Sided Stimulation of Endothelial Cells Modulates Neutrophil Trafficking in an in vitro Sepsis Model

Abstract Sepsis pathophysiology involves complex interactions between vascular endothelium and circulating immune cells. Importantly, while the role of dysregulated polymorphonuclear leukocyte (PMN) transmigration in septic mediated tissue damage is well documented, strategies to mitigate aberrant transmigration across endothelium have yet to yield viable therapeutics. Much of this can be attributed to the usage of animal models in preclinical trials that lack translational relevance. Recently, however, microphysiological systems (MPS) have emerged as novel in vitro mimetics that facilitate the development of human models of disease. With this advancement, we can now directly probe aspects of endothelial physiology that are difficult to assess with other models. Here, we study the role of endothelial cell (EC) apicobasal polarity and how sided presentation of inflammatory cytokines modulates subsequent leukocyte trafficking response by utilizing the µSiM‐MVM ( micro physiological system enabled by a si licon m embrane – m icro v ascular m imetic). The apicobasal polarity of ECs with respect to inflammation and leukocyte trafficking is a scarcely studied phenomenon that may be critical to understand the dynamic interplay between ECs and PMNs in sepsis and other causes of systemic inflammation. Here we stimulated ECs either apically or basally with a cytokine cocktail to model a septic‐like challenge before introducing healthy donor PMNs into the device. At low concentrations we found that a tissue sided (basally oriented) stimulation generated a stronger PMN transmigratory response versus apical stimulation. Importantly, healthy PMNs were unable to migrate towards a bacterial peptide chemoattractant when ECs were apically stimulated at low doses. This mimics the impaired ability of PMNs to identify a source of infection seen in sepsis, but identifies an EC role in the impairment for the first time, to our knowledge. Only by escalating the apical inflammatory stimulus by a factor of five were we able to overcome the EC barrier and solicit high PMN transmigration levels from the blood to the tissue side of the chip. These results, using the unique capabilities of the µSiM‐MVM, demonstrate that EC apicobasal polarity modulates differential PMN transmigratory behavior in a way that provides insight into the mechanisms underlying sepsis. This article is protected by copyright. All rights reserved