BACKGROUND: Endothelial cells (ECs) are capable of quickly responding in a coordinated manner to a wide array of stresses to maintain vascular homeostasis. Loss of EC cellular adaptation may be a potential marker for cardiovascular disease and a predictor of poor response to endovascular pharmacological interventions such as drug-eluting stents. Here, we report single-cell transcriptional profiling of ECs exposed to multiple stimulus classes to evaluate EC adaptation. METHODS: Human aortic ECs were costimulated with both pathophysiological flows mimicking shear stress levels found in the human aorta (laminar and turbulent, ranging from 2.5 to 30 dynes/cm ² ) and clinically relevant antiproliferative drugs, namely paclitaxel and rapamycin. EC state in response to these stimuli was defined using single-cell RNA sequencing. RESULTS: We identified differentially expressed genes and inferred the TF (transcription factor) landscape modulated by flow shear stress using single-cell RNA sequencing. These flow-sensitive markers differentiated previously identified spatially distinct subpopulations of ECs in the murine aorta. Moreover, distinct transcriptional modules defined flow- and drug-responsive EC adaptation singly and in combination. Flow shear stress was the dominant driver of EC state, altering their response to pharmacological therapies. CONCLUSIONS: We showed that flow shear stress modulates the cellular capacity of ECs to respond to paclitaxel and rapamycin administration, suggesting that while responding to different flow patterns, ECs experience an impairment in their transcriptional adaptation to other stimuli.

The Fused-Deposition Modelling (FDM) technique has transformed the manufacturing discipline by simplifying operational processes and costs associated with conventional technologies, with polymeric materials being indispensable for the development of this technology. A lack of quantification of viscoelastic/plastic behavior has been noted when addressing FDM parts with Polyetherimide (PEI), which is currently being investigated as a potential material to produce functional end-products for the aerospace and health industry. Primary and secondary creep along with stress relaxation tests have been conducted on FDM PEI specimens by applying stresses from 10 to 40 MPa for 100 to 1000 min. Specimens were 3D printed by varying the part build orientation, namely XY, YZ, and XZ. Creep results were fitted to the Generalized Time Hardening equation (GTH), and then this model was used to predict stress relaxation behavior. FDM PEI parts presented an isotropic creep and stress relaxation performance. The GTH model was proven to have a significant capacity to fit viscoelastic/plastic performances for each single build orientation (r > 0.907, p < 0.001), as well as a tight prediction of the stress relaxation behavior (r > 0.998, p < 0.001). Averaged-orientation coefficients for GTH were also closely correlated with experimental creep data (r > 0.958, p < 0.001) and relaxation results data (r > 0.999, p < 0.001). FDM PEI parts showed an isotropic time-dependent behavior, which contrasts with previous publications arguing the significant effect of part build orientation on the mechanical properties of FDM parts. These findings are strengthened by the high correlation obtained between the experimental data and the averaged-coefficient GTH model, which has been proven to be a reliable tool to predict time-dependent performance in FDM parts.

Atherosclerosis, the leading cause of cardiovascular disease, is associated with aberrant lipid metabolism, endothelial dysfunction, and chronic inflammation, yet its early manifestations and mechanisms remain incompletely understood. As low-density lipoprotein receptor loss of function is the most common monogenic cause of atherosclerosis, we employed low-density lipoprotein receptor knockout ( ldlr -/-) zebrafish to investigate the developmental origins of atherosclerotic cardiovascular disease. Single-cell RNA-sequencing under differential flow conditions in embryonic ldlr -/- zebrafish identified a population of disproportionately stressed endothelial cells marked by overexpression of heat shock protein 70 ( hsp70 ). Hsp70 is induced in stressed endothelial cells in a flow-dependent manner in zebrafish and a subset of human endothelial cells, and its activation is associated with disrupted remodeling angiogenesis in vivo. Genetic and pharmacological studies demonstrated that hsp70 upregulation inhibits vascular apoptosis and ciliogenesis, leading to altered angiogenic remodeling. Concurrently, pro-inflammatory processes, including enhanced myelopoiesis and thrombogenicity, are amplified at early stages in ldlr -/- zebrafish, which also exhibit impaired regenerative angiogenesis and heightened neutrophil recruitment post-vascular injury. Our findings reveal how abnormalities in flow-mediated endothelial remodeling and inflammation converge during embryogenesis to drive vascular susceptibility to hemodynamic and other stressors in ldlr loss of function.