The blood and vascular cell compatibility of heparin-modified ePTFE vascular grafts

Abstract

Prosthetic vascular grafts do not mimic the antithrombogenic properties of native blood vessels and therefore have higher rates of complications that involve thrombosis and restenosis. We developed an approach for grafting bioactive heparin, a potent anticoagulant glycosaminoglycan, to the lumen of ePTFE vascular grafts to improve their interactions with blood and vascular cells. Heparin was bound to aminated poly(1,8-octanediol-co-citrate) (POC) via its carboxyl functional groups onto POC-modified ePTFE grafts. The bioactivity and stability of the POC-immobilized heparin (POC–Heparin) were characterized via platelet adhesion and clotting assays. The effects of POC–Heparin on the adhesion, viability and phenotype of primary endothelial cells (EC), blood outgrowth endothelial cells (BOECs) obtained from endothelial progenitor cells (EPCs) isolated from human peripheral blood, and smooth muscle cells were also investigated. POC–Heparin grafts maintained bioactivity under physiologically relevant conditions in vitro for at least one month. Specifically, POC–Heparin-coated ePTFE grafts significantly reduced platelet adhesion and inhibited whole blood clotting kinetics. POC–Heparin supported EC and BOEC adhesion, viability, proliferation, NO production, and expression of endothelial cell-specific markers von Willebrand factor (vWF) and vascular endothelial-cadherin (VE-cadherin). Smooth muscle cells cultured on POC–Heparin showed increased expression of α-actin and decreased cell proliferation. This approach can be easily adapted to modify other blood contacting devices such as stents where antithrombogenicity and improved endothelialization are desirable properties.

Cooperative control of blood compatibility and re-endothelialization by immobilized heparin and substrate topography

“…These findings corroborate previous reports of the excellent anti-coagulant ability of immobilized heparin [18,26]. However, one study reported that the immobilization of thiol-modified heparin on the surface did not significantly increase anti-coagulant activity, which might be due to the depleted carboxylic acid groups and diminished bioactivity of heparin caused by random thiolation [34].…”

“…However, the effects of heparin on EC proliferation are ambiguous. While some groups have demonstrated the enhancement of EC growth induced by heparin [23,24], other groups did not detect significant effects of heparin on EC growth [25,26].…”

Vascular Grafting Strategies in Coronary Intervention

“…The authors also claimed that SMCs cultured on the heparin-POC-ePTFE grafts showed increased expression of α-actin and decreased cell proliferation, but the smooth muscle α-actin (SMαA) expression was only examined qualitatively. The cell proliferation data showed that the heparin conjugated POC-ePTFE grafts resulted in a decreased SMC proliferation rate only when compared to twodimensional cell culture on tissue culture polystyrene (TCPS) and not when compared to POC-ePTFE grafts (Hoshi et al, 2013). Although this data does not suggest that intimal hyperplasia may be reduced due to decreased SMC with the heparin immobilized POC-coated ePTFE grafts, Hoshi et al did demonstrate the combined benefit of anti-coagulant therapeutic delivery and improved endothelialization.…”

“…The authors demonstrated reduced whole blood clotting and platelet adhesion of the heparin immobilized POC-ePTFE grafts when compared to both POC-ePTFE and ePTFE grafts. In addition, the heparin conjugated grafts supported both endothelial cell and blood outgrowth endothelial cell adhesion as evidenced by expressions of von Willebrand factor (vWf) and vascular endothelial cadherin (Hoshi et al, 2013). The authors also claimed that SMCs cultured on the heparin-POC-ePTFE grafts showed increased expression of α-actin and decreased cell proliferation, but the smooth muscle α-actin (SMαA) expression was only examined qualitatively.…”

Coagulation at the Blood–Electrode Interface: The Role of Electrochemical Desorption and Degradation of Fibrinogen

“…Various strategies have been used to control surface coagulation including coating the surface with proteinresistant polymers, (7)(8)(9) active molecules such as anticoagulants [10,11] or fibrinolysis promoters, [12][13][14][15] endothelial cells [16,17] or polymers mimicking their membrane, [18,19] and last but not least inorganic thin films conferring various surface properties as reviewed by Mani and colleagues [20]. A strategy not comprised in this list was proposed by P. N. Sawyer more than 40 years ago and consisted in cathodically polarizing the implant's surface.…”