Machine Perfusions in Liver Transplantation: The Evidence-Based Position Paper of the Italian Society of Organ and Tissue Transplantation

Haemoadsorption cartridge connected to the machine perfusion for donation after circulatory death porcine liver marginal grafts

BACKGROUND

Marginal donation after circulatory death (DCD) liver grafts are carefully used to combat the constant shortage of donors. Clinically, the worst outcomes are mainly related to severe ischemia-reperfusion-injury and the dangerous effect of various inflammatory cytokines (CK). The machine perfusion (MP) is a promising device to rescue these grafts.

AIM

To analyze the role of MP connected to a sorbent cartridge (PerSorb^®) and used for very damaged DCD pig livers.

METHODS

Seven grafts were procured from pigs from a slaughterhouse. Grafts were made very marginal with at least 60 minutes of donor warm ischemia time and 24 hours of static-cold ischemia time: (1) 3 grafts were perfused in hypothermic MP with PerSorb (Sorb); (2) 2 other grafts in hypothermic MP (HMP) without the cartridge (NoSorb); and (3) The other 2 livers stored in the ice box (NoTreat). The CK were measured at HMP start (T0) and at the end (Tend). Biopsies were taken at T0 and Tend.

RESULTS

All 5 grafts treated with HMP had a negative lactate trend after 3 hours of treatment (8.83 at T0 vs 6.4 at Tend of Sorb; 15 at T0 vs 5.45 at Tend for NoSorb, P value > 0.05). At Tend, both Sorb and NoSorb groups had better hemodynamic parameters, comparable between the two groups. Enzyme-linked immunosorbent assay analysis showed a reduction of monocyte chemotactic protein-1, tumor necrosis factor-alpha and interleukin-1β for NoSorb group at Tend and a complete downregulation to physiological levels of the same CK in Sorb livers after 3 hours of treatment. Biopsies showed a reduction of the perisinusoidal edema for the Sorb grafts compared with the NoSorb livers.

CONCLUSION

These data suggest a potential protective role of treatment of grafts with MP and sorbent cartridge in reducing the inflammatory response after a severe ischemic injury.

Short (2-Hour) Non-Oxygenated End-Ischemic Hypothermic Perfusion Versus Cold Storage in the Setting of Renal Transplantation

BACKGROUND

Kidney transplantation (KT) is the most effective treatment for end-stage renal disease. End-ischemic hypothermic machine perfusion (EI-HMP) has emerged as a promising method for preserving grafts before transplantation. This study aimed to compare graft function recovery in KT recipients of deceased brain-death (DBD) grafts preserved with EI-HMP versus static cold storage (SCS). The primary outcome was the rate of delayed graft function (DGF). Secondary outcomes included urine output, intensive care unit (ICU) stay, hospital stay duration, and survival rates.

METHODS

A retrospective, single-center observational study was conducted at Sapienza University of Rome, analyzing 313 KT patients between January 2014 and September 2021. Patients were stratified into two groups based on graft preservation methods (EI-HMP, n = 95; SCS, n = 218). A stabilized inverse probability treatment weighting (IPTW) method was employed to adjust for potential confounders.

RESULTS

There were no significant differences in DGF rates between the two groups (17.9% vs. 15.6% in SCS and EI-HMP cases, respectively; p = 0.75). EI-HMP group demonstrated a higher urine output on day 2 (p = 0.046), a shorter ICU stay (p < 0.0001), and a trend toward a shorter overall hospital stay (p = 0.07). No statistically significant differences were found between EI-HMP and SCS cases in 1- and 3-year overall survival rates (3.2% and 6.7% vs. 5.6% and 6.6%, respectively; log-rank p = 0.53) or in death-censored graft loss rates (5.4% and 8.9% vs. 5.7% and 7.3%, respectively; log-rank p = 0.88). In a sub-analysis of expanded criteria donors (ECD), EI-HMP demonstrated a protective effect by reducing the risk of DGF (OR = 0.31, 95% CI = 0.09-0.95; p = 0.047).

CONCLUSION

EI-HMP was associated with certain short-term benefits, including increased urine output and reduced ICU stays, but showed no significant impact on long-term survival outcomes. A reduction in DGF rates was observed only in the ECD subgroup. Randomized controlled trials are necessary to further investigate the long-term clinical benefits of EI-HMP.

Ex-situ normothermic machine perfusion prevents ischemic cholangiopathy after liver transplantation: A meta-regression analysis

BACKGROUND & AIMS

Liver transplantation (LT) is the gold standard for end-stage liver disease, but ischemic cholangiopathy (IC) remains a significant complication. Ex-situ normothermic machine perfusion (ESNMP) has emerged as a potential strategy to mitigate ischemic injury. However, the effect of ESNMP on reducing post-LT IC remains controversial. This study aimed to perform an updated meta-analysis to evaluate the impact of ESNMP on IC incidence.

METHODS

A systematic review and meta-analysis were conducted following PRISMA guidelines. The literature search included studies from 2015 to 2025 comparing LT outcomes using ESNMP vs. static cold storage (SCS). The primary outcome was the incidence of IC. Risk of bias was assessed using the ROBINS-E tool. Statistical analysis, including random-effects meta-analysis, sensitivity analysis, and meta-regression, was performed to evaluate heterogeneity, potential confounders, and the impact of follow-up duration.

RESULTS

Seventeen studies, including 76,045 patients (4843 ESNMP; 71,202 SCS), were analyzed. No statistically significant difference in IC incidence was found between ESNMP and SCS (1.3 % vs. 0.6 %; RR = 0.68, 95 %CI = 0.41-1.13; P = 0.14). Sensitivity analysis excluding one outlier study revealed a reduction in IC risk with ESNMP (RR = 0.62, 95 %CI = 0.38-1.01; P = 0.054). Two sub-analyses of studies with ≥12 months of follow-up (RR = 0.51, 95 %CI = 0.26-0.99; P = 0.049) and DCDs (RR = 0.33, 95 %CI = 0.16-0.67; P = 0.002) showed risk reduction. The meta-regression revealed that the back-to-base perfusion approach was associated with the occurrence of IC, with an OR of 1.03 (95 %CI = 1.00-1.07, P = 0.035).

CONCLUSIONS

a correlation between ESNMP use and IC reduced risk appears to exist, especially with longer follow-up periods and DCDs, though more high-quality studies are needed to confirm this finding.

Sequential Hypothermic and Normothermic Machine Perfusion of Extended Criteria Donors in Liver Transplantation: A Single-Center Preliminary Experience

INTRODUCTION

Liver transplantation (LT) is the sole curative option for liver failure and other primary liver conditions. However, the limited number of suitable donors compared with the growing number of patients requiring LT remains a leading cause of mortality among those on the waiting list. This has resulted in the expansion of criteria for donor eligibility. The sequential combination of ex situ reperfusion, dHOPE, and NMP helps reduce the occurrence of ischemia-reperfusion injury and assess organ viability prior to transplantation.

METHODS

This is a retrospective, single-arm, single-center study including all cases of liver grafts that underwent sequential perfusion between October 2021 and July 2024. Eligibility criteria for sequential perfusion were extended criteria DBD with macrosteatosis > 35%, use of high-dose vasopressors during donor ICU stay or episodes of cardiac arrest, hemodynamic instability during procurement, prolonged ischemia time for logistic reasons, as well as DCD showing prolonged fWIT, flow alteration during normothermic regional perfusion (NRP), and DCDs in Maastricht 2 class. Viability was assessed following the Groeningen group criteria.

RESULTS

Thirty-three cases were included and 16 met the viability criteria at the end of the sequential perfusion and were transplanted. One patient developed an early allograft failure (EAF) and another a primary nonfunction (PNF). All the other patients had a regular postoperative course, with no retransplantation, 56% of the cohort showing no postoperative complication and all currently in good standing, median follow-up 19 months (range 4-39).

CONCLUSIONS

Sequential dHOPE and NMP is a strategy that can help assessing both viability and functionality of liver grafts from high-risk donors, expanding the donor pool and increasing the opportunities for patients on the waiting list to get a transplant.

Perfusate Liver Arginase 1 Levels After End-Ischemic Machine Perfusion Are Associated with Early Allograft Dysfunction

Background/Objectives: The rising use of liver grafts from donation after circulatory death (DCD) has been enabled by advances in normothermic regional perfusion (NRP) and machine perfusion (MP) technologies. We aimed to identify predictive biomarkers in DCD grafts subjected to NRP, followed by randomization to either normothermic machine perfusion (NMP) or dual hypothermic oxygenated perfusion (D-HOPE). Methods: Among 57 DCD donors, 32 liver grafts were transplanted, and recipients were monitored for one week post-transplant. Biomarkers linked with oxidative stress, hepatic injury, mitochondrial dysfunction, inflammation, regeneration, and autophagy were measured during NRP, end-ischemic MP, and one week post-transplant. Results: Arginase-1 (ARG-1) levels were consistently higher in discarded grafts and in recipients who later developed early allograft dysfunction (EAD). Specifically, ARG-1 levels at the end of MP correlated with markers of hepatic injury. Receiver operating characteristic analysis indicated that ARG-1 at the end of MP had a good predictive accuracy for EAD (AUC = 0.713; p = 0.02). Lipid peroxidation (TBARS) elevated at the start of NRP, declined over time, with higher levels in D-HOPE than in NMP, suggesting a more oxidative environment in D-HOPE. Metabolites like flavin mononucleotide (FMN) and NADH exhibited significant disparities between perfusion types, due to differences in perfusate compositions. Inflammatory biomarkers rose during NRP and NMP but normalized post-transplantation. Regenerative markers, including osteopontin and hepatocyte growth factor, increased during NRP and NMP and normalized post-transplant. Conclusions: ARG-1 demonstrates strong potential as an early biomarker for assessing liver graft viability during perfusion, supporting timely and effective decision-making in transplantation.

Innovations in Liver Preservation Techniques for Transplants from Donors after Circulatory Death: A Special Focus on Transplant Oncology

Liver transplantation is the preferred treatment for end-stage liver disease. Emerging evidence suggests a potential role for liver transplantation in treating liver tumors such as colorectal liver metastases and cholangiocarcinoma. However, due to a limited donor pool, the use of marginal grafts from donation after circulatory death (DCD) donors is increasing to meet demand. Machine perfusion is crucial in this context for improving graft acceptance rates and reducing ischemia-reperfusion injury. Few studies have evaluated the role of machine perfusion in the context of transplant oncology. Perfusion machines can be utilized in situ (normothermic regional perfusion-NRP) or ex situ (hypothermic and normothermic machine perfusion), either in combination or as a complement to conventional in situ cold flush and static cold storage. The objective of this analysis is to provide an up-to-date overview of perfusion machines and their function in donation after circulatory death with particular attention to their current and likely potential effects on transplant oncology. A literature review comparing standard cold storage to machine perfusion methods showed that, so far, there is no evidence that these devices can reduce the tumor recurrence rate. However, some evidence suggests that these innovative perfusion techniques can improve graft function, reduce ischemia-reperfusion injury, and, based on this mechanism, may lead to future improvements in cancer recurrence.

Evolution of transplant oncology indications: a single-institution experience over 40 years

Liver transplantation (LT) for uncommon tumoral indications has changed across the decades, with impaired results reported in the first historical series mainly for non-tumoral-related causes. Recently, renewed interest in liver transplant oncology has been reported. The study aims to analyze a mono-center experience exploring the evolution and the impact on patient survival of LT in uncommon tumoral indications. A retrospective analysis of 851 LT performed during 1982-2023 was investigated. 33/851 (3.9%) uncommon tumoral indications were reported: hepatocellular carcinoma (HCC) on non-cirrhotic liver (n = 14), peri-hilar (phCCA) (n = 8) and intrahepatic cholangiocarcinoma (i-CCA) (n = 3), metastatic disease (n = 4), hepatic hemangioendothelioma (n = 2), and benign tumor (n = 2). Uncommon tumoral indications were mainly transplanted during the period 1982-1989, with a complete disappearance after the year 2000 and a slight rise in the last years. Poor outcomes were reported: 5-year survival rates were 28.6%, 25.0%, 0%, and 0% in the case of HCC on non-cirrhotic liver, phCCA, i-CCA, and metastases, respectively. However, the cause of patient death was often related to non-tumoral conditions. LT for uncommon oncological diseases has increased worldwide in recent decades. Historical series report poor survival outcomes despite more recent data showing promising results. Hence, the decision to transplant these patients should be under the risk and overall benefit of the patient. The results of the ongoing protocol studies are expected to confirm the validity of the unconventional tumor indications.

Sequential Normothermic Regional Perfusion and End-ischemic Ex Situ Machine Perfusion Allow the Safe Use of Very Old DCD Donors in Liver Transplantation

BACKGROUND

In Italy, 20 min of continuous, flat-line electrocardiogram are required for death declaration. Despite prolonged warm ischemia time, Italian centers reported good outcomes in controlled donation after circulatory death (cDCD) liver transplantation by combining normothermic regional and end-ischemic machine perfusion (MP). The aim of this study was to evaluate the safety and feasibility of the use of septuagenarian and octogenarian cDCD donors with this approach.

METHODS

All cDCD older than 70 y were evaluated during normothermic regional perfusion and then randomly assigned to dual hypothermic or normothermic MP.

RESULTS

In the period from April 2021 to December 2022, 17 cDCD older than 70 y were considered. In 6 cases (35%), the graft was not considered suitable for liver transplantation, whereas 11 (65%) were evaluated and eventually transplanted. The median donor age was 82 y, being 8 (73%) older than 80. Median functional warm ischemia and no-flow time were 36 and 28 min, respectively. Grafts were randomly assigned to ex situ dual hypothermic oxygenated MP in 6 cases (55%) and normothermic MP in 5 (45%). None was discarded during MP. There were no cases of primary nonfunction, 1 case of postreperfusion syndrome (9%) and 2 cases (18%) of early allograft dysfunction. At a median follow-up of 8 mo, no vascular complications or ischemic cholangiopathy were reported. No major differences were found in terms of postoperative hospitalization or complications based on the type of MP.

CONCLUSIONS

The implementation of sequential normothermic regional and end-ischemic MP allows the safe use of very old donation after circulatory death donors.

Liver transplantation with uncontrolled versus controlled DCD donors using normothermic regional perfusion and ex-situ machine perfusion

In Italy, 20 minutes of continuous, flat-line electrocardiogram are required for death declaration, which significantly increases the risks of donation after circulatory death (DCD) LT. Despite prolonged warm ischemia time, Italian centers reported good outcomes in controlled donation after circulatory death LT by combining normothermic regional and end-ischemic machine perfusion. However, data on uncontrolled DCD (uDCD) LT performed by this approach are lacking. This was a multicenter, retrospective study performed at 3 large-volume centers comparing clinical outcomes of uncontrolled versus controlled DCD LT. The aim of the study was to assess outcomes of sequential normothermic regional perfusion and end-ischemic machine perfusion in uncontrolled DCD liver transplantation (LT). Of 153 DCD donors evaluated during the study period, 40 uDCD and 59 donation after circulatory death grafts were transplanted (utilization rate 52% vs. 78%, p = 0.004). Recipients of uDCD grafts had higher MEAF (4.9 vs. 3.5, p < 0.001) and CCI scores at discharge (24.4 vs. 8.7, p = 0.026), longer ICU stay (5 vs. 4 d, p = 0.047), and a trend toward more severe AKI. At multivariate analysis, 90-day graft loss was associated with recipient BMI and lactate downtrend during normothermic regional perfusion. One-year graft survival was lower in uDCD (75% vs. 90%, p = 0.007) but became comparable when non-liver-related graft losses were treated as censors (77% vs. 90%, p = 0.100). The incidence of ischemic cholangiopathy was 10% in uDCD versus 3% in donation after circulatory death, p = 0.356. uDCD LT with prolonged warm ischemia is feasible by the sequential use of normothermic regional perfusion and end-ischemic machine perfusion. Proper donor and recipient selection are key to achieving good outcomes in this setting.

Extended criteria liver donation after circulatory death with prolonged warm ischemia: a pilot experience of normothermic regional perfusion and no subsequent ex-situ machine perfusion

BACKGROUND

Livers from controlled donation after circulatory death (cDCD) with very prolonged warm ischemic time (WIT) are regularly transplanted after abdominal normothermic regional perfusion (aNRP) plus ex-situ machine perfusion (MP). Considering aNRP as in-situ MP, we investigated whether the results of a pilot experience of extended criteria cDCD liver transplantation (LT) with prolonged WIT, with aNRP alone, were comparable to the best possible outcomes in low-risk cDCD LT.

METHODS

Prospectively collected data on 24 cDCD LT, with aNRP alone, were analyzed.

RESULTS

The median total and asystolic WIT were 51 and 25 min. Measures within benchmark cut-offs were: median duration of surgery (5.9 h); median intraoperative transfusions (3 units of red blood cells); need for renal replacement therapy (2/24 patients); median intensive care stay (3 days); key complications; overall morbidity, graft loss, and retransplantation up to 12 months; 12-month mortality (2/21 patients). The median hospital stay (33 days, due to logistics) and mortality up to 6 months (2/24 patients, due to graft-unrelated causes) exceeded benchmark thresholds.

CONCLUSIONS

This pilot experience suggests that livers from cDCD with very prolonged WIT that appear viable during adequate quality aNRP may be safely transplanted, with no need for ex-situ MP, with considerable resource savings.

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.

An extensive evaluation of hepatic markers of damage and regeneration in controlled and uncontrolled donation after circulatory death

Livers from donations after circulatory death (DCDs) are very sensitive to ischemia/reperfusion injury and thus need careful reconditioning, such as normothermic regional perfusion (NRP). So far, its impact on DCDs has not been thoroughly investigated. This pilot cohort study aimed to explore the NRP impact on liver function by evaluating dynamic changes of circulating markers and hepatic gene expression in 9 uncontrolled DCDs (uDCDs) and 10 controlled DCDs. At NRP start, controlled DCDs had lower plasma levels of inflammatory and liver damage markers, including α-glutathione s-transferase, sorbitol-dehydrogenase, malate dehydrogenase 1, liver-type arginase-1, and keratin-18, but higher levels of osteopontin, sFas, flavin mononucleotide, and succinate than uDCDs. During 4-hour NRP, some damage and inflammatory markers increased in both groups, while IL-6, HGF, and osteopontin increased only in uDCDs. At the NRP end, the tissue expression of early transcriptional regulators, apoptosis, and autophagy mediators was higher in uDCDs than in controlled DCDs. In conclusion, despite initial differences in liver damage biomarkers, the uDCD group was characterized by a major gene expression of regenerative and repair factors after the NRP procedure. Correlative analysis among circulating/tissue biomarkers and the tissue congestion/necrosis degree revealed new potential candidate biomarkers.

The Role of Donor Gamma-Glutamyl Transferase as a Risk Factor for Early Graft Function after Liver Transplantation

BACKGROUND

Growing interest has been recently reported in the potential detrimental role of donor gamma-glutamyl transferase (GGT) peak at the time of organ procurement regarding the risk of poor outcomes after liver transplantation (LT). However, the literature on this topic is scarce and controversial data exist on the mechanisms justifying such a correlation. This study aims to demonstrate the adverse effect of donor GGT in a large European LT cohort regarding 90-day post-transplant graft loss.

METHODS

This is a retrospective international study investigating 1335 adult patients receiving a first LT from January 2004 to September 2018 in four collaborative European centers.

RESULTS

Two different multivariable logistic regression models were constructed to evaluate the risk factors for 90-day post-transplant graft loss, introducing donor GGT as a continuous or dichotomous variable. In both models, donor GGT showed an independent role as a predictor of graft loss. In detail, the log-transformed continuous donor GGT value showed an odds ratio of 1.46 (95% CI = 1.03-2.07; p = 0.03). When the donor GGT peak value was dichotomized using a cut-off of 160 IU/L, the odds ratio was 1.90 (95% CI = 1.20-3.02; p = 0.006). When the graft-loss rates were investigated, significantly higher rates were reported in LT cases with donor GGT ≥160 IU/L. In detail, 90-day graft-loss rates were 23.2% vs. 13.9% in patients with high vs. low donor GGT, respectively (log-rank p = 0.004). Donor GGT was also added to scores conventionally used to predict outcomes (i.e., MELD, D-MELD, DRI, and BAR scores). In all cases, when the score was combined with the donor GGT, an improvement in the model accuracy was observed.

CONCLUSIONS

Donor GGT could represent a valuable marker for evaluating graft quality at transplantation. Donor GGT should be implemented in scores aimed at predicting post-transplant clinical outcomes. The exact mechanisms correlating GGT and poor LT outcomes should be better clarified and need prospective studies focused on this topic.

Donation after circulatory death: Novel strategies to improve the liver transplant outcome

In many countries, donation after circulatory death (DCD) liver grafts are used to overcome organ shortages; however, DCD grafts have been associated with an increased risk of complications and even graft loss after liver transplantation. The increased risk of complications is thought to correlate with prolonged functional donor warm ischaemia time. Stringent donor selection criteria and utilisation of in situ and ex situ organ perfusion technologies have led to improved outcomes. Additionally, the increased use of novel organ perfusion strategies has led to the possibility of reconditioning marginal DCD liver grafts. Moreover, these technologies enable the assessment of liver function before implantation, thus providing valuable data that can guide more precise graft-recipient selection. In this review, we first describe the different definitions of functional warm donor ischaemia time and its role as a determinant of outcomes after DCD liver transplantation, with a focus on the thresholds proposed for graft acceptance. Next, organ perfusion strategies, namely normothermic regional perfusion, hypothermic oxygenated perfusion, and normothermic machine perfusion are discussed. For each technique, clinical studies reporting on the transplant outcome are described, together with a discussion on the possible protective mechanisms involved and the functional criteria adopted for graft selection. Finally, we review multimodal preservation protocols involving a combination of more than one perfusion technique and potential future directions in the field.

Impact of Hypothermic Oxygenated Machine Perfusion on Hepatocellular Carcinoma Recurrence after Liver Transplantation

BACKGROUND

Machine perfusion may be able to mitigate ischemia-reperfusion injury (IRI), which increases hepatocellular carcinoma (HCC) recurrence after liver transplantation (LT). This study aimed to investigate the impact of dual-hypothermic oxygenated machine perfusion (D-HOPE) on HCC recurrence in LT.

METHODS

A single-center retrospective study was conducted from 2016 to 2020. Pre- and postoperative data of HCC patients undergoing LT were analyzed. Recipients of a D-HOPE-treated graft were compared to those of livers preserved using static cold storage (SCS). The primary endpoint was recurrence-free survival (RFS).

RESULTS

Of 326 patients, 246 received an SCS-preserved liver and 80 received a D-HOPE-treated graft (donation after brain death (DBD), n = 66; donation after circulatory death (DCD), n = 14). Donors of D-HOPE-treated grafts were older and had higher BMI. All DCD donors were treated by normothermic regional perfusion and D-HOPE. The groups were comparable in terms of HCC features and estimated 5-year RFS according to the Metroticket 2.0 model. D-HOPE did not reduce HCC recurrence (D-HOPE 10%; SCS 8.9%; p = 0.95), which was confirmed using Bayesian model averaging and inverse probability of treatment weighting-adjusted RFS analysis. Postoperative outcomes were comparable between groups, except for lower AST and ALT peak in the D-HOPE group.

CONCLUSIONS

In this single-center study, D-HOPE did not reduce HCC recurrence but allowed utilizing livers from extended criteria donors with comparable outcomes, improving access to LT for patients suffering from HCC.

The perioperative period of liver transplantation from unconventional extended criteria donors: data from two high-volume centres

BACKGROUND

As literature largely focuses on long-term outcomes, this study aimed at elucidating the perioperative outcomes of liver transplant patients receiving a graft from two groups of unconventional expanded criteria donors: brain dead aged > 80 years and cardiac dead.

METHODS

Data of 247 cirrhotic patients transplanted at two high volume liver transplant centers were analysed. Confounders were balanced using a stabilized inverse probability therapy weighting and a propensity score for each patient on the original population was generated. The score was created using a multivariate logistic regression model considering a Comprehensive Complication Index ≥ 42 (no versus yes) as the dependent variable and 11 possible clinically relevant confounders as covariate.

RESULTS

Forty-four patients received the graft from a cardiac-dead donor and 203 from a brain-dead donor aged > 80 years. Intraoperatively, cardiac-dead donors liver transplant cases required more fresh frozen plasma units (P < 0.0001) with similar reduced need of fibrinogen to old brain-dead donors cases. The incidence of reperfusion syndrome was similar (P = 0.80). In the Intensive Care Unit, both the groups presented a comparable low need for blood transfusions, renal replacement therapy and inotropes. Cardiac-dead donors liver transplantations required more time to tracheal extubation (P < 0.0001) and scored higher Comprehensive Complication Index (P < 0.0001) however the incidence of a severe complication status (Comprehensive Complication Index  ≥ 42) was similar (P = 0.52). ICU stay (P = 0.97), total hospital stay (P = 0.57), in hospital (P = 1.00) and 6 months (P = 1.00) death were similar.

CONCLUSION

Selected octogenarian and cardiac-dead donors can be used safely for liver transplantation.

State-of-the-Art and Future Directions in Organ Regeneration with Mesenchymal Stem Cells and Derived Products during Dynamic Liver Preservation

Transplantation is currently the treatment of choice for end-stage liver diseases but is burdened by the shortage of donor organs. Livers from so-called extended-criteria donors represent a valid option to overcome organ shortage, but they are at risk for severe post-operative complications, especially when preserved with conventional static cold storage. Machine perfusion technology reduces ischemia-reperfusion injury and allows viability assessment of these organs, limiting their discard rate and improving short- and long-term outcomes after transplantation. Moreover, by keeping the graft metabolically active, the normothermic preservation technique guarantees a unique platform to administer regenerative therapies ex vivo. With their anti-inflammatory and immunomodulatory properties, mesenchymal stem cells are among the most promising sources of therapies for acute and chronic liver failure, but their routine clinical application is limited by several biosafety concerns. It is emerging that dynamic preservation and stem cell therapy may supplement each other if combined, as machine perfusion can be used to deliver stem cells to highly injured grafts, avoiding potential systemic side effects. The aim of this narrative review is to provide a comprehensive overview on liver preservation techniques and mesenchymal stem cell-based therapies, focusing on their application in liver graft reconditioning.

Viability Criteria during Liver Ex-Situ Normothermic and Hypothermic Perfusion

With the increased use of extended-criteria donors, machine perfusion became a beneficial alternative to cold storage in preservation strategy for donor livers with the intent to expand donor pool. Both normothermic and hypothermic approach achieved good results in terms of mid- and long-term outcome in liver transplantation. Many markers and molecules have been proposed for the assessment of liver, but no definitive criteria for graft viability have been validated in large clinical trials and key parameters during perfusion still require optimization.In this review, we address the current literature of viability criteria during normothermic and hypothermic machine perfusion and discuss about future steps and evolution of these technologies.

How useful is the machine perfusion in liver transplantation? An answer from a national survey

Machine perfusion (MP) has been shown worldwide to offer many advantages in liver transplantation, but it still has some gray areas. The purpose of the study is to evaluate the donor risk factors of grafts, perfused with any MP, that might predict an ineffective MP setting and those would trigger post-transplant early allograft dysfunction (EAD). Data from donors of all MP-perfused grafts at six liver transplant centers have been analyzed, whether implanted or discarded after perfusion. The first endpoint was the negative events after perfusion (NegE), which is the number of grafts discarded plus those that were implanted but lost after the transplant. A risk factor analysis for NegE was performed and marginal grafts for MP were identified. Finally, the risk of EAD was analyzed, considering only implanted grafts. From 2015 to September 2019, 158 grafts were perfused with MP: 151 grafts were implanted and 7 were discarded after the MP phase because they did not reach viability criteria. Of 151, 15 grafts were lost after transplant, so the NegE group consisted of 22 donors. In univariate analysis, the donor risk index >1.7, the presence of hypertension in the medical history, static cold ischemia time, and the moderate or severe macrovesicular steatosis were the significant factors for NegE. Multivariate analysis confirmed that macrosteatosis >30% was an independent risk factor for NegE (odd ratio 5.643, p = 0.023, 95% confidence interval, 1.27-24.98). Of 151 transplanted patients, 34% experienced EAD and had worse 1- and 3-year-survival, compared with those who did not face EAD (NoEAD), 96% and 96% for EAD vs. 89% and 71% for NoEAD, respectively (p = 0.03). None of the donor/graft characteristics was associated with EAD even if the graft was moderately steatotic or fibrotic or from an aged donor. For the first time, this study shows that macrovesicular steatosis >30% might be a warning factor involved in the risk of graft loss or a cause of graft discard after the MP treatment. On the other hand, the MP seems to be useful in reducing the donor and graft weight in the development of EAD.

A new ex-situ machine perfusion device. A preliminary evaluation using a model of donors after circulatory death pig livers

We herein describe a new ex-situ machine perfusion device as a "technology spotlight" using a model of donors after circulatory death liver grafts procured from slaughterhouse pigs. Fourteen pig liver grafts were included. The device allowed stable perfusion in both hypothermic (n = 6) and normothermic (n = 8) conditions and no technical failure was observed. During perfusion, perfusate and bile samples were collected to assess liver metabolism and viability. An integrated adsorption device showed efficient removal of inflammatory cytokines during treatment. This preliminary experience represents the starting point for further investigations on the potential clinical benefits of cytokines and other inflammatory mediators adsorption during machine perfusion.

Normothermic regional perfusion in liver transplantation from donation after cardiocirculatory death: Technical, biochemical, and regulatory aspects and review of literature

BACKGROUND

Organs from donation after circulatory death (DCD) are increasingly used for liver transplantation, due to the persisting organ shortage and waiting list mortality. However, the use of DCD grafts is still limited by the inferior graft survival rate and the increased risk of primary non-function and biliary complications when compared to brain death donors' grafts.

METHODS

Abdominal normothermic regional perfusion with extracorporeal membrane oxygenation (ECMO) is an in situ preservation strategy. which may mitigate ischemia-reperfusion injuries. and has been proposed to restore blood perfusion after the determination of death thus optimizing liver function before implantation.

RESULTS

In this systematic review, we highlighted the clinical evidence supporting the use of normothermic regional perfusion in DCD liver underlying the pathophysiological mechanisms, and technical, logistic, and regulatory aspects.

CONCLUSIONS

Despite the lack of properly designed, prospective, randomized trials, the current available data suggest beneficial effects of normothermic regional perfusion on clinical outcomes after liver transplantation.

Protective mechanisms and current clinical evidence of hypothermic oxygenated machine perfusion (HOPE) in preventing post-transplant cholangiopathy

The development of cholangiopathies after liver transplantation impacts on the quality and duration of graft and patient survival, contributing to higher costs as numerous interventions are required to treat strictures and infections at the biliary tree. Prolonged donor warm ischaemia time in combination with additional cold storage are key risk factors for the development of biliary strictures. Based on this, the clinical implementation of dynamic preservation strategies is a current hot topic in the field of donation after circulatory death (DCD) liver transplantation. Despite various retrospective studies reporting promising results, also regarding biliary complications, there are only a few randomised-controlled trials on machine perfusion. Recently, the group from Groningen has published the first randomised-controlled trial on hypothermic oxygenated perfusion (HOPE), demonstrating a significant reduction of symptomatic ischaemic cholangiopathies with the use of a short period of HOPE before DCD liver implantation. The most likely mechanism for this important effect, also shown in several experimental studies, is based on mitochondrial reprogramming under hypothermic aerobic conditions, e.g. exposure to oxygen in the cold, with a controlled and slow metabolism of ischaemically accumulated succinate and simultaneous ATP replenishment. This unique feature prevents mitochondrial oxidative injury and further downstream tissue inflammation. HOPE treatment therefore supports livers by protecting them from ischaemia-reperfusion injury (IRI), and thereby also prevents the development of post-transplant biliary injury. With reduced IRI-associated inflammation, recipients are also protected from activation of the innate immune system, with less acute rejections seen after HOPE.

Proposal and validation of a liver graft discard score for liver transplantation from deceased donors: a multicenter Italian study

Several studies have explored the risk of graft dysfunction after liver transplantation (LT) in recent years. Conversely, risk factors for graft discard before or at procurement have poorly been investigated. The study aimed at identifying a score to predict the risk of liver-related graft discard before transplantation. Secondary aims were to test the score for prediction of biopsy-related negative features and post-LT early graft loss. A total of 4207 donors evaluated during the period January 2004-Decemeber 2018 were retrospectively analyzed. The group was split into a training set (n = 3,156; 75.0%) and a validation set (n = 1,051; 25.0%). The Donor Rejected Organ Pre-transplantation (DROP) Score was proposed: - 2.68 + (2.14 if Regional Share) + (0.03*age) + (0.04*weight)-(0.03*height) + (0.29 if diabetes) + (1.65 if anti-HCV-positive) + (0.27 if HBV core) - (0.69 if hypotension) + (0.09*creatinine) + (0.38*log10AST) + (0.34*log10ALT) + (0.06*total bilirubin). At validation, the DROP Score showed the best AUCs for the prediction of liver-related graft discard (0.82; p < 0.001) and macrovesicular steatosis ≥ 30% (0.71; p < 0.001). Patients exceeding the DROP 90th centile had the worse post-LT results (3-month graft loss: 82.8%; log-rank P = 0.024).The DROP score represents a valuable tool to predict the risk of liver function-related graft discard, steatosis, and early post-LT graft survival rates. Studies focused on the validation of this score in other geographical settings are required.

The impact of hepatitis C virus direct acting agents in liver transplant using very old donor grafts: a real-world single-center analysis

The correct timing of use of direct acting agents (DAAs) among transplanted patients remains unknown. The aim of this paperwork is to evaluate the impact of DAAs treatment in pre- or peri-operative period in liver transplantation when grafts ≥ 70 years are used. This is a retrospective analysis comparing adult liver transplant performed for HCV-related cirrhosis and/or hepatocarcinoma using a graft ≥ 70 in the period 2015-2018 (Group DAA-HCV-OLD, study group) to three different groups: (a) anti-HCV-Ab-negative patients receiving graft ≥ 70 (no-HCV-OLD), (b) anti-HCV-Ab-negative patients receiving a graft aged 18-69 years (no-HCV-YOUNG), and (c) anti-HCV-Ab-positive patients receiving a donor graft ≥ 70 in the period 2007-2011 (no-DAA-HCV-OLD). Totally, 528 liver transplants were considered: 164 in DAA-HCV-OLD, 143 in no-HCV-OLD, 120 in no-HCV-YOUNG and 101 in no-DAA-HCV-OLD Group. Graft survival rates at 1 and 3 years were 88% and 81% in DAA-HCV-OLD Group, 82% and 68% in no-DAA-HCV-OLD (p = 0.007), 89% and 84% in no-HCV-OLD (p = 0.76), and 94% and 92% in no-HCV-YOUNG (p = 0.02). No differences were observed among groups in the incidence of primary non-function, primary dysfunction, vascular or biliary complications. DAAs were able to zero HCV-related graft loss, with a 3-year graft survival > 80%. The outcomes of older graft recipients became equal irrespectively of their HCV serological status.

Current practice of normothermic regional perfusion and machine perfusion in donation after circulatory death liver transplants in Italy

BACKGROUND

Normothermic regional perfusion (NRP) and machine perfusion (MP) are variously used in many European centers to improve the outcomes after liver transplantation from donation after circulatory death (DCD). In Italy, a combination of NRP and subsequent MP has been used since the start of the activity. While NRP is mandatory for every DCD recovery, the subsequent use of MP is left to each center.

METHODS

We have designed a national survey to investigate practices and policies of these techniques. The questionnaire included 46 questions and was distributed to all the 21 Italian centers using an online form between June and July 2021.

RESULTS

The overall response rate was 100%. A local NRP program for controlled Maastricht type 3 DCD was active in 11/21 (52.4%) centers. Organization and availability of personnel were perceived as the main difficulties in starting such a program. Between 2015 and 2020, 119 DCD livers were transplanted, with an overall utilization rate of 69.2%. Pump flow and gross aspect were considered the most reliable parameters in liver selection during NRP. Eight (72.7%) centers adopted subsequent hypothermic MP, 1 (9.1%) center normothermic MP, and the remaining 2 (18.2%) used both MP types.

CONCLUSION

This first snapshot survey shows that NRP with subsequent MP is the most used protocol in Italy for DCD livers, although some heterogeneity exists in the type and purpose of MP between centers. Overall, this policy ensures a high utilization rate, considering the high risk of the DCD donor population in Italy.

Quantitative Metabolomics of Tissue, Perfusate, and Bile from Rat Livers Subjected to Normothermic Machine Perfusion

Machine perfusion (MP) allows the maintenance of liver cells in a metabolically active state ex vivo and can potentially revert metabolic perturbations caused by donor warm ischemia, procurement, and static cold storage (SCS). The present preclinical research investigated the metabolic outcome of the MP procedure by analyzing rat liver tissue, bile, and perfusate samples by means of high-field (600 MHz) nuclear magnetic resonance (NMR) spectroscopy. An established rat model of normothermic MP (NMP) was used. Experiments were carried out with the addition of an oxygen carrier (OxC) to the perfusion fluid (OxC-NMP, n = 5) or without (h-NMP, n = 5). Bile and perfusate samples were collected throughout the procedure, while biopsies were only taken at the end of NMP. Two additional groups were: (1) Native, in which tissue or bile specimens were collected from rats in resting conditions; and (2) SCS, in which biopsies were taken from cold-stored livers. Generally, NMP groups showed a distinctive metabolomic signature in all the analyzed biological matrices. In particular, many of the differentially expressed metabolites were involved in mitochondrial biochemical pathways. Succinate, acetate, 3-hydroxybutyrate, creatine, and O-phosphocholine were deeply modulated in ex vivo perfused livers compared to both the Native and SCS groups. These novel results demonstrate a broad modulation of mitochondrial metabolism during NMP that exceeds energy production and redox balance maintenance.

Heterogeneous indications and the need for viability assessment: An international survey on the use of machine perfusion in liver transplantation

Although machine perfusion (MP) is being increasingly adopted in liver transplantation, indications, timing, and modality are debated. To investigate current indications for MP a web-based Google Forms survey was launched in January 2021 and addressed to 127 experts in the field, identified among first and corresponding Authors of MP literature in the last 10 years. The survey presented 10 real-life cases of donor-recipient matching, asking whether the liver would be accepted (Q1), whether MP would be used in that particular setting (Q2) and, if so, by which MP modality (Q3) and at what timing during preservation (Q4). Respondents could also comment on each case. The agreement was evaluated using Krippendorff's alpha coefficient. Answers from 39 (30.1%) participants disclosed significant heterogeneity in graft acceptance, MP indications, technique, and timing. Agreement between respondents was generally poor (Q1, α = 0.11; Q2, α = 0.14; Q3, α = 0.12, Q4, α = 0.11). Overall, respondents preferred hypothermic MP and an end-ischemic approach in 56.3% and 81.1% of cases, respectively. A total of 18 (46.2%) participants considered only one MP approach, whereas 17 (43.6%) and 3 (7.7%) considered using alternatively 2 or 3 different techniques. Of 38 comments, 17 (44.7%) were about the use of MP for graft viability assessment before implantation. This survey shows considerable variability in MP indications, emphasizing the need to identify scenarios of optimal utilization for each technique. Viability assessment emerges as a fundamental need of transplant professionals when considering the use of MP.

The use of normothermic machine perfusion to rescue liver allografts from expanded criteria donors

The use of expanded criteria donors is one of the strategies used to overcome the gap between the demand for organs and the number of donors. Physicians debate the extent to which marginal grafts can be used. In recent years, normothermic machine perfusion (NMP) has been used to test liver viability before transplantation. Grafts underwent NMP whenever histological steatosis was > 40% or there were at least three Eurotransplant criteria for expanded criteria donor (ECD). We used NMP to test 19 grafts, 3 from donation after type 3 controlled cardiac death (DCD), and 16 from donation after brain death (DBD). Only two grafts from DBD were not transplanted, because perfusion proved they were not suitable (total of 17 transplanted grafts of 19 tested grafts). Kaplan-Meier survival estimates at 30, 90, 180, and 1 year after transplant were all 94% (95% CI 84-100%); estimated 3-years survival was 82% (95% CI 62-100%). Overall survival rates did not differ from those of patients transplanted with non-perfused grafts from an ECD. In our experience, the use of very marginal grafts preventively tested by NMP does not negatively influence the patient's outcome, and increases the number of transplants in low donation areas.

The Role of Ex Situ Hypothermic Oxygenated Machine Perfusion and Cold Preservation Time in Extended Criteria Donation After Circulatory Death and Donation After Brain Death

Hypothermic oxygenated machine perfusion (HOPE) has the potential to counterbalance the detrimental consequences of cold and warm ischemia time (WIT) in both donation after brain death (DBD) and donation after circulatory death (DCD). Herein we investigated the protective effects of HOPE in extended criteria donor (ECD) DBD and overextended WIT DCD grafts. The present retrospective case series included 50 livers subjected to end-ischemic HOPE or dual DHOPE in 2 liver transplantation (LT) centers from January 2018 to December 2019. All DCD donors were subjected to normothermic regional perfusion before organ procurement. Results are expressed as median (interquartile range [IQR]). In the study period, 21 grafts were derived from overextended WIT DCD donors (total WIT 54 [IQR, 40-60] minutes and 75% classified as futile), whereas 29 were from ECD DBD. A total of 3 biliary complications and 1 case of ischemia-type biliary lesion were diagnosed. The rate of early allograft dysfunction (EAD) was 20%, and those patients had higher Comprehensive Complication Index scores. Through a changing point analysis, cold preservation time >9 hours was associated with prolonged hospital stays (P = 0.02), higher rates of EAD (P = 0.009), and worst post-LT complications (P = 0.02). Logistic regression analyses indicated a significant relationship between cold preservation time and EAD. No differences were shown in terms of the early post-LT results between LTs performed with DCD and DBD. Overall, our data are fully comparable with benchmark criteria in LT. In conclusion, the application of DHOPE obtained satisfactory and promising results using ECD-DBD and overextended DCD grafts. Our findings indicate the need to reduce cold preservation time also in the setting of DHOPE, particularly for grafts showing poor quality.

Static cold storage compared with normothermic machine perfusion of the liver and effect on ischaemic-type biliary lesions after transplantation: a propensity score-matched study

BACKGROUND

Given the susceptibility of organs to ischaemic injury, alternative preservation methods to static cold storage (SCS), such as normothermic machine perfusion (NMP) are emerging. The aim of this study was to perform a comparison between NMP and SCS in liver transplantation with particular attention to bile duct lesions.

METHODS

The outcomes of 59 consecutive NMP-preserved donor livers were compared in a 1 : 1 propensity score-matched fashion to SCS control livers. Postoperative complications, patient survival, graft survival and bile duct lesions were analysed.

RESULTS

While patients were matched for cold ischaemia time, the total preservation time was significantly longer in the NMP group (21 h versus 7 h, P < 0.001). Patient and graft survival rates at 1 year were 81 versus 82 per cent (P = 0.347) and 81 versus 79 per cent (P = 0.784) in the NMP and SCS groups, respectively. The postoperative complication rate was comparable (P = 0.086); 37 per cent NMP versus 34 per cent SCS patients had a Clavien-Dindo grade IIIb or above complication. There was no difference in early (30 days or less) (NMP 22 versus SCS 19 per cent, P = 0.647) and late (more than 30 days) (NMP 27 versus SCS 36 per cent, P = 0.321) biliary complications. However, NMP-preserved livers developed significantly fewer ischaemic-type bile duct lesions (NMP 3 versus SCS 14 per cent, P = 0.047).

CONCLUSION

The use of NMP allowed for a significantly prolonged organ preservation with a lower rate of observed ischaemic-type bile duct lesions.

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.

Ex vivo machine perfusion: current applications and future directions in liver transplantation

BACKGROUND

Liver transplantation is the only curative treatment option for end-stage liver disease; however, its use remains limited due to a shortage of suitable organs. In recent years, ex vivo liver machine perfusion has been introduced to liver transplantation, as a means to expand the donor organ pool.

PURPOSE

To present a systematic review of prospective clinical studies on ex vivo liver machine perfusion, in order to assess current applications and highlight future directions.

METHODS

A systematic literature search of both PubMed and ISI web of science databases as well as the ClinicalTrials.gov registry was performed.

RESULTS

Twenty-one articles on prospective clinical trials on ex vivo liver machine perfusion were identified. Out of these, eight reported on hypothermic, eleven on normothermic, and two on sequential perfusion. These trials have demonstrated the safety and feasibility of ex vivo liver machine perfusion in both standard and expanded criteria donors. Currently, there are twelve studies enrolled in the clinicaltrials.gov  registry, and these focus on use of ex vivo perfusion in extended criteria donors and declined organs.

CONCLUSION

Ex vivo liver machine perfusion seems to be a suitable strategy to expand the donor pool for liver transplantation and holds promise as a platform for reconditioning diseased organs.

Sequential Use of Normothermic Regional and Ex Situ Machine Perfusion in Donation After Circulatory Death Liver Transplant

In Italy, 20 minutes of a continuous flat line on an electrocardiogram are required for declaration of death. In the setting of donation after circulatory death (DCD), prolonged warm ischemia time prompted the introduction of abdominal normothermic regional perfusion (NRP) followed by postprocurement ex situ machine perfusion (MP). This is a retrospective review of DCD liver transplantations (LTs) performed at 2 centers using sequential NRP and ex situ MP. From January 2018 to April 2019, 34 DCD donors were evaluated. Three (8.8%) were discarded before NRP, and 11 (32.4%) were discarded based on NRP parameters (n = 1, 3.0%), liver macroscopic appearance at procurement and/or biopsy results (n = 9, 26.5%), or severe macroangiopathy at back-table evaluation (n = 1, 3.0%). A total of 20 grafts (58.8%; 11 uncontrolled DCDs, 9 controlled DCDs) were considered eligible for LT, procured and perfused ex situ (9 normothermic and 11 dual hypothermic MPs). In total, 18 (52.9%; 11 uncontrolled) livers were eventually transplanted. Median (interquartile range) no-flow time was 32.5 (30-39) minutes, whereas median functional warm ischemia time was 52.5 (47-74) minutes (controlled DCD), and median low-flow time was 112 minutes (105-129 minutes; uncontrolled DCD). There was no primary nonfunction, while postreperfusion syndrome occurred in 8 (44%) recipients. Early allograft dysfunction happened in 5 (28%) patients, while acute kidney injury occurred in 5 (28%). After a median follow-up of 15.1 (9.5-22.3) months, 1 case of ischemic-type biliary lesions and 1 patient death were reported. DCD LT is feasible even with the 20-minute no-touch rule. Strict NRP and ex situ MP selection criteria are needed to optimize postoperative results.