3D Printed Hydrogel Micro-Environments And Bioreactor Conditioning To Develop Native Heterogeneity In Tissue Engineered Heart Valves

Heart valve disease is a tremendous national and global burden. Prosthetic replacement is essentially the only treatment for a critically damaged or malformed valve, and current aortic valve replacement options for pediatric patients are grimly inadequate. Tissue engineering has the potential to generate living heart valve replacements capable of growth and integration needed to treat children with valve disease. Over the last 15 years, researchers have developed and implemented novel synthetic polymers as scaffolds for engineered heart valves. Although much progress has been made, a persistent problem is the difficulty incorporating native-like heterogeneity and controlled remodeling into TEHV. The work presented here demonstrates a 3D bioprinting approach that generates complex 3D geometry tissue constructs using extrudable materials and encapsulated cells based on native aortic valve tissue heterogeneity. As a fabrication strategy 3D printing overcomes the limitations associated with classical heart valve tissue engineering assembly of scaffolds. To enable direct cell-hydrogel printing and thereby maximize geometric control within valve constructs, viability experiments were used to establish photoencapsulation fabrication parameters tolerated by cells. Photocrosslinking experiments demonstrate that contrary to numerous 2D cytotoxicity studies, in a 3D hydrogel culture environment and fabrication setting, Irgacure 2959 photoinitiator can produce more viable encapsulated cells than VA086 photoinitiator in a higher stiffness hydrogel. A dynamic conditioning system designed specifically for the culture of 3D bioprinted valves was 1st validated using porcine aortic heart valves. Photoencapsulation viability experiments and bioreactor validation studies presented in this work provide a range of fabrication and conditioning parameters, that were utilized for the fabrication and dynamic culture of 3D bioprinted hydrogel heart valves. Our studies indicate that the bioprinted valves can be produced with high viability encapsulated mesenchymal stem cells for the purposes of a TEHV or with primary aortic valve cells for the purpose of in vitro testing and mechanistic study