Bioactive coating of decellularized vascular grafts with a temperature-sensitive VEGF-conjugated hydrogel accelerates autologous endothelialization in vivo

Abstract

No ideal small-diameter vascular graft for widespread clinical application has yet been developed and current approaches still suffer from graft failure because of thrombosis or degeneration. Decellularized vascular grafts are a promising strategy as they preserve native vessel architecture while eliminating cell-based antigens and allow for autologous recellularization. In the present study, a functional in vivo rodent aortic transplantation model was used in order to evaluate the benefit of bioactive coating of decellularized vascular grafts with vascular endothelial growth factor (VEGF) conjugated to a temperature-sensitive aliphatic polyester hydrogel (HG). Luminal HG-VEGF coating persistence up to 4 weeks was confirmed in vivo by rhodaminelabelling. Doppler-sonography showed that the grafts were functional for up to 8 weeks in vivo. Histological and immunohistochemical analysis of the explanted grafts after 4 weeks and 8 weeks in vivo demonstrated significantly increased endothelium formation in the HG-VEGF group compared with the control group (luminal surface covered with single-layered endothelium, 4 weeks: 64.8 ± 7.6% vs. 40.4 ± 8.3%, p = 0.025) as well as enhanced media recellularization (absolute cell count, 8 weeks: 22.1 ± 13.0 vs. 3.2 ± 3.6, p = 0.0039). However, HG-VEGF coating also led to increased neo-intimal hyperplasia, resulting in a significantly increased intima-to-media ratio in the perianastomotic regions (intima-to-media ratio, 8 weeks: 1.61 ± 0.17 vs. 0.93 ± 0.09, p = 0.008; HG-VEGF vs. control). The findings indicate that HG-VEGF coating has potential for the development of engineered small-diameter artificial grafts, although further research is needed to prevent neo-intimal hyperplasia.

Improving in vivo outcomes of decellularized vascular grafts via incorporation of a novel extracellular matrix

“…Thus, there has been a corresponding increase in the study of decellularized tissue modification to enhance endothelialization and reduce thrombogenicity. In attempts to accelerate endothelialization, researchers have coated decellularized grafts with VEGF, VEGF hydrogels, integrin ligands, and cell adhesion peptides [19–23]. Other groups have chosen to focus on decreasing graft thrombogenicity.…”

Small Diameter Xenogeneic Extracellular Matrix Scaffolds for Vascular Applications

“…76,78,204,206,207 Studies that include the use of coated small diameter vessel ECM scaffolds in vivo reported high patency rates (patency rate) over periods of 3 (83%-xenograft) and 8 (100%-allograft) weeks and 2 (90%-allograft) and 3 (83%-xenograft) months (Table 3). 76,78,204,205 In all cases, scaffolds demonstrated robust smooth muscle and EC recellularization. 76,78,204,205 Finally, the combination of barrier and cell modulating compounds resulted in reduced production of blood coagulation factor in vitro, as well as reduced platelet accumulation and fibrin deposition in vivo.…”

“…76,78,204,205 In all cases, scaffolds demonstrated robust smooth muscle and EC recellularization. 76,78,204,205 Finally, the combination of barrier and cell modulating compounds resulted in reduced production of blood coagulation factor in vitro, as well as reduced platelet accumulation and fibrin deposition in vivo. 69 High in vivo patency rates and high cell presence suggest that scaffold coating may serve as a solution to achieving rapid EC repopulation of ECM scaffolds.…”

“…The most common approach, identified in the articles reviewed for this article, to avoid thrombosis due to lack of an EC monolayer in ECM scaffolds has been to modify the luminal scaffold surface using a variety of coatings. 69,71,74,76,78,[204][205][206][207][208] Coatings have generally been designed to either target enhanced cell repopulation or serve as an antithrombotic barrier, with some researchers using combinations of both approaches in an attempt to enhance overall in vivo outcome. Proteins such as growth factors and integrins have been utilized as coating agents to stimulate cell repopulation.…”

“…Proteins such as growth factors and integrins have been utilized as coating agents to stimulate cell repopulation. 69,76,78,[204][205][206][207] The most widely utilized barrier compound is heparin. 69,71,74,204,208 One final approach has employed thrombospondin-2 knockout (TSP2 KO) ECM to examine the effect of elimination of prothrombotic molecules from the resultant scaffold.…”