Interspecies differences with in vitro and in vivo models of vascular tissue engineering

In arterial replacement there is a clear clinical need for a functional ă substitute possessing appropriate haemocompatible properties to be ă implanted as small diameter artery. Endothelial cell seeding constitutes ă an appreciated method to improve blood compatibility on the condition ă that cells firmly adhere to the support. Along this way, an innovative ă technique based on multilayered polyelectrolyte films (PEM) as cell ă adhesive substrate was previously validated in vitro and in vivo in a ă small-animal model. In this study, we extended the work on a larger ă animal (sheep) to validate furthermore the paradigm of PEM ă functionalization for vascular substitutes. We tested in vitro: the ă efficiency of PEM to induce endothelial progenitor differentiation in ă sheep endothelial cells; the ability of PEM to sustain cell ă proliferation and allow resistance to shear stress; the fate of ă PEM-coated de-endothelialized human saphenous veins under flow ă conditions, a prerequisite step before in vivo experiments. Despite in ă vitro differences we were encouraged by testing in vivo PEM-coated ă prosthesis as carotid replacement in sheep, but without success. In ă order to explain the implantation failure, an in vitro ă haemocompatibility evaluation was performed that highlighted ă interspecies differences able to explain, at least in part, the graft ă failure obtained. (C) 2013 Elsevier Ltd. All rights reserved