Abstract 15: Single-cell Immune Landscape Of Human Clot Retrieved At Mechanical Thrombectomy. Association With Stroke Origin.

Abstract

Background: Mechanical thrombectomy (MT) has significantly improved clinical outcomes in acute ischemic stroke. We used single-cell RNA sequencing (scRNA-seq) to describe the landscape of human clots at single cell resolution seeking to provide greater mechanistic insight into stroke pathophysiology and to uncover an association with stroke origin. Methods: scRNA-seq was performed on 14 clots retrieved from 14 patients undergoing MT between October 2020-July 2022. We followed standard molecular biology and bioinformatics workflows for sample processing and data to characterize differences in cellular composition between clots of different stroke origin (atrial fibrillation (AF) and carotid atherosclerosis (CA)). Results: Clots revealed a significant heterogeneity of immune cells with major constituents including cells of the mononuclear phagocyte system (MPS) and neutrophils. The cellular populations most enriched in CA clots were B-cells and CD4+ T-cells. The cellular population most enriched in AF clots was red blood cells. When looking at cellular subpopulations of the MPS component, we found that CD16+ monocytes (intermediate and non-classical) were significantly more abundant than CD14+CD16- (classical) monocytes in all clots. Moreover, the proportions of CD16+ monocytes varied with stroke origin: the proportion of non-classical (CD14-CD16+) monocytes was higher in CA clots (p=0.05) whereas the proportion of intermediate monocytes (CD14+CD16+) was higher in FA clots (p=0.03). AF clots had upregulated biomarkers and pathways involved with AF or contractile dysfunction (IFI30, FABP4, PPAR, HOTAIR, ILK, Integrin). CA clots had upregulated biomarkers and pathways associated with cardiovascular diseases and atherogenesis (RNSE1, POLR2J3.1, PLTP, Sirtuin, FAK). (Figure) Conclusions: These results reveal a significant heterogeneity of immune cells and point to important differences in cellular composition associated with stroke etiology.