Single-cell RNA sequencing reveals the cellular heterogeneity of aneurysmal infrarenal abdominal aorta

Abstract

Aims The artery contains numerous cell types which contribute to multiple vascular diseases. However, the heterogeneity and cellular responses of these vascular cells during abdominal aortic aneurysm (AAA) progression have not been well characterized. Methods and results Single-cell RNA sequencing was performed on the infrarenal abdominal aortas (IAAs) from C57BL/6J mice at Days 7 and 14 post-sham or peri-adventitial elastase-induced AAA. Unbiased clustering analysis of the transcriptional profiles from >4500 aortic cells identified 17 clusters representing nine-cell lineages, encompassing vascular smooth muscle cells (VSMCs), fibroblasts, endothelial cells, immune cells (macrophages, T cells, B cells, and dendritic cells), and two types of rare cells, including neural cells and erythrocyte cells. Seurat clustering analysis identified four smooth muscle cell (SMC) subpopulations and five monocyte/macrophage subpopulations, with distinct transcriptional profiles. During AAA progression, three major SMC subpopulations were proportionally decreased, whereas the small subpopulation was increased, accompanied with down-regulation of SMC contractile markers and up-regulation of pro-inflammatory genes. Another AAA-associated cellular response is immune cell expansion, particularly monocytes/macrophages. Elastase exposure induced significant expansion and activation of aortic resident macrophages, blood-derived monocytes and inflammatory macrophages. We also identified increased blood-derived reparative macrophages expressing anti-inflammatory cytokines suggesting that resolution of inflammation and vascular repair also persist during AAA progression. Conclusion Our data identify AAA disease-relevant transcriptional signatures of vascular cells in the IAA. Furthermore, we characterize the heterogeneity and cellular responses of VSMCs and monocytes/macrophages during AAA progression, which provide insights into their function and the regulation of AAA onset and progression.

Abdominal Aortic Aneurysm: Roles of Inflammatory Cells

“…There are generally two origins of macrophages involved in the pathogenesis of AAA: tissue-resident macrophages arising from embryonic precursors, and monocyte-differentiated macrophages from peripheral blood ( 18 ). Single-cell RNA sequencing has revealed markedly expansion and activation of aortic resident macrophages, blood-derived monocytes and inflammatory macrophages in the samples of elastase-induced AAA models ( 19 ). Tissue-resident macrophages are self-renewed independently of bone marrow activity and can continuously migrate to peripheral tissues.…”

CLARA: A web portal for interactive exploration of the cardiovascular cellular landscape in health and disease

“…To enable analysis of the cardiovascular cellular landscape, we prepared datasets from six cardiac and aortic single-cell transcriptomic datasets published in eight independent studies. These include four mouse heart datasets (Table 1) [2][3][4][5], one human heart dataset [6], one mouse aorta [8] and one human aorta [7]. All datasets allow examination of the uninjured heart or aorta.…”

“…Single-cell transcriptomics enables joint examination of cellular heterogeneity and gene expression patterns, in addition to revealing shifts in these parameters in context of development or tissue stress. Recently, multiple single-cell transcriptomic studies have been published-in human and non-human contexts-that have examined the cellular landscape of the heart [2][3][4][5][6] and aorta [7,8]. Collectively, these studies have shown that cell types respond in an orchestrated manner to a range of physiological stressors, and that the cardiovascular tissues are ecosystems of interdependent cell types.…”

Single-Cell Transcriptomics Reveals the Cellular Heterogeneity of Cardiovascular Diseases

“…In this study, the immune cells account for no more than 10% of the total cells in the angiotensin II-induced AAA model. However, in Zhang's study (22), immune cells accounted for more than 60% of total cells isolated from elastasetreated IAAs, this variation is more likely the result of the intrinsic differences in the pathophysiological aspects of the two models, besides, it is important to note that although scRNAseq data is valuable for analyzing gene expression changes in different populations, it is not the best way to estimate the proportion of cell populations, and more accurate methods, such as FACS, are needed to confirm or deny the actual cell composition. Detailed information about subtypes and functional characteristics of macrophages in vasculature are presented in Supplementary Table 1.…”

“…There are several AA mouse models that recapitulate important features of human AA, in a CaCl 2 model, inflammatory macrophages cluster is responsible for the accumulation of macrophages at an early stage in abdominal aortic aneurysm (AAA) development ( 23); however, the function of a proliferative cluster in AAA remains to be proven. In the infrarenal abdominal aortas (IAAs) from C57BL/6J mice who undergo elastase-induced AAA, five monocyte/macrophage clusters are identified (22). Notably, the authors determine the expression of M1 and M2 macrophage markers in all of the five monocyte and macrophage clusters.…”