Aortic Cellular Diversity and Quantitative Genome-Wide Association Study Trait Prioritization Through Single-Nuclear RNA Sequencing of the Aneurysmal Human Aorta

Abstract

Background: Mural cells in ascending aortic aneurysms undergo phenotypic changes that promote extracellular matrix destruction and structural weakening. To explore this biology, we analyzed the transcriptional features of thoracic aortic tissue. Methods: Single-nuclear RNA sequencing was performed on 13 samples from human donors, 6 with thoracic aortic aneurysm, and 7 without aneurysm. Individual transcriptomes were then clustered based on transcriptional profiles. Clusters were used for between-disease differential gene expression analyses, subcluster analysis, and analyzed for intersection with genetic aortic trait data. Results: We sequenced 71 689 nuclei from human thoracic aortas and identified 14 clusters, aligning with 11 cell types, predominantly vascular smooth muscle cells (VSMCs) consistent with aortic histology. With unbiased methodology, we found 7 vascular smooth muscle cell and 6 fibroblast subclusters. Differentially expressed genes analysis revealed a vascular smooth muscle cell group accounting for the majority of differential gene expression. Fibroblast populations in aneurysm exhibit distinct behavior with almost complete disappearance of quiescent fibroblasts. Differentially expressed genes were used to prioritize genes at aortic diameter and distensibility genome-wide association study loci highlighting the genes JUN, LTBP4, and IL34 in fibroblasts, ENTPD1 , PDLIM5 , ACTN4 , and GLRX in vascular smooth muscle cells, as well as LRP1 in macrophage populations. Conclusions: Using nuclear RNA sequencing, we describe the cellular diversity of healthy and aneurysmal human ascending aorta. Sporadic aortic aneurysm is characterized by differential gene expression within known cellular classes rather than by the appearance of novel cellular forms. Single-nuclear RNA sequencing of aortic tissue can be used to prioritize genes at aortic trait loci.

Coronary Artery Disease Risk GenePRDM16is Preferentially Expressed in Vascular Smooth Muscle Cells and a Potential Novel Regulator of Smooth Muscle Homeostasis

“…Enhanced TGF-b signaling is observed in the media of aortic tissues from aneurysm patients 48,49 and animal models 50 . Consistently, a recent single-nuclear RNA-seq study showed that TGFB2 expression is activated in SMC clusters of aneurysmal human aorta as compared to that of healthy control 51 . We reasoned that TGFB2 is a direct and bona fide target of PRDM16 because 1) it harbors PRDM16 ChIP-seq peaks within its proximal promoter region (Figure 2J); 2) increased Tgfb2 expression is consistently observed following Prdm16 deletion in cardiomyocytes in multiple independent studies 27,52,53 , a similar finding to our study.…”

Identification and Analysis of Hub Genes and Immune Cells Associated with the Formation of Acute Aortic Dissection

“…A clinical study showed that cardiovascular disease (CVD) patients with high GLRX (>0.622 ng/mL) levels were more likely to experience adverse events [63]. Recent scRNA-seq analysis of aortic aneurysms revealed that GLRX is expressed on SMCs [64]. There is a lack of research on the relationship between GLRX and AD at present.…”

Using Genomics to Identify Novel Therapeutic Targets for Aortic Disease

“…These genes exhibited differential expression in fibroblasts and VSMC subtypes, highlighting these cellular compartments as candidates for further investigation. 30 A similar analysis for AAA-associated SNPs disclosed SORT1 as a potential pathological mediator of AAA development in VSMCs. 32 Further single-cell transcriptomic studies in individuals with other aortic phenotypes, including hereditary aortopathies, will undoubtedly help expand our understanding of the complex genetic architecture of aortic disease.…”