Implementing an innovated preservation technology: The American Society of Transplant Surgeons' (ASTS) Standards Committee White Paper on Ex Situ Liver Machine Perfusion

Impact of Back-to-Base Normothermic Machine Perfusion on Complications and Costs: A Multicenter, Real-World Risk-Matched Analysis

OBJECTIVE

Assess cost and complication outcomes after liver transplantation (LT) using normothermic machine perfusion (NMP).

BACKGROUND

End-ischemic NMP is often used to aid logistics, yet its impact on outcomes after LT remains unclear, as does its true impact on costs associated with transplantation.

METHODS

Deceased donor liver recipients at 2 centers (January 1, 2019, to June 30, 2023) were included. Retransplants, splits, and combined grafts were excluded. End-ischemic NMP (OrganOx-Metra) was implemented in October 2022 for extended-criteria donation after brain death (DBDs), all donations after circulatory deaths (DCDs), and logistics. NMP cases were matched 1:2 with static cold storage controls (SCS) using the Balance-of-Risk [donation after brain death (DBD)-grafts] and UK-DCD Score (DCD-grafts).

RESULTS

Overall, 803 transplantations were included, 174 (21.7%) receiving NMP. Matching was achieved between 118 NMP-DBDs with 236 SCS; and 37 NMP-DCD with 74 corresponding SCS. For both graft types, median inpatient comprehensive complications index values were comparable between groups. DCD-NMP grafts experienced reduced cumulative 90-day comprehensive complications index (27.6 vs 41.9, P =0.028). NMP also reduced the need for early relaparotomy and renal replacement therapy, with subsequently less frequent major complications (Clavien-Dindo ≥IVa). This effect was more pronounced in DCD transplants. NMP had no protective effect on early biliary complications. Organ acquisition/preservation costs were higher with NMP, yet NMP-treated grafts had lower 90-day pretransplant costs in the context of shorter waiting list times. Overall costs were comparable for both cohorts.

CONCLUSIONS

This is the first risk-adjusted outcome and cost analysis comparing NMP and SCS. In addition to logistical benefits, NMP was associated with a reduction in relaparotomy and bleeding in DBD grafts, and overall complications and post-LT renal replacement for DCDs. While organ acquisition/preservation was more costly with NMP, overall 90-day health care costs-per-transplantation were comparable.

Machine perfusion in liver transplantation: recent advances and coming challenges

PURPOSE OF REVIEW

Machine perfusion has been adopted into clinical practice in Europe since the mid-2010s and, more recently, in the United States (US) following approval of normothermic machine perfusion (NMP). We aim to review recent advances, provide discussion of potential future directions, and summarize challenges currently facing the field.

RECENT FINDINGS

Both NMP and hypothermic-oxygenated perfusion (HOPE) improve overall outcomes after liver transplantation versus traditional static cold storage (SCS) and offer improved logistical flexibility. HOPE offers additional protection to the biliary system stemming from its' protection of mitochondria and lessening of ischemia-reperfusion injury. Normothermic regional perfusion (NRP) is touted to offer similar protective effects on the biliary system, though this has not been studied prospectively.The most critical question remaining is the optimal use cases for each of the three techniques (NMP, HOPE, and NRP), particularly as HOPE and NRP become more available in the US. There are additional questions regarding the most effective criteria for viability assessment and the true economic impact of these techniques. Finally, with each technique purported to allow well tolerated use of riskier grafts, there is an urgent need to define terminology for graft risk, as baseline population differences make comparison of current data challenging.

SUMMARY

Machine perfusion is now widely available in all western countries and has become an essential tool in liver transplantation. Identification of the ideal technique for each graft, optimization of viability assessment, cost-effectiveness analyses, and proper definition of graft risk are the next steps to maximizing the utility of these powerful tools.

Challenges With the Implementation of Machine Perfusion in Clinical Liver Transplantation

Dynamic organ preservation is a relatively old technique which has regained significant interest in the last decade. Machine perfusion (MP) techniques are applied in various fields of solid organ transplantation today. The first clinical series of ex situ MP in liver transplantation was presented in 2010. Since then, the number of research and clinical applications has substantially increased. Despite the notable beneficial effect on organ quality and recipient outcome, MP is still not routinely used in liver transplantation. Based on the enormous need to better preserve organs and the subsequent demand to continuously innovate and develop perfusion equipment further, this technology is also beneficial to test and deliver future therapeutic strategies to livers before implantation. This article summarizes the various challenges observed during the current shift from static to dynamic liver preservation in the clinical setting. The different organ perfusion strategies are discussed first, together with ongoing clinical trials and future study design. The current status of research and the impact of costs and regulations is highlighted next. Factors contributing to costs and other required resources for a worldwide successful implementation and reimbursement are presented third. The impact of research on cost-utility and effectivity to guide the tailored decision-making regarding the optimal perfusion strategy is discussed next. Finally, this article provides potential solutions to the challenging field of innovation in healthcare considering the various social and economic factors and the role of clinical, regulatory, and financial stakeholders worldwide.

Obstacles to implement machine perfusion technology in routine clinical practice of transplantation: Why are we not there yet?

Machine perfusion of solid human organs is an old technique, and the basic principles were presented as early as 1855 by Claude Barnard. More than 50 years ago, the first perfusion system was used in clinical kidney transplantation. Despite the well-known benefits of dynamic organ preservation and significant medical and technical development in the last decades, perfusion devices are still not in routine use. This article describes the various challenges to implement this technology in practice, critically analyzing the role of all involved stakeholders, including clinicians, hospitals, regulatory, and industry, on the background of regional differences worldwide. The clinical need for this technology is discussed first, followed by the current status of research and the impact of costs and regulations. Considering the need for strong collaborations between clinical users, regulatory bodies, and industry, integrated road maps and pathways required to achieve a wider implementation are presented. The role of research development, clear regulatory pathways, and the need for more flexible reimbursement schemes is discussed together with potential solutions to address the most relevant hurdles. This article paints an overall picture of the current liver perfusion landscape and highlights the role of clinical, regulatory, and financial stakeholders worldwide.

Cold stress-induced ferroptosis in liver sinusoidal endothelial cells determines liver transplant injury and outcomes

Although cold preservation remains the gold standard in organ transplantation, cold stress-induced cellular injury is a significant problem in clinical orthotopic liver transplantation (OLT). Because a recent study showed that cold stress activates ferroptosis, a form of regulated cell death, we investigated whether and how ferroptosis determines OLT outcomes in mice and humans. Treatment with ferroptosis inhibitor (ferrostatin-1) during cold preservation reduced lipid peroxidation (malondialdehyde; MDA), primarily in liver sinusoidal endothelial cells (LSECs), and alleviated ischemia/reperfusion injury in mouse OLT. Similarly, ferrostatin-1 reduced cell death in cold-stressed LSEC cultures. LSECs deficient in nuclear factor erythroid 2-related factor 2 (NRF2), a critical regulator of ferroptosis, were susceptible to cold stress-induced cell death, concomitant with enhanced endoplasmic reticulum (ER) stress and expression of mitochondrial Ca2+ uptake regulator (MICU1). Indeed, supplementing MICU1 inhibitor reduced ER stress, MDA expression, and cell death in NRF2-deficient but not WT LSECs, suggesting NRF2 is a critical regulator of MICU1-mediated ferroptosis. Consistent with murine data, enhanced liver NRF2 expression reduced MDA levels, hepatocellular damage, and incidence of early allograft dysfunction in human OLT recipients. This translational study provides a clinically applicable strategy in which inhibition of ferroptosis during liver cold preservation mitigates OLT injury by protecting LSECs from peritransplant stress via an NRF2-regulatory mechanism.

Normothermic Machine Perfusion Systems: Where Do We Go From Here?

Normothermic machine perfusion (NMP) aims to preserve organs ex vivo by simulating physiological conditions such as body temperature. Recent advancements in NMP system design have prompted the development of clinically effective devices for liver, heart, lung, and kidney transplantation that preserve organs for several hours/up to 1 d. In preclinical studies, adjustments to circuit structure, perfusate composition, and automatic supervision have extended perfusion times up to 1 wk of preservation. Emerging NMP platforms for ex vivo preservation of the pancreas, intestine, uterus, ovary, and vascularized composite allografts represent exciting prospects. Thus, NMP may become a valuable tool in transplantation and provide significant advantages to biomedical research. This review recaps recent NMP research, including discussions of devices in clinical trials, innovative preclinical systems for extended preservation, and platforms developed for other organs. We will also discuss NMP strategies using a global approach while focusing on technical specifications and preservation times.

Maximizing the Donor Potential for Patients with Acute-on-Chronic Liver Failure Listed for Liver Transplant

Owing to inherent limitations of static cold storage, marginal liver grafts from donors after circulatory death and extended criteria donors after brain death are prone to be discarded secondary to the increased risk of severe early allograft dysfunction and ischemic cholangiopathy. Marginal liver grafts resuscitated with hypothermic machine perfusion and normothermic machine perfusion demonstrate lower degree of ischemia-reperfusion injury and have decreased risk of severe early allograft dysfunction and ischemic cholangiopathy. Marginal grafts preserved by ex vivo machine perfusion technology can be used to rescue patients with acute-on-chronic liver failure who are underserved by the current deceased donor liver allocation system.

Trends and Obstacles to Implement Dynamic Perfusion Concepts for Clinical Liver Transplantation: Results from a Global Web-Based Survey

BACKGROUND

Organ perfusion technology is increasingly used in many countries, with a focus, however, on the Western world. This study investigates the current international trends and obstacles to the broader routine implementation of dynamic perfusion concepts in liver transplantation.

METHODS

A web-based anonymous survey was launched in 2021. Experts of all involved specializations from 70 centers in 34 countries were contacted, based on the published literature and experience in the field of abdominal organ perfusion.

RESULTS

Overall, 143 participants from 23 countries completed the survey. Most respondents were male (67.8%) and transplant surgeons (64.3%) working at university hospitals (67.9%). The majority had experience with organ perfusion (82%), applying mainly hypothermic machine perfusion (HMP; 38%) and other concepts. While most (94.4%) expect a higher utilization of marginal organs with machine perfusion, the majority considers HMP the best technique to reduce liver discard-rates. While most respondents (90%) believed machine perfusion should be fully commissioned, the lack of funding (34%) and knowledge (16%) as well as limited staff (19%) were the three main obstacles to a routine clinical implementation.

CONCLUSION

Although dynamic preservation concepts are increasingly used in clinical practice, significant challenges remain. Specific financial pathways, uniform regulations, and tight collaborations among involved experts are needed to achieve wider global clinical use.

Biomarkers and predictive models of early allograft dysfunction in liver transplantation - A systematic review of the literature, meta-analysis, and expert panel recommendations

BACKGROUND

Prompt identification of early allograft dysfunction (EAD) is critical to reduce morbidity and mortality in liver transplant (LT) recipients.

OBJECTIVES

Evaluate the evidence supporting biomarkers that can provide diagnostic and predictive value for EAD.

DATA SOURCES

Ovid MEDLINE, Embase, Scopus, Google Scholar, and Cochrane Central.

METHODS

Systematic review following PRISMA guidelines and recommendations using the GRADE approach was derived from an international expert panel. Studies that investigated biomarkers or models for predicting EAD in adult LT recipients were included for in-depth evaluation and meta-analysis. Olthoff's criteria were used as the standard reference for the diagnostic accuracy evaluation.

PROSPERO ID

CRD42021293838 RESULTS: Ten studies were included for the systematic review. Lactate, lactate clearance, uric acid, Factor V, HMGB-1, CRP to ALB ratio, phosphocholine, total cholesterol, and metabolomic predictive model were identified as potential early EAD predictive biomarkers. The sensitivity ranged between .39 and .92, while the specificity ranged from .63 to .90. Elevated lactate level was most indicative of EAD after adult LT (pooled diagnostic odds ratio of 7.15 (95%CI: 2.38-21.46)). The quality of evidence (QOE) for lactate as indicator was moderate according to the GRADE approach, whereas the QOE for other biomarkers was very low to low likely as consequence of study design characteristics such as single study, small sample size, and large ranges of sensitivity or specificity.

CONCLUSIONS

Lactate is an early indicator to predict EAD after LT (Quality of Evidence: Moderate | Grade of Recommendation: Strong). Further multicenter studies and the use of machine perfusion setting should be implemented for validation.

Hypothermic machine perfusion for liver graft preservation

PURPOSE OF REVIEW

Ex-vivo machine perfusion has emerged as a promising alternative to static cold storage (SCS) for preservation of liver grafts over the last decade. This review describes the mechanistic benefits associated with hypothermic machine perfusion (HMP) for preservation of liver grafts and highlights clinical outcomes of liver transplantation using HMP technology.

RECENT FINDINGS

Over the last decade, several single-centre studies have shown decreased biliary complications, decreased early allograft dysfunction (EAD) rates and improved patient survival in liver transplant recipients after application of HMP for liver graft preservation. This has led to initiation of prospective, multicentre, randomized controlled trials (RCTs) in both Europe and North America focused on clinical outcomes in liver transplant recipients using HMP-preserved liver grafts. In addition, recent single-centre studies have shown the utility of perfusate biomarker analysis during HMP in predicting EAD after liver transplantation.

SUMMARY

HMP technology has potential to increase the available donor liver organ pool for liver transplant recipients and improve clinical outcomes after liver transplantation. Broader clinical application of HMP in resuscitation and preservation of liver grafts is anticipated over the next decade once regulatory, logistical and financial challenges are overcome.

Lung transplantation after ex vivo lung perfusion versus static cold storage: An institutional cost analysis

Ex vivo lung perfusion (EVLP) is a novel lung preservation strategy that facilitates the use of marginal allografts; however, it is more expensive than static cold storage (SCS). To understand how preservation method might affect postoperative costs, we compared outcomes and index hospitalization costs among matched EVLP and SCS preserved lung transplant (LTx) recipients at a single, high-volume institution. A total of 22 EVLP and 66 matched SCS LTx recipients were included; SCS grafts were further stratified as either standard-criteria (SCD) or extended-criteria donors (ECD). Median total preservation time was 857, 409, and 438 min for EVLP, SCD, and ECD lungs, respectively (p < .0001). EVLP patients had similar perioperative outcomes and posttransplant survival compared to SCS SCD and ECD recipients. Excluding device-specific costs, total direct variable costs were similar among EVLP, SCD, and ECD recipients (median $200,404, vs. $154,709 vs. $168,334, p =  .11). The median direct contribution margin was positive for EVLP recipients, and similar to that for SCD and ECD graft recipients (all p > .99). These findings demonstrate that the use of EVLP was profitable at an institutional level; however, further investigation is needed to better understand the financial implications of EVLP in facilitating donor pool expansion in an era of broader lung sharing.

The Actual Operative Costs of Liver Transplantation and Normothermic Machine Perfusion in a Canadian Setting

BACKGROUND

Liver transplantation is an effective treatment for end-stage liver disease. However, waiting lists continue to lengthen as demand exceeds supply. Use of extended criteria donors has helped but is associated with increased rates of complications. The application of normothermic machine perfusion (NMP) has been shown to be protective, especially in more marginal grafts. Despite this benefit, no cost-effectiveness studies have been published.

OBJECTIVE

This study serves as a prelude to a cost-effectiveness analysis of the costs of liver procurement, transplantation, and machine perfusion in a Canadian setting.

METHODS

The total costs were calculated for 106 in-province procurements, the set cost for 237 out-of-province procurements, and 343 liver transplantations. These costs include overheads, supplies, anaesthesia technologist and nursing salaries, and physician billings. Base and modified costs for all procedures were calculated, with consideration of physician billing modifiers. The total cost per run of NMP was calculated, with a range based on variations in the exchange rates for Great British pounds (₤) to Canadian dollars ($Can), year 2019 values.

RESULTS

Costs were $Can30,770.22 for in-province and $Can44,636.73 for out-of-province liver procurement and transplantation. These increased to $Can35,659.22 and 48,076.18 when considering modifiers. The minimum cost per NMP run was $Can18,593.02.

CONCLUSIONS

Although the cost per run is substantial, NMP could potentially lead to cost savings by decreasing night-time salary premiums, complications, and patient length of stay. A formal cost-effectiveness study of NMP in liver transplantation is underway to help clarify the financial benefit or burden of this new technology.

Design, Analysis, and Pitfalls of Clinical Trials Using Ex Situ Liver Machine Perfusion: The International Liver Transplantation Society Consensus Guidelines

BACKGROUND

Recent trials in liver machine perfusion (MP) have revealed unique challenges beyond those seen in most clinical studies. Correct trial design and interpretation of data are essential to avoid drawing conclusions that may compromise patient safety and increase costs.

METHODS

The International Liver Transplantation Society, through the Special Interest Group "DCD, Preservation and Machine Perfusion," established a working group to write consensus statements and guidelines on how future clinical trials in liver perfusion should be designed, with particular focus on relevant clinical endpoints and how different techniques of liver perfusion should be compared. Protocols, abstracts, and full published papers of clinical trials using liver MP were reviewed. The use of a simplified Grading of Recommendations Assessment, Development, and Evaluation working group (GRADE) system was attempted to assess the level of evidence. The working group presented its conclusions at the International Liver Transplantation Society consensus conference "DCD, Liver Preservation, and Machine Perfusion" held in Venice, Italy, on January 31, 2020.

RESULTS

Twelve recommendations were proposed with the main conclusions that clinical trials investigating the effect of MP in liver transplantation should (1) make the protocol publicly available before the start of the trial, (2) be adequately powered, and (3) carefully consider timing of randomization in function of the primary outcome.

CONCLUSIONS

There are issues with using accepted primary outcomes of liver transplantation trials in the context of MP trials, and no ideal endpoint could be defined by the working group. The setup of an international registry was considered vital by the working group.

[Machine Perfusion for Liver Transplantation - What is Possible and Where Do We Stand in Germany? Review of the Literature and Results of a National Survey]

Machine perfusion of donor livers is currently regarded as the most important innovation in transplant surgery to address the continuing shortage of organs in liver transplantation. Hypothermic machine perfusion (HMP) is safe to use and appears to reduce the risk of biliary complications and improve the long-term survival of transplanted organs following preservation by cold static storage - even in donors after cardiac death. A potential functional test of donor organs during HMP uses flavin mononucleotide and is still under clinical investigation. Normothermic machine perfusion (NMP) has a greater risk of technical problems, but functional testing using conventional laboratory parameters during NMP allows significant expansion of the donor pool, even though no prospective randomised study has been able to demonstrate a survival advantage for transplanted organs after NMP. In addition, the preservation time of the donor organs can be significantly extended with the help of NMP, which is particularly advantageous for complex recipient operations and/or logistics. Both methods could be applied for various scenarios in transplantation medicine - theoretically also in combination. The majority of German transplant centres regard machine perfusion as an important innovation and already actively perform perfusions or are in preparation for doing so. However, the overall practical experience in Germany is still relatively low, with only 2 centres having performed more than 20 perfusions. In the coming years, multi-centre efforts to conduct clinical trials and to develop national guidelines on machine perfusion will therefore be indispensable in order to define the potential of these technological developments objectively and to exploit it optimally for the field of transplantation medicine.

Clinical transplantation using negative pressure ventilation ex situ lung perfusion with extended criteria donor lungs

Lung transplantation remains the best treatment option for end-stage lung disease; however, is limited by a shortage of donor grafts. Ex situ lung perfusion, also known as ex vivo lung perfusion, has been shown to allow for the safe evaluation and reconditioning of extended criteria donor lungs, increasing donor utilization. Negative pressure ventilation ex situ lung perfusion has been shown, preclinically, to result in less ventilator-induced lung injury than positive pressure ventilation. Here we demonstrate that, in a single-arm interventional study (ClinicalTrials.gov number NCT03293043) of 12 extended criteria donor human lungs, negative pressure ventilation ex situ lung perfusion allows for preservation and evaluation of donor lungs with all grafts and patients surviving to 30 days and recovered to discharge from hospital. This trial also demonstrates that ex situ lung perfusion is safe and feasible with no patients demonstrating primary graft dysfunction scores grade 3 at 72 h or requiring post-operative extracorporeal membrane oxygenation.

Machine Perfusion: Cold versus Warm, versus Neither. Update on Clinical Trials

Machine perfusion (MP) preservation is potentially one of the most significant improvements in the field of liver transplantation in the last 20 years, and it has been considered a promising strategy for improved preservation and ex situ evaluation of extended criteria donor (ECD) organs. However, MP preservation adds significant cost and logistical considerations to liver transplantation. MP protocols are mainly classified according to the perfusion temperature with hypothermic machine perfusion (HMP) and normothermic machine perfusion (NMP) being the two categories most studied so far. After extensive preclinical work, MP entered the clinical setting, and there are now several studies that demonstrated feasibility and safety. However, because of the limited quality of clinical trials, there is no compelling evidence of superiority in preservation quality, and liver MP is still considered experimental in most countries. MP preservation is moving to a more mature phase, where ongoing and future studies will bring new evidence in order to confirm their superiority in terms of clinical outcomes, organ utilization, and cost-effectiveness. Here, we present an overview of all preclinical MP studies using discarded human livers and liver MP clinical trials, and discuss their results. We describe the different perfusion protocols, pitfalls in MP study design, and provide future perspectives. Recent trials in liver MP have revealed unique challenges beyond those seen in most clinical studies. Randomized trials, correct trial design, and interpretation of data are essential to generate the data necessary to prove if MP will be the new gold standard method of liver preservation.

A Low-Cost Perfusate Alternative for Ex Vivo Lung Perfusion

BACKGROUND

Normothermic ex vivo lung perfusion (EVLP) has been used successfully to evaluate and recondition marginal donor lungs; however, multiple barriers continue to prevent its widespread adoption. We sought to develop a common hospital ingredient-derived perfusate (CHIP) with equivalent functional and inflammatory characteristics to a standard Krebs-Henseleit buffer with 8% serum albumin-derived perfusate (KHB-Alb) to improve access and reduce costs of ex vivo organ perfusion.

METHODS

Sixteen porcine lungs were perfused using negative pressure ventilation (NPV) EVLP for 12 hours in a normothermic state and were allocated equally to 2 groups: KHB-Alb vs CHIP. Physiological parameters, cytokine profiles, and edema formation were compared between treatment groups.

RESULTS

Perfused lungs in both groups demonstrated equivalent oxygenation (partial pressure of arterial oxygen/fraction of inspired oxygen ratio >350 mm Hg) and physiological parameters. There was equivalent generation of tumor necrosis factor-α and IL-6, irrespective of perfusate solution used, when comparing CHIP vs KHB-Alb. Pig lungs developed equivalent edema formation between groups (CHIP: 15.8 ± 4.8%, KHB-Alb 19.5 ± 4.4%, P > .05).

CONCLUSION

A perfusate derived of common hospital ingredients provides equivalent results to a standard Krebs-Henseleit buffer with 8% serum albumin-based perfusate in NPV-EVLP.

The role of normothermic machine perfusion in liver transplantation

To expand the donor pool of suitable organs for transplantation, there is an increased interest in utilizing extended criteria donor grafts (ECD). Ex-situ machine perfusion has shown to be a promising new modality in the organ preservation field to reduce injury and recover ECD liver grafts. Machine perfusion (MP) is considered a significant improvement in the field of transplantation over the past 20 years. Normothermic machine perfusion has entered the clinical arena in the last decade and has shown promising results to improve the quality of marginal organs and to increase the pool of liver grafts. It allows assessment of viability and function of grafts prior to transplantation. In addition, it has the potential to serve as a platform for pharmacologic organ treatment and graft optimization. Machine perfusion moved from the experimental phase to a more mature phase after safety was confirmed by initial clinical trials. Now, it is time to confirm its superiority and cost-effectiveness before a broader clinical use. In this paper we review the history, current status including outcomes of all clinical trials, limitations, and future trends of normothermic machine preservation.

Prospective, single-centre, randomised controlled trial to evaluate the efficacy and safety of ischaemia-free liver transplantation (IFLT) in the treatment of end-stage liver disease

INTRODUCTION

During conventional liver transplantation (CLT), ischaemia-reperfusion injury (IRI) is inevitable and is associated with complications such as early allograft dysfunction (EAD), primary non-function and ischaemic-type biliary lesions. We have established a novel procedure called ischaemia-free liver transplantation (IFLT). The results from a pilot study suggest that IFLT might prevent IRI and yield better transplant outcomes than CLT. The purpose of this study was to further assess the efficacy and safety of IFLT versus CLT in patients with end-stage liver disease.

METHODS AND ANALYSIS

This is an investigator-initiated, open-label, phase III, prospective, single-centre randomised controlled trial on the effects of IFLT in patients with end-stage liver disease. Adult patients (aged 18-75 years) eligible for liver transplantation will be screened for participation in this trial and will be randomised between the IFLT group (n=34) and the CLT group (n=34). In the IFLT group, the donor liver will be procured, preserved and implanted with continuous normothermic machine perfusion (NMP). In the CLT group, the donor liver will be procured after a fast cold flush, preserved in 0°C-4°C solution and implanted under hypothermic and hypoxic conditions. Patients in both groups will be managed according to the standard protocol of our centre. The primary end point is the incidence of EAD after liver transplantation. Intraoperative and postoperative parameters of donor livers and recipients will be observed and recorded, and postoperative liver graft function, complications and recipient and graft survival will be evaluated. After a 12-month follow-up of the last enrolled recipient, the outcomes will be analysed to evaluate the safety and efficacy of IFLT versus CLT in patients with end-stage liver disease.

ETHICS AND DISSEMINATION

The protocol was reviewed and approved by the Ethics Committee of The First Affiliated Hospital of Sun Yat-sen University. The findings will be disseminated to the public through conference presentations and peer-reviewed scientific journals.

TRIAL REGISTRATION NUMBER

ChiCTR1900021158.

Peritransplant VLA-4 blockade inhibits endogenous memory CD8 T cell infiltration into high-risk cardiac allografts and CTLA-4Ig resistant rejection

Recipient endogenous memory CD8 T cells expressing reactivity to donor class I MHC infiltrate MHC-mismatched cardiac allografts within 24 hours after reperfusion and express effector functions mediating graft injury. The current study tested the efficacy of Very Late Antigen-4 (VLA-4) blockade to inhibit endogenous memory CD8 T cell infiltration into cardiac allografts and attenuate early posttransplant inflammation. Peritransplant anti-VLA-4 mAb given to C57BL6 (H-2b ) recipients of AJ (H-2a ) heart allografts completely inhibited endogenous memory CD4 and CD8 T cell infiltration with significant decrease in macrophage, but not neutrophil, infiltration into allografts subjected to either minimal or prolonged cold ischemic storage (CIS) prior to transplant, reduced intra-allograft IFN-γ-induced gene expression and prolonged survival of allografts subjected to prolonged CIS in CTLA-4Ig treated recipients. Anti-VLA-4 mAb also inhibited priming of donor-specific T cells producing IFN-γ until at least day 7 posttransplant. Peritransplant anti-VLA plus anti-CD154 mAb treatment similarly prolonged survival of allografts subjected to minimal or increased CIS prior to transplant. Overall, these data indicate that peritransplant anti-VLA-4 mAb inhibits early infiltration memory CD8 T cell infiltration into allografts with a marked reduction in early graft inflammation suggesting an effective strategy to attenuate negative effects of heterologous alloimmunity in recipients of higher risk grafts.