Single‐cell RNA sequencing reveals a mechanism underlying the susceptibility of the left atrial appendage to intracardiac thrombogenesis during atrial fibrillation

Abstract

Background Atrial fibrillation (AF) is associated with an increased risk of thrombosis of the left atrial appendage (LAA). However, the molecular mechanisms underlying this site‐specificity remain poorly understood. Here, we present a comparative single‐cell transcriptional profile of paired atrial appendages from patients with AF and illustrate the chamber‐specific properties of the main cell types. Methods Single‐cell RNA sequencing analysis of matched atrial appendage samples from three patients with persistent AF was evaluated by 10× genomics. The AF mice model was created using Tbx5 knockout mice. Validation experiments were performed by glutathione S‐transferase pull‐down assays, coimmunoprecipitation (Co‐IP), cleavage assays and shear stress experiments in vitro. Results In LAA, phenotype switching from endothelial cells to fibroblasts and inflammation associated with proinflammatory macrophage infiltration were observed. Importantly, the coagulation cascade is highly enriched in LAA endocardial endothelial cells (EECs), accompanying the up‐regulation of a disintegrin and metalloproteinase with thrombospondin motifs 1 (ADAMTS1) and the down‐regulation of the tissue factor pathway inhibitor (TFPI) and TFPI2. Similar alterations were verified in an AF mouse model (Tbx5+/−) and EECs treated with simulated AF shear stress in vitro. Furthermore, we revealed that the cleavage of both TFPI and TFPI2 based on their interaction with ADAMTS1 would lead to loss of anticoagulant activities of EECs. Conclusions This study highlights the decrease in the anticoagulant status of EECs in LAA as a potential mechanism underlying the propensity for thrombosis, which may aid the development of anticoagulation therapeutic approaches targeting functionally distinct cell subsets or molecules during AF.

Single‐cell RNA sequencing in exploring the pathogenesis of diabetic retinopathy

“…This approach has advanced rapidly with diverse methods and platforms such as Smart‐seq, Drop‐seq, Microwell‐seq, etc., 11 providing unprecedentedly deep insights into the complex processes involved in development, physiology and disease. 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 In 2015, Macosko et al. 23 first applied scRNA‐seq in ophthalmology to create a molecular atlas of gene expression for known retinal cell classes and novel candidate cell subtypes in the mouse retina.…”

“…Single‐cell RNA sequencing (scRNA‐seq), a novel technology invented by Tang et al., 10 allows high‐throughput molecular profiling of cells across different modalities. This approach has advanced rapidly with diverse methods and platforms such as Smart‐seq, Drop‐seq, Microwell‐seq, etc., 11 providing unprecedentedly deep insights into the complex processes involved in development, physiology and disease 12–22 . In 2015, Macosko et al 23 .…”