Single-cell RNA Sequencing Technology Revealed the Pivotal Role of Fibroblast Heterogeneity in Ang II-Induced Abdominal Aortic Aneurysms

Abstract

Aim: The mechanism of abdominal aortic aneurysm (AAA) has not been fully elucidated. In this study, we aimed to map the cellular heterogeneity, molecular alteration, and functional transformation of angiotensin (Ang) II-induced AAA in mice based on single-cell RNA sequencing (sc-RNA seq) technology.Method: Single-cell RNA sequencing was performed on suprarenal abdominal aorta from male APOE-/- C57BL/6 mice of Ang II-induced AAA and shame models. Immunohistochemistry was used to determine the pathophysiological characteristics of AAA, and sc-RNA seq was used to determine the heterogeneity and phenotypic transformation of all cell types. A single-cell trajectory was performed to predict the differentiation of fibroblasts. Finally ligand–receptor analysis was used to evaluate intercellular communication between fibroblasts and smooth muscle cells.Results: More than 27,000 cells were isolated and 25 clusters representing 8 types of cells were identified, including fibroblasts, macrophages, endothelial cells, smooth muscle cells, T lymphocytes, B lymphocytes, granulocytes, and natural killer cells. During AAA progression, the function and phenotype of different type cells altered separately. The pro-inflammatory function of inflammatory cells was enhanced. The proliferation phenotype degreased while pro-inflammatory, regeneration and damage-related phenotypes increased in endothelial cells. Smooth muscle cells also transformed from contractile to secretory phenotype. The alterations of fibroblasts were the most conspicuous according sub-group clustering analysis. Single-cell trajectory revealed the critical reprogramming genes of fibroblasts mainly enriched in regulation of immune system. Finally, the ligand–receptor analysis confirmed that increases in secondary collagen synthesis led by fibroblasts were one of the most prominent characteristics of Ang II-induced AAA.Conclusion: Our study revealed the cellular heterogeneity of Ang II-induced AAA. Fibroblasts may play a central role in Ang II-induced AAA progression according multiple biological functions including immune regulation and extracellular matrix metabolic balance. Our study may provide us with a different perspective on the etiology and pathogenesis of AAA.