Single-Cell Transcriptomic Analysis Reveals Differential Cell Subpopulations and Distinct Phenotype Transition in Normal and Acute Dissected Ascending Aorta

Background: Acute thoracic aortic dissection (ATAD) is a fatal condition characterized by tear of intima and formation of false lumen whereby leading to the rupture of aorta. To better understand the potential mechanism of ATAD, we analyzed characterization of different cell types between ATAD and control group and predicted interactions among different cell types which might promote the progression of ATAD. Methods: Single-cell RNA sequencing (scRNA-seq) was performed including 5 patients with ATAD and 4 healthy controls. Cells were digested from ascending aortic tissues and subpopulations of most cell types were identified on the basis of scRNA-seq data. The gene expression profiles of each cell type and related changes between ATAD and control group were analyzed via bioinformatic analysis. We also predicted potential interaction among different cell types and verified the results by immunohistochemistry (IHC) and immunofluorescence (IF). Results: We got 8 cell types from human ascending aorta and 50 subpopulations were identified after re-clustering including vascular smooth muscle cells (VSMCs), endothelial cells, fibroblasts, neutrophils, monocytes and macrophages. Higher proportion of synthetic VSMCs, dysfunctional neutrophils and monocytes were seen in ATAD group compared with control group. Next, we predicted cell differentiation trajectory of VSMCs, fibroblasts and neutrophils via CytoTRACE, then identified subpopulations with higher differentiation potential. Moreover, the hub genes of VSMCs, fibroblasts and neutrophils were examined by weighted gene co-expression network analysis. Further analysis revealed that six transmembrane epithelial antigen of prostate 4 metalloreductase (STEAP4) might be a new marker for isolation of synthetic VSMCs by verification with IHC and IF. We also found synthetic VSMCs-derived C-X-C motif chemokine ligand 12 (CXCL12) might interact with neutrophils and fibroblasts via combination with C-X-C motif chemokine receptor 4 (CXCR4) and atypical chemokine receptor 3 (ACKR3), respectively, which might recruit neutrophils and induce transdifferentitation of FBs into synthetic VSMCs. Conclusion: In this study, we demonstrated integrative composition of different cell types in normal and dissected human ascending aorta and identified a new marker favorable to isolation of synthetic VSMCs. Furthermore, we also proposed a potential mechanism that synthetic VSMCs could interact with neutrophils and fibroblasts via CXCL12-CXCR4/ACKR3 axis whereby deteriorating the progression of ATAD. In total, these findings in our study might provide new insights to better understand the development and progression of ATAD.