A Split-Lung Ex Vivo Perfusion Model for Time- and Cost-Effective Evaluation of Therapeutic Interventions to the Human Donor Lung.

With the ongoing shortage of donor lungs, ex vivo lung perfusion (EVLP) offers the opportunity for objective assessment and potential therapeutic repair of marginal organs. There is a need for robust research on EVLP interventions to increase the number of transplantable organs. The use of human lungs, which have been declined for transplant, for these studies is preferable to animal organs and is indeed essential if clinical translation is to be achieved. However, experimental human EVLP is time-consuming and expensive, limiting the rate at which promising interventions can be assessed. A split-lung EVLP model, which allows stable perfusion and ventilation of two single lungs from the same donor, offers advantages scientifically, financially and in time to yield results. Identical parallel circuits allow one to receive an intervention and the other to act as a control, removing inter-donor variation between study groups. Continuous hemodynamic and airway parameters are recorded and blood gas, perfusate, and tissue sampling are facilitated. Pulmonary edema is assessed directly using ultrasound, and indirectly using the lung tissue wet:dry ratio. Evans blue dye leaks into the tissue and can quantify vascular endothelial permeability. The split-lung ex vivo perfusion model offers a cost-effective, reliable platform for testing therapeutic interventions with relatively small sample sizes.

Update on the ethical, legal and technical challenges of translating xenotransplantation.

This manuscript reports on a landmark symposium on the ethical, legal and technical challenges of xenotransplantation in the UK. King's College London, with endorsement from the British Transplantation Society (BTS), and the European Society of Organ Transplantation (ESOT), brought together a group of experts in xenotransplantation science, ethics and law to discuss the ethical, regulatory and technical challenges surrounding translating xenotransplantation into the clinical setting. The symposium was the first of its kind in the UK for 20 years. This paper summarises the content of the expert lectures showcasing the progress which has been made in xenotransplantation including-the history of xenotransplantation, advances in gene edited animals and progress towards clinical xenotransplantation. We then set out the ethical and legal issues still to be resolved. Finally, we report the themes of the roundtable discussion highlighting areas of consensus and controversy. While the detail of the legal discussion was directed towards the UK, the principles and summary reported here are intended to be applicable to any jurisdiction seeking to implement clinical xenotransplantation.

Spatially resolved multiomics of human cardiac niches.

The function of a cell is defined by its intrinsic characteristics and its niche: the tissue microenvironment in which it dwells. Here we combine single-cell and spatial transcriptomics data to discover cellular niches within eight regions of the human heart. We map cells to microanatomical locations and integrate knowledge-based and unsupervised structural annotations. We also profile the cells of the human cardiac conduction system1. The results revealed their distinctive repertoire of ion channels, G-protein-coupled receptors (GPCRs) and regulatory networks, and implicated FOXP2 in the pacemaker phenotype. We show that the sinoatrial node is compartmentalized, with a core of pacemaker cells, fibroblasts and glial cells supporting glutamatergic signalling. Using a custom CellPhoneDB.org module, we identify trans-synaptic pacemaker cell interactions with glia. We introduce a druggable target prediction tool, drug2cell, which leverages single-cell profiles and drug-target interactions to provide mechanistic insights into the chronotropic effects of drugs, including GLP-1 analogues. In the epicardium, we show enrichment of both IgG+ and IgA+ plasma cells forming immune niches that may contribute to infection defence. Overall, we provide new clarity to cardiac electro-anatomy and immunology, and our suite of computational approaches can be applied to other tissues and organs.

Risk of prolonged ischemic time linked to use of cardiopulmonary bypass during implantation for lung transplantation in the United Kingdom.

BACKGROUND: Some degree of ischemia is inevitable in organ transplantation, and for most, if not all organs, there is a relationship between ischemic time and transplant outcome. The contribution of ischemic time to lung injury is unclear, with conflicting recent data. In this study, we investigate the impact of ischemia time on survival after lung transplantation in a large national cohort. METHODS: We studied the outcomes for 1,565 UK adult lung transplants over a 12-year period, for whom donor, transplant, and recipient data were available from the UK Transplant Registry. We examined the effect of ischemia time (defined as donor cross-clamp to recipient reperfusion) and whether standard cardiopulmonary bypass was used using Cox proportional hazards models, adjusting for other risk factors. RESULTS: The total ischemic time increased from a median under 5 hours in 2003 to over 6.2 hours in 2013. Our findings show that, when the cardiopulmonary bypass was used, there was an increase in the hazard of death (of 13% [95% CI: 5%-21%] for 1-year patient survival) for each hour of total ischemic time. However, if the cardiopulmonary bypass was not used for implantation, this link disappeared-there was no statistically significant change in mortality with increasing ischemic time. CONCLUSIONS: We document that avoidance of bypass may remove ischemic time, within the limits of our observed range of ischemic times, as a risk factor for poor outcomes. Our data add to the evidence that bypass may be harmful to the donor lung.

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

BACKGROUND: The association between interleukin-1ß (IL-1ß) 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-1ß-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-1ß. 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-1ß-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-1ß. Blockade of IL-1ß significantly reduced neutrophil adhesion in vitro ( P = 0.025). CONCLUSION: These data illustrate the proinflammatory functions of IL-1ß in the context of EVLP, suggesting this pathway may be susceptible to therapeutic modulation before transplantation.

Organ Transplants From Deceased Donors With Primary Brain Tumors and Risk of Cancer Transmission.

Importance: Cancer transmission is a known risk for recipients of organ transplants. Many people wait a long time for a suitable transplant; some never receive one. Although patients with brain tumors may donate their organs, opinions vary on the risks involved. Objective: To determine the risk of cancer transmission associated with organ transplants from deceased donors with primary brain tumors. Key secondary objectives were to investigate the association that donor brain tumors have with organ usage and posttransplant survival. Design, Setting, and Participants: This was a cohort study in England and Scotland, conducted from January 1, 2000, to December 31, 2016, with follow-up to December 31, 2020. This study used linked data on deceased donors and solid organ transplant recipients with valid national patient identifier numbers from the UK Transplant Registry, the National Cancer Registration and Analysis Service (England), and the Scottish Cancer Registry. For secondary analyses, comparators were matched on factors that may influence the likelihood of organ usage or transplant failure. Statistical analysis of study data took place from October 1, 2021, to May 31, 2022. Exposures: A history of primary brain tumor in the organ donor, identified from all 3 data sources using disease codes. Main Outcomes and Measures: Transmission of brain tumor from the organ donor into the transplant recipient. Secondary outcomes were organ utilization (ie, transplant of an offered organ) and survival of kidney, liver, heart, and lung transplants and their recipients. Key covariates in donors with brain tumors were tumor grade and treatment history. Results: This study included a total of 282 donors (median [IQR] age, 42 [33-54] years; 154 females [55%]) with primary brain tumors and 887 transplants from them, 778 (88%) of which were analyzed for the primary outcome. There were 262 transplants from donors with high-grade tumors and 494 from donors with prior neurosurgical intervention or radiotherapy. Median (IQR) recipient age was 48 (35-58) years, and 476 (61%) were male. Among 83 posttransplant malignancies (excluding NMSC) that occurred over a median (IQR) of 6 (3-9) years in 79 recipients of transplants from donors with brain tumors, none were of a histological type matching the donor brain tumor. Transplant survival was equivalent to that of matched controls. Kidney, liver, and lung utilization were lower in donors with high-grade brain tumors compared with matched controls. Conclusions and Relevance: Results of this cohort study suggest that the risk of cancer transmission in transplants from deceased donors with primary brain tumors was lower than previously thought, even in the context of donors that are considered as higher risk. Long-term transplant outcomes are favorable. These results suggest that it may be possible to safely expand organ usage from this donor group.

Transplantation of Organs From DCD and DBD Donors Who Died After Ligature Asphyxiation.

BACKGROUND: The United Kingdom transplant registry data demonstrated similar transplant outcomes for recipients of kidneys from donors who died following ligature asphyxiation and those who received organs from donors dying from other causes. The impact that this donor cause of death has on the outcomes of other solid organ transplant recipients remains uncertain. METHODS: The United Kingdom transplant registry analysis was undertaken to determine transplant outcomes in recipients of lungs, hearts, livers' and pancreases from donors who died following ligature asphyxiation. RESULTS: Between January 01, 2003, and December 31, 2016, 2.7% (n = 521) of all potential United Kingdom donors died following ligature asphyxiation (mostly suicide by hanging). Of these, 416 (79.9%; 197 donation after brain stem death and 219 donation after circulatory death [DCD]) donated an organ for transplantation. These donors provided organs for 574 transplants (66 lung transplants, 75 heart transplants, 279 liver transplants, and 154 pancreas transplants). Patient and graft survival were similar for recipients of both donation after brain stem death and DCD hearts, livers, and pancreases from donors who died following ligature asphyxiation. Unadjusted graft and patient survival were significantly worse for recipients of lungs from DCD donors who died following ligature asphyxiation. This detrimental effect persisted after propensity score matching. CONCLUSIONS: Livers, hearts, and pancreases from donors who die following ligature asphyxiation suffer an additional warm ischemic insult, but this does not negatively impact transplant outcomes. Outcomes for recipients of DCD lungs appear to be significantly worse.

A human model of bilateral pulmonary vein sampling to assess the effects of one-lung ventilation on neutrophil function.

BACKGROUND: Neutrophil activation drives lung complications after cardiopulmonary bypass (CPB). Evidence suggests the healthy, ventilated lung may beneficially re-condition pro-inflammatory neutrophils. However, evidence in humans is lacking, due to a paucity of good models. CPB with simultaneous central venous and bilateral pulmonary vein sampling provides an opportunity to model effects of one-lung ventilation. The study's primary objectives were to establish a model of intra-operative, bilateral pulmonary vein sampling and to determine whether neutrophil function differed after passing through inflated or deflated lungs. METHODS: Seventeen patients having "on pump" coronary artery bypass grafting (CABG) with one-lung ventilation (in two cohorts with tidal volume 2ml kg-1 and FiO2 0.21, or tidal volume 4 ml kg-1 and FiO2 0.5 respectively) were recruited. Cohort 1 consisted of 9 patients (7 male, median age 62.0 years) and Cohort 2 consisted of 8 male patients (median age 65.5 years). Recruitment was via prospective screening of scheduled elective and non-elective CABG procedures with cardiopulmonary bypass. Each patient had five blood samples taken-central venous blood pre-operatively; central venous blood pre-CPB; central venous blood post-CPB; pulmonary venous blood draining the ventilated lung post-CPB; and pulmonary venous blood draining the deflated lung post-CPB. Neutrophil phagocytosis and priming status were quantified. Plasma cytokines were measured. RESULTS: Phagocytosis and priming were not significantly different in neutrophils returning from the ventilated lung as compared to the non-ventilated lung. Plasma IL-6, IL-8 and IL-10 were significantly elevated by CPB. CONCLUSIONS: The intra-operative, bilateral pulmonary vein sampling model provides unique opportunities to assess biological effects of interventions to one lung, with the other lung acting as an internal control. Single-lung ventilation during CPB had no significant effects on neutrophil function.

Controlled DCD lung transplantation: Circumventing imagined and real barriers-time for an international taskforce?

Controlled donation after circulatory death (DCD) has the potential to substantially increase the number of lung transplants thus offsetting some of the imbalance between need and organ availability. We examine the potential benefits associated with increased DCD utilization as well as the perceived barriers to the expansion of DCD. Solutions are offered as a means to expand DCD utilization across centers and nations.

Diagnosis and predicted outcomes of patients with cystic fibrosis related liver disease considered for lung transplantation.

INTRODUCTION: There is no gold standard criterion for the diagnosis of cystic fibrosis-related liver disease (CFRLD) and there is uncertainty over its impact on the outcome of lung transplantation. METHOD: Lung recipients (n = 238) were divided into two groups-CFRLD and non-CFRLD based on a modified aspartate aminotransferase-to-platelet ratio index (APRI) score (mAPRI) to diagnose CFRLD and predict severity of liver disease. Groups were compared to assess validity of the diagnosis and survival outcomes. RESULT: The new diagnostic criterion was effective at differentiating CFRLD from non-CFRLD. There was no significant difference in the survival between two groups at short, medium, or long term demonstrated by the Kaplan-Meier plot with survival of 85%, 73%, 47%, 18.6%, and 4.7% at 1, 2, 5, 10, and 15 years respectively. A mAPRI score of greater than .2 had a sensitivity of 43.0% but a specificity of 82.5 % for diagnosis of CFRLD and 46.5% sensitivity but 100% specificity in predicting an ultrasound/biopsy proven hepatic abnormality associated with CFRLD. CONCLUSION: A mAPRI sore is a highly specific non-invasive tool for diagnosis of CFRLD. Recipients with CFRLD but grossly preserved hepatocellular function have a similar outcome to patients without CFRLD.

Efficacy and Safety of Triiodothyronine Treatment in Cardiac Surgery or Cardiovascular Diseases: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

Background: Low levels of the active thyroid hormone triiodothyronine (T3) in cardiac patients are associated with worse outcomes. The aim of this analysis was to assess if T3 treatment is beneficial and safe in patients undergoing cardiac surgery or those with cardiovascular diseases in whom there is observed or expected reduction in serum T3 levels. Methods: A systematic review and meta-analysis of randomized controlled trials (RCTs) was performed as per the PRISMA guidelines. Pubmed, EMBASE, and Web of Science databases were searched for RCTs published between January 1, 1960 and March 30, 2022 that evaluated the effects of T3 therapy in patients undergoing cardiac surgery or with cardiovascular diseases. The primary outcomes were measures of cardiac function. Weighted mean difference (MD) or relative risk was calculated using a random effects model. PROSPERO registration number CRD42020211966. Results: Of the 3181 full-text articles screened, 34 studies with 2547 participants (number ranging between 13 and 223, mean ages between 0.5 and 73 years, mean percentage of women between 7% and 64%) were included. In 12 RCTs with 1093 adults undergoing cardiac surgery T3 therapy was associated with improvement in cardiac index (MD [95% confidence interval], 0.24 [0.08 to 0.40] L/min/m2, I2 = 74%). The quality of evidence was high to moderate. In 3 RCTs with 188 children undergoing cardiac surgery, 3 RCTs with 131 adult cardiac donors, 3 RCTs with 83 adult patients with heart failure, and 2 RCTs with 89 adults with acute myocardial infarction, T3 therapy did not improve cardiac index or left ventricular function; the quality of evidence ranged from high (pediatric cardiac surgery) to low (other groups). No detrimental effect of T3 therapy was observed on heart rate, risk of in-hospital atrial fibrillation, or mortality. Conclusions: Short-term T3 therapy is safe and trials in adults undergoing cardiac surgical procedures to evaluate longer term clinical endpoints are required. Current data do not support the routine use of T3 therapy in children undergoing cardiac surgery or in cardiac donors. Adequately designed trials are required to determine if T3 therapy improves cardiac function and clinical outcomes in patients with heart failure or acute myocardial infarction.

A systematic review and meta-analyses of regional perfusion in donation after circulatory death solid organ transplantation.

In donation after circulatory death (DCD), (thoraco)abdominal regional perfusion (RP) restores circulation to a region of the body following death declaration. We systematically reviewed outcomes of solid organ transplantation after RP by searching PubMed, Embase, and Cochrane libraries. Eighty-eight articles reporting on outcomes of liver, kidney, pancreas, heart, and lung transplants or donor/organ utilization were identified. Meta-analyses were conducted when possible. Methodological quality was assessed using National Institutes of Health (NIH)-scoring tools. Case reports (13/88), case series (44/88), retrospective cohort studies (35/88), retrospective matched cohort studies (5/88), and case-control studies (2/88) were identified, with overall fair quality. As blood viscosity and rheology change below 20 °C, studies were grouped as hypothermic (HRP, ≤20 °C) or normothermic (NRP, >20 °C) regional perfusion. Data demonstrate that RP is a safe alternative to in situ cold preservation (ISP) in uncontrolled and controlled DCDs. The scarce HRP data are from before 2005. NRP appears to reduce post-transplant complications, especially biliary complications in controlled DCD livers, compared with ISP. Comparisons for kidney and pancreas with ISP are needed but there is no evidence that NRP is detrimental. Additional data on NRP in thoracic organs are needed. Whether RP increases donor or organ utilization needs further research.

Consensus statement on normothermic regional perfusion in donation after circulatory death: Report from the European Society for Organ Transplantation's Transplant Learning Journey.

Normothermic regional perfusion (NRP) in donation after circulatory death (DCD) is a safe alternative to in situ cooling and rapid procurement. An increasing number of countries and centres are performing NRP, a technically and logistically challenging procedure. This consensus document provides evidence-based recommendations on the use of NRP in uncontrolled and controlled DCDs. It also offers minimal ethical, logistical and technical requirements that form the foundation of a safe and effective NRP programme. The present article is based on evidence and opinions formulated by a panel of European experts of Workstream 04 of the Transplantation Learning Journey project, which is part of the European Society for Organ Transplantation.

Heart transplantation in the UK during the first wave of the SARS-CoV-2 pandemic.

BACKGROUND: We aim to evaluate practice and understand the impact of the first wave of the SARS-CoV-2 pandemic on heart transplantation in the UK. METHODS: A retrospective review of the UK Transplant Registry (UKTR) and a national survey of UK heart transplant centers have been performed. The early pandemic period is defined here as 1 March to 31 May 2020. RESULTS: There was geographic variation in the prevalence of COVID-19 across the UK. All centers reported adaptations to maintain the safety of their staff, candidate, and recipient populations. The number of donors fell by 31% during the early pandemic period. Heart utilization increased to 35%, compared to 26% during the same period of 2019. The number of heart transplants was well maintained, across all centers, with 38 performed, compared to 41 during the same period of 2019, with no change in 30-day survival. Twenty-seven heart transplant recipients with confirmed COVID-19 infection were reported during the study period. CONCLUSION: All UK heart transplant centers have successfully adapted their programs to overcome the challenges of staff redeployment and ICU and hospital resource limitation, associated with the pandemic, whilst continuing heart transplant activity. On-going evaluation of practice changes, with sharing of lessons learned, is required as the pandemic continues.

The impact of the SARS-CoV-2 pandemic and COVID-19 on lung transplantation in the UK: Lessons learned from the first wave.

BACKGROUND: Lung transplantation is particularly susceptible to the impact of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) pandemic, and evaluation of changes to practice is required to inform future decision-making. METHODS: A retrospective review of the UK Transplant Registry (UKTR) and national survey of UK lung transplant centers has been performed. RESULTS: There was geographic variation in the prevalence of COVID-19 infection across the UK. The number of donors fell by 48% during the early pandemic period. Lung utilization fell to 10% (compared with 24% for the same period of 2019). The number of lung transplants performed fell by 77% from 53, March to May 2019, to 12. Seven (58%) of these were performed in a single-center, designated "COVID-light." The number of patients who died on the lung transplant waiting list increased, compared to the same period of 2019 (p = .0118). Twenty-six lung transplant recipients with confirmed COVID-19 infection were reported during the study period. CONCLUSION: As the pandemic continues, reviewing practice and implementing the lessons learned during this period, including the use of robust donor testing strategies and the provision of "COVID-light" hospitals, are vital in ensuring the safe continuation of our lung transplant program.