COMPENSATORY GROWTH OF PORCINE RIGHT LUNGS AFTER CHRONIC REJECTION OFTRANSPLANTED LEFT LUNGS

Neonatal lung hypoplasia is frequently a fatal condition often associa ted with congenital diaphragmatic hernia. Unilateral lung transplantat ion rarely has been performed for this indication, although it is a po tential solution. It is not known whether the transplant needs to func tion permanently or to act as a bridge until the native lung develops. It is also not known whether the native lung will grow in the face of an immunosuppressed state and chronic rejection of the transplanted l ung. We therefore developed a porcine model of left lung rejection to study this. Infant swine underwent left lung transplantation. Chronic rejection occurred in all, resulting in nonfunction of the transplante d lung. The right lungs of these animals were compared with the right lungs of size-matched and age-matched control animals not given immuno suppressive treatment and not undergoing transplantation. There were n o differences in terms of the functional residual capacity, airway com pliance, and airway resistance among the groups. There was a significa nt increase in the pulmonary vascular resistance in the animals with t ransplanted lungs. There was also a significant increase in the lung w eight in these animals. Unilateral pneumonectomies were done in 4 infa nt pigs to serve as controls. Three of the 4 did not survive the opera tion because of acute pulmonary failure. In conclusion, the study grou p exhibited evidence of compensatory growth that was not seen in the c ontrol animals, as shown by the increase in lung weight. This suggests that contralateral lung growth occurs in a growing animal, despite th e effects of immunosuppression therapy and chronic rejection of the tr ansplanted lung.