In vitro characterization of endothelial damage from rapid multiaxial mechanical loading

Lining the innermost surfaces of blood vessels, endothelial cells form a monolayer which regulates transport from and to the blood. Under physiological conditions, endothelial cells are exposed to various mechanical stimuli including hydrostatic pressure, wall shear stress, and circumferential stretch due to vessel dilation. In clinical procedures, such as venous graft implantation, mechanical thrombectomy, balloon angioplasty and stenting, acute multiaxial stretching of vessels occurs, leading to endothelial damage. Associated postoperative complications include neointimal hyperplasia and restenosis. In this work, we investigate the formation of damage in endothelial monolayers exposed to a variety of mechanical loading conditions in vitro. To this end, endothelial cells were cultured to form a confluent monolayer on an elastomer substrate, which was then stretched using a new bi-stable device. Endothelial damage, quantified as relative void area, is shown to be much higher in case of equibiaxial stretching than for uniaxial or strip-biaxial stretch states. A discrete network model was developed to rationalize the experimental observations. The computational model allowed to identify the strain energy density as a measure to predict endothelial damage for stretching in arbitrary kinematic states. These results represent an important step towards assessing the risk of iatrogenic endothelial denudation, and providing a criterion for optimization of clinical procedures and devices. Statement of Significance: Endothelial cell integrity is critical for vascular health but is often compromised during interventions such as angioplasty and stenting. These procedures impose acute, multiaxial mechanical loads on the vessel, leading to endothelial denudation - a factor contributing to restenosis. Despite its clinical relevance, the mechanisms leading to such cellular damage remain unclear. In this study, we present an in-vitro platform enabling rapid equibiaxial and strip-biaxial stretching of endothelial monolayers. Our findings demonstrate that equibiaxial loading produces significantly more damage than uniaxial or strip-biaxial loading. By developing a discrete network model, we identify strain energy density as predictive metric for endothelial damage. These insights contribute to a deeper understanding of endothelial mechanobiology and offer a mechanistic framework for optimizing vascular interventions to reduce iatrogenic injury.