Division of Cardiology, School of Medicine, Emory University, Atlanta, GA (J.S., E.A.P., K.E.S., J.W.).
Duke Regeneration Center, Department of Cell Biology, Duke University Medical Center, Durham, NC (A.Z.W., J.O., K.D.P.).
Circulation. 2022 Jul 5;146(1):48-63. doi: 10.1161/CIRCULATIONAHA.121.055468. Epub 2022 Jun 2.
Certain nonmammalian species such as zebrafish have an elevated capacity for innate heart regeneration. Understanding how heart regeneration occurs in these contexts can help illuminate cellular and molecular events that can be targets for heart failure prevention or treatment. The epicardium, a mesothelial tissue layer that encompasses the heart, is a dynamic structure that is essential for cardiac regeneration in zebrafish. The extent to which different cell subpopulations or states facilitate heart regeneration requires research attention.
To dissect epicardial cell states and associated proregenerative functions, we performed single-cell RNA sequencing and identified 7 epicardial cell clusters in adult zebrafish, 3 of which displayed enhanced cell numbers during regeneration. We identified paralogs of as factors associated with the extracellular matrix and largely expressed in cluster 1. We assessed expression in published single-cell RNA sequencing data sets from different stages and injury states of murine and human hearts, and we performed molecular genetics to determine the requirements for -expressing cells and functions of each paralog.
A particular cluster of epicardial cells had the strongest association with regeneration and was marked by expression of and . The paralogs are expressed in epicardial cells that enclose dedifferentiated and proliferating cardiomyocytes during regeneration. Induced genetic depletion of -expressing cells or genetic inactivation of altered deposition of the key extracellular matrix component hyaluronic acid, disrupted cardiomyocyte proliferation, and inhibited heart regeneration. We also found that -expressing epicardial cells first emerge at the juvenile stage, when they associate with and are required for focused cardiomyocyte expansion events that direct maturation of the ventricular wall.
Our findings identify a subset of epicardial cells that emerge in postembryonic zebrafish and sponsor regions of active cardiomyogenesis during cardiac growth and regeneration. We provide evidence that, as the heart achieves its mature structure, these cells facilitate hyaluronic acid deposition to support formation of the compact muscle layer of the ventricle. They are also required, along with the function of paralog, in the production and organization of hyaluronic acid-containing matrix in cardiac injury sites, enabling normal cardiomyocyte proliferation and muscle regeneration.
某些非哺乳动物物种，如斑马鱼，具有较高的先天心脏再生能力。了解这些物种中心脏再生是如何发生的，可以帮助阐明可作为心力衰竭预防或治疗靶点的细胞和分子事件。心外膜，一种覆盖心脏的间皮组织层，是斑马鱼心脏再生所必需的动态结构。不同细胞亚群或状态促进心脏再生的程度需要研究关注。
为了剖析心外膜细胞状态及其相关的促再生功能，我们进行了单细胞 RNA 测序，并在成年斑马鱼中鉴定出 7 个心外膜细胞簇，其中 3 个在再生过程中显示出细胞数量增加。我们鉴定出作为细胞外基质相关因子的 的旁系同源物，并在簇 1 中大量表达。我们评估了 在来自不同阶段和损伤状态的鼠类和人类心脏的已发表单细胞 RNA 测序数据集，进行分子遗传学实验以确定表达 的细胞的要求以及每个 旁系同源物的功能。
一个特定的心外膜细胞簇与再生的关系最强，其特征是表达 和 。 的旁系同源物在再生过程中围绕去分化和增殖的心肌细胞的心外膜细胞中表达。诱导遗传耗尽 表达细胞或遗传失活 改变了关键细胞外基质成分透明质酸的沉积，破坏了心肌细胞增殖，并抑制了心脏再生。我们还发现，表达 的心外膜细胞首先在幼年时期出现，此时它们与和心肌细胞扩张事件相关联，并需要这些事件来指导心室壁的成熟。
我们的研究结果确定了一个亚群的心外膜细胞，它们在斑马鱼的胚胎后时期出现，并在心脏生长和再生期间促进活跃的心肌发生区域。我们提供的证据表明，随着心脏达到其成熟结构，这些细胞促进透明质酸的沉积，以支持心室的致密肌肉层的形成。在心脏损伤部位，它们与 旁系同源物的功能一起，也需要产生和组织富含透明质酸的基质，以促进正常的心肌细胞增殖和肌肉再生。
