Machine perfusion of the liver and bioengineering

Use of Ex Situ Machine Perfusion for Liver Transplantation: The National Experience

BACKGROUND

Machine perfusion (MP) for liver transplantation has become more widespread in the United States, but national studies on this growing practice are lacking. We investigated national use and outcomes of MP for liver transplantation.

METHODS

Adult (≥18 y) liver recipients transplanted between January 1, 2016 and September 30, 2023 in the United Network for Organ Sharing database were included. We used Cox regression to compare 1-y posttransplant recipient survival and all-cause graft failure by use of MP and performed subgroup analyses among circulatory death (DCD) and brain death (DBD) donors.

RESULTS

Of 52 626 deceased donors with liver recovery, 1799 (3.5%) utilized MP. The proportion of all liver transplants using MP increased from 0.3% in 2016 to 15.5% in 2023. MP for DCD transplants increased from 0.8% in 2016 to 50.0% in 2023. Donors of MP grafts were older (47 [34-57] versus 42 [29-55] y, P < 0.001), had higher body mass indexes (28.3 [24.4-33.3] versus 27.3 [23.7-31.8] kg/m 2 , P < 0.001), and were more likely to be DCD (47.1% versus 9.3%, P < 0.001). Among DBD transplants, MP and non-MP DBD transplants had similar all-cause graft failure out to 1 y (adjusted hazards ratios, 1.12 [95% confidence interval, 0.87-1.43], P = 0.38). Among DCD transplants, MP recipients had improved survival out to 1 y (adjusted hazards ratios, 0.50 [95% confidence interval, 0.35-0.70], P < 0.001).

CONCLUSIONS

MP use in liver transplantation is rapidly expanding and is associated with favorable outcomes compared with cold storage. MP is associated with increased posttransplant survival for DCD transplants, highlighting the potential for MP to expand utilization of DCD grafts.

Cell therapy for liver disorders: past, present and future

The liver fulfils a plethora of vital functions and, due to their importance, liver dysfunction has life-threatening consequences. Liver disorders currently account for more than two million deaths annually worldwide and can be classified broadly into three groups, considering their onset and aetiology, as acute liver diseases, inherited metabolic disorders and chronic liver diseases. In the most advanced and severe forms leading to liver failure, liver transplantation is the only treatment available, which has many associated drawbacks, including a shortage of organ donors. Cell therapy via fully mature cell transplantation is an advantageous alternative that may be able to restore a damaged organ's functionality or serve as a bridge until regeneration can occur. Pioneering work has shown that transplanting adult hepatocytes can support liver recovery. However, primary hepatocytes cannot be grown extensively in vitro as they rapidly lose their metabolic activity. Therefore, different cell sources are currently being tested as alternatives to primary cells. Human pluripotent stem cell-derived cells, chemically induced liver progenitors, or 'liver' organoids, hold great promise for developing new cell therapies for acute and chronic liver diseases. This Review focuses on the advantages and drawbacks of distinct cell sources and the relative strategies to address different therapeutic needs in distinct liver diseases.

Mesenchymal stem cell-derived exosomes: an emerging therapeutic strategy for hepatic ischemia-reperfusion injury

Hepatic ischemia-reperfusion injury (HIRI) severely threatens the success rates of liver surgery and transplantation. Its complex pathological process involves multiple factors such as oxidative stress, inflammatory responses, and ferroptosis, creating an urgent need for new therapeutic strategies. Exosomes derived from mesenchymal stem cells (MSCs) are emerging as a next-generation acellular therapeutic approach. With their outstanding immune-regulatory capabilities, significant reparative functions, and good biocompatibility, they are leading innovations in the field of HIRI treatment. This article provides a systematic comparison of the therapeutic characteristics of MSC-derived exosomes(MSC-EXOs) from four different sources: adipose tissue, bone marrow, umbilical cord, and induced pluripotent stem cells. Although the clinical translation of MSC-EXOs still faces challenges such as variations in isolation methods, large-scale production, and safety assessments, their remarkable therapeutic effects and vast application potential signal the arrival of a new era of precision treatment for HIRI. This review not only provides a comprehensive theoretical foundation to promote the clinical application of MSC-EXOs but also opens up innovative research directions in the field of regenerative medicine.

Mastering the narrative: Precision reporting of risk and outcomes in liver transplantation

Liver transplantation is associated with a high risk of postoperative complications due to the complexity of the surgical procedure, recipient disease severity and the wide range of graft quality, which remains somewhat unpredictable. However, survival rates after transplantation continue to improve and the focus has thus turned to other clinically relevant endpoints including post-transplant complications, patient quality of life and costs. Procedures like liver transplantation offer the entire spectrum of post-surgical events, even in donor-recipient constellations deemed of low risk within recently defined benchmark criteria. The Clavien-Dindo classification and the CCI (comprehensive complication index) were established to assess postoperative morbidity and are widely utilised across surgical specialties. These scores depend on the number and grade of complications, which reflect the interventions required, and are frequently used to assess specific donor-recipient risk profiles and new approaches, such as machine perfusion. However, these scores are associated with inter-observer variability when used in practice, mainly due to the lack of uniform definitions. The concept of benchmarking was recently introduced in surgery and transplantation as a mechanism of standardising expected donor/recipient risk with outcomes within the first year after surgery. However, the management of complications differs significantly worldwide, as does the rating scale assigned to various complications. This may lead to inhomogeneous interpretation of study results, leading to difficulty in assessing the clinical effects of novel preservation technologies and other therapeutics in liver transplantation. This article critically discusses frequent challenges associated with risk and outcome assessment following liver transplantation.

Long-Term Liver Machine Perfusion Preservation: A Review of Recent Advances, Benefits and Logistics

BACKGROUND

The global shortage of suitable donor livers for transplantation has prompted efforts to expand the donor pool by using extended criteria donors. Machine preservation technology has shown promise in optimizing graft preservation and improving logistics. Additionally, it holds potential for organ repair, regeneration, therapeutic applications during extended preservation periods, and enhancing organ allocation.

METHODS

We conducted a comprehensive literature review using PubMed, Embase, and Web of Science databases. All studies published between January 1, 2022, and February 7, 2024, that described machine perfusion preservation of livers for more than 24 h were eligible for inclusion. The findings were synthesized in a narrative review format to highlight key benefits and advancements.

RESULTS

We identified eleven studies from multiple research groups, employing various techniques, devices, and preservation durations. Perfusion durations ranged from 1 to 13 days, with notable variations in protocols for long-term preservation beyond 24 h. Viability was assessed during perfusion only. No livers were transplanted. Among the reviewed studies, the introduction of a dialysis system emerged as the most effective strategy for managing waste accumulation during long-term liver perfusion. Differences were also observed in hemodynamics, oxygenation, organ chambers, supplemental regimens, and glycemic control.

CONCLUSION

Over the past two years, substantial progress has been made in refining protocols for long-term liver machine perfusion, with significant advancements in waste management, enabling successful multi-day perfusions. While these developments are promising, further research is necessary to standardize and optimize long-term perfusion protocols, establishing a reliable platform for both organ preservation and therapeutic applications.

Early Allograft Dysfunction after liver transplantation- definition, incidence and relevance in a single-centre analysis

PURPOSE

Early Allograft Dysfunction (EAD) is a serious complication following liver transplantation. With more marginal donors and critical recipients, identifying EAD risk factors and their impact on long-term outcomes is crucial.

METHODS

We reviewed all liver transplants performed between 2007 and 2017 at our institution, excluding pediatric recipients, combined thoracic transplants, and retransplants in the same hospital stay. EAD was defined as either: (i) AST/ALT > 2000 IU/l in first 7 postoperative days (POD), (ii) Bilirubin ≥ 10 mg/dl on POD 7, (iii) INR ≥ 1.6 on POD 7.

RESULTS

Of the 621 cases analyzed, the EAD rate was 53.6%. Multivariate analysis identified only donor-dependent variables as independent risk factors for the onset of EAD: donor age (p = 0.012), donor serum sodium (p = 0.021), cold ischemic time (p = 0.007) and graft weight (p < 0.001). EAD significantly impaired graft survival (69.2% vs. 86.2% after 1 year; p = 0.005) but did not impact long-term patient survival (76.3% vs. 87.6% after 1 year; p = 0.162). Of the EAD components, elevated INR proved to be the only reliable predictor of patient mortality. Additionally, an AST/ALT concentration of > 4000 IU/l significantly improved the predictive value of the EAD definition for patient survival (p = 0.002).

CONCLUSIONS

EAD risk factors are primarily donor-based and significantly impair graft but not patient survival. The high EAD rates and increased use of marginal grafts suggest the need to adjust conventional EAD definitions to optimize graft allocation in the future.

The importance of preclinical models for cholangiocarcinoma drug discovery

INTRODUCTION

Biliary tract cancer (BTC) comprises a clinically diverse and genetically heterogeneous group of tumors along the intra- and extrahepatic biliary system (intrahepatic and extrahepatic cholangiocarcinoma) and gallbladder cancer with the common feature of a poor prognosis, despite increasing molecular knowledge of associated genetic aberrations and possible targeted therapies. Therefore, the search for even more precise and individualized therapies is ongoing and preclinical tumor models are central to the development of such new approaches.

AREAS COVERED

The models described in the current review include simple and advanced in vitro and in vivo models, including cell lines, 2D monolayer, spheroid and organoid cultures, 3D bioprinting, patient-derived xenografts, and more recently, machine-perfusion platform-based models of resected liver specimens. All these models have individual advantages, disadvantages and limitations that need to be considered depending on the desired application.

EXPERT OPINION

In addition to potential cost limitations, availability of BTC cell types, time required for model establishment and growth success rate, the individual models differently reflect relevant characteristics such as tumor heterogeneity, spatial tumor-stroma microenvironment interactions, metabolic and nutritional gradients and immunological interactions. Therefore, a consequent combination of different models may be required to improve clinical study outcomes by strengthening the preclinical data basis.

Research progress of ischemia-free liver transplantation

Ischemia-reperfusion injury (IRI) is an inherent issue in organ transplantation. Because of the allograft shortage, more and more extended criteria donor (ECD) organs are used, unfortunately these grafts are more susceptible to IRI. Although machine perfusion technology has brought hope to alleviate IRI, this technology is still unable to eradicate IRI-related organ damage. Ischemia-free liver transplantation (IFLT) can completely avoid IRI, thereby improve graft function and recipient outcome, and allow to expand organ pool. This review summarized the latest progresses in IFLT, and speculated the future development of this concept.

Particular Chinese contributions to extracorporeal liver surgery

Extracorporeal liver surgery (ELS), also known as liver autotransplantation, is a hybrid (cross-fertilized) surgery incorporating the technical knowledge from extreme liver and transplant liver surgeries, and recently became more embraced and popularized among leading centers. ELS could be summarized into three major categories, namely, ex-situ liver resection and autotransplantation (ELRA), ante-situm liver resection and autotransplantation (ALRA) and auxiliary partial liver autotransplantation (APLA). The successful development of ELS during the past 37 years is definitely inseparable from continuous efforts done by Chinese surgeons and researchers. Especially, the precision liver surgery paradigm has allowed to transform ELS into a modularized, more simplified, and standardized surgery, to upgrade surgical skills, to improve peri-operative outcome and long-term survival, to increase the capability of surgeons to select more complex diseases and to expand the level of medical service to the population. This review highlights the Chinese contributions to the field of ELS, focusing thereby on features of different surgical types, technical innovations, disease selection and surgical indication, patient prognosis and future perspectives.

Challenges and opportunities in organ donation after circulatory death

In recent years, there has been resurgence in donation after circulatory death (DCD). Despite that, the number of organs transplanted from these donors remains low due to concerns about their function and a lack of an objective assessment at the time of donation. This overview examines the current DCD practices and the classification modifications to accommodate regional perspectives. Several risk factors underscore the reluctance to accept DCD organs, and we discuss the modern strategies to mitigate them. The advent of machine perfusion technology has revolutionized the field of DCD transplantation, leading to improved outcomes and better organ usage. With many strategies at our disposal, there is an urgent need for comparative trials to determine the optimal use of perfusion technologies for each donated organ type. Additional progress in defining therapeutic strategies to repair the damage sustained during the dying process should further improve DCD organ utilization and outcomes. However, there remains wide variability in access to DCD donation and transplantation, and organizational efforts should be doubled up with consensus on key ethical issues that still surround DCD donation in the era of machine perfusion.

Validation of a Pretransplant Risk Prediction Model for Early Allograft Dysfunction After Living-donor Liver Transplantation

BACKGROUND

Early allograft dysfunction (EAD) affects outcomes in liver transplantation (LT). Existing risk models developed for deceased-donor LT depend on posttransplant factors and fall short in living-donor LT (LDLT), where pretransplant evaluations are crucial for preventing EAD and justifying the donor's risks.

METHODS

This retrospective study analyzed data from 2944 adult patients who underwent LDLT at 17 centers between 2016 and 2020. We developed a logistic regression model to predict EAD based on this development cohort. We used data from 1020 patients at the King Faisal Transplant Center for external validation.

RESULTS

In the development cohort, 321 patients (10.9%) experienced EAD. These patients had poorer health status, more liver decompensation, and higher requirements of hospitalization than those without EAD. Multivariable logistic regression identified independent pretransplant predictors of EAD: laboratory Model for End-Stage Liver Disease score (odds ratio [OR], 1.08; 95% confidence interval [CI], 1.06-1.09), the necessity for hospitalization at the time of transplant (OR, 2.58; 95% CI, 2.00-3.30), and graft weight in kilogram (OR, 0.27; 95% CI, 0.17-0.45). Using these predictors, we developed the model for EAD after LDLT, which demonstrated strong discriminative ability in the development cohort with an area under the curve (AUC) of 0.71 (95% CI, 0.68-0.74). The model maintained high discrimination during internal validation (AUC, 0.70; 95% CI, 0.67-0.73) and showed a modest reduction in discriminative power in external validation (AUC, 0.65; 95% CI, 0.61-0.68).

CONCLUSIONS

EAD post-LDLT is influenced by the recipient's pretransplant health condition and the graft weight. Integrating the model for EAD after LDLT into the pretransplant process of pairing donors and recipients can enhance the safety and efficacy of LDLT.

Developing and Expanding Deceased Organ Donation to Its Maximum Therapeutic Potential: An Actionable Global Challenge From the 2023 Santander Summit

On November 9 and 10, 2023, the Organización Nacional de Trasplantes (ONT), under the Spanish Presidency of the Council of the European Union, convened in Santander a Global Summit entitled "Towards Global Convergence in Transplantation: Sufficiency, Transparency and Oversight." This article summarizes two distinct but related challenges elaborated at the Santander Summit by Working Group 2 that must be overcome if we are to develop and expand deceased donation worldwide and achieve the goal of self-sufficiency in organ donation and transplantation. Challenge 1: the need for a unified concept of death based on the permanent cessation of brain function. Working group 2 proposed that challenge 1 requires the global community to work toward a uniform, worldwide definition of human death, conceptually unifying circulatory and neurological criteria of death around the cessation of brain function and accepting that permanent cessation of brain function is a valid criterion to determine death. Challenge 2: reducing disparities in deceased donation and increasing organ utilization through donation after the circulatory determination of death (DCDD). Working group 2 proposed that challenge 2 requires the global community to work toward increasing organ utilization through DCDD, expanding DCDD through in situ normothermic regional perfusion, and expanding DCDD through ex situ machine organ perfusion technology. Recommendations for implementation are described.

Bridging Therapies-Ex Vivo Liver Xenoperfusion and the Role of Machine Perfusion: An Update

Advancements in xenotransplantation intersecting with modern machine perfusion technology offer promising solutions to patients with liver failure providing a valuable bridge to transplantation and extending graft viability beyond current limitations. Patients facing acute or acute chronic liver failure, post-hepatectomy liver failure, or fulminant hepatic failure often require urgent liver transplants which are severely limited by organ shortage, emphasizing the importance of effective bridging approaches. Machine perfusion is now increasingly used to test and use genetically engineered porcine livers in translational studies, addressing the limitations and costs of non-human primate models. Current reports about artificial and bioartificial liver support combined with xenografts showcase the potential in ex vivo xenogeneic perfusion. Breakthroughs, such as the perfusion of genetically modified porcine liver with FDA-approved machine perfusion systems connected to human blood circulation, underscore the interest and potential feasibility of a "liver dialysis" bridge to allotransplantation or recovery. This review provides an overview of the past and current research in the field of ex vivo pig liver xenoperfusion.

Liver transplantation for alcohol-associated liver disease

Alcohol-associated liver disease (ALD) is a major cause of morbidity and mortality worldwide, and a leading indication for liver transplantation (LT) in many countries, including the United States. However, LT for ALD is a complex and evolving field with ethical, social, and medical challenges. Thus, it requires a multidisciplinary approach and individualized decision-making. Short-term and long-term patient and graft survival of patients undergoing LT for ALD are comparable to other indications, but there is a continued need to develop better tools to identify patients who may benefit from LT, improve the pretransplant and posttransplant management of ALD, and evaluate the impact of LT for ALD on the organ donation and transplantation systems. In this review, we summarize the current evidence on LT for ALD, from alcohol-associated hepatitis to decompensated alcohol-associated cirrhosis. We discuss the indications, criteria, outcomes, and controversies of LT for these conditions and highlight the knowledge gaps and research priorities in this field.

Machine Perfusion as a Strategy to Decrease Ischemia-Reperfusion Injury and Lower Cancer Recurrence Following Liver Transplantation

Liver transplantation (LT) is a key treatment for primary and secondary liver cancers, reducing tumor burden with concurrent improvement of liver function. While significant improvement in survival is noted with LT, cancer recurrence rates remain high. Mitochondrial dysfunction caused by ischemia-reperfusion injury (IRI) is known to drive tumor recurrence by creating a favorable microenvironment rich in pro-inflammatory and angiogenic factors. Therefore, strategies that decrease reperfusion injury and mitochondrial dysfunction may also decrease cancer recurrence following LT. Machine perfusion techniques are increasingly used in routine clinical practice of LT with improved post-transplant outcomes and increased use of marginal grafts. Normothermic (NMP) and hypothermic oxygenated machine perfusion (HOPE) provide oxygen to ischemic tissues, and impact IRI and potential cancer recurrence through different mechanisms. This article discussed the link between IRI-associated inflammation and tumor recurrence after LT. The current literature was screened for the role of machine perfusion as a strategy to mitigate the risk of cancer recurrence. Upfront NMP ("ischemia free organ transplantation") and end-ischemic HOPE were shown to reduce hepatocellular carcinoma recurrence in retrospective studies. Three prospective randomized controlled trials are ongoing in Europe to provide robust evidence on the impact of HOPE on cancer recurrence in LT.

Long-term machine perfusion of human split livers: a new model for regenerative and translational research

Recent advances in machine perfusion have revolutionised the field of transplantation by prolonging preservation, permitting evaluation of viability prior to implant and rescue of discarded organs. Long-term perfusion for days-to-weeks provides time to modify these organs prior to transplantation. By using long-term normothermic machine perfusion to facilitate liver splitting and subsequent perfusion of both partial organs, possibilities even outside the clinical arena become possible. This model remains in its infancy but in the future, could allow for detailed study of liver injury and regeneration, and ex-situ treatment strategies such as defatting, genetic modulation and stem-cell therapies. Here we provide insight into this new model for research and highlight its great potential and current limitations.

Revolutionizing Liver Transplantation: Transitioning to an Elective Procedure Through Ex Situ Normothermic Machine Perfusion - A Benefit Analysis

OBJECTIVE

To assess the impact of normothermic machine perfusion (NMP) on patients, medical teams, and costs by gathering global insights and exploring current limitations.

BACKGROUND

NMP for ex situ liver graft perfusion is gaining increasing attention for its capability to extend graft preservation. It has the potential to transform liver transplantation (LT) from an urgent to a purely elective procedure, which could revolutionize LT logistics, reduce burden on patients and health care providers, and decrease costs.

METHODS

A 31-item survey was sent to international transplant directors to gather their NMP experiences and vision. In addition, we performed a systematic review on cost-analysis in LT and assessed studies on cost-benefit in converting urgent-to-elective procedures. We compared the costs of available NMPs and conducted a sensitivity analysis of NMP's cost benefits.

RESULTS

Of 120 transplant programs contacted, 64 (53%) responded, spanning North America (31%), Europe (42%), Asia (22%), and South America (5%). Of the total, 60% had adopted NMP, with larger centers (>100 transplants/year) in North America and Europe more likely to use it. The main NMP systems were OrganOx-metra (39%), XVIVO (36%), and TransMedics-OCS (15%). Despite NMP adoption, 41% of centers still perform >50% of LTs at nights/weekends. Centers recognized NMP's benefits, including improved work satisfaction and patient outcomes, but faced challenges like high costs and machine complexity. 16% would invest $100,000 to 500'000, 33% would invest $50,000 to 100'000, 38% would invest $10,000 to 50'000, and 14% would invest <$10,000 in NMP. These results were strengthened by a cost analysis for NMP in emergency-to-elective LT transition. Accordingly, while liver perfusions with disposables up to $10,000 resulted in overall positive net balances, this effect was lost when disposables' cost amounted to >$40,000/organ.

CONCLUSIONS

The adoption of NMP is hindered by high costs and operational complexity. Making LT elective through NMP could reduce costs and improve outcomes, but overcoming barriers requires national reimbursements and simplified, automated NMP systems for multiday preservation.

Efficiency of machine perfusion in pediatric liver transplantation

Liver transplantation is the only life-saving procedure for children with end-stage liver disease. The field is however heterogenic with various graft types, recipient age, weight, and underlying diseases. Despite recently improved overall outcomes and the expanded use of living donors, waiting list mortality remains unacceptable, particularly in small children and infants. Based on the known negative effects of elevated donor age, higher body mass index, and prolonged cold ischemia time, the number of available donors for pediatric recipients is limited. Machine perfusion has regained significant interest in the adult liver transplant population during the last decade. Ten randomized controlled trials are published with an overall advantage of machine perfusion techniques over cold storage regarding postoperative outcomes, including graft survival. The concept of hypothermic oxygenated perfusion (HOPE) was the first and only perfusion technique used for pediatric liver transplantation today. In 2018 the first pediatric candidate received a full-size graft donated after circulatory death with cold storage and HOPE, followed by a few split liver transplants after HOPE with an overall limited case number until today. One series of split procedures during HOPE was recently presented by colleagues from France with excellent results, reduced complications, and better graft survival. Such early experience paves the way for more systematic use of machine perfusion techniques for different graft types for pediatric recipients. Clinical reports of pediatric liver transplants with other perfusion techniques are awaited. Strong collaborative efforts are needed to explore the effect of perfusion techniques in this vulnerable population impacting not only the immediate posttransplant outcome but the development and success of an entire life.

Maladaptive regeneration and metabolic dysfunction associated steatotic liver disease: Common mechanisms and potential therapeutic targets

The normal liver has an extraordinary capacity of regeneration. However, this capacity is significantly impaired in steatotic livers. Emerging evidence indicates that metabolic dysfunction associated steatotic liver disease (MASLD) and liver regeneration share several key mechanisms. Some classical liver regeneration pathways, such as HGF/c-Met, EGFR, Wnt/β-catenin and Hippo/YAP-TAZ are affected in MASLD. Some recently established therapeutic targets for MASH such as the Thyroid Hormone (TH) receptors, Glucagon-like protein 1 (GLP1), Farnesoid X receptor (FXR), Peroxisome Proliferator-Activated Receptors (PPARs) as well as Fibroblast Growth Factor 21 (FGF21) are also reported to affect hepatocyte proliferation. With this review we aim to provide insight into common molecular pathways, that may ultimately enable therapeutic strategies that synergistically ameliorate steatohepatitis and improve the regenerating capacity of steatotic livers. With the recent rise of prolonged ex-vivo normothermic liver perfusion prior to organ transplantation such treatment is no longer restricted to patients undergoing major liver resection or transplantation, but may eventually include perfused (steatotic) donor livers or even liver segments, opening hitherto unexplored therapeutic avenues.

Normothermic Regional Perfusion in Controlled Donation After Circulatory Death Liver Transplantation: A Systematic Review and Meta-Analysis

Liver grafts from controlled donation after circulatory death (cDCD) donors have lower utilization rates due to inferior graft and patient survival rates, largely attributable to the increased incidence of ischemic cholangiopathy, when compared with grafts from brain dead donors (DBD). Normothermic regional perfusion (NRP) may improve the quality of cDCD livers to allow for expansion of the donor pool, helping to alleviate the shortage of transplantable grafts. A systematic review and metanalysis was conducted comparing NRP cDCD livers with both non-NRP cDCD livers and DBD livers. In comparison to non-NRP cDCD outcomes, NRP cDCD grafts had lower rates of ischemic cholangiopathy [RR = 0.23, 95% CI (0.11, 0.49), p = 0.0002], primary non-function [RR = 0.51, 95% CI (0.27, 0.97), p = 0.04], and recipient death [HR = 0.5, 95% CI (0.36, 0.69), p < 0.0001]. There was no difference in outcomes between NRP cDCD donation compared to DBD liver donation. In conclusion, NRP improved the quality of cDCD livers compared to their non-NRP counterparts. NRP cDCD livers had similar outcomes to DBD grafts. This provides further evidence supporting the continued use of NRP in cDCD liver transplantation and offers weight to proposals for its more widespread adoption.

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.

[Organ donation and organ assessment after primary circulatory death and secondary brain death]

BACKGROUND

The global organ shortage is the biggest obstacle to expand urgently needed liver transplantation activities. In addition to donation after brain death (DBD), donation after primary circulatory death (DCD) has also been introduced in many European countries to increase the number of donated organs.

OBJECTIVE

This article summarizes the legal and ethical aspects of DCD, the practical donation process of DCD, the clinical results of DCD liver transplantation with a special focus on organ assessment before a planned DCD liver transplantation.

RESULTS

In Europe 11 countries have active DCD liver transplantation programs and a total of 1230 DCD liver transplantations were performed in Europe in 2023. The highest proportion of DCD liver transplantations were recorded in Belgium (52.8%), the Netherlands (42.8%) and Switzerland (32.1%). The adequate selection of donors and recipients is crucial in DCD transplantation and the use of DCD livers particularly depends on the preparedness of the healthcare system for routine machine perfusion. The leaders are Belgium, France and Italy which implant around 68-74% of DCD organs. With an adequate organ assessment, the long-term results of DBD and DCD liver transplantations are comparable. To assess mitochondrial damage and thus organ quality, hypothermic oxygenated machine perfusion (HOPE) was introduced and has the secondary benefit of mitochondrial protection through oxygenation. The establishment of aerobic metabolism in mitochondria under hypothermia leads to a reduction of toxic metabolites and the restoration of ATP storage, which subsequently leads to a reperfusion light during implantation.

CONCLUSION

Expanding the donor pool with DCD donors can counteract the global organ shortage. With adequate patient selection and routine organ assessment short-term and also long-term outcomes of DBD and DCD liver transplantation are comparable.

Return of the cold: How hypothermic oxygenated machine perfusion is changing liver transplantation

Hypothermic Oxygenated machine PErfusion (HOPE) has recently emerged as a preservation technique which can reduce ischemic injury and improve clinical outcomes following liver transplantation. First developed with the advent solid organ transplantation techniques, hypothermic machine perfusion largely fell out of favour following the development of preservation solutions which can satisfactorily preserve grafts using the cheap and simple method, static cold storage (SCS). However, with an increasing need to develop techniques to reduce graft injury and better utilise marginal and donation after circulatory death (DCD) grafts, HOPE has emerged as a relatively simple and safe technique to optimise clinical outcomes following liver transplantation. Perfusing the graft with cold, acellular, oxygenated perfusate either via the portal vein (PV) alone, or via both the PV and hepatic artery (HA), HOPE is generally commenced for a period of 1-2 h immediately prior to implantation. The technique has been validated by multiple randomised control trials, and pre-clinical evidence suggests HOPE primarily reduces graft injury by decreasing the accumulation of harmful mitochondrial intermediates, and subsequently, the severity of post-reperfusion injury. HOPE can also facilitate real time graft assessment, most notably via the measurement of flavin mononucleotide (FMN) in the perfusate, allowing transplant teams to make better informed clinical decisions prior to transplantation. HOPE may also provide a platform to administer novel therapeutic agents to ex situ organs without risk of systemic side effects. As such, HOPE is uniquely positioned to revolutionise how liver transplantation is approached and facilitate optimised clinical outcomes for liver transplant recipients.

The Spread Pattern of New Practice in Liver Transplantation in the United States

BACKGROUND

Introducing new liver transplantation (LT) practices, like unconventional donor use, incurs higher costs, making evaluation of their prognostic justification crucial. This study reexamines the spread pattern of new LT practices and its prognosis across the United States.

METHODS

The study investigated the spread pattern of new practices using the UNOS database (2014-2023). Practices included LT for hepatitis B/C (HBV/HCV) nonviremic recipients with viremic donors, LT for COVID-19-positive recipients, and LT using onsite machine perfusion (OMP). One year post-LT patient and graft survival were also evaluated.

RESULTS

LTs using HBV/HCV donors were common in the East, while LTs for COVID-19 recipients and those using OMP started predominantly in California, Arizona, Texas, and the Northeast. K-means cluster analysis identified three adoption groups: facilities with rapid, slow, and minimal adoption rates. Rapid adoption occurred mainly in high-volume centers, followed by a gradual increase in middle-volume centers, with little increase in low-volume centers. The current spread patterns did not significantly affect patient survival. Specifically, for LTs with HCV donors or COVID-19 recipients, patient and graft survivals in the rapid-increasing group was comparable to others. In LTs involving OMP, the rapid- or slow-increasing groups tended to have better patient survival (p = 0.05) and significantly improved graft survival rates (p = 0.02). Facilities adopting new practices often overlap across different practices.

DISCUSSION

Our analysis revealed three distinct adoption groups across all practices, correlating the adoption aggressiveness with LT volume in centers. Aggressive adoption of new practices did not compromise patient and graft survivals, supporting the current strategy. Understanding historical trends could predict the rise in future LT cases with new practices, aiding in resource distribution.

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.

Shaping the Future of Cardiovascular Disease by 3D Printing Applications in Stent Technology and its Clinical Outcomes

Cardiovascular disease (CVD) is a leading cause of death worldwide. In recent years, 3D printing technology has ushered in a new era of innovation in cardiovascular medicine. 3D printing in CVD management encompasses various aspects, from patient-specific models and preoperative planning to customized medical devices and novel therapeutic approaches. In-stent technology, 3D printing has revolutionized the design and fabrication of intravascular stents, offering tailored solutions for complex anatomies and individualized patient needs. The advantages of 3D-printed stents, such as improved biocompatibility, enhanced mechanical properties, and reduced risk of in-stent restenosis. Moreover, the clinical trials and case studies that shed light on the potential of 3D printing technology to improve patient outcomes and revolutionize the field has been comprehensively discussed. Furthermore, regulatory considerations, and challenges in implementing 3D-printed stents in clinical practice are also addressed, underscoring the need for standardization and quality assurance to ensure patient safety and device reliability. This review highlights a comprehensive resource for clinicians, researchers, and policymakers seeking to harness the full potential of 3D printing technology in the fight against CVD.

Liver ischemia-reperfusion injury: From trigger loading to shot firing

An ischemia-reperfusion injury (IRI) results from a prolonged ischemic insult followed by the restoration of blood perfusion, being a common cause of morbidity and mortality, especially in liver transplantation. At the maximum of the potential damage, IRI is characterized by 2 main phases. The first is the ischemic phase, where the hypoxia and vascular stasis induces cell damage and the accumulation of damage-associated molecular patterns and cytokines. The second is the reperfusion phase, where the local sterile inflammatory response driven by innate immunity leads to a massive cell death and impaired liver functionality. The ischemic time becomes crucial in patients with underlying pathophysiological conditions. It is possible to compare this process to a shooting gun, where the loading trigger is the ischemia period and the firing shot is the reperfusion phase. In this optic, this article aims at reviewing the main ischemic events following the phases of the surgical timeline, considering the consequent reperfusion damage.

Extracellular Vesicles in Liver Transplantation: Current Evidence and Future Challenges

Extracellular vesicles (EVs) are emerging as a promising field of research in liver disease. EVs are small, membrane-bound vesicles that contain various bioactive molecules, such as proteins, lipids, and nucleic acids and are involved in intercellular communication. They have been implicated in numerous physiological and pathological processes, including immune modulation and tissue repair, which make their use appealing in liver transplantation (LT). This review summarizes the current state of knowledge regarding the role of EVs in LT, including their potential use as biomarkers and therapeutic agents and their role in graft rejection. By providing a comprehensive insight into this emerging topic, this research lays the groundwork for the potential application of EVs in LT.