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 P a O 2 :FiO 2 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.

中文翻译：

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体外人灌注肺产生促炎介质的内源性能力

背景 离体人体灌注肺模型已经能够优化供体肺用于移植和描绘肺损伤的机制。灌注液和空域生物标志物是肺对实验条件的反应的代表。然而，缺乏评估灌注期间和暴露于刺激后的生物标志物动力学的研究。在这项研究中，我们分析了体外灌注肺对三个关键扰动的反应：暴露于灌注回路、外源性新鲜全血和细菌。结果 99 个拒绝移植的肺进行了离体灌注。达到实验条件后一小时，将新鲜全血加入灌注液 (n = 55)。达到目标温度两小时后，将肺炎链球菌加入灌注液 (n = 42) 或空域 (n = 17)。在基线（一旦肺平衡 1 小时，但在添加血液或细菌之前）和 4 小时后收集灌注液和空域样本。白细胞介素 (IL)-6、IL-8、血管生成素 (Ang)-2 和可溶性肿瘤坏死因子受体 (sTNFR)-1 被量化。基线灌注液和空域生物标志物水平差异很大，这与采购前 P a O 2 :FiO 2 比率、冷缺血时间和基线肺泡液清除率 (AFC) 无关。离体灌注 4 小时后，肺表现出持续产生促炎介质。生物标志物水平的变化不受基线供体肺特征（冷缺血时间、基线 AFC）的影响，也与实验性上皮（最终 AFC）或内皮（体重增加百分比）损伤的测量值无关。在有外源血的情况下，生物标志物的上升减弱。与对照肺相比，暴露于静脉内 (IV) 细菌的肺表现出灌注液 IL-6 的显着升高。结论 体外灌注肺在短期灌注过程中具有显着的内源性产生炎症介质的能力，不受供体肺特征或外源性血液的影响，并且仅受引入全身性菌血症的影响很小. 生物标志物变化与供体肺冷缺血时间、最终肺泡液清除率和实验体重增加百分比之间缺乏关联表明，人肺产生生物标志物的能力不仅是肺上皮或内皮损伤的标志物，而且可能支持肺作为免疫细胞库的功能。