is lacking. Here, we review the adult zebrafish as an ideal and unique model in which to study the underlying mechanisms and cell types required to attain complete heart regeneration following cardiac injury. We provide an introduction to the role of the cardiac microenvironment in the complex regenerative process and discuss some of the key advances using this in vivo vertebrate model that have recently increased our understanding of the vital roles of multiple different cell types. Due to the sheer number of exciting studies describing new and unexpected roles for inflammatory cell populations in cardiac regeneration, this review will pay particular attention to these important microenvironment participants.

scholarly journals Polyploidy in Cardiomyocytes

2020 ◽  
Vol 126 (4) ◽  
pp. 552-565 ◽  
Author(s):  
Wouter Derks ◽  
Olaf Bergmann
Keyword(s):  
Cardiac Injury ◽  
Physiological Role ◽  
Cell Types ◽  
Cell Number ◽  
The Body ◽  
Cardiomyocyte Hypertrophy ◽  
Heart Regeneration ◽  
Cardiomyocyte Proliferation ◽  
Hypertrophic Growth

The hallmark of most cardiac diseases is the progressive loss of cardiomyocytes. In the perinatal period, cardiomyocytes still proliferate, and the heart shows the capacity to regenerate upon injury. In the adult heart, however, the actual rate of cardiomyocyte renewal is too low to efficiently counteract substantial cell loss caused by cardiac injury. In mammals, cardiac growth by cell number expansion changes to growth by cardiomyocyte enlargement soon after birth, coinciding with a period in which most cardiomyocytes increase their DNA content by multinucleation and nuclear polyploidization. Although cardiomyocyte hypertrophy is often associated with these processes, whether polyploidy is a prerequisite or a consequence of hypertrophic growth is unclear. Both the benefits of cardiomyocyte enlargement over proliferative growth of the heart and the physiological role of polyploidy in cardiomyocytes are enigmatic. Interestingly, hearts in animal species with substantial cardiac regenerative capacity dominantly comprise diploid cardiomyocytes, raising the hypothesis that cardiomyocyte polyploidy poses a barrier for cardiomyocyte proliferation and subsequent heart regeneration. On the contrary, there is also evidence for self-duplication of multinucleated myocytes, suggesting a more complex picture of polyploidy in heart regeneration. Polyploidy is not restricted to the heart but also occurs in other cell types in the body. In this review, we explore the biological relevance of polyploidy in different species and tissues to acquire insight into its specific role in cardiomyocytes. Furthermore, we speculate about the physiological role of polyploidy in cardiomyocytes and how this might relate to renewal and regeneration.

scholarly journals Ephrin-B1 blocks adult cardiomyocyte proliferation and heart regeneration

2019 ◽  
Author(s):  
Marie Cauquil ◽  
Céline Mias ◽  
Céline Guilbeau-Frugier ◽  
Clément Karsenty ◽  
Marie-Hélène Seguelas ◽  
...  
Keyword(s):  
Resting State ◽  
Cardiac Tissue ◽  
Hippo Pathway ◽  
Cardiac Regeneration ◽  
Mouse Heart ◽  
Heart Regeneration ◽  
Cardiomyocyte Proliferation ◽  
Postnatal Maturation

AbstractAimsDeciphering the innate mechanisms governing the blockade of proliferation in adult cardiomyocytes (CMs) is challenging for mammalian heart regeneration. Despite the exit of CMs from the cell cycle during the postnatal maturation period coincides with their morphological switch to a typical adult rod-shape, whether these two processes are connected is unknown. Here, we examined the role of ephrin-B1, a CM rod-shape stabilizer, in adult CM proliferation and cardiac regeneration.Methods and resultsTransgenic- or AAV9-based ephrin-B1 repression in adult mouse heart led to substantial proliferation of resident CMs and tissue regeneration to compensate for apex resection, myocardial infarction (MI) and senescence. Interestingly, in the resting state, CMs lacking ephrin-B1 did not constitutively proliferate, indicative of no major cardiac defects. However, they exhibited proliferation-competent signature, as indicated by higher mononucleated state and a dramatic decrease of miR-195 mitotic blocker, which can be mobilized under neuregulin-1 stimulation in vitro and in vivo. Mechanistically, the post-mitotic state of the adult CM relies on ephrin-B1 sequestering of inactive phospho-Yap1, the effector of the Hippo-pathway, at the lateral membrane. Hence, ephrin-B1 repression leads to phospho-Yap1 release in the cytosol but CM quiescence at resting state. Upon cardiac stresses (apectomy, MI, senescence), Yap1 could be activated and translocated to the nucleus to induce proliferation-gene expression and consequent CM proliferationConclusionsOur results identified ephrin-B1 as a new natural locker of adult CM proliferation and emphasize that targeting ephrin-B1 may prove a future promising approach in cardiac regenerative medicine for HF treatment.SignificanceThe mammalian adult heart is unable to regenerate due to the inability of cardiomyocytes (CMs) to proliferate and replace cardiac tissue lost. Exploiting CM-specific transgenic mice or AAV9-based gene therapy, this works identifies ephrin-B1, a specific rod-shape stabilizer of the adult CM, as a natural padlock of adult CM proliferation for compensatory adaptation to different cardiac stresses (apectomy, MI, senescence), thus emphasizing a new link between the adult CM morphology and their proliferation potential. Moreover, the study demonstrates proof-of-concept that targeting ephrin-B1 may be an innovative therapeutic approach for ischemic heart failure.

Abstract 225: Coordinated Transcriptome and Cell State Dynamics of Non-myocytes in Heart Regeneration

2020 ◽  
Vol 127 (Suppl_1) ◽  
Author(s):  
Hong Ma ◽  
Ziqing Liu ◽  
Yuchen Yang ◽  
Dong Feng ◽  
Yanhan Dong ◽  
...  
Keyword(s):  
Cardiac Regeneration ◽  
Cell Types ◽  
Multiple Time ◽  
Heart Regeneration ◽  
Cardiomyocyte Proliferation ◽  
Cellular Functions ◽  
Molecular Features ◽  
Functional Dynamics ◽  
Cell Diversity ◽  
Multiple Time Points

Cardiac regeneration occurs primarily through proliferation of existing cardiomyocytes, yet the regenerative response also involves complex interactions between distinct cardiac cell types including not only cardiomyocytes, but also non-cardiomyocytes (nonCMs). However, the subpopulations, distinguishing molecular features, cellular functions, and intercellular interactions of nonCMs in heart regeneration remain largely unexplored. Using the LIGER algorithm, we assembled an atlas of cell states from 61,977 individual nonCM scRNA-seq profiles isolated at multiple time points during heart regeneration in both wildtype and mutant fish. This analysis revealed extensive nonCM cell diversity, including multiple macrophage, fibroblast and endothelial subpopulations with unique spatiotemporal distributions and cooperative interactions during the process of cardiac regeneration. Genetic and pharmacological perturbation of macrophage functional dynamics compromised interactions among nonCM subpopulations, reduced cardiomyocyte proliferation, and caused defective cardiac regeneration. Furthermore, we developed a computational algorithm called Topologizer to map the topological relationships and dynamics of nonCMs during heart regeneration. We uncovered dynamic transitions between macrophage functional states and identified factors involved in mRNA processing and transcriptional regulation associated with the transition. Together, our single-cell transcriptomic analysis of nonCMs during cardiac regeneration provides a blueprint for interrogating the molecular and cellular basis of cardiac regeneration.

scholarly journals Current Advances in Comprehending Dynamics of Regenerating Axons and Axon–Glia Interactions after Peripheral Nerve Injury in Zebrafish

2021 ◽  
Vol 22 (5) ◽  
pp. 2484
Author(s):  
David Gonzalez ◽  
Miguel L. Allende
Keyword(s):  
Nervous System ◽  
Peripheral Nerves ◽  
Molecular Mechanisms ◽  
Current Knowledge ◽  
Time Lapse ◽  
Cell Types ◽  
Regenerative Process ◽  
Time Lapse Microscopy ◽  
Different Cell Types

Following an injury, axons of both the central nervous system (CNS) and peripheral nervous system (PNS) degenerate through a coordinated and genetically conserved mechanism known as Wallerian degeneration (WD). Unlike central axons, severed peripheral axons have a higher capacity to regenerate and reinnervate their original targets, mainly because of the favorable environment that they inhabit and the presence of different cell types. Even though many aspects of regeneration in peripheral nerves have been studied, there is still a lack of understanding regarding the dynamics of axonal degeneration and regeneration, mostly due to the inherent limitations of most animal models. In this scenario, the use of zebrafish (Danio rerio) larvae combined with time-lapse microscopy currently offers a unique experimental opportunity to monitor the dynamics of the regenerative process in the PNS in vivo. This review summarizes the current knowledge and advances made in understanding the dynamics of the regenerative process of PNS axons. By using different tools available in zebrafish such as electroablation of the posterior lateral line nerve (pLLn), and laser-mediated transection of motor and sensory axons followed by time-lapse microscopy, researchers are beginning to unravel the complexity of the spatiotemporal interactions among different cell types during the regenerative process. Thus, understanding the cellular and molecular mechanisms underlying the degeneration and regeneration of peripheral nerves will open new avenues in the treatment of acute nerve trauma or chronic conditions such as neurodegenerative diseases.

Abstract 17364: G-protein Signaling Regulation of the Hippo Pathway in Neonatal Heart Regeneration

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Masahide Sakabe ◽  
Aishlin Hassan ◽  
Mei Xin
Keyword(s):  
G Protein ◽  
Molecular Mechanisms ◽  
Hippo Pathway ◽  
Cardiac Injury ◽  
Cardiac Regeneration ◽  
Heart Regeneration ◽  
Cardiomyocyte Proliferation ◽  
Adult Age ◽  
Rhoa Activity ◽  
Β Blocker

Introduction: The regeneration potential in the adult mammalian heart is very limited due to the cessation of cardiomyocyte proliferation shortly after birth. Recent studies have revealed that changes after birth such as metabolic state, oxygen level, cardiomyocyte structure and maturity, immune system and polyploidy are among the factors contributing to the loss of the regenerative potential in the heart. The mechanisms that regulate the cardiac regenerative window are not well understood. Here we report that G-protein mediated signaling regulates Hippo-YAP in neonatal cardiomyocyte proliferation and heart regeneration through Rho activity. Hypothesis: Gas encoded by the Gnas gene, a downstream effector of beta-adrenergic receptor (βAR) inhibits cardiomyocyte proliferation via regulation of YAP activity. Methods: We pharmacologically inhibited the G protein coupled receptor mediated β adrenergic signaling with a β-blocker (metoprolol) at early postnatal stages, and genetically by deleting Gnas in the heart with αMHC-Cre. We accessed the cardiomyocyte proliferation, heart regeneration in these mice and elucidated molecular mechanisms. Results: We found that β-blocker enhanced cardiomyocyte proliferation and promoted cardiac regeneration post cardiac injury with improved cardiac function. Consistent with β-blocker treated mice, mice lacking Gnas in cardiomyocytes exhibited enlarged hearts with an increase in cardiomyocyte proliferation. RNA-seq analysis revealed that these cardiomyocytes maintained an immature status even at young-adult age. The genes associated with mitochondrial oxidative metabolism, the major energy source for mature cardiomyocytes, were downregulated. Moreover, YAP activity was upregulated in both cases. We also found that loss of Gαs function caused upregulation of RhoA activity, and inhibitor of Rho signaling pathway suppressed the YAP activity in cardiomyocytes. Conclusions: Our study reveals that Gαs negatively regulate cardiomyocyte proliferation and provides mechanistic insight for β-blocker treatment as a strategy for inducing cardiac dedifferentiation and proliferation in injured heart.

scholarly journals Polyploid cardiomyocytes: implications for heart regeneration

Development ◽  
2021 ◽  
Vol 148 (14) ◽  
Author(s):  
Anna Kirillova ◽  
Lu Han ◽  
Honghai Liu ◽  
Bernhard Kühn
Keyword(s):  
Cellular Proliferation ◽  
Cardiac Regeneration ◽  
Cell Types ◽  
Heart Regeneration ◽  
Cardiomyocyte Proliferation ◽  
Form And Function ◽  
Differentiated Cells ◽  
New Findings ◽  
Polyploid Cells ◽  
And Function

ABSTRACT Terminally differentiated cells are generally thought to have arrived at their final form and function. Many terminally differentiated cell types are polyploid, i.e. they have multiple copies of the normally diploid genome. Mammalian heart muscle cells, termed cardiomyocytes, are one such example of polyploid cells. Terminally differentiated cardiomyocytes are bi- or multi-nucleated, or have polyploid nuclei. Recent mechanistic studies of polyploid cardiomyocytes indicate that they can limit cellular proliferation and, hence, heart regeneration. In this short Spotlight, we present the mechanisms generating bi- and multi-nucleated cardiomyocytes, and the mechanisms generating polyploid nuclei. Our aim is to develop hypotheses about how these mechanisms might relate to cardiomyocyte proliferation and cardiac regeneration. We also discuss how these new findings could be applied to advance cardiac regeneration research, and how they relate to studies of other polyploid cells, such as cancer cells.

scholarly journals Prrx1b restricts fibrosis and promotes Nrg1-dependent cardiomyocyte proliferation during zebrafish heart regeneration

Development ◽  
2021 ◽  
Author(s):  
Dennis E.M. de Bakker ◽  
Mara Bouwman ◽  
Esther Dronkers ◽  
Filipa C. Simões ◽  
Paul R. Riley ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Cardiac Injury ◽  
Lineage Tracing ◽  
Heart Regeneration ◽  
Cardiomyocyte Proliferation ◽  
Fibrotic Scar ◽  
Ligand Expression ◽  
Zebrafish Heart

Fibroblasts are activated to repair the heart following injury. Fibroblast activation in the mammalian heart leads to a permanent fibrotic scar that impairs cardiac function. In other organisms, like zebrafish, cardiac injury is followed by transient fibrosis and scar-free regeneration. The mechanisms that drive scarring versus scar-free regeneration are not well understood. Here we show that the homeo-box containing transcription factor Prrx1b is required for scar-free regeneration of the zebrafish heart as the loss of Prrx1b results in excessive fibrosis and impaired cardiomyocyte proliferation. Through lineage tracing and single-cell RNA-sequencing we find that Prrx1b is activated in epicardial-derived cells (EPDCs) where it restricts TGF-β ligand expression and collagen production. Furthermore, through combined in vitro experiments in human fetal EPDCs and in vivo rescue experiments in zebrafish, we conclude that Prrx1 stimulates Nrg1 expression and promotes cardiomyocyte proliferation. Collectively, these results indicate that Prrx1 is a key transcription factor that balances fibrosis and regeneration in the injured zebrafish heart.

scholarly journals BITC induces cardiomyocyte proliferation and heart regeneration

2021 ◽  
Author(s):  
Akane Sakaguchi ◽  
Miwa Kawasaki ◽  
Kozue Murata ◽  
Hidetoshi Masumoto ◽  
Wataru Kimura
Keyword(s):  
Cell Cycle ◽  
Cardiac Regeneration ◽  
Heart Regeneration ◽  
Cardiomyocyte Proliferation ◽  
Hypoxia Exposure ◽  
Cell Cycle Reentry ◽  
Regeneration Period ◽  
Mild Hypoxia

AbstractMammalian cardiomyocytes have the ability to proliferate from the embryonic stage until early neonatal stage, with most of them being arrested from the cell cycle shortly after birth. Therefore, adult mammalian heart cannot regenerate myocardial injury. Despite much attention, pharmacological approaches for the induction of cardiomyocyte proliferation and heart regeneration have yet to be successful. To induce cardiomyocyte proliferation by drug administration, we focused on benzyl isothiocyanate (BITC). Firstly, we showed that BITC induces cardiomyocyte proliferation both in vitro and in vivo through the activation of the cyclin-dependent kinase (CDK) pathway. In addition, we demonstrated that BITC treatment induces heart regeneration in the infarcted neonatal heart even after the regeneration period. Furthermore, we administered BITC to adult mice in parallel with mild hypoxia (10% O2) treatment and showed that a combination of BITC administration and mild hypoxia exposure induces cell cycle reentry in the adult heart. The present study suggests that pharmacological activation of the CDK pathway with BITC concurrently with the activation of hypoxia-related signaling pathways may enable researchers to establish a novel strategy to induce cardiac regeneration in patients with heart disease.

Abstract 370: Hedgehog Signaling Regulates Cardiac Regeneration in vivo

2016 ◽  
Vol 119 (suppl_1) ◽  
Author(s):  
Bhairab N Singh ◽  
Wuming Gong ◽  
Mary G Garry ◽  
Naoko Koyano-Nakagawa ◽  
Daniel J Garry
Keyword(s):  
Hedgehog Signaling ◽  
Cardiac Regeneration ◽  
Lineage Tracing ◽  
Heart Regeneration ◽  
Cardiomyocyte Proliferation ◽  
Post Injury ◽  
Time Period ◽  
Hh Signaling ◽  
Regenerative Therapies

The adult mammalian heart has a limited regenerative capacity due primarily to reduced cardiomyocyte (CM) proliferation. Here, we demonstrated hedgehog (HH) signaling pathway as an essential regulator of heart regeneration and CM proliferation. We undertook genome-wide screening using a novel algorithm, bootstrap, which showed an induction of HH signals in the regenerating newt heart. Blockade of HH signaling in the resected newt heart resulted in complete ablation of cardiac regeneration and scar formation. EdU-labeling revealed that inhibition of the HH pathway significantly reduced CM proliferation by 3-fold (n=4 at each time period post-injury). In mammals, cardiac specific loss- and gain-of-function of HH signals demonstrated its role in CM proliferation and regeneration in the postnatal heart. Genetic deletion of floxed-Smoothened ( Smo L/L ) allele at postnatal day 2 (P2) inhibited neonatal heart regeneration with impaired cardiac function and scarring following injury. Conversely, induction of constitutively active Smoothened (SmoM2) at P7 stimulated CM proliferation by 2.5-fold (n=3) and regeneration after myocardial infarction during the non-regenerative window. Lineage-tracing experiments showed that activation of Smo contributed to heart regeneration by promoting proliferation of the pre-existing cardiomyocytes. Activation of HH signals in the cultured CM at P1 and P7 showed an increased proliferative response by 2- and 3-fold (n=4; 1900 cells evaluated for each condition), respectively. Mechanistically, ChIP-seq analysis revealed that HH signals promoted the proliferative program by directly regulating the expression of cyclin-dependent kinases including cyclinD2, cyclinE1 and Cdc7. Finally, activation of HH signaling in the terminally differentiated hiPSC-derived CM resulted in an increase in the number of α-Actinin + /EdU + and α-Actinin + /Ki67 + cells by 2.5-fold (n=3; 645 cells assessed for each condition) and 3-fold (n=3; 685 cells assessed for each condition), respectively. These studies defined an evolutionarily conserved function of HH signaling from newt to mouse to human, as a key regulator of cardiomyocyte proliferation and regeneration that may serve as a platform for regenerative therapies.

scholarly journals Fast revascularization of the injured area is essential to support zebrafish heart regeneration

2016 ◽  
Vol 113 (40) ◽  
pp. 11237-11242 ◽  
Author(s):  
Rubén Marín-Juez ◽  
Michele Marass ◽  
Sebastien Gauvrit ◽  
Andrea Rossi ◽  
Shih-Lei Lai ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Cell Types ◽  
Dominant Negative ◽  
Heart Regeneration ◽  
Cardiomyocyte Proliferation ◽  
Cell Stage ◽  
Injured Area ◽  
Fibrotic Scar ◽  
The One ◽  
Different Cell Types

Zebrafish have a remarkable capacity to regenerate their heart. Efficient replenishment of lost tissues requires the activation of different cell types including the epicardium and endocardium. A complex set of processes is subsequently needed to support cardiomyocyte repopulation. Previous studies have identified important determinants of heart regeneration; however, to date, how revascularization of the damaged area happens remains unknown. Here, we show that angiogenic sprouting into the injured area starts as early as 15 h after injury. To analyze the role of vegfaa in heart regeneration, we used vegfaa mutants rescued to adulthood by vegfaa mRNA injections at the one-cell stage. Surprisingly, vegfaa mutants develop coronaries and revascularize after injury. As a possible explanation for these observations, we find that vegfaa mutant hearts up-regulate the expression of potentially compensating genes. Therefore, to overcome the lack of a revascularization phenotype in vegfaa mutants, we generated fish expressing inducible dominant negative Vegfaa. These fish displayed minimal revascularization of the damaged area. In the absence of fast angiogenic revascularization, cardiomyocyte proliferation did not occur, and the heart failed to regenerate, retaining a fibrotic scar. Hence, our data show that a fast endothelial invasion allows efficient revascularization of the injured area, which is necessary to support replenishment of new tissue and achieve efficient heart regeneration. These findings revisit the model where neovascularization is considered to happen concomitant with the formation of new muscle. Our work also paves the way for future studies designed to understand the molecular mechanisms that regulate fast revascularization.

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