ABSTRACT RESUBMISSION 1R21 HL164436-01 IN RESPONSE TO NHLBI “NOT-HL-21-024 BOLD AND NEW BIOENGINEERING RESEARCH” In contrast with other organs, preservation times of lung grafts for transplantation are limited to no more than 8 hours with standard cold preservation. Declining quality with extending preservation times increases the risk of primary graft dysfunction, a risk factor for developing chronic rejection, which could account for the low 5-year survival rate (50%) following lung transplantation (LTx). Ex Vivo Lung Perfusion (EVLP) is expected to improve lung preservation and transplant outcomes by providing normothermic circulation and ventilation. A problem is that current EVLP is self-limited by normothermia-activated lung metabolism. The accumulation of toxic metabolites leads to a proinflammatory state, activating Receptor of Advanced Glycation End-Products (RAGE) and nuclear factor (NF)-B mechanisms, which in turn upregulate proinflammatory cytokine signaling. Experimentally, cross-circulation of a whole swine with EVLP by others demonstrated improved lung resuscitation, but the exact contributors to this improvement remain unclear. Own in vitro preliminary data suggest a role for hepatic function in enhancing endothelial preservation. In previous work, we have maintained normal hepatic detoxification, synthesis, and regulation in in vitro circuits using liver cell bioreactors (BRx). We hypothesize first that the liver function in the swine cross-circulation model played a major role in enhancing EVLP and tissue viability. We also hypothesize that a hepatocyte BRx can partly substitute for whole-swine liver function on EVLP and maintain the observed improvements lung preservation and LTx outcomes. Our Specific Aim is to provide proof-of-principle for the ability of hepatocyte BRx to enhance lung graft preservation. We will incorporate a hepatic BRx in our established EVLP circuits and demonstrate its effect on short-term LTx in experimental rat models. We will repeat these experiments using a cadaveric human EVLP model. We will conduct comprehensive phenotypic, transcriptional, and functional endpoint assessments on lung tissue and hepatic cells in BRx, such as RAGE and NF-B. If successful, our technology will provide the means to change the current state of EVLP for lung preservation and allow lungs to be maintained longer outside the donor body with less cellular injury. Ultimately, our work will address current limitations in LTx, including increasing viable donor organ transportation time and distance, helping reduce LTx waiting lists, and improving post-transplant patient survival.

NARRATIVE Lung tissue removed for transplantation currently cannot be preserved for more than 8 hours, and even then, damage to the lung tissue likely contributes to the low survival rate following lung transplantation (50% of patients do not survive more than 5 years). Our studies seek to improve lung tissue preservation and transplant outcomes; we will test using a liver cell bioreactor to improve lung tissue metabolism and reduce inflammation while the lungs are being transported for transplantation. Ultimately, our work will address current limitations in lung transplantation by helping to extend donor organ transportation time and distance beyond 8 hours and to improve post-transplant patient survival.