Study Of Tissue Engineering Heart Valve Under Pulsatile Stress Condition In Vitro

Objective: The valve replacement is the main therapy for the end-stage valvular heart disease.Patients received mechanical valve replacement need the long-termed anticoagulationtherapy, which increases the postoperative complication incidence of the thrombolization.Although, those received heterogenous bioprosthetic valves replacement needn't lifelonganticoagulation, they are easily deteriorated and calcified. The homologous valves areknown to have superior hemodynamics and needn't anticoagulation therapy, however it'shard to get donor. To develop an ideal heart valve is the hot target in the field of valvesurgery. Tissue engineering heart valve (TEHV), avoiding the complication of the othervalve replacement: thrombolization, hemorrhage and calcifying, is very important in thevalve surgery. Now, there are two hot problems in the study of TEHV. The one is the endothelial cellson the TEHV leaflets have very weak adhesion and are brushed off easily from the valveleaflets once under the hemodynamic condition. The other is the mechanical function of theTEHV created under the static condition is significantly weaker than the normal valve. Theoverseas researches of TEHV have had great progress; however the domestic study has beenin the primary stage. In our study, the first is to design and develop a pulsatile stress cultural system in vitro,and evaluate its function: whether the system can simulate the hydrodynamic character ofheart valve and be used in the study of TEHV. In such system, the TEHV created under thestatic condition will be preconditioned, and the changes of morphology and adhesivefunction of endothelial cells observed. Furthermore, its molecular mechanism will beinvestigated primarily. Methods: 1.the development of pulsatile stress cultural system in vitro The pulsatile stress cultural system consisted of the cultural part and dynamical part.The cultural part, made of the polymethylmetacrylate (PMMA) and silicon rubber, wasdesigned and developed according to the principle of the flexible membrane pump .The 6第二军医大学博士学位论文 英文摘要 胸心外科专业nucleus of it was the pulsatile reactor, which consisted of two principal chambers: thedynamical chamber, under the membrane; and the fluid chamber, upper the membrane. Themembrane was made of the silicon rubber and had the super stretch. There was a specialvalve fixer in the outlet of the fluid chamber, the radium of which can be adjusted to adapt tothe different valves. The reservoir connected with the inlet and outlet of the fluid chamberthrough the silicon tube and one-way valves. The described part can be placed into astandard humidified incubator at 37℃ and 5%CO2.The pulsatile flow attributed to thedynamical part, a special air pump outside of the incubator which was changed from SC-3respirator. 2.the functional evaluation of pulsatile stress cultural system The first is to evaluate its mechanical stability through a bioprosthetic valve. Weobserve whether it can produce the pulsatile flow and work in order or not, and its stableworking for 5 days. Meantime, by ultrasonic we observed its working situation, includingthe opening and closing of valve leaflet, the regurgitation, stress decreases and velocity ofvalve. Then we verified the ability of anti-infection by the cultural test of the LB mediumonto the agar board. The third is to test the hydrodynamic function. Compared with the staticcondition in vitro and the dog aortic valve in vivo, we verified its hydrodynamic functionusing the bioprothesis as a experimental valve according to these parameters: the variation ofvolume and velocity, the highest stress and the highest shear stress. The last is the cellulartoxicity test in vitro of materials used to create the system. We cultured the human umbilicalvein endothelial cells together with the materials of PMMA, silicon me...