Hydrogels to Study Synergistic Effects of Signaling Factors and Matrix Mechanics on Valve Disease Progression

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Myofibroblast activation of Valvular Interstitial Cells (VICs) is considered to be a primary driver of valvular fibrosis and stenosis. For this reason, the external cues that act to control the myofibroblast phenotype of VICs have been topics of considerable attention in the field. Increasing evidence suggests that beyond receptor-mediated activation of VICs by soluble growth factors, physical cues from the matrix play a critical role in this process. Unfortunately, traditional methods used to culture VICs inherently leads to their myofibroblast activation, such that it becomes difficult to determine the effects of environmental stiffness on activation and especially de-activation. To address this issue, our group has demonstrated that unique hydrogel materials can be used to create soft, non-activating substrates for VIC culture that allow VICs to maintain a phenotype that more closely resembles that of freshly isolated cells. Now, we aim to examine how matrix stiffness in combination with pro-inflammatory cytokines influence the VIC fibroblast-to- myofibroblast transition, the epigenetic changes that may occur to these cells over time, and the pathways in matrix signaling that might be useful in reversing the pathogenic myofibroblast phenotype. Specifically, we propose to: 1) Use a combinatorial approach to study the effect of pro-inflammatory cytokines on VIC phenotypes as a function of microenvironmental stiffness 2) Identify the effects of mechanical and inflammatory cues on the fibroblast-to-myofibroblast transition and its reversal using hydrogels with dynamically tunable mechanical properties, and 3) Discover new molecular targets for therapeutics to temper pathogenic VIC myofibroblast activation under inflammatory conditions. Together, work completed within each of these Aims will provide unique insight into the progression of fibrotic aortic valvular stenosis. The creation of tunable cell culture platforms will allow us to answer questions about differences between reversible (transient, wound healing state) and irreversible (persistent, pathogenic state) VIC myofibroblasts that cannot be adequately addressed with traditional methods. Subsequent analysis of the signaling pathways and genes will be used to identify new targets with therapeutic potential to reverse VIC activation and treat valve disease. Moreover, successful completion of these Aims should be of general interest to the field of medicine, as mechanisms of fibrosis are likely shared among most fibrosis-related diseases.