Hydrodynamic shear‐stress‐dependent retention of endothelial and endothelial progenitor cells adhered to vascular endothelial growth factor‐fixed surfaces

Abstract

The luminal surfaces of small-diameter artificial vascular grafts must be fully endothelialized to be nonthrombogenic following implantation. To achieve this goal, we have attempted to capture circulating endothelial progenitor cells (EPCs) in situ on the luminal surfaces of implanted grafts. We examined potential receptor-ligand pairs that promote selective and tight adhesion of EPCs using a radial flow chamber comprising three regions, each containing a specific protein-bound substrate: fibronectin (FN) for integrin, and vascular endothelial growth factor (VEGF) and anti-Flk-1 antibody for VEGF receptor. In the presence of shear stress, the greatest retention of endothelial cells and EPCs was observed with FN followed by VEGF and then anti-Flk-1 antibody. Regardless of the bound protein, cell adhesion increased with larger areas of cell adhesion and enhanced cell spreading; the latter was also greatest with FN followed by VEGF and then anti-Flk-1 antibody. The distribution of vinculin-a key protein in focal adhesion plaques-in adherent endothelial cells was examined using total internal reflection fluorescence microscopy; FN-bound surfaces resulted in larger areas of adhesion and more focal adhesion plaques compared with surfaces bound with VEGF. On the other hand, examining these parameters relative to the area of cell adhesion revealed that VEGF-bound surfaces resulted in larger focal adhesion areas and greater fluorescence signals, both of which indicate increased resistance to shear stress. We also discuss in situ capturing of EPCs on surfaces bound with VEGF or anti-Flk-1 antibody, with the goal of creating endothelialized small-diameter vascular grafts.