Assessing trans-endothelial transport of nanoparticles for delivery to abdominal aortic aneurysms.

Abdominal aortic aneurysms (AAAs) are localized, rupture-prone expansions of the abdominal aorta wall. In this condition, structural extracellular matrix (ECM) proteins of the aorta wall, elastic fibers and collagen fibers, that impart elasticity and stiffness respectively, are slowly degraded by overexpressed matrix metalloproteinases (MMPs) following an injury stimulus. We are seeking to deliver therapeutics to the AAA wall using polymer nanoparticles (NPs) that are capable of stimulating on-site matrix regeneration and repair. This study aimed to determine how NP shape and size impacts endocytosis and transmigration past the endothelial cell (EC) layer from circulation into the medial layer of the AAA wall. First, rod-shaped NPs were shown to be created based mechanical stretching of PLGA NPs while embedded in a PVA film with longer rod-shaped NPs created based of the degree in which the PVA films are stretched. Live/dead assay reveals that our PLGA NPs are safe and do not cause cell death. Immunofluorescence staining reveal cytokine activation causes endothelial dysfunction in ECs by increasing expression of inflammatory marker Integrin αVβ3 and decreasing expression of adhesion protein vascular endothelial (VE)-cadherin. We showed this disruption enable greater EC uptake and translocation of NPs. Fluorescence studies demonstrate high endothelial transmigration and endocytosis with rod-shaped NPs in cytokine activated ECs compared to healthy control cells, arguing for the benefits of using higher aspect ratio (AR) NPs for accumulation at the aneurysm site. We also demonstrated that the mechanisms of NP transmigration across an activated EC layer depend on NP AR. These results show the potential of using shape as a modality for enhancing permeation of NPs into the aneurysm wall. These studies are also significance to understanding the mechanisms that are likely engaged by NPs for penetrating the endothelial lining of aneurysmal wall segments.