Abstract 18488: Metabolic Modulation of the Diseased Human Lung; A Translational, Novel ex vivo Lung Perfusion Model
Introduction: Pulmonary arterial hypertension (PAH) and idiopathic pulmonary fibrosis (IPF) are deadly diseases that often require lung transplantation. Preclinical evidence suggests that mitochondrial suppression underlies the pro-proliferative and anti-apoptotic phenotype of pulmonary artery smooth muscle cells and pulmonary fibroblasts, respectively. Two therapies to improve mitochondrial function are a) dichloroacetate (DCA), an activator of pyruvate dehydrogenase (PDH), the gate-keeping enzyme for glucose oxidation, and b) 4-phenylbutyrate (4-PBA), an inhibitor of endoplasmic reticulum stress, a response that suppresses mitochondrial function during cellular stress. Although these drugs can be studied in vitro or in animals, their metabolic effects on the whole human lung may only by studied through ex vivo lung perfusion (EVLP).
Methods: We used a custom-made EVLP system to study explanted, diseased human lungs of patients undergoing lung transplant for PAH (n=2), or IPF (n=4). The bronchi were connected to a ventilator, while a pump-driven system perfused the pulmonary artery (PA) with modified Krebs-Henseleit buffer or STEEN solution™ in recirculation. Lung biopsies were collected to measure mitochondrial respiration (using a Seahorse analyzer) and PDH activity at baseline, and after drug intervention with DCA or 4-PBA for 1 hour.
Results: In the PAH lungs, hypoxic pulmonary vasoconstriction, a validated marker of lung health, was absent. However administrating the prostacyclin analogue treprostinil reduced PA pressure by 31.6% (at a level of flow corresponding to the patient’s cardiac output), confirming abnormal but present vasoreactivity in the model. DCA caused a 61.1% increase in oxygen consumption, and a 34-fold increase in PDH activity. In IPF lungs, PBA increased oxygen consumption by 62.0%.
Conclusions: EVLP is a feasible model to study the direct effects of drugs on diseased human lungs. Since before-after biopsies are not possible in clinical trials, this is a valuable model to facilitate translation of preclinical therapies to clinical trials. Our results show, for the first time in human lungs, that the metabolic remodeling of the PAH and IPF can be reversed by clinically available small molecules like DCA and 4-PBA.
Author Disclosures: V. Gurtu: None. A. Kinnaird: None. C. White: None. R. Paulin: None. D. Freed: None. J. Nagendran: None. E. Michelakis: None.
- © 2015 by American Heart Association, Inc.