Integrative Single-Cell and Spatial Transcriptomics Reveal Functional and Spatial Heterogeneity of Atrial and Ventricular Cardiomyocytes in the Heart.

Cardiomyocytes, pivotal for heart contractility, are categorized into atrial (aCM) and ventricular (vCM) subtypes, each playing distinct roles in modulating blood flow, electrical signal conduction, pump function, and energy metabolism. Recent advancements in single-cell RNA sequencing (scRNA-seq) and spatial transcriptomics have enhanced our understanding of cellular heterogeneity and intercellular communication within cardiac tissues. This study integrates scRNA-seq with spatial mapping to elucidate the spatial distribution and intercellular communication of aCM and vCM, focusing on their roles in energy metabolism, pump function, and regulatory functions. We performed scRNA-seq on isolated cardiac cells, followed by data normalization, PCA, and t-SNE clustering, identifying distinct cardiomyocyte subclusters. Ligand-receptor interaction analyses were conducted to explore cellular communication networks, and annotated single-cell data were projected onto heart tissue sections using spatial transcriptomics. Our results revealed distinct spatial distributions: vCM subclusters (vCM-1, vCM-2, vCM-3) predominantly occupied ventricular regions, while aCM subclusters (aCM-1, aCM-2) were primarily located in atrial regions with an increased presence of fibroblasts near atria. Igf2-Igf2r and Vegfb-Vegfr1 mediated communications were prominent in both regions, with extensive interactions between aCM-2 and vCM subclusters. This integration of scRNA-seq and spatial transcriptomics provides a comprehensive overview of cardiac tissue organization and intercellular communication, elucidating critical roles of vCM in energy metabolism and pump function, and aCM in regulating blood flow and electrical conduction. Understanding these interactions in anatomical context enhances our grasp of cardiac function complexity and identifies new therapeutic targets for cardiac diseases.