Calcified aortic valve disease (CAVD) is an increasingly prevalent pathology that often manifests in the degenerative calcification of the valve tissue. Currently, the only treatment for aortic valve calcification is surgical intervention, and a clinically useful molecular signature of CAVD progression has not yet been found. Recent clinical trials testing lipid-lowering therapies were ineffective against aortic stenosis progression, which emphasizes that CAVD may undergo a distinctly different pathogenesis from that of atherosclerosis. While CAVD is no longer believed to be a passive degenerative process, the cellular mechanisms by which the valve calcifies are not wholly understood. There remains a need to understand cellular mechanisms of valve pathogenesis, as well as an in-depth analysis of the altogether unique calcified lesions that form as a result of the disease. The focus of this dissertation was the development of a 3D construct in which the interplay between valve endothelial (VEC) and valve interstitial cells (VIC) could be illuminated in various calcification-prone environments. The completion of this work yielded insights into cellular responses to osteogenic, mineralized, and altered mechanical environments, which could be used to identify potential therapeutic targets or early diagnosis strategies in the future. A 3D hydrogel construct was first developed for the co-culture of interstitial and endothelial cells, which is more physiologically relevant than current 2D models. Under osteogenic conditions, endothelial cells were found to have a protective effect against VIC activation and calcification (Chapter 2). Next, the mineralized lesions and surrounding organic tissue in calcified valves were characterized and found to have a heterogeneous composition of apatite and calcium phosphate mineral crystals (Chapter 3). These findings prompted the use of synthetically derived hydroxyapatite nanoparticles of two different maturation states in order to better evaluate cellular response to a highly mineralized matrix, characteristic of later stages of valve disease (Chapter 4). Finally, the effects of an altered mechanical environment, as is typical in valve disease, were examined by increasing mechanical tension in 3D hydrogel constructs and applying cyclic mechanical strain (Chapter 5). Overall, this body of work has made significant advancements in understanding individual and incorporative cellular responses to osteogenic, mineralized and mechanical 3D environments. This work has contributed to the emerging appreciation that 3-dimensional multi-cellular co-cultures are vital to mechanistic understanding of valve pathogenesis. Our 3D platform shows great promise for future studies, and could enable direct screening of molecular mechanisms of calcification and testing of potential molecular inhibitors.