Abstract 404: Basement Membrane Of Small Diameter Vascular Extracellular Matrix Scaffolds Modulate Human Endothelial Cell Quiescence

Chronic vascular diseases affect over 25 million patients in the U.S, alone. While non-invasive therapies are available, approximately 4.5 million individuals are estimated to require a vascular bypass annually, worldwide. Autologous vascular grafts remain the standard of care; yet the absence of a suitable donor vessel results in approximately one third of patients being ineligible for autologous grafting. “Off-the-shelf” alternatives have been proposed, but have had limited pre-clinical success, primarily due to graft failure via thrombosis. Thrombotic failure risk has been shown to be dramatically reduced by the formation of a luminal quiescent endothelial cell monolayer. Recently, our group engineered an unfixed, antigen-removed (AR) extracellular matrix (ECM) scaffold from bovine saphenous vein (SV) which is minimally immunogenic and avoids in vivo thrombosis. However, the mechanism by which AR-ECM SV scaffolds prevent thrombosis remains unknown. In this study, we utilized cell culture, immunofluorescence, and RNA-seq to assess the hypothesis that hAECs seeded on the basement membrane (BM) surface of AR-ECM SV scaffolds adopt a quiescent phenotype. Cells seeded on the BM surface proliferated and underwent significantly greater XY migration than those seeded on the non-BM surface. Additionally, unlike non-BM seeded cells, BM seeding resulted in quiescent hAEC phenotype (i.e., apical polarization of podocalyxin and adherence junction protein (i.e., cadherin and β-catenin) colocalization). Finally, the transcriptional phenotype of hAECs seeded on the BM surface was similar to cells treated with simvastatin (i.e. “quiescent”) and significantly different from those treated with TNFα (i.e. “activated”) (n=6/group), as assessed by gene set enrichment and t-SNE analysis. We conclude that seeding hAECs on the BM surface of AR-SV ECM scaffolds induces a favorable “quiescent” phenotype, while an unfavorable “activated” phenotype is avoided. Ultimately, these results show that the BM surface of AR-SV-ECM scaffolds possesses inherent characteristics which promote quiescent hAEC behavior and resultant vascular homeostasis and will help inform future pre-clinical studies of this novel small diameter vascular grafting biomaterial.