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Background & Objective: In the field of vascular surgery, the use of tissueengineered vascular grafts is advancing and new synthetic tissues are being utilized to replace damaged blood vessels. These synthetic vessels, made through tissue engineering techniques, must mimic the shape and mechanical properties of native vessels. This study was performed to assess the function of an artificial vascular graft in an animal model. Materials & Methods: The evaluation of artificial vessels was carried out on rat and sheep models. The artificial vascular scaffolds were made of Polyethylene terephthalate (PET), Polyurethane (PU), and Polycaprolactone (PCL) polymers. In the first phase, the fabricated scaffolds were implanted in rats and after 45 days, the grafts were removed and evaluated pathologically. In the second phase, the structures were implanted into the carotid arteries of sheep. Doppler ultrasound and angiography imaging were done to assess changes in carotid blood flow. Eleven months later, the artificial grafts and surrounding tissues were removed and evaluated pathologically. Results: In the rat samples, no hypodermic infections, systemic inflammation, or fibrosis of adjacent tissues were observed. In the sheep samples, no local or systemic complications were reported one week after surgery. No complications were seen after 11 months in the two sheep that received PCL/PU grafts. In contrast, ultrasound evaluation showed thrombosis in the two other sheep that received PET/PU/PCL grafts. Conclusion: This study shows that the implanted artificial vessel used in sheep carotid arteries has a favorable patency rate and satisfactory clinical results, and in terms of mechanical properties, it may be a good candidate for vascular replacement. [ABSTRACT FROM AUTHOR]

The main objective of the present review article is to investigate the in-vitro and in-vivo biocompatibility behavior of hybrid PCL-based scaffolds with collagen, gelatin, and chitosan to improve endothelialization for VTE applications. It is reported that the high-rate failure of small diameters vascular grafts (SDVGs, <6 mm) due to adhesion of platelets and plasma protein and aggregation, over-proliferation of smooth muscle cells (SMCs), and neointimal hyperplasia at the implantation site is main challenge in vascular tissue engineering (VTE). The fast re-establishment of a functional endothelial cell (EC) layer representing a crucial importance strategy has been proposed to reduce these adverse outcomes. Polycaprolactone (PCL), with optimum mechanical properties, it showed great potential in biomedical applications, but its biocompatibility is still highly concerned in VTE. Modifications of the PCL vascular grafts by developing the hybrid structures using natural polymers with optimum hydrophilicity and biocompatibility properties in order to speed up the re-endothelialization process have been proposed over the last years. Analyzing the mentioned results in the present study can offer a better understanding of the benefits and challenges of applying the natural polymer as a thrombotic response upon implantation in clinical trials. Also, it can suggest the PCL-Collagen as the best framework for the fabrication of rationally designed SDVGs for VTE. [ABSTRACT FROM AUTHOR]