Abstract 9479: Defined Subsets of Sympathetic Neurons Innervate the Heart and Differentially Respond to Cardiac Pathology

Abstract

Introduction: Sympathetic regulatory aspect of cardiac functions is governed by neural circuit originating from postganglionic sympathetic neurons (PGNs) that primarily reside in stellate ganglia. PGNs is comprised of a diversified neuronal population that innervate heart and other tissue beds. Hypothesis: We hypothesize that cardiac innervating stellate ganglionic neurons (SGNs) exhibit diversity and distinction from those innervating other organs. In the settings of cardiac pathology, distribution of cardiac neuronal subtypes is altered, yielding a dominant neuronal subtype. Methods: We utilized method of retrograde axonal transport from heart and paw using adeno-associated virus (AAV-GFP/tdTomato, 1+e12 gc/ml, 10μl) followed by single cell RNA sequencing (scRNAseq) to identify and resolve transcriptomic profiles of SGNs in normal (n=8) and heart-failure mice (n=4). Using NPY-hrGFP mice, we characterized membrane excitability for NPY high and NPY low neurons (n=11). We delineated impact of NPY on cardiac sympathoexcitation by injecting AAV5-Flex-taCasp3 in NPY-Cre mice (n=8) and afterwards electrically stimulating right stellate ganglia (RSG). Results: In our scRNAseq study, we identified 3 adrenergic neuronal subtypes (NA1a, NA1b, and NA3) innervate heart. These subtypes differentiated as NPY high (NA1a) and NPY low (NA1b and NA3) subpopulations. NPY high (4.250±0.90) showed higher number of action potentials compared to NPY low (1.818±0.18). Cardiac sympathoexcitation was diminished in NPY-ablated mice compared to controls in response to escalating intensities (1, 5, 10, 15, & 20 Hz). Maximal heart-rate change was detected at 10 Hz (p = 0.0240) for NPY-ablated mice (91.061±12.62 bpm) vs. controls (27.017±11.88). Across mice, ~70% of cardiac neurons are NPY+. In dilated cardiomyopathy mice, NA1b is a predominant subtype, consists of increased expression of Kcnq2 (M-current) and significant enriched pathways neurodegenerative disorders and neurotrophic signaling. Conclusion: These findings provide novel insights into the unique properties of neurons responsible for cardiac sympathetic regulation, with implications for novel strategies to target specific neuronal subtypes for sympathetic blockade in cardiac disease.