Lung transplantation is increasingly used to treat an expanding list of end-stage lung diseases, resulting in an over >50% increase in the number of lung transplant procedures in the US in the last decade. Unfortunately, survival following lung transplant is the worst amongst solid organs with only 80% and 50% of patients alive at 1 and 5 years, respectively. Primary graft dysfunction (PGD) affects over 50% of recipients within 24 hours of transplantation and has emerged as the most important risk factor for both short-term mortality and long-term graft loss from chronic lung allograft dysfunction (CLAD). The investigators in this PPG have made important contributions to a growing molecular understanding of the complex interplay between immune and lung parenchymal cells that underlie PGD and CLAD. In Project 1, we dissect molecular mechanisms underlying our discovery that lung restricted alloantibodies (LRA), present in over 30% of lung transplant recipients, are associated with PGD. In Project 2, we dissect physiologic and molecular mechanisms underlying prevalent abnormalities in esophageal function that lead to acid aspiration and worsen CLAD severity. In Project 3, we will credential profibrotic MoAMs as causal drivers of lung fibrosis in murine models and in patients with CLAD. In Project 4, ESI, we test whether mitochondrial dysfunction in the alveolar epithelium predisposes lung transplant recipients to pathologic activation of the integrated stress response (ISR) that precludes lung repair. Together our published and preliminary data support our overarching hypothesis that acute neutrophil-mediated lung injury mechanisms such as PGD and acid aspiration drive CLAD progression by promoting the development of LRA, recruiting profibrotic MoAM, and inducing epithelial cell mitochondrial damage causing an ISR-mediated barrier to epithelial repair. We will test this hypothesis in 4 interrelated and synergistic projects. Project 1. To determine whether LRA interact with donor derived NCM and recipient CM to worsen PGD via the activation of complement dependent and independent pathways. Project 2. To determine whether physiologic abnormalities in the esophagus after lung transplant cause gastric aspiration that induces LRA and CLAD progression via neutrophils and MoAM. Project 3. To determine whether CSF1 drives the recruitment and retention of profibrotic MoAM and whether their detection in bronchoalveolar lavage fluid can serve as a biomarker for CLAD. Project 4. To determine whether mitochondrial dysfunction in the airway and alveolar epithelium results in pathologic activation of the ISR that precludes normal epithelial repair to promote CLAD. The Human and Clinical Phenotyping Core (Core B), Mouse and Cell Phenotyping Core (Core C) and Administrative Core (Core A) will support these synergistic projects using murine models and clinical and molecular data collected from lung transplant recipients to identify actionable pathways that can be therapeutically targeted to improve lung transplant outcomes.

Unfortunately, survival following lung transplantation is the worst amongst solid organs with only 80% and 50% of patients alive at 1 and 5 years, respectively. Acute and chronic rejection, known as primary graft dysfunction (PGD) and chronic lung allograft rejection (CLAD) are the major drivers of these poor outcomes. The PPG investigators seek to identify common mechanisms that cause PGD and CLAD in mouse models and in patients with a goal of identifying new treatments that will improve survival for lung transplant recipients.