TRANSPLANTATION OF THE LUNG

Ex vivo lung perfusion and the Organ Care System: a review

With the increasing prevalence of heart failure and end-stage lung disease, there is a sustained interest in expanding the donor pool to alleviate the thoracic organ shortage crisis. Efforts to extend the standard donor criteria and to include donation after circulatory death have been made to increase the availability of suitable organs. Studies have demonstrated that outcomes with extended-criteria donors are comparable to those with standard-criteria donors. Another promising approach to augment the donor pool is the improvement of organ preservation techniques. Both ex vivo lung perfusion (EVLP) for the lungs and the Organ Care System (OCS, TransMedics) for the heart have shown encouraging results in preserving organs and extending ischemia time through the application of normothermic regional perfusion. EVLP has been effective in improving marginal or borderline lungs by preserving and reconditioning them. The use of OCS is associated with excellent short-term outcomes for cardiac allografts and has improved utilization rates of hearts from extended-criteria donors. While both EVLP and OCS have successfully transitioned from research to clinical practice, the costs associated with commercially available systems and consumables must be considered. The ex vivo perfusion platform, which includes both EVLP and OCS, holds the potential for diverse and innovative therapies, thereby transforming the landscape of thoracic organ transplantation.

Therapeutic benefits of nitric oxide in lung transplantation

Lung transplantation is an evolutionary procedure from its experimental origin in the twentieth century and is now recognized as an established and routine life-saving intervention for a variety of end-stage pulmonary diseases refractory to medical management. Despite the success and continuous refinement in lung transplantation techniques, the widespread application of this important life-saving intervention is severely hampered by poor allograft quality offered from donors-after-brain-death. This has necessitated the use of lung allografts from donors-after-cardiac-death (DCD) as an additional source to expand the pool of donor lungs. Remarkably, the lung exhibits unique properties that may make it ideally suitable for DCD lung transplantation. However, primary graft dysfunction (PGD), allograft rejection and other post-transplant complications arising from unavoidable ischemia-reperfusion injury (IRI) of transplanted lungs, increase morbidity and mortality of lung transplant recipients annually. In the light of this, nitric oxide (NO), a selective pulmonary vasodilator, has been identified as a suitable agent that attenuates lung IRI and prevents PGD when administered directly to lung donors prior to donor lung procurement, or to recipients during and after transplantation, or administered indirectly by supplementing lung preservation solutions. This review presents a historical account of clinical lung transplantation and discusses the lung as an ideal organ for DCD. Next, the author highlights IRI and its clinical effects in lung transplantation. Finally, the author discusses preservation solutions suitable for lung transplantation, and the protective effects and mechanisms of NO in experimental and clinical lung transplantation.

History of Lung Transplantation

Lung transplantation remains the only available therapy for many patients with end-stage lung disease. The number of lung transplants performed has increased significantly, but development of the field was slow compared with other solid-organ transplants. This delayed growth was secondary to the increased complexity of transplanting lungs; the continuous needs for surgical, anesthetics, and critical care improvements; changes in immunosuppression and infection prophylaxis; and donor management and patient selection. The future of lung transplant remains promising: expansion of donor after cardiac death donors, improved outcomes, new immunosuppressants targeted to cellular and antibody-mediated rejection, and use of xenotransplantation or artificial lungs.

The history of organ transplantation

Since ancient times, mythology has included tales of creatures made of an amalgamation of others, transferring body parts and skin. In the 1950s, with no other medical options for then incurable diseases, including nephritis, teams of scientists, surgeons, and generous patients started the field of organ transplant with the first successful kidney transplant in a human. The scientific discoveries and innovations since that first successful transplant in 1954 have turned the mythical concept of transplant into reality. The overall success and public acceptance of organ donation and transplant today is thanks to multidisciplinary teams of basic scientists, immunologists, surgeons, and public advocates. Today, research is propelling the field forward with advancements like face transplants, experiments of lab-grown organs, and much more. In the United States alone, over 800,000 patients have had their lives saved or significantly improved thanks to transplant since national recording began by the Organ Procurement and Transplant Network in 1988.

Relaxin Positively Influences Ischemia-Reperfusion Injury in Solid Organ Transplantation: A Comprehensive Review

In recent decades, solid organ transplantation (SOT) has increased the survival and quality of life for patients with end-stage organ failure by providing a potentially long-term treatment option. Although the availability of organs for transplantation has increased throughout the years, the demand greatly outweighs the supply. One possible solution for this problem is to extend the potential donor pool by using extended criteria donors. However, organs from such donors are more prone to ischemia reperfusion injury (IRI) resulting in higher rates of delayed graft function, acute and chronic graft rejection and worse overall SOT outcomes. This can be overcome by further investigating donor preconditioning strategies, graft perfusion and storage and by finding novel therapeutic agents that could reduce IRI. relaxin (RLX) is a peptide hormone with antifibrotic, antioxidant, anti-inflammatory and cytoprotective properties. The main research until now focused on heart failure; however, several preclinical studies showed its potentials for reducing IRI in SOT. The aim of this comprehensive review is to overview currently available literature on the possible role of RLX in reducing IRI and its positive impact on SOT.

Defining the Burden of Emergency General Surgery in Transplant Patients: A Nationwide Examination

BACKGROUND

Transplant patients are at the risk of serious sequelae from medical and surgical intervention. The incidence and burden of emergency general surgery (EGS) in transplant patients are scarcely known. This study aims to identify predictors of outcomes in transplant patients with EGS needs.

METHODS

The Nationwide Inpatient Sample (2007-2011) was queried for adult patients (aged ≥16 y) who underwent abdominal visceral transplantation. These were further queried for a secondary diagnosis of an American Association for the Surgery of Trauma-defined EGS condition. Outcome measures included mortality, complications, length of stay, and cost of care. Propensity scores were used to match patients across baseline characteristics. Multivariate analysis was used to further adjust propensity score quintiles and hospital-level characteristics.

RESULTS

A total of 35,573 transplant patients were identified. Of these, 30% (n = 10,676) developed an EGS condition. Most common EGS conditions were resuscitation (7.7%), intestinal obstruction (7.3%), biliary conditions (3.9%), and hernias (3.2%). Patients with public insurance, those in the highest income quartile, and those treated at larger hospitals had a lower likelihood of developing an EGS condition (P < 0.05). Patients with an EGS condition had a ninefold higher likelihood of mortality and a threefold higher likelihood of developing complications (odds ratio [95% confidence interval (CI)]: 9.21 [1.80-10.89] and 3.17 [3.02-3.34], respectively). Transplant patients after EGS had a longer risk-adjusted length of stay and cost of index hospitalization (Absolute difference [95% CI]: 12.70 [12.14-13.26] and $57,797 [55,415-60,179], respectively]).

CONCLUSIONS

Transplant patients fare poorly after developing an EGS condition. The results of this study will help in identifying at-risk patients and determining outcomes.

Diagnosis, Pathophysiology and Experimental Models of Chronic Lung Allograft Rejection

Chronic rejection is the Achilles heel of modern lung transplantation, characterized by a slow, progressive decline in allograft function. Clinically, this manifests as obstructive disease, restrictive disease, or a mixture of the 2 depending on the underlying pathology. The 2 major phenotypes of chronic rejection include bronchiolitis obliterans syndrome and restrictive allograft syndrome. The last decade of research has revealed that each of these phenotypes has a unique underlying pathophysiology which may require a distinct treatment regimen for optimal control. Insights into the intricate alloimmune pathways contributing to chronic rejection have been gained from both large and small animal models, suggesting directions for future research. In this review, we explore the pathological hallmarks of chronic rejection, recent insights gained from both clinical and basic science research, and the current state of animal models of chronic lung rejection.

History of lung transplantation

Lung transplantation nowadays is a well-accepted and routine treatment for well selected patients with terminal respiratory disease. However, it took several decades of experimental studies and clinical attempts to reach this success. In this paper, we describe the early experimental activity from the mid-forties until the early sixties. The first clinical attempt in humans was reported by Hardy and Webb in 1963 followed by others with short survival only except for one case by Derom et al. who lived for 10 months. Long-term successes were not reported until after the discovery of cyclosporine as a new immunosuppressive agent. Successful heart-lung transplantation (HLTx) for pulmonary vascular disease was performed by the Stanford group starting in 1981 while the Toronto group described good outcome after single-lung transplantation (SLTx) for pulmonary fibrosis in 1983 and after double-lung transplantation for emphysema in 1986. Further evolution in surgical techniques and in transplant type for the various forms of end-stage lung diseases are reviewed. The evolution in lung transplantation still continues nowadays with the use of pulmonary allografts coming from living-related donors, from donors after circulatory death, or after prior assessment and reconditioning during ex vivo lung perfusion (EVLP) in an attempt to overcome the critical shortage of suitable organs. Early outcome has significantly improved over the last three decades. Better treatment and prevention of chronic lung allograft dysfunction will hopefully result in further improvement of long-term survival after lung transplantation.

Lung regeneration: steps toward clinical implementation and use

PURPOSE OF REVIEW

Whole lung tissue engineering is a relatively new area of investigation. In a short time, however, the field has advanced quickly beyond proof of concept studies in rodents and now stands on the cusp of wide-spread scale up to large animal studies. Therefore, this technology is ever closer to being directly clinically relevant.

RECENT FINDINGS

The main themes in the literature include refinement of the fundamental components of whole lung engineering and increasing effort to direct induced pluripotent stem cells and lung progenitor cells toward use in lung regeneration. There is also increasing need for and emphasis on functional evaluation in the lab and in vivo, and the use of all of these tools to construct and evaluate forthcoming clinically scaled engineered lung.

SUMMARY

Ultimately, the goal of the research described herein is to create a useful clinical product. In the intermediate time, however, the tools described here may be employed to advance our knowledge of lung biology and the organ-specific regenerative capacity of lung stem and progenitor cells.

Lung transplantation: an overview of candidacy and outcomes

BACKGROUND

Various factors must be taken into account when considering lung transplantation, including candidacy, contraindications, and outcomes.

METHODS

This article presents a review of the data and literature on lung transplantation, tracking the evolution of the treatment as it applies to different conditions, as well as an examination of patient survival rates in relation to pathology and treatment.

RESULTS

Timely referral and careful selection of candidates for lung transplantation maximize the outcomes of the procedure, resulting in a longer lifespan with improved physical health for patients.

CONCLUSION

Lung transplantation is a therapeutic option for patients with various lung diseases. Adapting treatment options and follow-up treatment to the individual patient's lifestyle and pathology optimizes patient survival rates after transplantation.

Protection of isolated lung from reperfusion injuries by rinsing with high colloidal osmotic solution with deferoaxmine

We examined the efficacy of rinsing isolated lungs subjected to prolonged hypothermic storage with a high colloidal osmotic pressure solution prior to ex vivo blood reperfusion in order to preserve physiologic functions, suppress peroxidation of mitochondrial membranes, and inhibit infiltration of neutrophils. Isolated rabbit lungs were flushed with a Rinse-1 solution (289 mOsm/kg H2O) to remove remaining blood and immersed in physiologic saline at 8 degrees C for 24 hr. The control group received blood reperfusion immediately after storage; the Rinse-1 group was rinsed with Rinse-1 solution before blood reperfusion and the Rinse-2 group with Rinse-2 solution (312 mOsm/kg H20) including deferoxamine. Reperfused blood was passed through an artificial membranous lung to reduce oxygen tension (PO2) to the venous level, and time-dependent changes in airway pressure (AWP), pulmonary artery pressure (PAP), and PO2, as a measure of gas-exchange capability were examined. We estimated the lipid peroxide level in mitochondrial membranes as thiobarbituric acid-reactive substances (TBARS), i.e., malonedialdehyde, and neutrophil infiltration into lung tissue by measuring myeloperoxidase activity after 60 min of blood reperfusion. The PO2 was significantly higher in both rinsed groups compared with the control, while neither AWP nor PAP was significantly different in the three treatment groups. Both mitochondrial TBARS and myeloperoxidase activity were significantly higher in the control group compared with either rinsed group. These results indicate that rinsing stored lungs with a solution of high colloidal osmotic pressure prior to blood reperfusion was effective in preserving physiologic function and inhibiting neutrophil infiltration. Addition of deferoxamine was markedly effective in reducing TBARS formation and lessening reperfusion injury of stored lungs.

Glutathione decreases the pulmonary reimplantation response in canine lung autotransplants

The pulmonary reimplantation response (PRR) is a form of membrane permeability pulmonary edema occurring in lung transplants. The severity of the PRR reflects the quality and duration of lung graft preservation. Free radicals formed during ischemia with reperfusion in the autotransplanted dog lung may play a role in producing PRR. We hypothesized that the addition of reduced glutathione (GSH) to the preservative solution could decrease PRR if hydroperoxides are being formed. Six dogs underwent left lung autotransplantation after the lung was flushed with Euro-Collins solution (EC). These dogs demonstrated radiographic and histopathologic evidence of bilateral pulmonary edema, greatest in the transplanted left lung. They also had increases in lung wet to dry weight (W/D) ratios in both lungs (left, 12.0 +/- 0.9; right, 10.1 +/- 0.8) as compared with a group of five unmanipulated control animals (left, 6.0 +/- 0.5; right, 7.0 +/- 0.4). Malondialdehyde (MDA) concentrations were significantly increased in the transplanted left lungs (14 +/- 4) from this group as compared with the controls (5 +/- 7). Five additional dogs underwent left lung autotransplantation with GSH added to the EC cryopreservation fluid. These animals did not develop histologic or radiographic evidence of pulmonary edema, and W/D ratios as well as MDA concentrations were not different from those in controls. To evaluate the effect of ischemia alone on changes in lung GSH concentrations, ten additional dogs underwent left pneumonectomy. Left lungs were cryopreserved in EC + GSH. In five of the animals, the right lung was removed and preserved in EC alone. In the other five animals, the right lung remained in vivo for 3 h and was then removed. Lung GSH concentrations were doubled after 3 h of ischemia when incubated in EC + GSH compared to in vivo controls and to EC-treated lungs. These data suggest that GSH added to the preservation fluid prevents PRR following transplantation and that lung GSH concentrations actually increase during preservation prior to reimplantation and reperfusion if the lung graft is exposed to GSH in the preservation fluid.

Physiologic sufficiency of regenerated lung lymphatics

The physiologic sufficiency of regenerated lung lymphatics after surgical transection of the lung hilum was studied experimentally. Dogs were prepared by surgical interruption of all left lung hilar tissues and structures except the skeletonized pulmonary artery and the pulmonary veins; continuity of the bronchus was restored by anastomosis. Anatomic reconnection of lung lymphatics to mediastinal lymph vessels was determined by injecting a sky blue dye marker into peribronchial tissues distal to the bronchial anastomosis at different intervals after surgical preparation. From a series of 50 experimental animals it was demonstrated that the surgical procedcure interrupted lymphatic drainage and that anatomic reconnection with mediastinal lymphatics developed 7-28 days after preparation. Physiologic sufficiency of regenerated lymphatics was studied in 60 animals by rapid intravascular volume expansion as a test of lymph flow capacity. By gravimetric determination of lung water and histologic examination of lung specimens this study revealed a significant incapacity to maintain lung water homeostasis 3 days after preparation with return toward normal lymph flow capacity 35 days after preparation. This study indicated that lung lymphatic drainage is re-established 7--28 days after surgical interruption and becomes relatively sufficient after 35 days.

Lung transplantation: better survival results after graft pretreatment with concanavalin A or chondroitin sulfate

Pretreatment of the lung graft with concanavalin A (Con A) or chondroitin sulfate (CIS) was used to modify the lung allograft response after transplantation into moderately immunosuppressed (low doses of azathioprine and prednisone) recipients. Significant (p less than 0.05) prolongation of survival was observed after graft pretreatment. Pneumonia and rejection were the most frequent causes of death for all groups of dogs. However, only 3 out of 6 animals from each of the groups with pretreated grafts died of pneumonia or rejection, whereas 5 of the 6 animals in the control group died of these causes. Furthermore, when rejection occurred in the dogs with lung grafts pretreated with Con A or CIS, it was considerably delayed compared with the controls. Partial pressure of arterial oxygen, chest roentgenograms, and lung histology were good indicators of lung viability after transplantation.

Pulmonary mechanics and surfactant measurement in canine lungs following reimplantation

The left lung was reimplanted in 18 dogs. Failure of the venous anastomosis was the chief technical complication. Thirteen dogs survived until killed from eight days to 15 weeks after the operation. There was an immediate fall in total pulmonary compliance following the procedure, then a return to near normal within eight days. Surfactant and lung stability were normal. In each case there was a marked reduction in the gas volume of the reimplanted lung.

Perfusion and ventilation of isolated canine lungs

In order to evaluate methods of preserving lungs for use in transplantation, experiments on 28 mongrel dogs were carried out. Two methods were tried—first, mechanical respiration of isolated lungs under deep hypothermia, with the vascular bed filled with blood; and, secondly, the perfusion of isolated lungs with the aid of a modified DeWall's apparatus. Allogenic transplantations of lungs preserved in both ways were carried out. Gasometric and histological examinations of preserved lungs, before and after transplantation, were performed. The best results were obtained with perfusion under hypothermic conditions; ventilation without perfusion resulted in failure. Lung transplantation was successful when, after being preserved, the lung remained unchanged. Major discrepancies between the macroscopic and microscopic findings in preserved lungs were observed. An original classification of the changes occurring in preserved lungs is proposed.

Paraquat poisoning--lung transplantation

A 15-year-old boy ingested a mouthful of paraquat and developed severe respiratory distress. Treatment included the transplantation of one lung, but subsequently changes developed in the graft which are thought to have been due to paraquat, and the patient died two weeks after the operationThe dangers of keeping poisonous substances in incorrectly labelled bottles has once again been demonstrated, while the pattern of paraquat poisoning, especially the development of proliferative alveolitis and terminal bronchiolitis, is confirmed.Immediate forced diuresis followed by haemodialysis is necessary to remove paraquat, thereby perhaps avoiding initiation of the changes in the lungs. The technical feasibility of human lung transplantation has again been demonstrated. It has also been shown that infection does not necessarily pose an insuperable problem, at any rate if, as in the case described, there was no preoperative pulmonary infection in either recipient or donor.

Homotransplantation of the lung in dogs, with special reference to the circulation system in the transplant

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