Diversity among highly specialized cells underlies the fundamental biology of complex multi-cellular organisms. One of the essential scientific questions in cardiac biology has been to define subpopulations within the heart. The heart parenchyma comprises specialized cardiomyocytes (CMs). CMs have been canonically classified into a few phenotypically diverse subpopulations largely based on their function and anatomic localization. However, there is growing evidence that CM subpopulations are in fact numerous, with a diversity of genetic origin and putatively different roles in physiology and pathophysiology. In this chapter, we introduce a recently discovered CM subpopulation: phenylethanolamine-N-methyl transferase (Pnmt)-derived cardiomyocytes (PdCMs). We discuss: (i) canonical classifications of CM subpopulations; (ii) discovery of PdCMs; (iii) Pnmt and the role of catecholamines in the heart; similarities and dissimilarities of PdCMs and canonical CMs; and (iv) putative functions of PdCMs in both physiological and pathological states and future directions, such as in intra-cardiac adrenergic signalling.

高度特化的细胞之间的多样性是复杂多细胞生物体的基础生物学的基础。心脏生物学中的基本科学问题之一是定义心脏内的亚群。心脏实质由特殊的心肌细胞（CM）组成。主要根据其功能和解剖定位，CM 被规范地分为几个表型不同的亚群。然而，越来越多的证据表明，CM 亚群实际上数量众多，具有多种遗传起源，并且在生理学和病理生理学中发挥着不同的作用。在本章中，我们介绍了最近发现的 CM 亚群：苯乙醇胺-N-甲基转移酶 (Pnmt) 衍生的心肌细胞 (PdCM)。我们讨论：(i) CM 亚群的规范分类； (ii) PdCM 的发现； (iii) Pnmt 和儿茶酚胺在心脏中的作用； PdCM 和规范 CM 的异同； (iv) PdCM 在生理和病理状态以及未来方向中的假定功能，例如心脏内肾上腺素信号传导。