title: Physiologically Modeled Pulse Dynamics to Improve Function in In Vitro-Endothelialized Small-Diameter Vascular Grafts.
abstract: The lack of a functional endothelium on small-diameter vascular grafts leads to intimal hyperplasia and thrombotic occlusion. Shear stress conditioning through controlled hydrodynamics within in vitro perfusion bioreactors has shown promise as a mechanism to drive endothelial cell (EC) phenotype from an activated, pro-inflammatory wound state toward a quiescent functional state that inhibits responses that lead to occlusive failure. As part of an overall design strategy to engineer functional vascular grafts, we present a novel two-phase shear conditioning approach to improve graft endothelialization. Axial rotation was first used to seed uniform EC monolayers onto the lumenal surface of decellularized scaffolds derived from the human umbilical vein. Using computer-controlled perfusion circuits, a flow-ramping paradigm was applied to adapt endothelia to arterial levels of fluid shear stress and pressure without graft denudation. The effects of constant pulse frequencies (CF) on EC quiescence were then compared with pulse frequencies modeled from temporal fluctuations in blood flow observed in vivo, termed physiologically modeled pulse dynamics (PMPD). Constructs exposed to PMPD for 72 h expressed a more functional transcriptional profile, lower metabolic activity (39.8% ± 8.4% vs. 62.5% ± 11.5% reduction, p = 0.012), and higher nitric oxide production (80.42 ± 23.93 vs. 48.75 ± 6.93 nmol/10(5) cells, p = 0.028) than those exposed to CF. By manipulating in vitro flow conditions to mimic natural physiology, endothelialized vascular grafts can be stimulated to express a nonactivated phenotype that would better inhibit peripheral cell adhesion and smooth muscle cell hyperplasia, conditions that typically lead to occlusive failure. Development of robust, functional endothelia on vascular grafts by modulation of environmental conditions within perfusion bioreactors may ultimately improve clinical outcomes in vascular bypass grafting.
authors.affiliation: J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida , Gainesville, Florida.
authors.forename: Joseph S
authors.initials: JS
authors.lastname: Uzarski
authors.affiliation: J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida , Gainesville, Florida.
authors.forename: Jhon
authors.initials: J
authors.lastname: Cores
authors.affiliation: J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida , Gainesville, Florida.
authors.forename: Peter S
authors.initials: PS
authors.lastname: McFetridge
mesh_terms: D019149:Bioreactors; D001807:Blood Vessel Prosthesis; D018929:Cell Culture Techniques; D002454:Cell Differentiation; D049109:Cell Proliferation; D004730:Endothelium, Vascular / Q000166:cytology*; D005786:Gene Expression Regulation; D061307:Human Umbilical Vein Endothelial Cells / Q000166:cytology; D006801:Humans; D009569:Nitric Oxide / Q000096:biosynthesis; D010477:Perfusion; D012212:Rheology; D015398:Signal Transduction; D023822:Tissue Engineering / Q000379:methods*; D014158:Transcription, Genetic
chemical_list: D009569:Nitric Oxide