Project Summary This R01 proposal outlines a research plan which uses targeted nanomedicine to enhance disease- modifying molecular mechanisms both in the acute injurious phase and in the subsequent chronic fibrotic phase of viral-induced pneumonitis. The overall goal of this proposal is to use nanomedicine to modify specific cellular subtypes during the lung disease process. Acute and chronic lung diseases are major causes of mortality and morbidity in the US. Acute respiratory distress syndrome (ARDS), caused by widespread endothelial barrier disruption and uncontrolled cytokine storm, is the major cause of death in critically ill influenza and COVID-19 patients. Furthermore, pulmonary fibrosis, progressive scarring in injured lung, is a major sequelae of viral pneumonia. Early analyses showed that discharged COVID-19 patients are at high risk for developing pulmonary fibrosis. Currently, there are few pharmacological treatments that directly targets ARDS, and available therapeutic options for pulmonary fibrosis remain suboptimal, underscoring unmet medical needs in a heightened state due to COVID-19 pandemic. Strongly supported by our published and unpublished in vivo results, we believe that targeted nanomedicine approaches have tremendous potential to treat ARDS and pulmonary fibrosis, which will be comprehensively tested in vivo in this application. Aim 1 will test the therapeutic effectiveness of specifically reducing endothelial dysfunction in acute lung injury (influenza or SARS-CoV-2) in mice and perfused human lungs using a VCAM1-targeting, KLF2 mRNA-encapsulated nanoparticles. We anticipate that specific endothelial KLF2 overexpression will reduce acute lung injury. Aim 2 will test the therapeutic effectiveness of specifically targeting lung fibroblasts in chronic pulmonary fibrosis (bleomycin) in mice and human lung slices using PDGFRB-targeting nanoparticles to deliver shRNAs against TXNDC5. We anticipate that specific fibroblast inhibition of TXNDC5 will reduce lung fibrosis.