The endogenous capacity to produce proinflammatory mediators by the ex vivo human perfused lung

Abstract

Background The ex vivo human perfused lung model has enabled optimizing donor lungs for transplantation and delineating mechanisms of lung injury. Perfusate and airspace biomarkers are a proxy of the lung response to experimental conditions. However, there is a lack of studies evaluating biomarker kinetics during perfusion and after exposure to stimuli. In this study, we analyzed the ex vivo-perfused lung response to three key perturbations: exposure to the perfusion circuit, exogenous fresh whole blood, and bacteria. Results Ninety-nine lungs rejected for transplantation underwent ex vivo perfusion. One hour after reaching experimental conditions, fresh whole blood was added to the perfusate (n = 55). Two hours after reaching target temperature, Streptococcus pneumoniae was added to the perfusate (n = 42) or to the airspaces (n = 17). Perfusate and airspace samples were collected at baseline (once lungs were equilibrated for 1 h, but before blood or bacteria were added) and 4 h later. Interleukin (IL)-6, IL-8, angiopoietin (Ang)-2, and soluble tumor necrosis factor receptor (sTNFR)-1 were quantified. Baseline perfusate and airspace biomarker levels varied significantly, and this was not related to pre-procurement PaO2:FiO2 ratio, cold ischemia time, and baseline alveolar fluid clearance (AFC). After 4 h of ex vivo perfusion, the lung demonstrated a sustained production of proinflammatory mediators. The change in biomarker levels was not influenced by baseline donor lung characteristics (cold ischemia time, baseline AFC) nor was it associated with measures of experimental epithelial (final AFC) or endothelial (percent weight gain) injury. In the presence of exogenous blood, the rise in biomarkers was attenuated. Lungs exposed to intravenous (IV) bacteria relative to control lungs demonstrated a significantly higher rise in perfusate IL-6. Conclusions The ex vivo-perfused lung has a marked endogenous capacity to produce inflammatory mediators over the course of short-term perfusion that is not significantly influenced by donor lung characteristics or the presence of exogenous blood, and only minimally affected by the introduction of systemic bacteremia. The lack of association between biomarker change and donor lung cold ischemia time, final alveolar fluid clearance, and experimental percent weight gain suggests that the maintained ability of the human lung to produce biomarkers is not merely a marker of lung epithelial or endothelial injury, but may support the function of the lung as an immune cell reservoir.

Molecular programs of fibrotic change in aging human lung

“…S1d). We have also previously reported in a study of 99 lungs that cold ischemia time did not have any effect on the level of cytokines produced by the intact lung in response to proinflammatory stimuli delivered by whole-lung perfusion 18 . Next, correlation analyses were done to confirm that time to cryopreservation did not correlate with gene expression of the senescence markers or the apoptosis and necrosis signatures from IPA (Fig.…”

Effects of cold or warm ischemia and ex-vivo lung perfusion on the release of damage associated molecular patterns and inflammatory cytokines in experimental lung transplantation

“…A candidate might be mitochondrial DNA, which has been detected in the EVLP perfusate of rat lungs (35), and in the BAL and plasma following LTx (36,37). Another possibility is that inflammation arises during EVLP independently from DAMP release, for example through the activation of the enzyme poly(ADP-ribose) polymerase (PARP), as recently proposed by our group (5,38), or could simply reflect the presence of endogenous inflammatory cells in the graft (39).…”

“…Second, we measured biomarkers in the airways and not in the circulation, where the results could have been different. Direct measurements of the graft production of mediators by sampling the pulmonary vein would be even more instructive in this respect (9,39). A third limitation may be related to our procedure of exsanguination of the animals before lung procurement, which may have removed a potential reservoir of immune cells inside the lung and thus may have influenced the inflammatory response.…”

Auto‐inflammation and auto‐immunity pathways are associated with emergence of BOS in pediatric lung transplantation

“…Similarly, sTNFRI is a known mediator of damage and inflammation in the lung. It has been linked to a number of inflammatory pathologies of the lung, including acute lung injury (ALI) and idiopathic pulmonary fibrosis (IPF) 22 , 23 . Our data implicate an association of higher levels of IL‐31, a cytokine associated with fibrosis (as shown in Figure 7), are associated with developing BOS.…”