Abstract Body (Do not enter title and authors here):
Introduction: The biology of early human hypertensive heart disease (HHD) is largely unexplored due to limited cardiac tissue access. Site-specific transcriptomics of human cardiac tissue before development of overt HHD offers a unique vantage to understand the biology of HHD in human cardiac tissue.

Hypothesis: We hypothesize that transcriptomic signatures and cell subtype proportions differ in human heart tissue from HTN donors compared to normotensive (NTN) donors in a site-specific manner.

Methods: We performed bulk RNA-seq on rRNA-depleted libraries from left (LV) and right (RV) mid-ventricular-wall tissue (average depth 114 million reads/sample) collected postmortem from HTN (n=3, 67% Black/Latinx) and NTN (n=2, 50% Black/Latinx) donors. We performed single-nucleus RNA-seq (snRNA-Seq) on cardiac tissue from the same donors (average of 4,062 LV nuclei). Differential gene expression, lineage identification, and Gene Set Enrichment Analysis (GSEA) were performed with publicly available software.

Results: All donors were female with matched postmortem intervals (time from death to tissue preservation; HTN 19±9 hours, NTN 18±6 hours). HTN donors were older (65±7 years) than NTN donors (36±16 years). A total of 416 genes were associated with HTN (Wald test, FDR q<0.05) across both ventricles (correcting for site). When tested separately, 72 (LV) or 83 (RV) genes were associated with HTN (FDR q<0.05), with 13 common genes, indicating site-specific differences. GSEA of genes ranked by Wald statistic computed across both ventricles showed that transcripts involved in single-stranded DNA helicase activity, branched-chain amino acid catabolism, and NAD-dependent deacetylase activity were coordinately associated with HTN (FDR q<0.05). snRNA-seq revealed 9 cell types in these samples, including immune cells and chamber-specific cardiomyocytes (CMs) with higher proportions of LV CMs and lymphocytes associated with HTN compared to NTN. MYH6 and MYL7 expression was unchanged with respect to HTN by RNA-seq but lower in LV HTN CMs compared to NTN by snRNA-seq, suggesting dysregulation of contractile programming in HTN LV CMs.

Conclusion: HTN is associated with altered cardiomyocyte/lymphocyte ratios, and site-specific differential expression of cardiac contractile elements. Further study is required to validate these findings with additional samples and elucidate mechanisms driving transcriptional program differences in the hypertensive human heart.