Abstract 490: High-dimensional Proteogenomics Of Human Carotid Atherosclerosis Reveals Significant Diversity Of Smooth Muscle Cells Within Plaques

Abstract

Atherosclerotic lesions are cellularly heterogeneous tissue comprised of diverse cell types including smooth muscle cells (SMCs), endothelial cells, and immune cells. The development of single cell technologies has provided the granular resolution required to identify new cell types present in plaques, aiding in our understanding of the pathophysiology of the disease. Transdifferentiation of SMCs during atherosclerosis progression to a synthetic phenotype has a major influence on disease severity and development. Therefore, to deeply characterize and immunophenotype SMCs in atherosclerotic plaques we performed cellular indexing of transcriptomes and epitopes by sequencing (CITE-seq) on six patients and scRNA-sequencing on fifteen patients undergoing carotid endarterectomy. Our initial analysis identified 25 unique cell populations, which consisted of 4 SMC populations which comprised about 14% of all cells in the dataset. Three of the SMC populations appeared to have a contractile phenotype, with high expression of SMC-specific genes like ACTA2, MYH11, and CNN1. The fourth SMC cluster had a modulated phenotype with downregulation of SMC genes and an up regulation of fibroblast genes such as COL1A2 and LUM. We also identified novel and uncharacterized SMC-specific cell surface proteins such as CD29, CD142, and EGR. The modulated SMC cluster specifically expressed CD90, giving us the unique ability to differentiate these similar yet distinct cell types. We then performed a subclustering analysis on SMC and fibroblast populations, identifying 8 SMC subpopulations. This was followed by Canonical Pathway analysis with Ingenuity Pathway Analysis (IPA) using the most highly expressed genes in each cluster to identify enriched pathways. This revealed a diverse array of functional differences between SMC populations. Our data support the idea that SMCs have a vast array of phenotypic states and functions. Future work will uncover the relevance of these newly identified cell types in the development of atherosclerosis and clinical events.