POSITIONAL TRANSCRIPTOMICS SHED LIGHT ON SITE-SPECIFIC PATHOLOGIES OF THE AORTA
Pathologies of large vessels, such as atherosclerosis and aneurysms tend to develop at specific sites in the vascular tree. The consistency with which these events emerge suggests that a combination of unique local stressors, particularly physical forces and disturbances in gene expression profiles underlies disease etiology. We sought to investigate whether transcriptional diversity in specific segments of the aorta could be used to identify emergence of site-restricted vascular disease. Transcriptional profiling was performed using single cell RNA-seq in the carotids, aortic arch, thoracic and abdominal aorta across both sexes. Analyses of the data identified sex-invariant region-specific differences that were further validated by immunocytochemistry. Analysis of vascular smooth muscle cell transcriptomics from distinct regions of the aorta and carotids showed a high degree of similarity, but also uncovered skewed expression of a small percentage of transcripts (7.2%) towards particular vascular segments (carotid, aortic arch, thoracic and abdominal aorta). In silico cross-reference of genes known to be associated with vascular disease with the unique transcriptional signatures validated our proposed hypothesis. Specifically, we found correlations between localized-diseased causing GWAS candidate genes and region-enriched signatures. Pair-wise comparison between anatomic regions across sexes identified regional sex-specific gene signatures highlighting prominent regional-sex dependent differences were observed in vSMCs of the thoracic and abdominal aorta, consistent with sex-specific burden of aneurysm in these regions. Of these regional sex-enriched candidates', Mcam/CD146, showed ventral thoraco-abdominal distribution, enriched expression in females and it was significantly reduced in the AngII / hypercholesterolemic model of aortic aneurysm. Furthermore, induction of aneurysms in mice lacking Mcam/CD146 resulted in larger lesions and accelerated death due to dissection. Overall design: Carotid arteries and aorta spanning the aortic root to the iliac bifurcation were isolated from 12 week old female and male mice and dissected into 4 segments based on anatomic landmarks.  Samples were segregated by sex and anatomic location and digested into single cell preperations prior to library preperation.