Lung rehabilitation using xenogeneic cross-circulation does not lead to hyperacute rejection in a human lung transplantation model

Access to life-saving lung transplantation remains limited by a shortage of donor organs. We have previously described rehabilitation of discarded human donor lungs to a quality suitable for transplantation using cross-circulation of whole blood between xeno-support swine and human lungs. However, the immunologic implications of transplanting rehabilitated lungs remain unknown. Human donor lungs declined for clinical transplantation (N=5) underwent xenogeneic cross-circulation for up to 12 hours. To model subsequent human transplantation, lungs were re-exposed to autologous human whole blood via normothermic ex vivo machine perfusion for up to six hours. Upon human blood re-exposure, lungs were evaluated for evidence of hyperacute rejection through physiologic assessments and tissue analyses including histology, immunostaining, and flow cytometry. Upon human blood re-exposure, lungs showed no significant change in physiologic function relative to end of cross-circulation (PaO2/FiO2: P=0.41; vascular resistance: P=0.27; dynamic compliance: P=0.24) and histologic features of hyperacute rejection were absent in all lungs. Despite pulmonary deposition of porcine IgG during cross-circulation, human blood re-exposure resulted in decreased complement deposition (P=0.019) with no change in membrane attack complex formation (P=0.65) or apoptotic signaling (P=0.93). Endothelial integrity was maintained after human blood re-exposure with preservation of microvascular tight junctions, decreasing endothelial injury marker P-selectin (P=0.34), and intact vascular response to alpha adrenergic stimulation. Our findings indicate that transient exposure of human donor lungs to xenogeneic cross-circulation does not result in hyperacute rejection upon simulated human transplantation, representing an important step towards clinical translation of this donor organ rehabilitation platform.