The in vivo characterization of electrospun heparin-bonded polycaprolactone in small-diameter vascular reconstruction.

OBJECTIVE: To evaluate the possibility of using heparin-bonded polycaprolactone grafts to replace small-diameter arteries. METHODS: Polycaprolactone was bonded with heparin. The activated partial thromboplastin time of heparin-bonded polycaprolactone grafts was determined in vitro. Small-diameter grafts were electrospun with heparin-bonded polycaprolactone and polycaprolactone and were implanted in dogs to substitute part of the femoral artery. Angiography was used to investigate the patency and aneurysm of the grafts after transplantation. After angiography, the patent grafts were explanted for histology analysis. The degradation of the grafts and the collagen content of the grafts were measured. RESULTS: Activated partial thromboplastin time tests in vitro showed that heparin-bonded polycaprolactone grafts exhibit obvious anticoagulation. Arteriography showed that two heparin-bonded polycaprolactone and three polycaprolactone grafts were obstructed. Other grafts were patent, without aneurysm formation. Histological analysis showed that the tested grafts degraded evidently over the implantation time and that the luminal surface of the tested grafts had become covered by endothelial cells. Collagen deposition in heparin-bonded polycaprolactone increased with time. There were no calcifications in the grafts. Gel permeation chromatography showed the heparin-bonded polycaprolactone explants at 12 weeks lose about 32% for Mw and 24% for Mn. The collagen content on the heparin-bonded polycaprolactone grafts increased over time. CONCLUSION: This preliminary study demonstrates that heparin-bonded polycaprolactone is a suitable graft for small artery reconstruction. However, heparin-bonded polycaprolactone degrades more rapidly than polycaprolactone in vivo.

Klotho functionalization on vascular graft for improved patency and endothelialization.

The Klotho (KL) gene is related to aging. In this study, SKL (secreted KL) and heparin were cross-linked to the acellular small intestinal submucosa (SIS). Based on this, tissue-engineered bioactive small blood vessels were constructed. The goal of this study was to determine whether the release of SKL could improve the patency of small-diameter tissue-engineered blood vessels (TEVs) through promoting cell adhesion. The recombinant human SKL protein was generated from HEK293 cells with overexpression of SKL. Then the SIS membrane was cross-linked with heparin and SKL respectively, to prepare heparin group and SKL group artificial vascular grafts. SKL treatment promoted endothelial cells proliferation and upregulated the levels of Focal adhesion kinase (FAK) phosphorylation and Ras homolog gene family, member A (RhoA). SKL effectively enhanced the endothelial cells adhesion on the SIS membrane. In vivo evaluation of SKL modified SIS grafts in rabbits exhibited increased patency rate, endothelialization, and smooth muscle regeneration. In this study, SKL-modified SIS grafts can effectively improve patency of small-diameter TEVs through enhancing cell adhesion, and it is expected to exhibit an important effect in the construction of substitutes for coronary artery bypass grafting.

Hemodynamic aspects of reduced platelet adhesion on bioinspired microstructured surfaces.

Occlusion by thrombosis due to the absence of the endothelial cell layer is one of the most frequent causes of failure of artificial vascular grafts. Bioinspired surface structures may have a potential to reduce the adhesion of platelets contributing to hemostasis. The aim of this study was to investigate the hemodynamic aspects of platelet adhesion, the main cause of thrombosis, on bioinspired microstructured surfaces mimicking the endothelial cell morphology. We tested the hypothesis that platelet adhesion is statistically significantly reduced on bioinspired microstructured surfaces compared to unstructured surfaces. Platelet adhesion as a function of the microstructure dimensions was investigated under flow conditions on polydimethylsiloxane (PDMS) surfaces by a combined experimental and theoretical approach. Platelet adhesion was statistically significantly reduced (by up to 78%; p≤0.05) on the microstructured PDMS surfaces compared to that on the unstructured control surface. Finite element method (FEM) simulations of blood flow dynamic revealed a micro shear gradient on the microstructure surfaces which plays a pivotal role in reducing platelet adhesion. On the surfaces with the highest differences of the shear stress between the top of the microstructures and the ground areas, platelet adhesion was reduced most. In addition, the microstructures help to reduce the interaction strength between fluid and surfaces, resulting in a larger water contact angle but no higher resistance to flow compared to the unstructured surface. These findings provide new insight into the fundamental mechanisms of reducing platelet adhesion on microstructured bioinspired surfaces and may lay the basis for the development of innovative next generation artificial vascular grafts with reduced risk of thrombosis.