Single Cell Transcriptomics Reveals Dynamic Role of Smooth Muscle Cells and Enrichment of Immune Cell Subsets in Human Abdominal Aortic Aneurysms

Ann Surg. 2022 Jun 28. doi: 10.1097/SLA.0000000000005551. Online ahead of print.

Abstract

Objective: To determine cell-specific gene expression profiles that contribute to development of abdominal aortic aneurysms (AAAs).

Background: AAAs represent the most common pathological aortic dilation leading to the fatal consequence of aortic rupture. Both immune and structural cells contribute to aortic degeneration, however, gene specific alterations in these cellular subsets are poorly understood.

Methods: We performed single-cell RNA sequencing (scRNA-seq) analysis of AAAs and control tissues. AAA-related changes were examined by comparing gene expression profiles as well as detailed receptor-ligand interactions. An integrative analysis of scRNA-seq data with large genome wide association study (GWAS) data was conducted to identify genes critical for AAA development.

Results: Using scRNA-seq we provide the first comprehensive characterization of the cellular landscape in human AAA tissues. Unbiased clustering analysis of transcriptional profiles identified seventeen clusters representing eight cell lineages. For immune cells, clustering analysis identified four T-cell and five monocyte/macrophage subpopulations, with distinct transcriptional profiles in AAAs compared to controls. Gene enrichment analysis on immune subsets identified multiple pathways only expressed in AAA tissue, including those involved in mitochondrial dysfunction, proliferation, and cytokine secretion. Moreover, receptor-ligand analysis defined robust interactions between vascular smooth muscle cells (SMCs) and myeloid populations in AAA tissues. Lastly, integrated analysis of scRNA-seq data with GWAS studies determined that VSMC expression of SORT1 is critical for maintaining normal aortic wall function.

Conclusions: Here we provide the first comprehensive evaluation of single cell composition of the abdominal aortic wall and reveal how the gene expression landscape is altered in human AAAs.