Reconditioning of an injured lung graft with intrabronchial surfactant instillation in an ex vivo lung perfusion system followed by transplantation

Recovery of extracorporeal lungs using cross-circulation with injured recipient swine

OBJECTIVE

Lung transplantation remains limited by the shortage of healthy organs. Cross-circulation with a healthy swine recipient provides a durable physiologic environment to recover injured donor lungs. In a clinical application, a recipient awaiting lung transplantation could be placed on cross-circulation to recover damaged donor lungs, enabling eventual transplantation. Our objective was to assess the ability of recipient swine with respiratory compromise to tolerate cross-circulation and support recovery of donor lungs subjected to extended cold ischemia.

METHODS

Swine donor lungs (n = 6) were stored at 4 °C for 24 hours while recipient swine (n = 6) underwent gastric aspiration injury before cross-circulation. Longitudinal multiscale analyses (blood gas, bronchoscopy, radiography, histopathology, cytokine quantification) were performed to evaluate recipient swine and extracorporeal lungs on cross-circulation.

RESULTS

Recipient swine lung injury resulted in sustained, impaired oxygenation (arterial oxygen tension/inspired oxygen fraction ratio 205 ± 39 mm Hg vs 454 ± 111 mm Hg at baseline). Radiographic, bronchoscopic, and histologic assessments demonstrated bilateral infiltrates, airway cytokine elevation, and significantly worsened lung injury scores. Recipient swine provided sufficient metabolic support for extracorporeal lungs to demonstrate robust functional improvement (0 hours, arterial oxygen tension/inspired oxygen fraction ratio 138 ± 28.2 mm Hg; 24 hours, 539 ± 156 mm Hg). Multiscale analyses demonstrated improved gross appearance, aeration, and cellular regeneration in extracorporeal lungs by 24 hours.

CONCLUSIONS

We demonstrate that acutely injured recipient swine tolerate cross-circulation and enable recovery of donor lungs subjected to extended cold storage. This proof-of-concept study supports feasibility of cross-circulation for recipients with isolated lung disease who are candidates for this clinical application.

Treatment of Staphylococcus aureus infection with sphingosine in ex vivo perfused and ventilated lungs

BACKGROUND

Ex vivo lung perfusion (EVLP) has expanded the donor pool for lung transplantation. Pulmonary Staphylococcus aureus infection, especially that caused by multidrug-resistant strains, is a severe threat to posttransplantation outcomes. Sphingosine is a lipid compound that exhibits broad-spectrum antibacterial activity. Therefore, we aimed to evaluate the effects of S aureus infection on EVLP and whether sphingosine administration during EVLP prevents infection with S aureus.

METHODS

Eighteen pigs were randomly assigned to 3 groups: uninfected, infected with S aureus with NaCl treatment, or infected with sphingosine treatment. Bacterial numbers were determined before and after treatment. Sphingosine concentrations in the lung tissues were determined using biochemical assays. Lung histology, lung physiological parameters, perfusate content, lung weight, and cell death were measured to analyze the effects of infection and sphingosine administration on EVLP.

RESULTS

Sphingosine administration significantly reduced the bacterial load. The concentration of sphingosine in the bronchial epithelium was elevated after sphingosine administration. S aureus infection increased pulmonary artery pressure and pulmonary vascular resistance. Lung edema, histology scores, lactate and lactate dehydrogenase levels in the perfusate, ΔPO2 in the perfusate, static lung compliance, and lung peak airway pressure did not differ among the groups.

CONCLUSIONS

Infection of S aureus did not affect the lung function during EVLP but induced higher pulmonary artery pressure and pulmonary vascular resistance. Administration of sphingosine effectively eliminated S aureus without side effects in isolated, perfused, and ventilated pig lungs.

L-alanyl-L-glutamine modified perfusate improves human lung cell functions and extend porcine ex vivo lung perfusion

BACKGROUND

The clinical application of normothermic ex vivo lung perfusion (EVLP) has increased donor lung utilization for transplantation through functional assessment. To develop it as a platform for donor lung repair, reconditioning and regeneration, the perfusate should be modified to support the lung during extended EVLP.

METHODS

Human lung epithelial cells and pulmonary microvascular endothelial cells were cultured, and the effects of Steen solution (commonly used EVLP perfusate) on basic cellular function were tested. Steen solution was modified based on screening tests in cell culture, and further tested with an EVLP cell culture model, on apoptosis, GSH, HSP70, and IL-8 expression. Finally, a modified formula was tested on porcine EVLP. Physiological parameters of lung function, histology of lung tissue, and amino acid concentrations in EVLP perfusate were measured.

RESULTS

Steen solution reduced cell confluence, induced apoptosis, and inhibited cell migration, compared to regular cell culture media. Adding L-alanyl-L-glutamine to Steen solution improved cell migration and decreased apoptosis. It also reduced cold preservation and warm perfusion-induced apoptosis, enhanced GSH and HSP70 production, and inhibited IL-8 expression on an EVLP cell culture model. L-alanyl-L-glutamine modified Steen solution supported porcine lungs on EVLP with significantly improved lung function, well-preserved histological structure, and significantly higher levels of multiple amino acids in EVLP perfusate.

CONCLUSIONS

Adding L-alanyl-L-glutamine to perfusate may provide additional energy support, antioxidant, and cytoprotective effects to lung tissue. The pipeline developed herein, with cell culture, cell EVLP, and porcine EVLP models, can be used to further optimize perfusates to improve EVLP outcomes.

Diagnostic and Therapeutic Implications of Ex Vivo Lung Perfusion in Lung Transplantation: Potential Benefits and Inherent Limitations

Ex vivo lung perfusion (EVLP), a technique in which isolated lungs are continually ventilated and perfused at normothermic temperature, is emerging as a promising platform to optimize donor lung quality and increase the lung graft pool. Over the past few decades, the EVLP technique has become recognized as a significant achievement and gained much attention in the field of lung transplantation. EVLP has been demonstrated to be an effective platform for various targeted therapies to optimize donor lung function before transplantation. Additionally, some physical parameters during EVLP and biological markers in the EVLP perfusate can be used to evaluate graft function before transplantation and predict posttransplant outcomes. However, despite its advantages, the clinical practice of EVLP continuously encounters multiple challenges associated with both intrinsic and extrinsic limitations. It is of utmost importance to address the advantages and disadvantages of EVLP for its broader clinical usage. Here, the pros and cons of EVLP are comprehensively discussed, with a focus on its benefits and potential approaches for overcoming the remaining limitations. Directions for future research to fully explore the clinical potential of EVLP in lung transplantation are also discussed.

Surfactant therapy in lung transplantation: A systematic review and meta-analysis

BACKGROUND

Despite numerous reports demonstrating the efficacy of exogenous surfactant therapy during lung transplantation, this strategy remains absent in routine clinical use. Here, we systematically review and meta-analyze the effect of exogenous surfactant on respiratory pathophysiological variables during lung transplantation.

METHODS

To identify relevant clinical and pre-clinical studies, we performed an electronic search of MEDLINE, EMBASE, and Cochrane CENTRAL from inception to June 11, 2021. In addition, research-in-progress databases were searched. Randomized and non-randomized adult and pediatric clinical studies and animal experiments that compared the use of surfactant for lung transplantation with a control group were included. The primary outcome was the ratio of arterial oxygen partial pressure to fractional inspired oxygen (PaO₂/FiO₂ ratio).

RESULTS

From 1,041 citations, we identified 35 studies, of which 6 were clinical studies and 29 were pre-clinical. Thirty-two studies were included in the quantitative analysis. The administration of surfactant therapy during clinical lung transplantation significantly improved PaO₂/FiO₂ ratio in recipients (mean difference [MD] 93 mmHg, 95% confidence interval [CI] 25-160 mmHg, p < 0.01). Similar results were seen in pre-clinical settings (MD 201 mmHg, 95% CI 145-256 mmHg, p < 0.01). Moreover, surfactant benefited a range of important physiologic and biologic outcomes after preclinical lung transplantation. The overall certainty of evidence was very low.

CONCLUSIONS

Exogenous surfactant therapy improves post-transplant lung function; however, its effects on clinical outcomes remain uncertain. High-quality randomized controlled trials are needed to determine whether the physiologic benefits of surfactant therapy affect patient-important outcomes in lung transplant recipients.

Current status and further potential of lung donation after circulatory death

Chronic organ shortage remains the most limiting factor in lung transplantation. To overcome this shortage, a minority of centers have started with efforts to reintroduce donation after circulatory death (DCD). This review aims to evaluate the experimental background, the current international clinical experience, and the further potential and challenges of the different DCD categories. Successful strategies have been implemented to reduce the problems of warm ischemic time, thrombosis after circulatory arrest, and difficulties in organ assessment, which come with DCD donation. From the currently reported results, controlled-DCD lungs are an effective and safe method with good mid-term and even long-term survival outcomes comparable to donation after brain death (DBD). Primary graft dysfunction and onset of chronic allograft dysfunction seem also comparable. Thus, controlled-DCD lungs should be ceased to be treated as marginal and instead be promoted as an equivalent alternative to DBD. A wide implementation of controlled-DCD-lung donation would significantly decrease the mortality on the waiting list. Therefore, further efforts in establishment of legislation and logistics are crucial. With regard to uncontrolled DCD, more data are needed analyzing long-term outcomes. To help with the detailed assessment and improvement of uncontrolled or otherwise questionable grafts after retrieval, ex-vivo lung perfusion is promising.

Ex Vivo Lung Perfusion: Current Achievements and Future Directions

There is a severe shortage in the availability of donor organs for lung transplantation. Novel strategies are needed to optimize usage of available organs to address the growing global needs. Ex vivo lung perfusion has emerged as a powerful tool for the assessment, rehabilitation, and optimization of donor lungs before transplantation. In this review, we discuss the history of ex vivo lung perfusion, current evidence on its use for standard and extended criteria donors, and consider the exciting future opportunities that this technology provides for lung transplantation.

Functional, Metabolic and Morphologic Results of Ex Vivo Donor Lung Perfusion with a Perfluorocarbon-Based Oxygen Carrier Nanoemulsion in a Large Animal Transplantation Model

Background: Ex vivo lung perfusion (EVLP) is a technology that allows the re-evaluation of questionable donor lung before implantation and it has the potential to repair injured donor lungs that are otherwise unsuitable for transplantation. We hypothesized that perfluorocarbon-based oxygen carrier, a novel reconditioning strategy instilled during EVLP would improve graft function. Methods: We utilized perfluorocarbon-based oxygen carrier (PFCOC) during EVLP to recondition and improve lung graft function in a pig model of EVLP and lung transplantation. Lungs were retrieved and stored for 24 h at 4 °C. EVLP was done for 6 h with or without PFCOC. In the transplantation groups, left lung transplantation was done after EVLP with or without PFCOC. Allograft function was assessed by means of pulmonary gas exchange, lung mechanics and vascular pressures, histology and transmission electron microscopy (TEM). Results: In the EVLP only groups, physiological and biochemical markers during the 6-h perfusion period were comparable. However, perfusate lactate potassium levels were lower and ATP levels were higher in the PFCOC group. Radiologic assessment revealed significantly more lung infiltrates in the controls than in the PFCOC group (p = 0.04). In transplantation groups, perfusate glucose consumption was higher in the control group. Lactate levels were significantly lower in the PFCOC group (p = 0.02). Perfusate flavin mononucleotide (FMN) was significantly higher in the controls (p = 0.008). Post-transplant gas exchange was significantly better during the 4-h reperfusion period in the PFCOC group (p = 0.01). Plasma IL-8 and IL-12 levels were significantly lower in the PFCOC group (p = 0.01, p = 0.03, respectively). ATP lung tissue levels at the end of the transplantation were higher and myeloperoxidase (MPO) levels in lung tissue were lower in the PFCOC group compared to the control group. In the PFCOC group, TEM showed better tissue preservation and cellular viability. Conclusion: PFCOC application is safe during EVLP in lungs preserved 24 h at 4 °C. Although this strategy did not significantly affect the EVLP physiology, metabolic markers of the donor quality such as lactate production, glucose consumption, neutrophil infiltration and preservation of mitochondrial function were better in the PFCOC group. Following transplantation, PFCOC resulted in better graft function and TEM showed better tissue preservation, cellular viability and improved gas transport.

Review of Current Machine Perfusion Therapeutics for Organ Preservation

Because of the high demand of organs, the usage of marginal grafts has increased. These marginal organs have a higher risk of developing ischemia-reperfusion injury, which can lead to posttransplant complications. Ex situ machine perfusion (MP), compared with the traditional static cold storage, may better protect these organs from ischemia-reperfusion injury. In addition, MP can also act as a platform for dynamic administration of pharmacological agents or gene therapy to further improve transplant outcomes. Numerous therapeutic agents have been studied under both hypothermic (1-8°C) and normothermic settings. Here, we review all the therapeutics used during MP in different organ systems (lung, liver, kidney, heart). The major categories of therapeutic agents include vasodilators, mesenchymal stem cells, antiinflammatory agents, antiinfection agents, siRNA, and defatting agents. Numerous animal and clinical studies have examined MP therapeutic agents, some of which have even led to the successful reconditioning of discarded grafts. More clinical studies, especially randomized controlled trials, will need to be conducted in the future to solidify these promising results and to define the role of MP therapeutic agents in solid organ transplantation.

Endothelin receptor antagonist improves donor lung function in an ex vivo perfusion system

BACKGROUND

A lung transplant is the last resort treatment for many patients with advanced lung disease. The majority of donated lungs come from donors following brain death (BD). The endothelin axis is upregulated in the blood and lung of the donor after BD resulting in systemic inflammation, lung damage and poor lung graft outcomes in the recipient. Tezosentan (endothelin receptor blocker) improves the pulmonary haemodynamic profile; however, it induces adverse effects on other organs at high doses. Application of ex vivo lung perfusion (EVLP) allows the development of organ-specific hormone resuscitation, to maximise and optimise the donor pool. Therefore, we investigate whether the combination of EVLP and tezosentan administration could improve the quality of donor lungs in a clinically relevant 6-h ovine model of brain stem death (BSD).

METHODS

After 6 h of BSD, lungs obtained from 12 sheep were divided into two groups, control and tezosentan-treated group, and cannulated for EVLP. The lungs were monitored for 6 h and lung perfusate and tissue samples were processed and analysed. Blood gas variables were measured in perfusate samples as well as total proteins and pro-inflammatory biomarkers, IL-6 and IL-8. Lung tissues were collected at the end of EVLP experiments for histology analysis and wet-dry weight ratio (a measure of oedema).

RESULTS

Our results showed a significant improvement in gas exchange [elevated partial pressure of oxygen (P = 0.02) and reduced partial pressure of carbon dioxide (P = 0.03)] in tezosentan-treated lungs compared to controls. However, the lungs hematoxylin-eosin staining histology results showed minimum lung injuries and there was no difference between both control and tezosentan-treated lungs. Similarly, IL-6 and IL-8 levels in lung perfusate showed no difference between control and tezosentan-treated lungs throughout the EVLP. Histological and tissue analysis showed a non-significant reduction in wet/dry weight ratio in tezosentan-treated lung tissues (P = 0.09) when compared to control.

CONCLUSIONS

These data indicate that administration of tezosentan could improve pulmonary gas exchange during EVLP.

Treatment with 3-aminobenzamide during ex vivo lung perfusion of damaged rat lungs reduces graft injury and dysfunction after transplantation

Ex vivo lung perfusion (EVLP) with pharmacological reconditioning may increase donor lung utilization for transplantation (LTx). 3-Aminobenzamide (3-AB), an inhibitor of poly(ADP-ribose) polymerase (PARP), reduces ex vivo lung injury in rat lungs damaged by warm ischemia (WI). Here we determined the effects of 3-AB reconditioning on graft outcome after LTx. Three groups of donor lungs were studied: Control (Ctrl): 1 hour WI + 3 hours cold ischemia (CI) + LTx; EVLP: 1 hour WI + 3 hours EVLP + LTx; EVLP + 3-AB: 1 hour WI + 3 hours EVLP + 3-AB (1 mg^. mL^-1 ) + LTx. Two hours after LTx, we determined lung graft compliance, edema, histology, neutrophil counts in bronchoalveolar lavage (BAL), mRNA levels of adhesion molecules within the graft, as well as concentrations of interleukin-6 and 10 (IL-6, IL-10) in BAL and plasma. 3-AB reconditioning during EVLP improved compliance and reduced lung edema, neutrophil infiltration, and the expression of adhesion molecules within the transplanted lungs. 3-AB also attenuated the IL-6/IL-10 ratio in BAL and plasma, supporting an improved balance between pro- and anti-inflammatory mediators. Thus, 3-AB reconditioning during EVLP of rat lung grafts damaged by WI markedly reduces inflammation, edema, and physiological deterioration after LTx, supporting the use of PARP inhibitors for the rehabilitation of damaged lungs during EVLP.

Regeneration of severely damaged lungs using an interventional cross-circulation platform

The number of available donor organs limits lung transplantation, the only lifesaving therapy for the increasing population of patients with end-stage lung disease. A prevalent etiology of injury that renders lungs unacceptable for transplantation is gastric aspiration, a deleterious insult to the pulmonary epithelium. Currently, severely damaged donor lungs cannot be salvaged with existing devices or methods. Here we report the regeneration of severely damaged lungs repaired to meet transplantation criteria by utilizing an interventional cross-circulation platform in a clinically relevant swine model of gastric aspiration injury. Enabled by cross-circulation with a living swine, prolonged extracorporeal support of damaged lungs results in significant improvements in lung function, cellular regeneration, and the development of diagnostic tools for non-invasive organ evaluation and repair. We therefore propose that the use of an interventional cross-circulation platform could enable recovery of otherwise unsalvageable lungs and thus expand the donor organ pool.

Organ preservation: from the past to the future

Organ transplantation is the most effective therapy for patients with end-stage disease. Preservation solutions and techniques are crucial for donor organ quality, which is directly related to morbidity and survival after transplantation. Currently, static cold storage (SCS) is the standard method for organ preservation. However, preservation time with SCS is limited as prolonged cold storage increases the risk of early graft dysfunction that contributes to chronic complications. Furthermore, the growing demand for the use of marginal donor organs requires methods for organ assessment and repair. Machine perfusion has resurfaced and dominates current research on organ preservation. It is credited to its dynamic nature and physiological-like environment. The development of more sophisticated machine perfusion techniques and better perfusates may lead to organ repair/reconditioning. This review describes the history of organ preservation, summarizes the progresses that has been made to date, and discusses future directions for organ preservation.

Current state of ex-vivo lung perfusion

PURPOSE OF REVIEW

The purpose of the current report is to review the ex-vivo peer-reviewed literature published in the last 5 years and to summarize the findings.

RECENT FINDINGS

Encouraging data have been published by several centers utilizing ex-vivo lung perfusion (EVLP) as a means to identify viable grafts from the high-risk donor pool. The outcomes of transplanted lungs that were initially declined because of poor quality, but reevaluated with ex-vivo perfusion, are equivalent to standard criteria donor lungs. Further, research reports have emphasized the role of ex-vivo perfusion as a platform to improve graft quality and reduce the injurious effects of ischemia-reperfusion.

SUMMARY

Over the last 10 years, EVLP has proved its value as a reassessment tool to increase donor utilization. As short- and long-term data demonstrate the safety of EVLP, its use as a therapeutic platform is emerging, along with the promise of a new era in lung transplantation.

Donors after cardiocirculatory death and lung transplantation

The number of patients actively awaiting lung transplantation (LTx) is more than the number of suitable donor lungs. The percentage of lung retrieval rate is lower when compared to other solid organs. The use of lungs from donation after cardiocirculatory death (DCD) donors is one of the options to avoid organ shortage in LTx. After extensive experimental research, clinical application of DCD donation is becoming wider. The results from most of the centers show at least equal survival rate compared to donors from brain death. This review paper will summarize experimental background and clinical experience from DCD donors.

Ex vivo treatment with inhaled N-acetylcysteine in porcine lung transplantation

BACKGROUND

We have shown the beneficial effects of N-acetylcysteine (NAC) on posttransplant lung function, when both donor and recipient were pretreated intravenously. However, systemic treatment of multiorgan donors may not be clinically relevant. Thus, we hypothesized that ex vivo treatment of donors with nebulized NAC would be adequate to prevent from ischemia-reperfusion injury after lung transplantation.

METHODS

Lungs were retrieved from domestic pigs and stored at 4°C for 24 h followed by 2 h of ex vivo lung perfusion (EVLP) to administer 50 mg/kg of NAC via nebulization in the NAC group (n = 6). The control group received nebulized saline (n = 5). Left lungs were transplanted and isolated at 1 h of reperfusion by occluding the right main bronchus and pulmonary artery, followed by 5 h of observation. Physiological data during EVLP and after reperfusion were recorded. Inflammatory response, markers of oxidative stress, and microscopic lung injury were analyzed.

RESULTS

There was a trend toward better oxygenation throughout reperfusion period in the treatment group, which was accompanied by inhibited inflammatory response related to reduction in myeloperoxidase activity during EVLP and nuclear factor-κB activation at the end of reperfusion.

CONCLUSIONS

Ex vivo treatment of donor lungs with inhaled NAC reduced inflammatory response via its antioxidant activity in experimental porcine lung transplantation.

Comparison of two strategies for ex vivo lung perfusion

BACKGROUND

Two clinically used strategies for ex vivo lung perfusion (EVLP) were compared in a porcine model with respect to lung function, metabolism, inflammatory response, oxidative stress, and cell viability.

METHODS

Porcine lungs (n = 20) were preserved, harvested, and kept cooled for 2 hours. After randomization, EVLP was performed using a cellular perfusate and open left atrium (COA group) or an acellular perfusate and a closed left atrium (ACA group). Oxygenation (partial pressure of arterial oxygen/fraction of inspired oxygen), compliance, dead space, weight, and perfusate oncotic pressure were registered before and after a 4-hour period of reconditioning. Lung tissue samples were collected before and after EVLP for quantitative polymerase chain reaction analysis of gene expression for inflammatory markers, measurement of tissue hypoxia (hypoxia inducible factor-1α) and oxidative stress (ascorbyl radical), and viability (trypan blue staining) and lung histopathology.

RESULTS

In 3 of 10 lungs undergoing EVLP in the ACA group, EVLP was terminated prematurely because of severe lung edema and inability to perfuse the lungs. There were no significant differences in changes of lung oxygenation or pulmonary vascular resistance between groups. Compliance decreased and lung weights increased in both groups, but more in the ACA group (p = 0.083 and p = 0.065, respectively). There was no obvious difference in gene expression for hypoxia inducible factor-1α, inflammatory markers, free radicals, or lung injury between groups.

CONCLUSIONS

Lung edema formation and decreased lung compliance occurs with both EVLP techniques but were more pronounced in the ACA group. Otherwise, there were no differences in lung function, inflammatory response, ischemia/reperfusion injury, or histopathologic changes between the EVLP techniques.

Cytokine filtration modulates pulmonary metabolism and edema formation during ex vivo lung perfusion

BACKGROUND

Ex vivo lung perfusion (EVLP) has improved the process of donor lung management. Cytokine accumulation during EVLP has been shown to correlate with worse outcome after lung transplantation. Our objective in this study was to test the safety and efficacy of cytokine filtration during EVLP in a large animal model.

METHODS

Pig donor lungs were preserved for 24 hours at 4°C, followed by 12 hours of EVLP, according to the Toronto protocol. The perfusate was continuously run through an absorbent device (CytoSorb) via a veno-venous shunt from the reservoir in the filter group. EVLP was performed according to the standard protocol in the control group (n = 5 each). EVLP physiology, lung X-ray, perfusate biochemistry, inflammatory response and microscopic injury were assessed.

RESULTS

Cytokine filtration significantly improved airway pressure and dynamic compliance during the 12-hour perfusion period. Lung X-rays acquired at the end of perfusion showed increased consolidation in the control group. Electrolyte imbalance, determined by increased hydrogen, potassium and calcium ion concentrations in the perfusate, was markedly worsened in the control group. Glucose consumption and lactate production were markedly reduced, along with the lactate/pyruvate ratio in the filter group. Cytokine expression profile, tissue myeloperoxidase activity and microscopic lung injury were significantly reduced in the filter group.

CONCLUSIONS

Continuous perfusate filtration through sorbent beads is effective and safe during prolonged EVLP. Cytokine removal decreased the development of pulmonary edema and electrolyte imbalance through the suppression of anaerobic glycolysis and neutrophil activation in this setting. Further studies are needed to test the beneficial effect of cytokine filtration on post-transplant lung function.

The evolving potential for pediatric ex vivo lung perfusion

Despite the rise in the number of adult lung transplantations performed, rates of pediatric lung transplantation remain low. Lung transplantation is an accepted therapy for pediatric end-stage lung disease; however, it is limited by a shortage of donor organs. EVLP has emerged as a platform for assessment and preservation of donor lung function. EVLP has been adopted in adult lung transplantation and has successfully led to increased adult lung transplantations and donor lung utilization. We discuss the future implications of EVLP utilization, specifically, its potential evolving role in overcoming donor shortages in smaller children and adolescents to improve the quality and outcomes of lung transplantation in pediatric patients.

The porcine innate immune system: an update

Over the last few years, we have seen an increasing interest and demand for pigs in biomedical research. Domestic pigs (Sus scrofa domesticus) are closely related to humans in terms of their anatomy, genetics, and physiology, and often are the model of choice for the assessment of novel vaccines and therapeutics in a preclinical stage. However, the pig as a model has much more to offer, and can serve as a model for many biomedical applications including aging research, medical imaging, and pharmaceutical studies to name a few. In this review, we will provide an overview of the innate immune system in pigs, describe its anatomical and physiological key features, and discuss the key players involved. In particular, we compare the porcine innate immune system to that of humans, and emphasize on the importance of the pig as model for human disease.

Plasmin administration during ex vivo lung perfusion ameliorates lung ischemia-reperfusion injury

BACKGROUND

Donor lung thrombus is considered a significant etiology for primary graft dysfunction (PGD). We hypothesized that thrombolysis in ex vivo lung perfusion (EVLP) before lung transplantation could alleviate ischemia-reperfusion injury (IRI), resulting in a decreased incidence of PGD.

METHODS

Rats were divided into control (n = 5), non-plasmin (n = 7) and plasmin (n = 7) groups. In the non-plasmin and plasmin groups, cardiac arrest was induced by withdrawal of ventilation without heparinization. After 120 minutes of warm ischemia, the lungs were ventilated and flushed. Hearts and both lungs were excised en bloc. The lungs were perfused and ventilated in the EVLP for 30 minutes, and plasmin or placebo was administered on EVLP initiation. The lungs were then stored at 4°C for 90 minutes and finally perfused with rat blood for 80 minutes. We assessed physiologic and histologic findings during reperfusion and the correlation between physiologic data during EVLP and after reperfusion.

RESULTS

Physiologic results were better in the plasmin group than in the non-plasmin group. The plasmin group lungs had fewer signs of histologic injury. Caspase-3 and -7 activity in the plasmin group was lower in the non-plasmin group. Pulmonary vascular resistance (PVR) during EVLP correlated with that at the end of reperfusion.

CONCLUSIONS

Plasmin administration during EVLP protected the donor lungs after reperfusion. We also found that several physiologic values in EVLP may be predictive markers of lung function after reperfusion.