Successful endothelialization and remodeling of a cell-free small-diameter arterial graft in a large animal model

Abstract

The large number of coronary artery bypass procedures necessitates development of off-the-shelf vascular grafts that do not require cell or tissue harvest from patients. However, immediate thrombus formation after implantation due to the absence of a healthy endothelium is very likely. Here we present the successful development of an Acellular Tissue Engineered Vessel (A-TEV) based on small intestinal submucosa that was functionalized sequentially with heparin and VEGF. A-TEVs were implanted into the carotid artery of an ovine model demonstrating high patency rates and significant host cell infiltration as early as one week post-implantation. At one month, a confluent and functional endothelium was present and the vascular wall showed significant infiltration of host smooth muscle cells exhibiting vascular contractility in response to vaso-agonists. After three months the endothelium aligned in the direction of flow and the medial layer comprised of circumferentially aligned smooth muscle cells. A-TEVs demonstrated high elastin and collagen content as well as impressive mechanical properties and vascular contractility comparable to native arteries. This is the first demonstration of successful endothelialization, remodeling, and development of vascular function of a cell-free vascular graft that was implanted in the arterial circulation of a pre-clinical animal model.

Cadherin-11 is a novel regulator of extracellular matrix synthesis and tissue mechanics

“…Furthermore, the initial rate of compaction was ∼2.38% per hour for WT cells but less than half of that at ∼1.01% per hour for Cdh11 −/− cells. We also measured the mechanical properties and collagen content of tissue constructs prepared from Cdh11 −/− or WT mouse dermal fibroblasts, as we described in previous publications (DiazChavez et al, 2008;Liang et al, 2013;Koobatian et al, 2016). To this end, we prepared cylindrical tissue equivalents by embedding cells in fibrin hydrogels that were polymerized around cylindrical mandrels and cultured in the presence of TGF-β1 for 2 weeks.…”

“…A ninhydrin assay was used for evaluation of elastin content and a hydroxylproline assay was used for the quantification of collagen as described previously (Koobatian et al, 2016). Briefly, tissues used for quantification of elastin and collagen were lyophilized to obtain the dry weight, which served as a normalization factor.…”

Cell-free vascular grafts: Recent developments and clinical potential

“…In a recent study from our lab, heparin was employed to coat SIS by means of EDC-NHS chemistry, followed by immobilization of VEGF via binding to the heparin binding domain. These grafts exhibited high patency rates in the high flow environment of ovine carotid arteries and produced fully endothelialized, functional arteries as soon as one month post-implantation 50 . Unlike antibodies which have also been applied to capture EPCs from the host bloodstream 51,52 , VEGF enhances the survival, proliferation and cell spreading of captured progenitors 53–56 , making it a more attractive option for functionalizing TEBVs.…”

“…Another study used a biodegradable elastomer that was replaced by a neoartery in a rat animal model 59 . ECs have been replaced by growth factors and antibodies which are capable of capturing host circulating EPCs 50 . Zhou et al have utilized heparin and VEGF to replace the endothelial lining, and have shown successful implantation in a canine arterial model 60 .…”

“…These grafts were based on SIS that was functionalized sequentially with heparin and VEGF, in order to prevent thrombosis and attract endothelial progenitor cells. When implanted as interpositional grafts in the carotid arteries of an ovine model, they exhibited 92% patency rate 50 . By employing VEGF, which captures progenitor cells from the bloodstream, these grafts were fully endothelialized within a month, as evidenced by immunostaining for mature endothelial markers such as vWF, CD144 and eNOS.…”