| Calcific aortic valve disease (CAVD) is the most prevalent aortic valve disorder, yet its etiology remains unclear. The failure to understand the cellular and molecular factors that regulate CAVD etiology and progression is important, because it is directly related to the fact that there is currently no treatment to stop its onset or progression. The study of early CAVD in particular has been limited by the scarcity of human specimens at this disease stage and a lack of physiologically relevant in vivo and in vitro models. The goal of this thesis was to address this need to develop platforms that mimic the early stages of CAVD in order to elucidate the sequence of events in disease progression. First, a swine model of familial hypercholesterolemia was analyzed and found to recapitulate the valvular pathology characteristic of early-stage human CAVD, including lipoprotein deposition/oxidation, inflammation, and extracellular matrix (ECM) disarray characterized by glycosaminoglycan (GAG) enrichment. Based on these findings, complementary bottom-up and top-down approaches were generated, using biomaterials and genetic engineering techniques respectively, to produce GAG-enriched environments. Additionally, a simple and novel method was also developed for the culture of valvular interstitial cells (VICs) to better mimic the VIC behavior observed in healthy leaflets. Through both of these approaches, it was determined that GAG enrichment appears to precede other early hallmarks of the disease. Specifically, the GAG-enriched ECM entraps lipoproteins, and oxidized lipoproteins are then able to induce VIC dysfunction and inflammation. Furthermore, oxidized lipoproteins can also drive further GAG enrichment, forming a positive feedback loop. Both GAG enrichment and oxidized lipoproteins were also shown to contribute to angiogenesis, a late hallmark of the disease. Thus, a complex yet detailed picture of the sequence of events in the pathogenesis of CAVD was elucidated through the use of these platforms. The application of this type of approach to the study of valve disease could also lead to the identification and testing of potential targets for treatment. |
