Customized Interface Biofunctionalization of Decellularized Extracellular Matrix: Toward Enhanced Endothelialization

Abstract

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 custommade 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.

Implantation of VEGF‐functionalized cell‐free vascular grafts: regenerative and immunological response

“…Over the past decade, several groups have demonstrated the feasibility of completely acellular, off-the-shelf grafts in various animal models as well as human clinical trials. Decellularized and devitalized tissue-engineered constructs have been utilized with increasing frequency and have demonstrated improved patency and regeneration potential (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13). Devitalized constructs are based on bioengineered tissue constructs that are stripped of the cellular components while leaving extracellular matrix (ECM) components intact and then implanted into the animal model of choice (14).…”

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

“…Although, in agreement with previous studies (Aubin et al ., ), immunohistological analysis revealed complete absence of T‐cells (CD3 + cells) or cells of macrophage lineage (CD68 + cells) within the majority of coated and non‐coated grafts after either 4 weeks or 8 weeks in vivo , in some isolated cases, the presence of single CD68 + cells in the media or clustering of mostly CD68 + cells and single CD3 + cells in adventitial graft regions could also be observed at irregular intervals. As the presence of macrophages within the neovessel might lead to positive remodelling (Ogle et al ., ), and this process may inadequately be captured by punctual immunohistochemical staining, further studies assessing the possible impact of a low‐profile immune response to graft remodelling are warranted.…”

“…Finally, after 8 weeks in vivo the non‐coated control group started to show a degree of endothelialization similar to that observed in the HG‐VEGF group, however, at this point intimal hyperplasia was significantly increased in the HG‐VEGF‐coated grafts compared with the non‐coated control group. Interestingly, increased neo‐intimal hyperplasia after bioactive luminal surface coating of vascular grafts has been observed in the same rodent aortic transplantation model (Assmann et al ., ; Aubin et al ., ), but also in different preclinical animal models (Bastijanic et al ., ) independent of the coating agent employed. Reasons for this still remain unclear, although in a clinical setting, such as polytetrafluoroethylene (PTFE) graft failure, neo‐intimal hyperplasia is commonly triggered by foreign body reaction, which, however, could neither be observed in this nor in the previous studies (Assmann et al ., ; Aubin et al ., ).…”

“…Interestingly, increased neo‐intimal hyperplasia after bioactive luminal surface coating of vascular grafts has been observed in the same rodent aortic transplantation model (Assmann et al ., ; Aubin et al ., ), but also in different preclinical animal models (Bastijanic et al ., ) independent of the coating agent employed. Reasons for this still remain unclear, although in a clinical setting, such as polytetrafluoroethylene (PTFE) graft failure, neo‐intimal hyperplasia is commonly triggered by foreign body reaction, which, however, could neither be observed in this nor in the previous studies (Assmann et al ., ; Aubin et al ., ). Further, as neo‐intimal hyperplasia was significantly less in the non‐coated grafts than in the coated grafts, the trigger may lie in the bioactive agent itself, rather than in the engineered graft or in an inflammatory and/or immune response of the host organism.…”

“…Recently, it was shown that bioactive coating of decellularized vascular grafts enhances autologous endothelialization and promotes functional neovessel remodelling (Cai et al, 2009;Assmann et al, 2013;Aubin et al, 2016;Koobatian et al, 2016). In the present study, a functional rodent aortic transplantation model (Assmann et al, 2012) was used in order to evaluate the functional performance of decellularized genuine small-diameter grafts (vessel diameter ≤ 2 mm) coated with a temperature-sensitive, aliphatic polyester hydrogel (HG) conjugated with vascular endothelial growth factor (VEGF) allowing sustained growth factor release (Wu et al, 2011), which has already successfully been used for infarct stabilization and cardiac repair in a smallanimal myocardial infarction model (Wu et al, 2011).…”