Arterial Replacement with Compliant Hierarchic Hybrid Vascular Graft: Biomechanical Adaptation and Failure
Department of Bioengineering, National Cardiovascular Center Research Institute, Osaka, Japan. Tissue Engineering
(Impact Factor: 4.25).
05/2002; 8(2):213-24. DOI: 10.1089/107632702753724987
Two types of hybrid vascular grafts were hierarchically structured with an autologous smooth muscle cell (SMC)-inoculated collagen gel layer and an endothelial cell (EC) monolayer, and wrapped with different elasomeric scaffolds. Type A graft was wrapped with poly(urethane)-nylon mesh, and type B graft was wrapped with an excimer laser-directed microporous segmented polyurethane (SPU) film as the scaffold. Type A graft was more compliant than canine carotid arteries, whereas compliance of type B graft was close to that of native arteries. After implantation into canine carotid arteries for 1 month, all type A grafts were dilated due to loosening of the mesh, resulting in loss of prelined ECs and thrombus formation. In contrast, type B grafts developed a well-organized neoarterial wall composed of a confluent EC monolayer and SMC-resided medial tissue, resulting in only slightly appreciable thrombus and minimal tissue ingrowth 6 months after implantation. Compliance of type B graft was reduced at 6 month's implantation, which is mostly due to encapsulated connective tissue formed around the graft.
Available from: Robert Nerem
- "A key issue is obtaining appropriate mechanical properties , which includes not only mechanical strength, but also compliance and elasticity. Several approaches have been taken to achieving these properties, including the use of support sleeves  and the incorporation of other matrix components . The blood clotting protein fibrin has recently been investigated as an alternative scaffold in vascular tissue engineering  , and has been shown to be suitable for producing three-dimensional constructs containing live embedded cells . "
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ABSTRACT: Vascular constructs were formed by embedding rat aortic smooth muscle cells in three-dimensional matrices of Type I collagen, fibrin, or a mixture of collagen and fibrin in a 1:1 ratio, at total matrix protein concentrations of 2 and 4 mg/ml. Morphological and mechanical properties were evaluated after 6 days in culture, and the effect of cyclic mechanical strain on collagen-fibrin mixture constructs was also studied. Constructs made with the lower protein concentration compacted to the greatest degree, and fibrin was found to enhance gel compaction. Each matrix type exhibited a characteristic stress-strain profile. Pure collagen had the highest linear modulus and pure fibrin had the lowest. The ultimate tensile stress was strongly dependent on the degree of gel compaction, and collagen-fibrin mixtures at 2mg/ml total protein content exhibited the highest values. Application of cyclic mechanical strain to collagen-fibrin mixture constructs caused a significant increase in gel compaction and a decrease in cell proliferation. The linear modulus, ultimate tensile stress and toughness of the constructs were all augmented by mechanical strain. These results demonstrate that the properties of engineered vascular tissues can be modulated by the combination of selected extracellular matrix components, and the application of mechanical stimulation.
Biomaterials 09/2004; 25(17):3699-706. DOI:10.1016/j.biomaterials.2003.10.073 · 8.56 Impact Factor
Available from: A* Seifalian
- "The problems include increased risk of thrombosis and infection, limited durability, lack of compliance both of the graft and around the anastomosis , and failure due to restenosis, thus necessitating further interventions   . Currently several groups are working towards the development of 'living grafts'    , seeded grafts    and hybrid grafts      . "
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ABSTRACT: Cardiovascular disease remains one of the major causes of death and disability in the Western world. Tissue engineering offers the prospect of being able to meet the demand for replacement of heart valves, vessels for coronary and lower limb bypass surgery and the generation of cardiac tissue for addition to the diseased heart. In order to test prospective tissue-engineered devices, these constructs must first be proven in animal models before receiving CE marking or FDA approval for a clinical trial. The choice of animal depends on the nature of the tissue-engineered construct being tested. Factors that need to be considered include technical requirements of implanting the construct, availability of the animal, cost and ethical considerations. In this paper, we review the history of animal studies in cardiovascular tissue engineering and the uses of animal tissue as sources for tissue engineering.
Biomaterials 05/2004; 25(9):1627-37. DOI:10.1016/S0142-9612(03)00522-2 · 8.56 Impact Factor
Available from: onlinelibrary.wiley.com
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ABSTRACT: Vascular grafts are in large demand for coronary and peripheral bypass surgeries. Although synthetic grafts have been developed, replacement of vessels with purely synthetic polymeric conduits often leads to the failure of such graft, especially in the grafts less than 6 mm in diameter or in the areas of low blood flow, mainly due to the early formation of thrombosis. Moreover, the commonly used materials lack growth potential, and long-term results have revealed several material-related failures, such as stenosis, thromboembolization, calcium deposition and infection. Tissue engineering has become a promising approach for generating a bio-compatible vessel graft with growth potential. Since the first success of constructing blood vessels with collagen and cultured vascular cells by Weinberg and Bell, there has been considerable progress in the area of vessel engineering. To date, tissue- engineered blood vessels (TEBVs) could be successfully constructed in vitro, and be used to repair the vascular defects in animal models. This review describes the major progress in the field, including the seeding cell sources, the biodegradable scaffolds, the construction technologies, as well as the encouraging achievements in clinical applications. The remaining challenges are also discussed.
Journal of Cellular and Molecular Medicine 09/2007; 11(5):945-57. DOI:10.1111/j.1582-4934.2007.00099.x · 4.01 Impact Factor
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