Vascular-type heterogeneity is associated with differential gene expression profiles of endothelial cells under shear stress
Background: Endothelial cell (ECs) heterogeneity is an emerging area of research in EC biology. Veins, arteries, and microvascular endothelial cells, termed “vascular-type” heterogeneity in this report, have been shown to have heterogeneity in gene expression and function. In addition to this innate heterogeneity, we hypothesized that different vascular-type ECs would also demonstrate heterogeneity in their response to shear stress. Objectives: We interrogated whether vascular-type ECs would demonstrate variations in transcriptional expression patterns under shear stress. Methods: Human umbilical vein endothelial cells (HUVECs), human pulmonary arterial endothelial cells (HPAECs), and human microvascular endothelial cells (HMVECs) were commercially purchased and subjected to shear stress conditions of 0, 1, 4, and 10 dynes/cm2 of laminar shear stress. After exposure to shear stress, cells were analyzed for cellular alignment and RNA was extracted and evaluated via bulk RNA-sequencing (RNA-seq). Results: All ECs demonstrated significant changes in alignment under shear stress. Shear stress significantly affected the transcriptomes of ECs resulting in differentially expressed genes and pathways; while several genes were differentially expressed across all three vascular-types (44.2%), most differentially expressed genes were limited to 1 or 2 of the vascular-types. Hemostatic and thrombotic genes were found to have differential expression patterns under conditions of shear stress, and VWF demonstrated a pattern of vascular-type heterogeneity in response to shear stress.  Conclusions: Shear stress causes changes in cellular alignment and transcriptional patterns in ECs that is dependent upon underlying vascular-type. Therefore, endothelial vascular-type heterogeneity can regulate response to shear stress, especially in hemostatic and thrombotic gene expression. Overall design: Bulk RNA-sequencing of HUVECs, HMVECs, and HPAECs under laminar stress conditions of 0, 1, 4, and 10 dynes/cm^2