An experimental rat model of ex vivo lung perfusion for the assessment of lungs regarding histopathological findings and apoptosis: low-potassium dextran vs. histidine-tryptophan-ketoglutarate

Ex vivo lung perfusion for donor lung assessment and repair: a review of translational interspecies models

For patients with end-stage lung disease, lung transplantation is a lifesaving therapy. Currently however, the number of patients who require a transplant exceeds the number of donor lungs available. One of the contributing factors to this is the conservative mindset of physicians who are concerned about transplanting marginal lungs due to the potential risk of primary graft dysfunction. Ex vivo lung perfusion (EVLP) technology has allowed for the expansion of donor pool of organs by enabling assessment and reconditioning of these marginal grafts before transplant. Ongoing efforts to optimize the therapeutic potential of EVLP are underway. Researchers have adopted the use of different large and small animal models to generate translational preclinical data. This includes the use of rejected human lungs, pig lungs, and rat lungs. In this review, we summarize some of the key current literature studies relevant to each of the major EVLP model platforms and identify the advantages and disadvantages of each platform. The review aims to guide investigators in choosing an appropriate species model to suit their specific goals of study, and ultimately aid in translation of therapy to meet the growing needs of the patient population.

Lung Protection Strategies during Cardiopulmonary Bypass Affect the Composition of Bronchoalveolar Fluid and Lung Tissue in Cardiac Surgery Patients

Pulmonary dysfunction is among the most frequent complications to cardiac surgeries. Exposure of blood to the cardiopulmonary bypass (CPB) circuit with subsequent lung ischemia-reperfusion leads to the production of inflammatory mediators and increases in microvascular permeability. The study aimed to elucidate histological, cellular, and metabolite changes following two lung protective regimens during CPB with Histidine-Tryptophan-Ketoglutarate (HTK) enriched or warm oxygenated blood pulmonary perfusion compared to standard regimen with no pulmonary perfusion. A total of 90 patients undergoing CPB were randomized to receiving HTK, oxygenated blood or standard regimen. Of these, bronchoalveolar lavage fluid (BALF) and lung tissue biopsies were obtained before and after CPB from 47 and 25 patients, respectively. Histopathological scores, BALF cell counts and metabolite screening were assessed. Multivariate and univariate analyses were performed. Profound histological, cellular, and metabolic changes were identified in all patients after CPB. Histological and cellular changes were similar in the three groups; however, some metabolite profiles were different in the HTK patients. While all patients presented an increase in inflammatory cells, metabolic acidosis, protease activity and oxidative stress, HTK patients seemed to be protected against severe acidosis, excessive fatty acid oxidation, and inflammation during ischemia-reperfusion. Additional studies are needed to confirm these findings.

Inflation with carbon monoxide in rat donor lung during cold ischemia phase ameliorates graft injury

Carbon monoxide (CO) attenuates lung ischemia reperfusion injury (IRI) via inhalation, and as an additive dissolved in flush/preservation solution. This study observed the effects of lung inflation with CO on lung graft function in the setting of cold ischemia. Donor lungs were inflated with 40% oxygen + 60% nitrogen (control group) or with 500 ppm CO + 40% oxygen + nitrogen (CO group) during the cold ischemia phase and were kept at 4℃ for 180 min. Recipients were sacrificed by exsanguinations at 180 min after reperfusion. Rats in the sham group had no transplantation and were performed as the recipients. Compared with the sham group, the oxygenation determined by blood gas analysis and the pressure-volume curves of the lung grafts decreased significantly, while the wet weight/dry weight (W/D) ratio, inflammatory reaction, oxidative stress, and cell apoptosis increased markedly (P < 0.05). However, compared to the control group, CO treatment improved the oxygenation (381 ± 58 vs. 308 ± 78 mm Hg) and the pressure-volume curves (15.8 ± 2.4 vs. 11.6 ± 1.7 mL/kg) (P < 0.05). The W/D ratio (4.6 ± 0.6) and the serum levels of interleukin-8 (279 ± 46 pg/mL) and tumor necrosis factor-α (377 ± 59 pg/mL) in the CO group decreased significantly compared to the control group (5.8 ± 0.8, 456 ± 63 pg/mL, and 520 ± 91 pg/mL) (P < 0.05). In addition, CO inflation also significantly decreased malondialdehyde activity and apoptotic cells in grafts, and increased the superoxide dismutase content. Briefly, CO inflation in donor lungs in the setting of cold ischemia attenuated lung IRI and improved the graft function compared with oxygen.