Interaction of Extracellular Vesicles with Endothelial Cells Under Physiological Flow Conditions

Development of Personalized Thrombogenesis and Thrombin Generation Assays to Assess Endothelial Dysfunction in Cardiovascular Diseases

The study of endothelial dysfunction (ED) is crucial to identify the pathogenetic mechanism(s) and provide indications for patient management in cardiovascular diseases. It is currently hindered by the limited availability of patient-specific primary endothelial cells (ECs). Endothelial colony-forming cells (ECFCs) represent an optimal non-invasive tool to overcome this issue. Therefore, we investigated the use of ECFCs as a substrate in thrombogenesis and thrombin generation assay (TGA) to assess ED. Both assays were set up on human umbilical vein endothelial cells (HUVECs) and then tested on ECFCs obtained from healthy donors. To prove the ability of the assays to detect endothelial activation, ECs stimulated with TNFα were compared with unstimulated ECs. EC activation was confirmed by the upregulation of VCAM-1 and Tissue Factor expression. Both assays discriminated between unstimulated and activated HUVECs and ECFCs, as significantly higher platelet deposition and fibrin formation in thrombogenesis assay, and thrombin generation in TGA, were observed when TNFα-activated ECs were used as a substrate. The amount of fibrin and thrombin measured in the two assays were directly correlated. Our results support the combined use of a thrombogenesis assay and TGA performed on patient-derived ECFCs to provide a personalized global assessment of ED relevant to the patient's hemostatic profile.

Endothelial Extracellular Vesicles: From Keepers of Health to Messengers of Disease

Endothelium has a rich vesicular network that allows the exchange of macromolecules between blood and parenchymal cells. This feature of endothelial cells, along with their polarized secretory machinery, makes them the second major contributor, after platelets, to the particulate secretome in circulation. Extracellular vesicles (EVs) produced by the endothelial cells mirror the remarkable molecular heterogeneity of their parent cells. Cargo molecules carried by EVs were shown to contribute to the physiological functions of endothelium and may support the plasticity and adaptation of endothelial cells in a paracrine manner. Endothelium-derived vesicles can also contribute to the pathogenesis of cardiovascular disease or can serve as prognostic or diagnostic biomarkers. Finally, endothelium-derived EVs can be used as therapeutic tools to target endothelium for drug delivery or target stromal cells via the endothelial cells. In this review we revisit the recent evidence on the heterogeneity and plasticity of endothelial cells and their EVs. We discuss the role of endothelial EVs in the maintenance of vascular homeostasis along with their contributions to endothelial adaptation and dysfunction. Finally, we evaluate the potential of endothelial EVs as disease biomarkers and their leverage as therapeutic tools.

Supported Membrane Platform to Assess Surface Interactions between Extracellular Vesicles and Stromal Cells

Extracellular vesicles (EVs) are membrane-encapsulated particles secreted by eukaryotic cells that stimulate cell communication and horizontal cargo exchange. EV interactions with stromal cells can result in molecular changes in the recipient cell and, in some cases, lead to disease progression. However, mechanisms leading to these changes are poorly understood. A few model systems are available for studying the outcomes of surface interactions between EV membranes with stromal cells. Here, we created a hybrid supported bilayer incorporating EVs membrane material, called an extracellular vesicle supported bilayer, EVSB. Using EVSBs, we investigated the surface interactions between breast cancer EVs and adipose-derived stem cells (ADSCs) by culturing ADSCs on EVSBs and analyzing cell adhesion, spreading, viability, vascular endothelial growth factor (VEGF) secretion, and myofibroblast differentiation. Results show that cell viability, adhesion, spreading, and proangiogenic activity were enhanced, conditions that promote oncogenic activity, but cell differentiation was not. This model system could be used to develop therapeutic strategies to limit EV-ADSC interactions and proangiogenic conditions. Finally, this model system is not limited to the study of cancer but can be used to study surface interactions between EVs from any origin and any target cell to investigate EV mechanisms leading to cellular changes in other diseases.

HMGB1 contributes to the irradiation-induced endothelial barrier injury through receptor for advanced glycation endproducts (RAGE)

This study aimed to investigate whether HMGB1 (high mobility group box-1 protein) and receptor for advanced glycation end products (RAGE) were involved in the irradiation-induced endothelial barrier damage and their mechanism. We constructed the damage model of endothelium barrier model with bEnd.3 cells. The permeability of endothelial barrier was detected by sodium fluorescein (Na-F) permeation test, and the irradiation dose which could induce permeability transition was determined by being exposed to different irradiation doses (5, 10, 15, 20 Gy). MTT assay was applied to detect cell viability under different concentrations of HMGB1, glycyrrhizic acid (GA, a specific inhibitor of HMGB1), and FPS-ZM1 (a blood-brain-barrier permeant blocker of RAGE V domain-mediated ligand binding). The expression of HMGB1, RAGE, and related molecules involved in MAPK signaling pathway, MMP-2, MMP-9, ZO-1, and claudin 5 of differently treated groups were measured by qRT-PCR, western blot, and immunofluorescence. Cells possessed stable endothelial barrier function on 4-7 days after seeded on transwell plates. The permeability of endothelial barrier would change under at least 10 Gy radiation. Both radiation and HMGB1 treatment alone could improve the permeability. After irradiation, the expressions of HMGB1 and RAGE increased and MAPK signal pathway was activated. Meanwhile, MMP-2 and MMP-9 were overexpressed, while the expression of tight junction proteins ZO-1 and claudin 5 was decreased. Radiation could activate MAPK signaling pathway through promoting the expression of HMGB1 and RAGE, which further led to endothelial barrier injury and changed its permeability.