Under pressure: altered endothelial flow response.

Blood flow within the vasculature is a critical determinant of endothelial cell (EC) identity and functionality, yet the intricate interplay of various hemodynamic forces and their collective impact on endothelial and vascular responses are not fully understood. Specifically, the role of hydrostatic pressure in the context of flow response is understudied, despite its known significance in vascular development and disease. To address this gap, we developed in vitro models to investigate how pressure influences EC responses to flow. Our study demonstrates that elevated pressure conditions significantly modify shear-induced flow alignment and increase endothelial cell density, a phenomenon often observed in vascular diseases. Utilizing both bulk and single-cell RNA sequencing, we found that while flow is the primary driver of transcriptional changes from static conditions, pressure distinctly modulates this flow response by upregulating gene sets linked to arterial cell phenotypes. Conserved pressure-responsive transcriptional signatures identified in human ECs were upregulated during the onset of circulation in early mouse embryonic vascular development, where pressure was notably associated with transcriptional programs essential to arterial and hemogenic EC fates. Our findings emphasize the necessity of an integrative approach to endothelial cell mechanotransduction, one that encompasses the effects induced by pressure alongside other hemodynamic forces. Overall design: single cell RNA-sequencing (10X Genomics platform) of HUVECs cultured in microfluidic vessels and subjected to various levels of hydrostatic pressure (0, 20 and 60 mmHg), while maintained under constant shear stress (flow). A static sample was also included as a negative control.