Single-cell transcriptomic insights into the intrinsic cardiac nervous system: diversity, development, and neuro-cardiac interactions.

The intrinsic cardiac nervous system (ICNS), composed of sympathetic, parasympathetic, and sensory neurons embedded within the heart, plays a pivotal role in regulating cardiac electrophysiology and contractility. Functional imbalance within this network represents a central mechanism driving myocardial infarction, heart failure (HF), atrial fibrillation (AF), and hypertension. Despite decades of investigation, the precise pathophysiological basis of ICNS involvement in cardiovascular disease remains poorly understood. Traditional bulk RNA sequencing, which measures averaged gene expression across pooled cells, fails to capture the cellular heterogeneity of ICNS, particularly rare neuronal and glial subpopulations. Consequently, critical regulatory pathways have been obscured. Single-cell RNA sequencing (scRNA-seq) has overcome this limitation by enabling transcriptional profiling at single-cell resolution. This breakthrough has refined cellular taxonomy within the ICNS and revealed dynamic molecular networks that underlie heart-neural interactions. This review summarizes technological breakthroughs in single-cell isolation, lineage tracing, and spatial transcriptomics, and highlights key discoveries including the identification of cardiac nexus glia (CNG), arrhythmogenic neuron subtypes, and neuroimmune interactions in cardiovascular diseases. We also discuss existing methodological bottlenecks and current challenges in data integration, species translation, and clinical application, and future research goals that could bridge the gap between molecular insight and therapeutic application.