ABSTRACT
Mammals exhibit limited heart regeneration ability, which can lead to heart failure after myocardial infarction. In contrast, zebrafish exhibit remarkable cardiac regeneration capacity. Several cell types and signaling pathways have been reported to participate in this process. However, a comprehensive analysis of how different cells and signals interact and coordinate to regulate cardiac regeneration is unavailable. We collected major cardiac cell types from zebrafish and performed high-precision single-cell transcriptome analyses during both development and post-injury regeneration. We revealed the cellular heterogeneity as well as the molecular progress of cardiomyocytes during these processes, and identified a subtype of atrial cardiomyocyte exhibiting a stem-like state which may transdifferentiate into ventricular cardiomyocytes during regeneration. Furthermore, we identified a regeneration-induced cell (RIC) population in the epicardium-derived cells (EPDC), and demonstrated Angiopoietin 4 (Angpt4) as a specific regulator of heart regeneration. angpt4 expression is specifically and transiently activated in RIC, which initiates a signaling cascade from EPDC to endocardium through the Tie2-MAPK pathway, and further induces activation of cathepsin K in cardiomyocytes through RA signaling. Loss of angpt4 leads to defects in scar tissue resolution and cardiomyocyte proliferation, while overexpression of angpt4 accelerates regeneration. Furthermore, we found that ANGPT4 could enhance proliferation of neonatal rat cardiomyocytes, and promote cardiac repair in mice after myocardial infarction, indicating that the function of Angpt4 is conserved in mammals. Our study provides a mechanistic understanding of heart regeneration at single-cell precision, identifies Angpt4 as a key regulator of cardiomyocyte proliferation and regeneration, and offers a novel therapeutic target for improved recovery after human heart injuries.
Subject(s)
Humans , Mice , Rats , Cell Proliferation , Heart/physiology , Mammals , Myocardial Infarction/metabolism , Myocytes, Cardiac/metabolism , Pericardium/metabolism , Single-Cell Analysis , Zebrafish/metabolismABSTRACT
Unlike adult mammalian heart, zebrafish heart has a remarkable capacity to regenerate after injury. Previous study has shown Notch signaling activation in the endocardium is essential for regeneration of the myocardium and this activation is mediated by hemodynamic alteration after injury, however, the molecular mechanism has not been fully explored. In this study we demonstrated that blood flow change could be perceived and transmitted in a primary cilia dependent manner to control the hemodynamic responsive klf2 gene expression and subsequent activation of Notch signaling in the endocardium. First we showed that both homologues of human gene KLF2 in zebrafish, klf2a and klf2b, could respond to hemodynamic alteration and both were required for Notch signaling activation and heart regeneration. Further experiments indicated that the upregulation of klf2 gene expression was mediated by endocardial primary cilia. Overall, our findings reveal a novel aspect of mechanical shear stress signal in activating Notch pathway and regulating cardiac regeneration.
ABSTRACT
Unlike adult mammalian heart, zebrafish heart has a remarkable capacity to regenerate after injury. Previous study has shown Notch signaling activation in the endocardium is essential for regeneration of the myocardium and this activation is mediated by hemodynamic alteration after injury, however, the molecular mechanism has not been fully explored. In this study we demonstrated that blood flow change could be perceived and transmitted in a primary cilia dependent manner to control the hemodynamic responsive klf2 gene expression and subsequent activation of Notch signaling in the endocardium. First we showed that both homologues of human gene KLF2 in zebrafish, klf2a and klf2b, could respond to hemodynamic alteration and both were required for Notch signaling activation and heart regeneration. Further experiments indicated that the upregulation of klf2 gene expression was mediated by endocardial primary cilia. Overall, our findings reveal a novel aspect of mechanical shear stress signal in activating Notch pathway and regulating cardiac regeneration.
ABSTRACT
Myocardial infarction afflicts close to three quarters of a million Americans annually, resulting in reduced heart function, arrhythmia, and frequently death. Cardiomyocyte death reduces the heart's pump capacity while the deposition of a non-conductive scar incurs the risk of arrhythmia. Direct cardiac reprogramming emerged as a novel technology to simultaneously reduce scar tissue and generate new cardiomyocytes to restore cardiac function. This technology converts endogenous cardiac fibroblasts directly into induced cardiomyocyte-like cells using a variety of cocktails including transcription factors, microRNAs, and small molecules. Although promising, direct cardiac reprogramming is still in its fledging phase, and numerous barriers have to be overcome prior to its clinical application. This review discusses current findings to optimize reprogramming efficiency, including reprogramming factor cocktails and stoichiometry, epigenetic barriers to cell fate reprogramming, incomplete conversion and residual fibroblast identity, requisite growth factors, and environmental cues. Finally, we address the current challenges and future directions for the field.
Subject(s)
Animals , Humans , Cellular Reprogramming , Epigenesis, Genetic , Intercellular Signaling Peptides and Proteins , Metabolism , Intracellular Space , Metabolism , Myocardium , Cell Biology , Signal TransductionABSTRACT
El concepto tradicional mantenido por años sobre la incapacidad del corazón adulto para renovar sus células ha tenido que ser revisado ante la evidencia de los resultados obtenidos por numerosos estudios que demuestran la existencia en el corazón humano de células con capacidad proliferativa. El trasplante cardíaco aunque ha demostrado ser solución definitiva de la insuficiencia cardíaca no es aplicable a todos los pacientes, fundamentalmente por el déficit de donantes, los avances terapéuticos y quirúrgicos, si bien mejoran la calidad de vida, no son capaces de mejorar la contractilidad miocárdica ni sustituir el cardiomiocito. La terapia celular en la regeneración miocárdica surge como una de las estrategias terapéutica con un futuro prometedor en el tratamiento de la insuficiencia cardíaca, aunque no exenta de controversias, lo que obliga a un mayor conocimiento ante su aplicación clínica, lo cual no contrapone el iniciar ensayos clínicos que permitan un avance en esta dirección.
The traditional concept maintained for years on the incapacity of the adult heart to renew its cells had to be reviewed taking into account the results obtained by numerous studies that demonstrate the existence of cells with proliferative capacity in the human heart. Although the heart transplant has proved to be the definitive solution for heart failure, it may not be applied to all patients due mainly to the deficit of donors. The therapeutic and surgical advances improve the quality of life, but they cannot enhance the myocardial contractility, or replace the cardiomyocite. The cellular therapy in the myocardial regeneration appears as one of the strategical therapeutics with a promising future in the treatment of heart failure, even though it is not exempt from controversies that oblige to have a greater knowledge about its clinical application, but do not impede to start making clinical trials that allow to advance in this direction.