The heart is lined by a single layer of mesothelial cells called the epicardium that provides important cellular contributions for embryonic heart formation. The epicardium harbors a population of progenitor cells that undergo epithelial-to-mesenchymal transition displaying characteristic conversion of planar epithelial cells into multipolar and invasive mesenchymal cells before differentiating into nonmyocyte cardiac lineages, such as vascular smooth muscle cells, pericytes, and fibroblasts. The epicardium is also a source of paracrine cues that are essential for fetal cardiac growth, coronary vessel patterning, and regenerative heart repair. Although the epicardium becomes dormant after birth, cardiac injury reactivates developmental gene programs that stimulate epithelial-to-mesenchymal transition; however, it is not clear how the epicardium contributes to disease progression or repair in the adult. In this review, we will summarize the molecular mechanisms that control epicardium-derived progenitor cell migration, and the functional contributions of the epicardium to heart formation and cardiomyopathy. Future perspectives will be presented to highlight emerging therapeutic strategies aimed at harnessing the regenerative potential of the fetal epicardium for cardiac repair.

中文翻译：

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心外膜在心脏发育和修复中的作用。

心脏由称为心外膜的单层间皮细胞排列，该层为胚胎心脏的形成提供重要的细胞作用。心外膜拥有大量的祖细胞，这些祖细胞经历了上皮到间充质的转变，表现出平面上皮细胞向多极性和浸润性间充质细胞的特征性转化，然后分化为非肌细胞心脏谱系，例如血管平滑肌细胞，周细胞和成纤维细胞。心外膜还是旁分泌信号的来源，这对于胎儿心脏生长，冠状动脉图案形成和心脏再生修复至关重要。尽管出生后心外膜进入休眠状态，但心脏损伤会重新激活刺激上皮向间充质转变的发育基因程序。然而，尚不清楚心外膜如何促进成人的疾病进展或修复。在这篇综述中，我们将总结控制心外膜来源的祖细胞迁移的分子机制，以及心外膜对心脏形成和心肌病的功能性贡献。将提出未来的观点，以突出新兴的治疗策略，旨在利用胎儿心外膜的再生潜力进行心脏修复。