Experimental Study Of Tissue Engineered Heart Valve

Cardiac valvular disease is a significant cause of mortality and morbidity in human being. The most common therapeutic procedure for the cardiac valvular disease is valve replacement. There are two kinds of valvular prosthesis: mechanical valve and bioprosthetic valve. Though it has been proved that all these valves are effective and has been shown to significantly alter the course of valvular disease, they are still far from an ideal one. Mechanical valves are associated with a significant risk of thromboembolism and require life-long anticoagulation. Bioprosthetic valves do not need life-long anticoagulation, but they are far less durable and are subject to progressive tissue deterioration. Homograft valves also have a limited resources and durability. None of available valve replacements has the capacity for growth and repair.With the development of tissue engineering, we now put our attention to the tissue engineered heart valve. It is an interdisciplinary field that applies the principles and methods of engineering and the life science toward the development of a biological valvular substitute that can restore and maintain the the valvular function. Tissue engineered heart valve have good histocompatibility, long durability, no immunogenecity and no need for anticoagulation. They have the ability for growth and repair.In this study, the feasibility of porcine acellular aortic valve, collagenmembrane, PLGA ( poly-lactic/glycolic acid ) and PHB( poly-3-hydroxybutyrate) as the scaffolds of tissue engineered heart valve was investigated. Tissue engineered heart valve leaflets were constructed in vitro using the canine aortic wall interstitial cells and aortic endothelial cells (ECs) as the seeded cells and the porcine acellular aortic valve leaflets, collagen membrane as the scaffolds. Furthermore, these tissue engineered heart valve leaflets were implanted into the abdominal aorta of the canine to observe its morphologic and histologic changes in vivo. This article is divided into four parts.Part l:Porcine acellular aortic valve were obtained through a cellular exrtaction procedure. The structure characteristics, mechanical properties, biocompatibility and degradation rate of porcine acellular aortic valve, collagen membrane, PLGA and PHB were studied. Results: Using our cellular extraction procedure, nearly all cells were extracted and the fibrous integrity of the valve was maintained. The structure of porcine acellular aortic valve, collagen membrane, PLGA are porous and suitable for the seeding and growing of the cells. Mechanical test demonstrated the maximal tensile strength of scaffolds are: PHB >porcine acellular aortic valve > collagen membrane > PLGA. Subcutaneous implantation of the scaffolds shows mild inflammatory response and all materials are suitable to be applied in vivo. The subcutaneous degradation duration of the porcine acellular aortic valve, collagen membrane and PLGA are 8 to 12 weeks.Part2: The canine aortic valvular interstitial cells, aortic wall interstitial cells, skin fibroblast cells (FBCs) and aortic ECs were cultured. The expression of smooth muscle a actin, microstrucrure characteristics and cellular growth curves of these cells were studied. Results: Transparentelectron microscopy (TEM) shows there are abundant rough endogenous reticulum (RER) in the cytoplasm of the canine aortic valvular interstitial cells and aortic wall interstitial cells. Immunohistochemistry shows part of the canine aortic valvular interstitial cells and aortic wall interstitial cells express smooth muscle a actin, while skin FBCs dose not express it. Cellular growth curves are similar between these two kinds of cells. ECs were confirmed with anti-factor VIII antibody.PartS : Optimal precondition of the scaffolds and intervals for seeding cells were investigated using the MTT assay. The cellular growth curves of the canine aortic wall interstitial cells on the porcine acellular aortic valve, collagen membrane, PLGA and PHB were detected. Canine aortic wall interstit...