Abstract 5398: Single-cell transcriptomic analysis of partial endothelial-to-mesenchymal transition in sprouting angiogenesis

Abstract Endothelial-to-mesenchymal transition (EndoMT) is a process of morphological, functional, and molecular shift of endothelial cells (EC) towards a mesenchymal identity. This process is critical for embryonic development, and knockout animals lacking copies of the individual master EndoMT transcription factors – including Slug, Snail, and Twist – exhibit significant cardiovascular defects. We previously showed that while Slug knockout animals have a modest developmental vascular phenotype, there is a striking loss of tumor angiogenesis in these animals. Based on these and other data, we hypothesize that sprouting angiogenesis involves transient acquisition of an intermediate state of the EndoMT program –i.e., partial EndoMT (pEndoMT). To test this hypothesis, we used single cell RNA sequencing at day 2 and day 6 following TGF-β activation to map the transcriptomic changes associated with complete endothelial-to-mesenchymal transition. In parallel, we sequenced EC activated to undergo sprouting angiogenesis in vitro at the same timepoints. We show that angiogenic EC transiently acquire a transcriptomic profile of the pEndoMT state, but then later reacquire the transcriptomic profile of committed EC rather than transition completely into mesenchymal cells. We further use this dataset to identify several candidate genes that appear to be regulated by Slug and associated with the pEndoMT state. Future work will use in vitro and in vivo angiogenesis models to identify how pEndoMT is regulated in angiogenesis, and how this regulation may differ in the presence of tumor stroma. Citation Format: Kapil Thapa, Christopher J. Hatch, Christopher Hughes, Jennifer S. Fang. Single-cell transcriptomic analysis of partial endothelial-to-mesenchymal transition in sprouting angiogenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5398.