The endothelium is the cellular monolayer that covers the inner lining of the entire circulatory system. Endothelial dysfunction is a feature of pulmonary arterial hypertension (PAH), a life-threatening disease associated with abnormally high pulmonary pressures and chronic right heart failure. Due to the limitations of available static cell culture and animal models, our understanding of the mechanisms that orchestrate the initiation and perseverance of endothelial dysfunction in PAH remains incomplete. Given that endothelial dysfunction is a common finding in PAH, an understanding of the mechanism behind maladaptive endothelial responses could help accelerate the discovery of novel therapies for PAH. Presently, it is believed that endothelial derived exosomes contribute to PAH by carrying signals that trigger maladaptive endothelial responses in the setting of injury. Exosomes are cell-derived small (~30-150 nm) extracellular vesicles that carry proteins, metabolites and nucleic acids involved in a variety of physiological and pathological processes. While it is known that exosomes carry molecular and genetic factors associated with angiogenesis, inflammation and vasoreactivity, a comprehensive assessment of exosome cargo of healthy and dysfunctional PMVECs has been hindered by current low-yield exosome isolation techniques. These techniques cannot perform real-time dynamic exosome isolation from pulmonary microvascular endothelial cells (PMVECs) exposed to PAH-associated stressors. To address this unmet need, we have designed the MFES (Multifunctional Exosome Sorter) that can dissect the whole exosome population into subpopulations based on size and surface markers. MFES is the first lab-on-a-chip platform that integrates: 1) a vessel-on-a-chip module for real-time characterization of PMVEC functional responses across a wide range of physiological and pathological parameters, 2) a module for high-yield exosome size-based isolation, 3) a surface marker based exosome sorting using magnetic beads, and 4) multi-omics phenotyping of exosomes of PMVECs. Here, we are proposing a technology that can enable broadly to investigate the two main defining characteristics of exosomal subtypes, i.e., size and surface markers, both separately independently, and in combination sequentially. We will characterize changes in exosome cargo in healthy and PAH PMVECs exposed to shear stress-related conditions in the MFES. We will isolate subpopulations of exosomes based on size and surface markers and characterize them for their cargo (Aim 1). Then, we will determine whether exosomes derived from stressed PMVECs can induce pathological changes in healthy PMVECs cultured in a microfluidic culture chip (Aim 2). This technological innovation enables to study endothelial exosome biology in a setting that represents the flow dynamics associated with PAH. Further, the use of cutting-edge -omics technologies, bioinformatic analysis integrated with machine learning algorith...