Single-Cell Transcriptomic Profiling of Immune Cell Phenotype Modulation in Murine Abdominal Aortic Aneurysm

Background: Abdominal aortic aneurysm (AAA) is recently recognized as an autoimmune-induced vascular disease. Nonetheless, the inflammatory cellular heterogeneity and specialty within the aortic wall have not been fully identified. Methods: Infrarenal abdominal aortas of WT mice were perfused with PBS or elastase to simulate sham or AAA models. The aortas were harvested 14 days after surgery and digested for single-cell preparation. The cell pellet was mixed with CD45 microbeads, and proceeded with magnetic separation to isolate CD45 positive immune cell suspension. The cell suspension was loaded into Chromium microfluidic chips with 3’ chemistry and barcoded with 10х Chromium Controller (10X Genomics). All downstream single-cell analyses were performed using the CellRanger, Seurat, or clusterProliler R package. Results: Based on the filtered gene expression matrix, 18 clusters were identified in the final datasets. Enrichment analysis was performed to finger out the specific biological behaviors, such as inflammatory cytokine secretions and promotion of cell proliferation, in each clusters of immune cells. According to the highly expressed cell markers and biological behaviors, we divided each clusters of immune cells into macrophages, dendritic cells (DCs), T or B lymphocytes. It was shown in the t-SNE plot that the cellular quantity of CD45 positive immune cells, especially macrophages and DCs, were prominently altered in the AAA group. The refined subtypes of each kinds of inflammatory cells were distinguished and identified by limiting essential cell markers and increase dimensionality resolution. The specific marker-based analysis showed that the cell count difference of resident macrophages and monocyte-derived DCs (moDCs) are most noticeable between the AAA and the sham group, which might suggest these cells have eventful influence in aneurysm development. Conclusions: The integrated data exhibited the distinctive heterogeneity of CD45 positive immune cells within elastase-induced AAA samples. Some of these cells, such as resident macrophages and moDCs, may play an essential role through several pathways in the pathogenesis of AAA formation according to our scRNA-sequencing result.