PROJECT SUMMARY: Pulmonary arterial hypertension (PAH), a rare pulmonary vascular disease, was first reported more than 150 years ago. However, PAH remains incurable, even in this modern era of medicine. A prerequisite to the development of effective anti-PAH therapeutics is a firmer grasp of the intrinsic and environmental factors that cause the disease, including the basis of the sex-disparity in PAH−the disease disproportionately affects women. Approaches to understanding PAH biology and developing PAH drugs have traditionally used various cellular and animal models. Both have shortcomings in terms of relevance to human PAH, and the use of animal models is burdened with welfare, lead-time, and cost disadvantages. While traditional models have aided in advancing the field of PAH, none of the models capture the pathological alterations that occur in the pulmonary arteries of human PAH patients. Recently, cell-laden microfluidic devices, called “organ- or disease-on-chip”, have been developed to recapitulate the pathologies of various diseases, but not PAH. In the absence of any such device for PAH, we hypothesized that a multichannel microfluidic device seeded with three major human pulmonary arterial cells (PACs)−endothelial, smooth muscle and adventitial cells−could be used as an alternative to traditional models of PAH. In a recent NHLBI- funded study, we tested this hypothesis by growing three major PACs in a microfluidic device, “PAH-on-a-chip”, prepared using the elastomer polydimethylsiloxane (PDMS). We showed that our PAC-laden device can capture the major pathologies of PAH, including mis-localized growth of PACs, plexiform lesions, and sex-based differences in PAH pathology and therapy. However, this PDMS PAH-on-a-chip is limited to small, lab-scale studies because PDMS is not amenable to large-scale fabrication. PDMS can also affect the experimental outcome by absorbing/adsorbing various molecules from the circulating fluid or by deforming upon contact with solvents. Thus, we propose a second-generation PAH-on-a-chip for scale up: one composed of a thermoplastic polymer, cyclic olefin copolymer (COC), that has superior mechanical properties and optical transmissivity, does not undergo deformation, and, importantly, is amenable to mass production. We will use a Computer Numerical Control (CNC) milling machine and injection molding for fabricating the COC chips. Subsequently, we will validate the chip by seeding PACs and creating various PAH-mimicking pathologies as well as the sex disparity. We will also utilize the chip for investigating the therapeutic efficacy of anti-PAH medications. This is an extraordinarily innovative study that will deploy the ingenuity of microfluidic engineering to elucidate the complexity of PAH biology while addressing the NIH Precision Medicine Initiative and the FDA 2021 Modernization Act. If successful, our mass-produced PAH- on-a-chip will spur a shift in the experimental tools used to study various typ...