Biomimetic Surfaces for the Study of Outside-In Signaling in Neutrophils

Inflammation is a response to injury or infection in the host’s body. Neutrophils are rapidly recruited to the site of tissue damage through a series of adhesive steps involving selectin-mediated rolling, integrin-mediated adhesion and transmigration via receptor-ligand interactions. In order for neutrophils to emigrate from post-capillary venules to the site of tissue injury, they must transmigrate through the endothelium lining, a process known as transendothelial migration (TEM). Platelet endothelial cell adhesion molecule 1 (PECAM-1) is recruited through the lateral border recycling complex (LBRC) to the apical sites of inflamed endothelial junctions and is required for TEM. PECAM-1 is expressed in both endothelial cells and neutrophils, and PECAM-1 homotypic interaction is the initial step in leukocyte diapedesis. Although the critical role of PECAM-1 in TEM was discovered in 1993, it remains poorly understood how PECAM-1 homotypic interactions contribute to neutrophil migratory function and signaling. Moreover, the exact role of PECAM-1 in diapedesis remains controversial due to the most common mouse strain, C57/bl6, in vivo and in vitro through co-culture of murine endothelial and polymorphonuclear immune cells exhibit PECAM-1 independent diapedesis. However, most mouse strains, including, but not limited to SJL and FVB, require PECAM-1 as an initial step to transmigration. Moreover, endothelial cells and leukocytes isolated from human donors also demonstrate that PECAM-1 is required to initiate diapedesis. Here we demonstrate through the development of biomimetic surfaces in a novel plug-and-play miniaturized total analysis system that PECAM-PECAM homotypic interaction alters the normative morphology, polarity, and signaling of migrating neutrophils on the endothelial surface on the junctional permissive sites of the luminal side of the endothelium.