Detailed Insights into Heart Histology and Cardiomyocyte Molecular Architecture

The heart is a unique muscular organ, and understanding its complex ultrastructure is essential for studying the pathophysiology of genetic and iatrogenic diseases. Many recently discovered cells and molecular structures serve as therapeutic targets, making knowledge of normal cardiac structure fundamental for preclinical and clinical research.This review focuses on recently discovered cells and their roles in health and disease, including valve endothelial cells, multipotent progenitor cells of the pericardium, circulating multipotent stem cells, and telocytes. Telocytes, in particular, play a significant role under physiological and pathological conditions and show promise in treating myocardial infarction.Various cellular structures and their fundamental relations to cardiac conditions are also explored. These include the structure of titin and cMyBP-C proteins, whose mutations are linked to dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM). Additionally, the normal structure of T-tubules and their dilation in certain forms of cardiotoxicity, the role of RyR2 dysfunction and SERCA leak in atrial fibrillations, mitochondrial biology and its role in cardiac senescence, the role of Cav proteins in signal transduction, and the normal structure of area composita are described. Mutations in area composita contribute to the development of DCM and HCM.Furthermore, this review covers several experimental drugs and techniques targeting specific cardiac structures. These include myosin modulators for treating heart failure, RyR2 stabilizers for anti-arrhythmia therapy, mitochondrial transfer for treating cardiotoxicity, and 144DG11, a new polyglucosan-reducing compound for treating glycogen storage disease.Finally, a detailed description of the histology of normal cardiac tissue is provided.