Project Summary: The ductus arteriosus (DA) is a critical vascular shunt connecting the pulmonary and systemic circulations during fetal life. At birth, the DA must close to allow adequate perfusion of the newly inflated lungs. However, the DA fails to close in some cases, a condition termed patent ductus arteriosus (PDA). PDA is a significant cardiovascular disorder affecting 1 out of every 500-2000 term infants and 30-40% of the most critically ill premature neonates. Current therapies are limited and have worrisome off-target effects. Work over the past thirty years has identified the ?master regulators? of DA patency, namely oxygen, prostaglandins, and nitric oxide signaling. However, the clinical conundrum of PDA persists, suggesting there are other unidentified critical regulators of DA tone. The DA experiences a unique set of biomechanical forces that set it apart from all other vessels in the body. Blood flow patterns and vessel wall stretching changes dramatically during the course of DA closure. And yet, mechanosensing has not been previously investigated as a regulator of DA tone. Others have identified a class of ion channels, KATP channels, that sense and respond to changes in biomechanical forces in endothelial and smooth muscle cells. We demonstrated that the DA is sensitive to changes in biomechanical forces and that KATP channels are enriched in the DA and serve to regulate tone. Moreover, humans with mutations in KATP channel genes suffer from Cantu Syndrome, a disorder characterized by PDA. Therefore, the major hypothesis of this proposal is that KATP channels regulate DA tone by acting as novel biomechanical sensors that trigger DA closure and drive circulatory adaptation at birth. We will address this hypothesis using primary DA endothelial and smooth muscle cells cultured in microfluidic or stretch devices. These experiments will elucidate the parameters under which DA KATP channels are activated or inhibited by specific hemodynamic forces. Additionally we will move from individual cells to intact DAs via flow-myography experiments in order to determine the molecular mechanism underlying KATP channel mechanosensing in the DA. Taken together, these studies will identify a previously unknown role for KATP channels as biomechanical sensors in the DA. Moreover, by determining the molecular mechanisms of KATP channel mechanosensing, these studies will place KATP channels within the hierarchy of established regulators of DA tone and add a novel biomechanical component to the current paradigm of DA closure. Finally, these studies will allow us to integrate our findings into the pathophysiology of PDA in humans to gain a more complete understanding of the PDAs that often occur in pre-term infants and Cantu syndrome patients with the hopes of developing more efficient therapeutic options.