| The aortic valve regulates the unidirectional flow of oxygenated blood from the left ventricle to the systemic circulation. When severe congenital defects occur in aortic valves, valve replacement is inevitable in children. However, current options including mechanical valves and bioprosthetic valves, lack the ability to grow and remodel, which necessitates multiple valve replacements as children grow. Tissue engineering provides a possible avenue to generate a living valve substitute that can grow and remodel via combining cells, scaffolds and environmental cues. The cells used in this work were valvular interstitial cells (VICs), the predominant cell population in the valves, and responsible for extracellular matrix (ECM) synthesis in the valve tissue. VICs are highly heterogeneous and dynamic in phenotype, with the majority assuming a quiescent, fibroblast phenotype in healthy adult valves. During valve injury or disease conditions, VICs may undergo myofibroblast activation or osteogenic differentiation. Myofibroblast activation is characterized by the expression of smooth muscle alpha-actin (alphaSMA), and may cause valve fibrosis; osteogenic differentiation is characterized by the upregulation of alkaline phosphatase (ALP), followed by tissue calcification, which is the leading cause of valve disease in the elderly (>60 years of age) and the failure of bioprosthetic valves. However, the most common method of in vitro VIC culture on two-dimensional (2D) stiff substrates leads to myofibroblast activation of VICs. For better physiological relevance and future application in valve substitutes, there is a need to understand and regulate VIC behaviors within three-dimensional (3D) scaffolds that are more reminiscent to their native environments. This dissertation describes the development of a poly(ethylene glycol) (PEG)-based hydrogel platform to support VIC growth in 3D, and the exploration of free and immobilized bioactive cues to dictate VIC phenotype and behaviors toward the development of a living valve substitute. (Abstract shortened by ProQuest.). |
