Cell Identity and Functional Diversity of Sinoatrial Node Pacemaker Cell Subpopulations in the Physiology and Pathology of Cardiac Pacemaking - Abstract This research project aims to provide a step-change in our comprehension of cardiac pacemaking and sinus node dysfunction (SND) by introducing the concept of “conditional pacemaker cells” within anatomically and functionally distinct “specialized pacemaker cell subpopulations (SPCS)”. SND, which disrupts the heart’s natural pacing, is linked to significant cardiovascular morbidity and mortality, posing a global health challenge. SND manifests in various types, reflecting its complex and multidimensional etiologies. Despite the critical need for effective treatments, currently, no therapy is available to prevent or reserve the primary cause of SND. Previous research has primarily focused on the conventional pacemaker cells typically defined by their inherent basal automaticity, overlooking the potential crucial role of cells that activate only under specific conditions – “conditional pacemaker cells”. Our preliminary studies link specific types of SND to these previously unrecognized “conditional pacemaker cells” rather than conventional pacemaker cells, underscoring the necessity of identifying and characterizing these cells for better recognition of SND pathology and the development of targeted therapeutic strategies. To achieve this, we will leverage a refined advanced high-resolution optical mapping technology to directly “visualize” the pacemaking activities within distinct specialized pacemaker cell subpopulations in real time, which robustly preserves the cellular integrity, viability and RNA quality, facilitating the systematic investigations of these cell subpopulations at multiple levels as well as the precise integration of the organ-wide functionality, macroscope innervation, and single-cell transcriptomics in same SPCS in situ – a first in the field. Utilizing genetic perturbation, we aim to ascertain the unique pacemaking mechanisms of distinct SPCS and uncover the subcellular mechanism of each specific type of SND that links to its corresponding SPCS in an aged rabbit model. This project transcends the traditional concept of SAN heterogeneity by extending its focus beyond cells solely exhibiting basal automaticity. It challenges the conventional limits of SAN transcriptomics, which limited to marker genes identified solely from basal beating cells in pacemaker cell identification and clustering, and failed to connect genetically heterogeneous cell populations with specific pacemaking functions, or anatomical regions, therefore, offering novel insights into the complex of SAN pacemaking and SND.
