Smooth Muscle Cell Populations of Differing Embryonic Origins in the Ascending Aorta Exhibit Minor Differences in Angiotensin II-driven Transcriptional Alterations in Mice

Ascending thoracic aortopathy is a life-threatening disease significantly influenced by angiotensin II (AngII). Thoracic aortopathy exhibits regional heterogeneity with the ascending region being susceptible. Smooth muscle cells (SMCs), a major component of the aortic wall, originate from two embryonic origins in the ascending aorta: second heart field (SHF) and cardiac neural crest (CNC). However, functional differences between the origins in AngII-induced thoracic aortopathy formation remain unknown. The present study determined transcriptomic differences between origins in response to AngII by single-cell RNA sequencing using the lineage tracing approach. Mef2c-Cre +/0 mT/mG mice were infused with AngII (1,000 ng/kg/day). To investigate causative mechanisms, ascending aortas were harvested after 3 days of AngII infusion, representing the prepathological phase of thoracic aortopathy. Aortic samples were also harvested from Mef2c-Cre +/0 mT/mG mice without AngII infusion as a control. Following single-cell suspension, cells were sorted based on their origin using mTotamto and mGFP signals. mGFP proteins were present on Mef2c-Cre-driven cells indicating the cells were derived from the SHF, while cells with mTomato signal were not derived from the SHF (nSHF). After sorting cells by origin, single-cell RNA sequencing was performed. Two-way ANOVA analysis identified 1718 differentially expressed genes (DEGs) in the interaction between origin and infusion. Among these DEGs, 1207 genes significantly differed between origins in response to AngII infusion. However, the magnitude of difference in most of these DEGs was modest, ranging between −0.05 and 0.05 Log2FC. Commonly studied molecules, such as TGF-β, SMC contraction, and extracellular matrix molecules, were undetectable or modestly different. In conclusion, transcriptomic differences in SMCs between origins in response to AngII were modest in the pre-pathological phase of AngII-induced thoracic aortopathy.