Development of a Tissue Engineered Mitral Valve

Heart valve diseases affect nearly 8 million people every year in the United States. Of these patients, 72% are affected by mitral valve diseases. Stenosis, regurgitation, and prolapse of the mitral valve are the primary pathologies affecting valve function resulting in atrial fibrillation, arterial thromboembolism, pulmonary edema, pulmonary hypertension, cardiac hypertrophy and heart failure. Surgical options to repair or replace the mitral valve are only palliative, especially for children with congenital defects, and do not exclude the need for reoperation. A tissue-engineered option is feasible and holds great potential through the combination of decellularized scaffolds, patient stem cells, and heart valve bioreactors. Development of living tissue engineered mitral valves have not been reported in the recent literature. The primary focus of my research was threefold: 1) develop an acellular ECM scaffold which is mechanically robust, and allows for sufficient bioactivity for cellular seeding and signaling by use of a non-toxic matrix-binding polyphenolic antioxidant, pentagalloyl glucose (PGG); 2) confirm this scaffold to be biologically compatible with future hosts and limiting inflammatory responses in vivo by virtue of PGG\u27s antioxidant properties; 3) achieve recellularization of the mitral valve scaffold and direct differentiation and maturation through bioreactor preconditioning. First, a complete decellularization of porcine mitral valves was established and optimized to remove all cellular and nuclear material from the scaffolds while still preserving ECM components and basal lamina proteins. Treatment with PGG recovered lost mechanical integrity due to the decellularization process. Seeded cells were able to grow and proliferate on and in the acellular scaffold confirming cytocompatibility. An in vivo rat study was conducted to evaluate the scaffolds\u27 biocompatibility. In comparing non-treated and PGG-treated groups, PGG –treatment regularly and significantly showed increased resistance to degradation, polarization of macrophages to the pro-healing M2 phenotype, discouragement of inflammatory markers, and no limitations towards cell infiltration. Lastly, PGG-treated acellular scaffolds were recellularized with pre-differentiated fibroblasts and endothelial cells and placed in a newly developed mitral valve bioreactor. Design of the bioreactor required a full understanding and appreciation for the four tissue types present in the mitral apparatus. Preconditioning of the seeded constructs yielded a mitral construct similar to a native valve. The overarching goal of this research was to develop a stable mitral valve construct. It is expected that the progress made by this project will have a positive impact on those that suffer from mitral valve pathologies. Our translatable approach towards this tissue engineered mitral valve should allow clinicians to readily adopt this regenerative replacement and contribute as a whole to the field of cardiovascular tissue engineering