Single cell RNA sequencing identifies transcriptional signature of atherosusceptible endothelium of aorta in diabetes associated atherosclerosis
Authors: Khan A , Lee S , Watson A , Maxwell S , Cooper M , Murphy A , Jandeleit-Dahm K 
Published: November 2020

Abstract

Background
Transcriptomic analyses have provided invaluable information for linking genotypes to phenotypes. However, despite the near identical genotype, each cell types in our body has a unique gene expression signature. Deep sequencing at single cell resolution has provided a unique opportunity to unbiasedly discover cellular heterogeneity, disease associated cell populations and to characterise the cell specific transcriptomic landscape. Cardiovascular (CV) disease, a leading cause of death worldwide, is caused mainly by atherosclerosis, a pathological build-up of plaque within arterial vessel walls. Fluid mechanical forces generated by disturbed blood flow are long known to cause structural and transcriptional changes in the vascular endothelium. Atherosclerosis develops near branches and bends of arteries exposed to disturbed blood flow. Diabetes accelerates atherosclerosis development and indeed, represents an independent risk factor. However, the transcriptional signature of atheroprone endothelium in the diabetic aorta has not been investigated previously for this CV complication.

Purpose
This study was designed to apply a single cell RNA sequencing (scRNA-seq) approach to identify the transcriptional signature of atherosusceptible endothelium in diabetes associated atherosclerosis.

Methods
Diabetes was induced with streptozotocin in ApoEs−/− mice and followed for 10 weeks. Cells from digested aortae of control and diabetic mice were FACS-sorted for viable and metabolically active cells. These cells were loaded onto the Chromium Single Cell Controller (10X Genomics) to generate a single cell and gel bead emulsion. ScRNA-seq libraries were prepared with Single Cell 3' Solution V2 kit (10X Genomics) and sequenced with Illumina Nova-seq 6000. We have applied scRNA-seq to identify atheroprone endothelial cells in the aorta.

Results and conclusion
The atheroprone endothelial cells show distinct transcriptional profile with more than six hundred genes differentially expressed. ScRNA-seq allowed us not only to distinguish the two transcriptionally distinct endothelial subpopulations but also to identify a diabetes associated gene expression signature unique to atheroprone endothelial cells as compared to all other cell types in the aorta. We identified seventeen genes uniquely dysregulated in the diabetic atheroprone endothelial cell (Cut off = FDR s&lt;0.05, Fold change at least 2-fold). This includes Protein C receptor (Procr) which has recently been identified as a marker for blood vascular endothelial stem cells (VESCs). Downregulation of Procr in the atheroprone endothelial cells of diabetic aorta as identified in our scRNA-seq data indicates that diabetes may limit the vascular repair by targeting VESCs thus contributing to accelerated atherosclerosis. These exciting novel findings have uncovered the transcriptomic landscape of atherosusceptible endothelium of aorta at the single cell level as seen in diabetes associated atherosclerosis.

Funding Acknowledgement
Type of funding source: Foundation. Main funding source(s): National Heart Foundation of Australia; NHMRC National Health and Medical Research Council of Australia