Effects of immediate versus delayed ex-vivo lung perfusion in a porcine cardiac arrest donation model

Advances in Xenotransplantation: Evaluation of αGal-KO Porcine Livers and Lungs Using Normothermic Machine Perfusion in a Collaborative Perfusion Hub

Recently, initial clinical experience has been gained with the xenotransplantation of pig organs such as heart and kidney into terminally ill human patients in an effort to overcoming organ shortage. Here, we investigated the use of normothermic machine perfusion (NMP) to advance xenotransplantation research and develop bridging therapies for acute organ failure such as the use of pig livers as a liver dialysis system. We simultaneously analyzed livers and lungs from genetically modified pigs, carrying a knock-out of the GGTA1 gene, which is essential for xenoreactive αGal-KO-epitopes, by applying clinically established normothermic perfusion systems, solutions and human blood. Experiments involved perfusing organs with cell-free solutions as well as human erythrocyte concentrates for up to six hours, analyzing organ quality using invasive and non-invasive methods, and the isolation and analysis of immune cells from the perfusate. The results obtained show stable flow characteristics with physiological perfusion and oxygenation levels of the organs, and a largely intact organ architecture, confirmed by histological sections before and after perfusion. Overall, this study demonstrates the feasibility of normothermic machine perfusion of xenogeneic organs by an interdisciplinary team, thus paving the way for clinical applications of porcine xenografts involving NMP.

Modeling the Effects of IL-1β-mediated Inflammation During Ex Vivo Lung Perfusion Using a Split Human Donor Model

BACKGROUND

The association between interleukin-1β (IL-1β) concentrations during ex vivo lung perfusion (EVLP) with donor organ quality and post-lung transplant outcome has been demonstrated in several studies. The mechanism underlying IL-1β-mediated donor lung injury was investigated using a paired single-lung EVLP model.

METHODS

Human lung pairs were dissected into individual lungs and perfused on identical separate EVLP circuits, with one lung from each pair receiving a bolus of IL-1β. Fluorescently labeled human neutrophils isolated from a healthy volunteer were infused into both circuits and quantified in perfusate at regular timepoints. Perfusates and tissues were subsequently analyzed, with perfusates also used in functional assays.

RESULTS

Neutrophil numbers were significantly lower in perfusate samples collected from the IL-1β-stimulated lungs consistent with increased neutrophil adhesion ( P = 0.042). Stimulated lungs gained significantly more weight than controls ( P = 0.046), which correlated with soluble intercellular adhesion molecule-1 (R 2 = 0.71, P = 0.0043) and von-Willebrand factor (R 2 = 0.39, P = 0.040) in perfusate. RNA expression patterns for inflammatory genes were differentially regulated via IL-1β. Blockade of IL-1β significantly reduced neutrophil adhesion in vitro ( P = 0.025).

CONCLUSION

These data illustrate the proinflammatory functions of IL-1β in the context of EVLP, suggesting this pathway may be susceptible to therapeutic modulation before transplantation.

Composition of ex vivo perfusion solutions and kinetics define differential cytokine/chemokine secretion in a porcine cardiac arrest model of lung preservation

Background

Ex vivo lung perfusion (EVLP) uses continuous normothermic perfusion to reduce ischemic damage and to improve post-transplant outcomes, specifically for marginal donor lungs after the donation after circulatory death. Despite major efforts, the optimal perfusion protocol and the composition of the perfusate in clinical lung transplantation have not been identified. Our study aims to compare the concentration levels of cytokine/chemokine in different perfusion solutions during EVLP, after 1 and 9 h of cold static preservation (CSP) in a porcine cardiac arrest model, and to correlate inflammatory parameters to oxygenation capacities.

Methods

Following cardiac arrest, the lungs were harvested and were categorized into two groups: immediate (I-EVLP) and delayed EVLP (D-EVLP), after 1 and 9 h of CSP, respectively. The D-EVLP lungs were perfused with either Steen or modified Custodiol-N solution containing only dextran (CD) or dextran and albumin (CDA). The cytokine/chemokine levels were analyzed at baseline (0 h) and after 1 and 4 h of EVLP using Luminex-based multiplex assays.

Results

Within 4 h of EVLP, the concentration levels of TNF-α, IL-6, CXCL8, IFN-γ, IL-1α, and IL-1β increased significantly (P < 0.05) in all experimental groups. The CD solution contained lower concentration levels of TNF-α, IL-6, CXCL8, IFN-γ, IL-2, IL-12, IL-10, IL-4, IL-1RA, and IL-18 (P < 0.05) compared with those of the Steen solution. The concentration levels of all experimental groups have correlated negatively with the oxygenation capacity values (P < 0.05). Protein concentration levels did not reach statistical significance for I-EVLP vs. D-EVLP and CD vs. CDA solutions.

Conclusion

In a porcine cardiac arrest model, a longer period of CSP prior to EVLP did not result in an enhanced protein secretion into perfusates. The CD solution reduced the cytokine/chemokine secretion most probably by iron chelators and/or by the protecting effects of dextran. Supplementing with albumin did not further reduce the cytokine/chemokine secretion into perfusates. These findings may help in optimizing the preservation procedure of the lungs, thereby increasing the donor pool of organs.

Evaluation of 10°C as the optimal storage temperature for aspiration-injured donor lungs in a large animal transplant model

BACKGROUND

Our recent work has challenged 4°C as an optimal lung preservation temperature by showing storage at 10°C to allow for the extension of preservation periods. Despite these findings, the impact of 10°C storage has not been evaluated in the setting of injured donor lungs.

METHODS

Aspiration injury was created through bronchoscopic delivery of gastric juice (pH: 1.8). Injured donor lungs (n = 5/group) were then procured and blindly randomized to storage at 4°C (on ice) or at 10°C (in a thermoelectric cooler) for 12 hours. A third group included immediate transplantation. A left lung transplant was performed thereafter followed by 4 hours of graft evaluation.

RESULTS

After transplantation, lungs stored at 10°C showed significantly better oxygenation when compared to 4°C group (343 ± 43 mm Hg vs 128 ± 76 mm Hg, p = 0.03). Active metabolism occurred during the 12 hours storage period at 10°C, producing cytoprotective metabolites within the graft. When compared to lungs undergoing immediate transplant, lungs preserved at 10°C tended to have lower peak airway pressures (p = 0.15) and higher dynamic lung compliances (p = 0.09). Circulating cell-free mitochondrial DNA within the recipient plasma was significantly lower for lungs stored at 10°C in comparison to those underwent immediate transplant (p = 0.048), alongside a tendency of lower levels of tissue apoptotic cell death (p = 0.075).

CONCLUSIONS

We demonstrate 10°C as a potentially superior storage temperature for injured donor lungs in a pig model when compared to the current clinical standard (4°C) and immediate transplantation. Continuing protective metabolism at 10°C for donor lungs may result in better transplant outcomes.

Endothelin-Converting Enzyme 1 and Vascular Endothelial Growth Factor as Potential Biomarkers during Ex Vivo Lung Perfusion with Prolonged Hypothermic Lung-Sparing

Lung transplantation requires optimization of donor's organ use through ex vivo lung perfusion (EVLP) to avoid primary graft dysfunction. Biomarkers can aid in organ selection by providing early evidence of suboptimal lungs during EVLP and thus avoid high-risk transplantations. However, predictive biomarkers of pulmonary graft function such as endothelin-converting enzyme (ECE-1) and vascular endothelial growth factor (VEGF) have not been described under EVLP with standard prolonged hypothermic preservation, which are relevant in situations where lung procurement is difficult or far from the transplantation site. Therefore, this study is aimed at quantifying ECE-1 and VEGF, as well as determining their association with hemodynamic, gasometric, and mechanical ventilatory parameters in a swine model of EVLP with standard prolonged hypothermic preservation. Using a protocol with either immediate (I-) or delayed (D-) initiation of EVLP, ECE-1 levels over time were found to remain constant in both study groups (p > 0.05 RM-ANOVA), while the VEGF protein was higher after prolonged preservation, but it decreased throughout EVLP (p > 0.05 RM-ANOVA). Likewise, hemodynamic, gasometric, mechanical ventilatory, and histological parameters had a tendency to better results after 12 hours of hypothermic preservation in the delayed infusion group.

Custodiol-MP for ex vivo lung perfusion - A comparison in a porcine model of donation after circulatory determination of death

INTRODUCTION

Ex vivo lung perfusion (EVLP) is an established technique to evaluate and eventually recondition lungs prior to transplantation. Custodiol-MP (C-MP) solution is a new solution, designed for clinical machine perfusion, that has been used for kidneys. The aim of this study was to compare the effects of EVLP with Custodiol-MP on lung functional outcomes to the gold standard of EVLP with Steen Solution™.

MATERIAL AND METHODS

In a porcine EVLP model of DCDD (Donation after Circulatory Determination of Death), lungs were perfused with Steen Solution™ (SS, n = 7) or Custodiol-MP solution supplemented with 55 g/l albumin (C-MP, n = 8). Lungs were stored cold for 4 h in low potassium dextran solution and subsequently perfused ex vivo for 4 h. During EVLP pulmonary gas exchange, activities of lactate dehydrogenase (LDH) and alkaline phosphatase (AP) as well as levels of lactate in the perfusate were recorded hourly.

RESULTS

Oxygenation capacity differed significantly between groups (averaged over 4 h: SS 274 ± 178 mmHg; C-MP 284 ± 151 mmHg p = 0.025). Lactate dehydrogenase activities and lactate concentrations were significantly lower in Custodiol-MP perfused lungs.In a porcine model of DCDD with 4 h of EVLP the use of modified Custodiol-MP as perfusion solution was feasible. The use of C-MP showed at least comparable lung functional outcomes to the use of Steen SolutionTM. Furthermore C-MP perfusion resulted in significantly lower lactate dehydrogenase activity and lactate levels in the perfusate and higher oxygenation capacity.

Normothermic machine perfusion of donor-lungs ex-vivo: promoting clinical adoption

PURPOSE OF REVIEW

Lung transplantation offers the only realistic therapeutic option for patients with end-stage lung disease. However, this is impacted by a shortfall in availability of suitable donor-lungs. Normothermic machine perfusion of donor-lungs outside the donor body also known as ex-vivo lung perfusion (EVLP) offers a potential solution through objective assessment, reconditioning and treatment of donor-lungs initially deemed unsuitable for use. This review discusses key advances and challenges in the wider clinical adoption of this technology.

RECENT FINDINGS

This review will summarize key research within the following areas: recent clinical trials utilizing EVLP, logistical challenges, EVLP protocol innovations, novel assessment methods and current research into therapeutic modulation of lung function during EVLP.

SUMMARY

Normothermic machine perfusion of donor-lungs ex-vivo offers a promising platform to assess and modulate donor-lung quality prior to transplantation. Consensus on how and when to best utilize EVLP is yet to be reached, meaning that widespread clinical adoption of the technology has not yet become a reality. Further work is needed on agreed indications, perfusion protocols and organization of services before becoming a regularly used procedure prior to lung transplantation.