Abstract Body: Atherosclerosis is the driving pathology of many manifestations of cardiovascular disease (CVD) states. The incidence of atherosclerosis, and CVD, increase with aging. However, clinically, we observe that some vascular beds are more athero-prone while some select beds are athero-resistant. We investigated the difference in these arteries to better elucidate the risk of atherosclerosis development in healthy arteries.

Using single cell RNA sequencing (scRNAseq), we evaluated healthy donors from which the coronary and pulmonary artery was isolated. Analysis was completed using Seurat and additional packages. Confirmation of these data were completed using qPCR, Western blot, and functional assays using immunohistochemistry, and scratch assay were evaluated.

The scRNAseq data showed distinct differences in the vascular smooth muscle (VSMC) populations of coronary and pulmonary arteries but not vascular endothelial cells (VEC). Computationally, an elevation in inflammatory cytokines (IL-1a, IL-1b, IL-6, CSF3, IL-8) were seen in coronary but not pulmonary VSMCs. These were validated with similar expression using qPCR, with expression in the internal mammary artery (IMA) VSMCs like that of pulmonary VSMCs. Given the prominent role of aging in CVD, we evaluated expression of senescence and senescence associated secretory phenotype (SASP) markers in VSMCs. We found that p21, Fibronectin 1, and NOX-4 were significantly elevated in coronary vs pulmonary/IMA VSMCs. Investigating why this constellation of SASP and senescence markers are elevated in coronary VSMCs, we found that SIRT1 expression was significantly higher in pulmonary/IMA VSMCs compared to coronary. Using siRNA directed against SIRT1, we found that expression of the SASP increased in the pulmonary VSMCs. Furthermore, we find that in a scratch/migration assay, pulmonary VSMCs were significantly more responsive/migrated more than coronary VSMCs. SA-βgal assay showed significantly higher presence of senescent cells in coronary VSMCs compared to pulmonary.

Collectively, we find that coronary VSMCs have a significantly increased expression of basal inflammatory cytokines with significant reduction in SIRT1 expression. Senescence/SASP was validated using expression of markers, presence of senescent cells, and less migratory cells in the coronary VSMCs compared to pulmonary/IMA VSMCs. Modulation of SIRT1 expression in pulmonary VSMCs shifted the phenotype closer to that of the baseline coronary VSMCs.