PROJECT SUMMARY Pulmonary hypertension (PH) is characterized by progressive pulmonary vascular remodeling that leads to exertional dyspnea, severe hypoxemia, and ultimately to right heart failure and death. For patients with PH and significant remodeling, treatment options are limited and new therapies urgently needed. This proposal examines a novel mechanobiological feedback mechanism involving signaling by YAP (Yes-associated protein) and TAZ (transcriptional co-activator with PDZ-binding motif) that may be critical in PH development. Pulmonary artery (PA) stiffness causes right ventricular stress and is associated with increased PH mortality. Utilizing atomic force microscopy on PH lung slices, Dr. Dieffenbach has demonstrated increased PA stiffness at the cellular level in human PH and early local arterial stiffening in rodent PH models. Furthermore, increased matrix stiffness drives remodeling phenotypes in pulmonary artery smooth muscle cells and endothelial cells, indicating that PA stiffness itself can fundamentally bias cells towards pathologic behaviors. Dr. Dieffenbach has recently found that stiffness-dependent phenotypes require signaling by YAP and TAZ, transcriptional modifiers activated by mechanical stress. These data led to the hypothesis that YAP and TAZ are key sensors of the PA local mechanical microenvironment and drivers of pathologic arterial remodeling. This investigation focuses on the scope and mechanism of microenvironment-driven YAP/TAZ activation, and furthermore whether YAP/TAZ inhibition can arrest or reverse vascular remodeling in vivo. In the first aim, Dr. Dieffenbach will use cutting-edge bioengineering techniques to investigate microenvironment-driven remodeling phenotypes and their dependence on intact YAP/TAZ signaling. In the second aim, he will study specific downstream mechanisms that mediate the pro-remodeling effects of YAP/TAZ mechanoactivation. Finally, in the third aim, he will determine the impact of inhibiting YAP/TAZ activity in vivo in rodent PH models. This research will be performed at Brigham and Women’s Hospital, a core teaching hospital of Harvard Medical School, and at the Harvard School of Public Health. Dr. Dieffenbach will work under the mentorship of Dr. Fredenburgh, an expert in pulmonary vascular biology and pulmonary disease modeling, and Dr. Fredberg, an expert in bioengineering, cellular dynamics, and mechanobiology. With the guidance of his mentors and scientific advisory committee, Dr. Dieffenbach has developed a comprehensive five-year training program that includes mentored research, didactic coursework, seminars, presentations at scientific meetings, manuscript preparation, and future grant planning. Dr. Dieffenbach is dedicated to a career in academi...