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

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 rhodamine-labelling. 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. Copyright © 2016 John Wiley & Sons, Ltd.

Customized Interface Biofunctionalization of Decellularized Extracellular Matrix: Toward Enhanced Endothelialization.

Interface biofunctionalization strategies try to enhance and control the interaction between implants and host organism. Decellularized extracellular matrix (dECM) is widely used as a platform for bioengineering of medical implants, having shown its suitability in a variety of preclinical as well as clinical models. In this study, specifically designed, custom-made synthetic peptides were used to functionalize dECM with different cell adhesive sequences (RGD, REDV, and YIGSR). Effects on in vitro endothelial cell adhesion and in vivo endothelialization were evaluated in standardized models using decellularized ovine pulmonary heart valve cusps (dPVCs) and decellularized aortic grafts (dAoGs), respectively. Contact angle measurements and fluorescent labeling of custom-made peptides showed successful functionalization of dPVCs and dAoGs. The functionalization of dPVCs with a combination of bioactive sequences significantly increased in vitro human umbilical vein endothelial cell adhesion compared to nonfunctionalized controls. In a functional rodent aortic transplantation model, fluorescent-labeled peptides on dAoGs were persistent up to 10 days in vivo under exposure to systemic circulation. Although there was a trend toward enhanced in vivo endothelialization of functionalized grafts compared to nonfunctionalized controls, there was no statistical significance and a large biological variability in both groups. Despite failing to show a clear biological effect in the used in vivo model system, our initial findings do suggest that endothelialization onto dECM may be modulated by customized interface biofunctionalization using the presented method. Since bioactive sequences within the dECM-synthetic peptide platform are easily interchangeable and combinable, further control of host cell proliferation, function, and differentiation seems to be feasible, possibly paving the way to a new generation of multifunctional dECM scaffolds for regenerative medicine.