Abstract 503: Single Cell Transcriptomics Uncovers The Functional Complexity Of Peripheral Veins And Arteries

Methods: Twenty-six hundred cells from 4 human peripheral veins and 2 arteries were droplet-based single cell sequenced using the 10X Chromium protocol . Paired bulk RNA-seq from seven veins and arteries obtained from the same patient and immunofluorescence validated findings. Results: Arteries were richer in smooth muscle cell (39.1 vs. 13.8%) while vein contained abundant immune cells (14.5 vs. 39.8%). Both vessels had abundant fibroblasts, (28.1 vs. 34.5%), and endothelial Cells (16.5 vs. 11.1 %). Concordantly, contractility and ECM-related pathways were significantly highlighted in arteries while veins were enrich ed in leukocyte migration, antigen presentation, neutrophil activation, and other immune related genes . Quantitate immunofluorescence further confirmed SMC abundance in the arterial wall ( 56% vs. 18% n=11 pairs, p <0.001). There were two main fibroblast clusters equally abundant, the synthetic fibroblasts with high expression of ECM related genes (COL1A1, COL3A1), while the other cluster was defined by the immunomodulatory mediators (CXCL14, CFD). Vein were enriched for Mhem-like (CD163, HMOX1) macrophages important for detoxification and hemoglobin recycling and inflammatory macrophages (IL1B, CXCL8) were similar similarly distributed in both groups . We found a significant number of vasa vasorum (CD34, ICAM2) and luminal ECs(PECAM1,VWF) present in both groups. Furthermore, Intelectin-1 (ITLN1) was elucidated as a specific arterial endothelial marker, both at the single cell and bulk transcriptomic levels. There was also a minor lymphatic endothelial cell subcluster (PROX1 + ) detected in both veins and arteries. Finally, CellCall analysis identified 46 overrepresented ligand-receptor communication pathways in all clusters, including CXCL, FGF, IL-6, and complement signaling. Conclusions: We present a comparative single-cell atlas of peripheral human vein and arteries highlighting important vein enriched functions such as detoxification and hemoglobin recycling. We are now better able to identify cell subpopulations relevant for venous pathologies, without relying on extrapolations from arterial biology of distant models and focusing instead on the uniqueness of vein tissues.