Living liver transplantation has become a significant and evolving aspect of organ transplantation, with a notable proportion of cases involving pediatric patients. Metabolic-associated fatty liver disease (MAFLD) is the most prevalent chronic liver disease. The growing number of individuals with MAFLD has led to an annual increase in the proportion of non-alcoholic fatty liver donors for pediatric living liver transplantation. Hypothermic oxygenated perfusion (HOPE) has been demonstrated to improve graft quality through the implementation of a continuous mechanical perfusion cycle. However, there is currently a paucity of evidence regarding its ability to reduce steatosis and improve prognosis within a shorter time window of living-organ transplantation, especially in primate models. This study simulated steatotic liver grafts in living liver transplantation using the MAFLD model of the cynomolgus monkey and explored the effects of HOPE combined with the AMPK activator AICAR on the amelioration of the donor liver. The left outer lobe livers were statically cold preserved for two hours, subjected to HOPE for two hours, or treated with HOPE + AICAR (1 mmol/L) for two hours, respectively. Subsequently, a normothermic ex vivo reperfusion model (IRM) simulating post-transplant reperfusion was established using diluted autologous blood. Following simulated reperfusion in vitro, steatotic liver grafts in the static cold preservation group exhibited notable reperfusion injury. The degree of reperfusion injury induced by the remaining two groups was reduced, with the HOPE + AICAR group showing the most significant reduction (P < 0.05). The adenosine triphosphate (ATP) level of the hepatic tissues in the HOPE + AICAR group was observed to improve at two hours of reperfusion, exhibiting a significantly higher level than that in the cold-preserved group (P < 0.05). Furthermore, the HOPE + AICAR group exhibited a notable decline in MDA levels (P < 0.05), accompanied by a considerable reduction in 8-OHdG and lactate concentrations in both the liver tissue and perfusate. Additionally, there was a marked decrease in the release of TNF-α and IL-6 cytokines, along with a reduction in TLR-4 activation (P < 0.05). In comparison to the cold-preserved and HOPE groups, the HOPE + AICAR group demonstrated the capacity to alter the degree of steatosis following a two-hour treatment period, as evidenced by a notable reduction in liver tissue triglyceride and cholesterol levels (P < 0.05). Additionally, p-AMPK levels in liver tissue were significantly increased in the HOPE + AICAR group (P < 0.05). The combination of HOPE and AMPK activators has been shown to reduce the degree of steatotic liver grafts in a relatively short time, significantly reduce reperfusion injury, and improve liver function. This study contributes to the existing body of knowledge on mechanical perfusion in primate models, addressing a previously identified gap in the literature.

Ex-situ machine perfusion of the liver has surmounted traditional limitations associated with static cold storage in the context of organ preservation. This innovative technology has changed the landscape of liver transplantation by mitigating ischemia perfusion injury, offering a platform for continuous assessment of organ quality, and providing an avenue for optimizing the use of traditionally marginal allografts. This review summarizes the contemporary clinical applications of machine perfusion devices and discusses potential future strategies for real-time viability assessment, therapeutic interventions, and modulation of organ function after recovery.

Over the past six decades, liver transplantation (LT) has evolved from an experimental procedure into a standardized and life-saving intervention, reshaping the landscape of organ transplantation. Driven by pioneering breakthroughs, technological advancements, and a deepened understanding of immunology, LT has seen remarkable progress. Some of the most notable breakthroughs in the field include advances in immunosuppression, a revised model for end-stage liver disease, and artificial intelligence (AI)-integrated imaging modalities serving diagnostic and therapeutic roles in LT, paired with ever-evolving technological advances. Additionally, the refinement of transplantation procedures, resulting in the introduction of alternative transplantation methods, such as living donor LT, split LT, and the use of marginal grafts, has addressed the challenge of organ shortage. Moreover, precision medicine, guiding personalized immunosuppressive strategies, has significantly improved patient and graft survival rates while addressing emergent issues, such as short-term complications and early allograft dysfunction, leading to a more refined strategy and enhanced post-operative recovery. Looking ahead, ongoing research explores regenerative medicine, diagnostic tools, and AI to optimize organ allocation and post-transplantation car. In summary, the past six decades have marked a transformative journey in LT with a commitment to advancing science, medicine, and patient-centered care, offering hope and extending life to individuals worldwide.

During orthotopic liver transplantation, allograft reperfusion is a dynamic point in the operation and often requires vasoactive medications and blood transfusions. Normothermic machine perfusion (NMP) of liver allografts has emerged to increase the number of transplantable organs and may have utility during donation after circulatory death (DCD) liver transplantation in reducing transfusion burden and vasoactive medication requirements.

This is a single-center retrospective study involving 226 DCD liver transplant recipients who received an allograft transported with NMP (DCD-NMP group) or with static cold storage (DCD-SCS group). Veno-venous bypass was not used in any patients. Infusion doses of norepinephrine, epinephrine, and vasopressin as well as bolus doses of vasoactive medications during reperfusion were recorded. Blood component therapy was recorded according to phase of liver transplantation and during the first 24 hours postprocedure.

A total of 103 recipients in the DCD-NMP group and 123 patients in the DCD-SCS group were included. Post-reperfusion syndrome (PRS) incidence was reduced in the DCD-NMP group compared to the DCD-SCS group (10.7% [95% confidence interval, CI, 5.5%-18.3%] vs 42.3% [95% CI, 33.4%-51.5%]; P < .001). During the reperfusion period, patients in the DCD-SCS group required increased bolus doses of epinephrine and vasopressin compared to the DCD-NMP group (24.6 vs 7.5 µg; P < .001) and (5.4 vs 2.4 units; P < .001), respectively. The DCD-SCS group received a higher infusion dose of epinephrine during anhepatic phase, at reperfusion, and up to 90 minutes after reperfusion. In the postreperfusion period, there were significant increases in the transfusion of red blood cells (RBCs; 5.3 vs 3.7 units; P = .006), fresh frozen plasma (FFP; 3.4 vs 1.9 units; P < .001), cryoprecipitate (2.7 vs 1.8 pooled units; P = .015) and platelets (0.9 vs 0.4 units; P = .008) in the DCD-SCS group compared to the DCD-NMP group. During the first 24 hours postprocedure, transfusion of RBCs, FFP, and cryoprecipitate in the DCD-SCS group was increased compared to the DCD-NMP group ([2.6 vs 1.7 units; P = .028], [1.6 vs 0.8 units; P < .001], [1.5 vs 0.9 pooled units; P = .031]) respectively. Administration of tranexamic acid was more frequent in the DCD-SCS group during the post-reperfusion period compared to the DCD-NMP group (13% [95% CI, 5.7%-17.4%] vs 3.9% [95% CI, 1.1%-9.6% 95%]; P = .018).

In DCD liver transplantation, use of NMP was associated with reduced incidence of PRS and decreased vasopressor and inotrope requirements at the time of allograft reperfusion compared to using SCS. Additionally, NMP was associated with reduced transfusion of all blood product components as well as antifibrinolytic agent administration in the post-reperfusion period. Reduced transfusion burden in the DCD-NMP group also occurred during the first 24 hours posttransplant.

Normothermic machine perfusion (NMP) is a technique for donor liver preservation and assessment in transplantation. NMP has gained momentum recently by enabling safer use of higher risk organs via organ viability assessment. It also offers a platform for investigating ex vivo organ biology.

In this exploratory study, we completed a complex vascular reconstruction of explanted, diseased livers from patients undergoing transplantation and then perfused them normothermically on a closed perfusion circuit. We compared these livers to non-diseased donor livers via perfusate samples collected during perfusion.

Five hepatectomized grafts and eight donor livers were perfused for 1 h or longer. Four hepatectomized livers cleared lactate, and all consumed glucose; all control livers cleared lactate, and seven utilized glucose. Significantly higher portal vein flows were achieved in the control group.

Our findings illustrate the feasibility of using closed-circuit NMP as a platform to study hepatectomized organs, which could reshape the research landscape in mechanisms of disease and applied therapeutics for patients with end-stage liver disease.

Normothermic machine perfusion (NMP) represents an alternative to prolong liver preservation and reduce organ discard rates. We performed an updated systematic review and meta-analysis to compare NMP with static cold storage (SCS) in liver transplantation.

MEDLINE, Embase, and Cochrane were searched for randomized controlled trials (RCTs) or observational studies. Risk ratios (RR) and mean differences were calculated. p < 0.05 was considered significant. A random-effects model was applied for all outcomes.

CRD42023486184.

We included 1295 patients from 5 RCTs and 6 observational studies from 2016 to 2023. 592 (45.7%) underwent NMP. A subgroup RCT analysis favored NMP for non-anastomotic strictures (RR 0.4; 95% CI 0.2, 0.9), postreperfusion syndrome (RR 0.4; 95% CI 0.27, 0.56), and early allograft dysfunction (RR 0.6; 95% CI 0.4, 0.9). NMP favored higher organ utilization rates (RR 1.1; 95% CI 1.02, 1.18). No significant differences between NMP and SCS were observed in graft survival or patient survival at 12 months, primary non-function, serious adverse events, overall biliary complications, AST, or bilirubin levels peak within the first 7 days, ICU or hospital length of stay.

Our findings suggest that NMP is associated with lower non-anastomotic biliary stricture rates, postreperfusion syndrome, early allograft dysfunction, and higher organ utilization in the RCT subgroup analysis, without increasing adverse events.

Normothermic machine perfusion (NMP) has been shown to reduce peritransplant complications. Despite increasing NMP use in liver transplant (LT), there is a scarcity of real-world clinical experience data.

To compare LT outcomes between donation after brain death (DBD) and donation after circulatory death (DCD) allografts preserved with NMP or static cold storage (SCS).

This single-center, retrospective observational cohort study included all consecutive adult LTs performed between January 2019 and December 2023 at the Mayo Clinic in Arizona. Data analysis was performed between February 2024 and June 2024. Outcomes of DBD-SCS, DBD-NMP, DCD-SCS, and DCD-NMP transplants were compared.

DBD and DCD livers preserved on NMP or SCS.

The primary outcomes were early allograft dysfunction (EAD), intraoperative transfusion, and post-LT hospital resource use, including length of stay (LOS) and readmissions. Secondary outcomes included acute kidney injury (AKI) and 1-year graft and patient survival.

A total of 1086 LTs were included in the following 4 groups: DBD-SCS (n = 480), DBD-NMP (n = 63), DCD-SCS (n = 264), and DCD-NMP (n = 279). Among LT recipients, median (IQR) age was 60.0 years (52.0-66.0); 399 LT recipients (36.7%) were female. DCD-NMP had the lowest EAD rate (17.5%), followed by DCD-SCS (50.0%), DBD-NMP (36.8%), and DBD-SCS (27.3%) (P < .001). DCD-NMP had the lowest intraoperative transfusion requirement compared to all other groups. Hospital and intensive care unit (ICU) LOS were shortest in DCD-NMP (median [IQR] hospital LOS, 5.0 days [4.0-7.0]; P = .01; median [IQR] ICU LOS, 1.5 days [1.2-3.1]; P = .01). One-year cumulative readmission probability was 86% lower for DCD-NMP vs DCD-SCS (95% CI, 0.09-0.22; P < .001) and 53% lower for DBD-NMP vs DBD-SCS (95% CI, 0.26-0.87; P < .001). AKI events were lower in DCD-NMP (31.1%) vs DCD-SCS (47.4%) (P = .001). Compared to SCS, the NMP group had a 78% overall reduction in graft failure (hazard ratio [HR], 0.22; 95% CI, 0.10-0.49; P < .001). For those receiving DCD allografts, the risk reduction was even more pronounced, with an 87% decrease in graft failure (HR, 0.13; 95% CI, 0.05-0.33; P < .001). NMP was significantly protective from patient mortality vs SCS (HR, 0.31; 95% CI, 0.12-0.80; P = .02).

In this observational high-volume cohort study, NMP significantly improved LT clinical outcomes and reduced hospital resource use, especially in DCD allografts. NMP may enhance access to LT by addressing the challenges historically linked with DCD liver use.

Therapeutic efficacy and safety of adeno-associated virus (AAV) liver gene therapy depend on capsid choice. To predict AAV capsid performance under near-clinical conditions, we established side-by-side comparison at single-cell resolution in human livers maintained by normothermic machine perfusion. AAV-LK03 transduced hepatocytes much more efficiently and specifically than AAV5, AAV8 and AAV6, which are most commonly used clinically, and AAV-NP59, which is better at transducing human hepatocytes engrafted in immune-deficient mice. AAV-LK03 preferentially transduced periportal hepatocytes in normal liver, whereas AAV5 targeted pericentral hepatocytes in steatotic liver. AAV5 and AAV8 transduced liver sinusoidal endothelial cells as efficiently as hepatocytes. AAV capsid and steatosis influenced vector episome formation, which determines gene therapy durability, with AAV5 delaying concatemerization. Our findings inform capsid choice in clinical AAV liver gene therapy, including consideration of disease-relevant hepatocyte zonation and effects of steatosis, and facilitate the development of AAV capsids that transduce hepatocytes or other therapeutically relevant cell types in the human liver with maximum efficiency and specificity.

Membrane oxygenators facilitate extracorporeal gas exchange, necessitating the monitoring of blood gas. Recent advances in normothermic machine perfusion (NMP) for ex vivo liver offer solutions to the shortage of donor liver. However, maintaining physiological blood gas levels during prolonged NMP is complex and costly.

We introduce a noninvasive and economical approach for regulating the blood gas during NMP of ex vivo porcine livers. By monitoring gas fractions at the outlet of oxygenator, real-time adjustments of blood gas can be made without the online blood gas analyzer. The method involves constructing multivariate linear regression (MLR) models, aligning target setpoints of gas, and employing active disturbance rejection control (ADRC) to achieve closed-loop regulation.

Ex vivo porcine liver perfusion experiments demonstrated the effectiveness of the method, maintaining blood gas within physiological levels over 24 h (oxygen partial pressure: 150.36 ± 3.33 mmHg, carbon dioxide partial pressure: 41.34 ± 0.91 mmHg).

ADRC-based continuous regulation of gas fraction at the outlet of oxygenator is a feasible and effective approach for managing blood gas during ex vivo porcine liver perfusion.

Background: Liver transplantation constitutes a well-established treatment for patients with end-stage liver disease and selected hepatic malignancies. The introduction of normothermic machine perfusion (NMP) offers a platform for both extracorporeal organ maintenance and viability assessment, especially for organs with suspicious malfunction. These organs, discarded by the majority of transplant centers (so-called 'orphan livers'), may help to safely expand the donor pool thanks to pre-transplant appraisal; Methods: We identified all grafts undergoing normothermic ma-chine perfusions performed in the Department of General, Transplant, and Liver Surgery between December 2022 and August 2023. Their perfusion characteristics and immediate postoperative periods, as well as complications that occurred in the 90-day postoperative periods, were analyzed; Results: There were eight orphan liver grafts that underwent NMP in our Department. Postoperative complications occurring in patients receiving grafts after NMP did not seem associated with the procedure. One patient required laparotomy within the 90-day postoperative period due to biliary fistula and underwent bile duct stenting due to both fistula and nonanastomotic stricture. In one patient we observed the occurrence of anastomotic biliary stricture more than 90 days after LTx; Conclusions: NMP allows for the viability assessment of grafts with suspicious prepreservation malfunction. Some of these organs may help to expand the donor pool.

The programmed cell death protein 1 (PD-1) acts as a central inhibitory immune checkpoint receptor. The soluble form of its primary ligand, sPD-L1, was found to be elevated in the serum of patients with cancer, infectious diseases, and chronic inflammation. So far, the hepatic origin of sPD-L1 has received relatively little attention and is therefore the subject of this study in the context of normothermic machine perfusion (NMP) of liver grafts. sPD-L1 concentrations as well as several well-established clinically relevant laboratory parameters were determined in the perfusate of 16 donor liver grafts undergoing NMP up to 30 hours. sPD-L1 levels continuously increased during NMP and significantly correlated with markers of hepatic synthesis (cholinesterase), acute-phase proteins (von Willebrand factor, procalcitonin, antithrombin, interleukin-6, fibrinogen), and liver decay markers (gamma-glutamyltransferase, alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase). Perfusate leukocytes were in the lower reference range and decreased after 12 hours. Mean sPD-L1 levels in the perfusate correlated with donor levels of gamma-glutamyltransferase, alanine aminotransferase, creatinine, and blood urea nitrogen. Our study reveals a significant increase in the concentration of sPD-L1 following ischemia-reperfusion injury in a hepatic ex vivo model. sPD-L1 concentrations during NMP correlate with established acute-phase proteins and liver cell decay markers, suggesting that hepatic sPD-L1 synthesis or shedding increases during the acute phase and cell decay. Furthermore, sPD-L1 correlates with established liver function and synthesis parameters as well as with donor laboratory values and might therefore be a potential biomarker for the hepatic function of liver grafts.

Organ transplantation, a critical treatment for end-stage organ failure, has witnessed significant advancements due to the integration of improved surgical techniques, immunosuppressive therapies, and donor-recipient matching. This review explores the progress of organ preservation, focusing on the shift from static cold storage (SCS) to advanced machine perfusion techniques such as hypothermic (HMP) and normothermic machine perfusion (NMP). Although SCS has been the standard approach, its limitations in preserving marginal organs and preventing ischemia-reperfusion injury (IRI) have led to the adoption of HMP and NMP. HMP, which is now the gold standard for high-risk donor kidneys, reduces metabolic activity and improves posttransplant outcomes. NMP allows real-time organ viability assessment and reconditioning, especially for liver transplants. Controlled oxygenated rewarming further minimizes IRI by addressing mitochondrial dysfunction. The review also highlights the potential of cryopreservation for long-term organ storage, despite challenges with ice formation. These advances are crucial for expanding the donor pool, improving transplant success rates, and addressing organ shortages. Continued innovation is necessary to meet the growing demands of transplantation and save more lives.

Efforts to improve the quality of marginal grafts for transplantation are essential. Machine perfusion preservation appears as a promising solution.

The United Network for Organ Sharing (UNOS) database was queried for deceased liver donor records between 2016 and 2022. The primary outcome of interest was the organ nonutilization rate. Long-term graft and patient survival among extended criteria donors (ECDs) were also analyzed.

During the study period, out of 54 578 liver grafts recovered for transplant, 5085 (9.3%) were nonutilized. Multivariable analysis identified normothermic machine perfusion (NMP) preservation as the only predictor associated with a reduction in graft nonutilization (OR = 0.12; 95% CI = 0.06-0.023, p < 0.001). Further analysis of ECD grafts that were transplanted revealed comparable 1-,2- and 3-years graft survival (89%/88%/82% vs. 90%/85%/81%, p = 0.60), and patient survival (92%/91%/84% vs. 92%/88%/84%, p = 0.65) between grafts that underwent MP vs. those who did not, respectively.

Liver nonutilization rates in the United States are at an all-time high. Available data, most likely including cases from clinical trials, showed that NMP reduced the odds of organ nonutilization by 12% among the entire deceased donor pool and by 16% among grafts from ECD. Collective efforts and further evidence reflecting day-to-day clinical practice are needed to fully reach the potential of MP for liver transplant.

Liver injury caused by various factors significantly impacts human health. Stem cell transplantation has potential for enhancing liver functionality, but safety concerns such as immune rejection, tumorigenesis, and the formation of emboli in the lungs remain. Recent studies have shown that stem cells primarily exert their effects through the secretion of extracellular vesicles (EVs). EVs have been shown to play crucial roles in reducing inflammation, preventing cell death, and promoting liver cell proliferation. Additionally, they can function as carriers to deliver targeted drugs to the liver, thereby exerting specific physiological effects. EVs possess several advantages, including structural stability, low immunogenicity, minimal tumorigenicity targeting capabilities, and convenient collection. Consequently, EVs have garnered significant attention from researchers and are expected to become alternative therapeutic agents to stem cell therapy. This article provides a comprehensive review of the current research progress in the use of stem cell-derived EVs in the treatment of liver injury.

Normothermic machine perfusion of donor livers has become standard practice in the field of transplantation, allowing the assessment of organs and safe extension of preservation times. Alongside its clinical uses, there has been expanding interest in extended normothermic machine perfusion (eNMP) of livers as a potential vehicle for medical research. Reproducible extended normothermic machine perfusion has remained elusive due to its increased complexity and monitoring requirements. We set out to develop a reproducible protocol for the extended normothermic machine perfusion of whole human livers.

Human livers declined for transplantation were perfused using a blood-based perfusate at 36 °C using the Liver Assist device (XVIVO, Sweden), with continuous veno-venous haemofiltration in-parallel. We developed the protocol in a stepwise fashion.

Perfusion techniques utilised included: targeted physiological vascular flows, phosphate replacement (to prevent hypophosphataemia), N-acetylcysteine (to prevent methaemoglobin accumulation), and the utilisation of sodium lactate as both a nutritional source and real-time measure of hepatocyte function. All five human livers perfused with the developed protocol showed preserved function with a median perfusion time of 168 h (range 120-184 h), with preserved viability throughout.

Livers can be reproducibly perfused in excess of 120 (range 121-184) hours with evidence of preserved hepatocyte and cholangiocyte function.

The scarcity of available liver grafts necessitates the use of organs from extended criteria donors, a practice associated with an increased risk of graft failure. A notable percentage of deceased donor liver allografts are rejected due to subjective criteria. Normothermic machine perfusion holds promise for introducing objective parameters into this decision-making process. The aim of this study was to compare the outcomes of standard criteria and extended criteria donor allografts after liver transplantation, following viability assessment, using normothermic machine perfusion.

Liver allografts preserved by normothermic machine perfusion before liver transplantation at the University Hospital of Münster were retrospectively analyzed. Organs were stratified according to the Eurotransplant Donor Risk Index. In total, 101 liver grafts were included in this study and divided into 2 groups: (1) standard criteria donors with a Donor Risk Index <1.8 (DRI-low) and (2) extended criteria donors with a Donor Risk Index ≥1.8 (DRI-high).

An increased risk profile of donor livers, as assessed by the Eurotransplant Donor Risk Index, did not correlate with patient or graft survival. High-risk liver grafts were effectively transplanted into recipients with different risk levels after viability assessment by normothermic machine perfusion. However, the recipients' model for end-stage liver disease scores showed a significant association with both overall patient and graft survival.

The use of normothermic machine perfusion for viability assessment allows safe transplantation of high-risk donor livers and effectively addresses the disparity between donor liver availability and transplantation demand.

Ischemia/reperfusion injury (IRI) is a key determining agent in the pathophysiology of clinical organ dysfunction. It is characterized by an aseptic local inflammatory reaction due to a decrease in blood supply, hence deprivation of dependent oxygen and nutrients. In instances of liver transplantation, this injury may have irreversible implications, resulting in eventual organ rejection. The deterioration associated with IRI is affected by the hepatic health status and various factors such as alterations in metabolism, oxidative stress, and pro-inflammatory cytokines. The primary cause of inflammation is the initial immune response of pro-inflammatory cytokines, while Kupffer cells (KFCs) and neutrophil-produced chemokines also play a significant role. Upon reperfusion, the activation of inflammatory responses can elicit further cellular damage and organ dysfunction. This review discusses the interplay between chemokines, pro-inflammatory cytokines, and other inflammatory mediators that contribute to the damage to hepatocytes and liver failure in rats following IR. Furthermore, it delves into the impact of anti-inflammatory therapies in safeguarding against liver failure and hepatocellular damage in rats following IR. This review investigates the correlation between cytokine factors and liver dysfunction via examining databases, such as PubMed, Google Scholar, Science Direct, Egyptian Knowledge Bank (EKB), and Research Gate.

Current graft evaluation during normothermic ex situ liver perfusion lacks real-time parameters for predicting posttransplant hepatocyte and biliary function. Indocyanine green (ICG) imaging has been widely used in liver surgery, enabling the visualization of hepatic uptake and excretion through bile using near-infrared light. In this research, porcine livers under various ischemic conditions were examined during a 5-hour normothermic ex situ liver perfusion procedure, introducing ICG at 1 hour through the hepatic artery. These conditions included livers from heart-beating donors, donation after circulatory death (DCD) with warm ischemic durations of 60 minutes (DCD60) and 120 minutes (DCD120), as well as interventions utilizing tissue plasminogen activator in DCD120 cases (each n = 5). Distinct hepatic fluorescence patterns correlated with different degrees of ischemic injury ( p = 0.01). Low ICG uptake in the parenchyma (less than 40% of maximum intensity) was more prevalent in DCD120 (21.4%) compared to heart-beating donors (6.2%, p = 0.06) and DCD60 (3.0%, p = 0.02). Moreover, ICG clearance from 60 minutes to 240 minutes was significantly higher in heart-beating donors (69.3%) than in DCD60 (17.5%, p < 0.001) and DCD120 (32.1%, p = 0.01). Furthermore, thrombolytic intervention using tissue plasminogen activator in DCD120 resulted in noteworthy outcomes, including significantly reduced ALP levels ( p = 0.04) and improved ICG clearance ( p = 0.02) with a trend toward mitigating fibrin deposition similar to DCD60, as well as enhancements in bile production ( p = 0.09). In conclusion, ICG fluorescence imaging during normothermic ex situ liver perfusion provides real-time classification of hepatic vascular and biliary injuries, offering valuable insights for the more accurate selection and postintervention evaluation of marginal livers in transplantation.

Transplanted organs experience several episodes of ischemia and ischemia-reperfusion. The graft injury resulting from ischemia-reperfusion (IRI) remains a significant obstacle to the successful survival of transplanted grafts. Temperature significantly influences cellular metabolic rates because biochemical reactions are highly sensitive to temperature changes. Consequently, lowering the temperature could reduce the degradative reactions triggered by ischemia. In mitigating IRI in liver grafts, the potential protective effect of localized hypothermia on the liver prior to blood flow obstruction has yet to be explored. In this study, we applied local hypothermia to mouse donor livers for a specific duration before stopping blood flow to liver lobes, a procedure called "liver precooling". Mouse donor liver temperature in control groups was controlled at 37 °C. Subsequently, the liver donors were preserved in cold University of Wisconsin solution for various durations followed by orthotopic liver transplantation. Liver graft injury, function and inflammation were assessed at 1 and 2 days post-transplantation. Liver precooling exhibited a significant improvement in graft function, revealing more than a 47% decrease in plasma aspartate transaminase (AST) and alanine aminotransferase (ALT) levels, coupled with a remarkable reduction of approximately 50% in liver graft histological damage compared to the control group. The protective effects of liver precooling were associated with the preservation of mitochondrial function, a substantial reduction in hepatocyte cell death, and a significantly attenuated inflammatory response. Taken together, reducing the cellular metabolism and enzymatic activity to a minimum level before ischemia protects against IRI during transplantation.

The shortage of donor organs remains an unresolved issue in livertransplantation worldwide. Consequently, strategies for expanding the donor pool are currently being developed. Donors meeting extended criteria undergo thorough evaluation, as livers obtained from marginal donors yield poorer outcomes in recipients, including exacerbated reperfusion injury, acute kidney injury, early graft dysfunction, and primary nonfunctioning graft. However, the implementation of machine perfusion has shown excellent potential in preserving donor livers and improving their characteristics to achieve better outcomes for recipients. In this review, we analyzed the global experience of using machine perfusion in livertransplantation through the history ofthe development ofthis method to the latest trends and possibilities for increasing the number of liver transplants.

Donation after circulatory death (DCD) grafts are vital for increasing available donor organs. Gradual rewarming during machine perfusion has proven effective in mitigating reperfusion injury and enhancing graft quality. Limited data exist on artificial oxygen carriers as an effective solution to meet the increasing metabolic demand with temperature changes. The aim of the present study was to assess the efficacy and safety of utilizing a hemoglobin-based oxygen carrier (HBOC) during the gradual rewarming of DCD rat livers.

Liver grafts were procured after 30 min of warm ischemia. The effect of 90 min of oxygenated rewarming perfusion from ice cold temperatures (4 °C) to 37 °C with HBOC after cold storage was evaluated and the results were compared with cold storage alone. Reperfusion at 37 °C was performed to assess the post-preservation recovery.

Gradual rewarming with HBOC significantly enhanced recovery, demonstrated by markedly lower lactate levels and reduced vascular resistance compared to cold-stored liver grafts. Increased bile production in the HBOC group was noted, indicating improved liver function and bile synthesis capacity. Histological examination showed reduced cellular damage and better tissue preservation in the HBOC-treated livers compared to those subjected to cold storage alone.

This study suggests the safety of using HBOC during rewarming perfusion of rat livers as no harmful effect was detected. Furthermore, the viability assessment indicated improvement in graft function.

Liver disease is the third leading cause of premature death in the UK. Transplantation is the only successful treatment for end-stage liver disease but is limited by a shortage of suitable donor organs. As a result, up to 20% of patients on liver transplant waiting lists die before receiving a transplant. A third of donated livers are not suitable for transplant, often due to steatosis. Hepatic steatosis, which affects 33% of the UK population, is strongly associated with obesity, an increasing problem in the potential donor pool. We have recently tested defatting interventions during normothermic machine perfusion (NMP) in discarded steatotic human livers that were not transplanted. A combination of therapies including forskolin (NKH477) and L-carnitine to defat liver cells and lipoprotein apheresis filtration were investigated. These interventions resulted in functional improvement during perfusion and reduced the intrahepatocellular triglyceride (IHTG) content. We hypothesise that defatting during NMP will allow more steatotic livers to be transplanted with improved outcomes.

In the proposed multi-centre clinical trial, we will randomly assign 60 livers from donors with a high-risk of hepatic steatosis to either NMP alone or NMP with defatting interventions. We aim to test the safety and feasibility of the defatting intervention and will explore efficacy by comparing ex-situ and post-reperfusion liver function between the groups. The primary endpoint will be the proportion of livers that achieve predefined functional criteria during perfusion which indicate potential suitability for transplantation. These criteria reflect hepatic metabolism and injury and include lactate clearance, perfusate pH, glucose metabolism, bile composition, vascular flows and transaminase levels. Clinical secondary endpoints will include proportion of livers transplanted in the two arms, graft function; cell-free DNA (cfDNA) at follow-up visits; patient and graft survival; hospital and ITU stay; evidence of ischemia-reperfusion injury (IRI); non-anastomotic biliary strictures and recurrence of steatosis (determined on MRI at 6 months).

This study explores ex-situ pharmacological optimisation of steatotic donor livers during NMP. If the intervention proves effective, it will allow the safe transplantation of livers that are currently very likely to be discarded, thereby reducing waiting list deaths.

ISRCTN ISRCTN14957538. Registered in October 2022.

The number of patients on the liver transplant waitlist continues to grow and far exceeds the number of livers available for transplantation. Normothermic machine perfusion (NMP) allows for ex-vivo perfusion under physiologic conditions with the potential to significantly increase organ yield and expand the donor pool.

Several studies have found increased utilization of donation after cardiac death and extended criteria brain-dead donor livers with implementation of NMP, largely due to the ability to perform viability testing during machine perfusion. Recently, proposed viability criteria include lactate clearance, maintenance of perfusate pH more than 7.2, ALT less than 6000 u/l, evidence of glucose metabolism and bile production. Optimization of liver grafts during NMP is an active area of research and includes interventions for defatting steatotic livers, preventing ischemic cholangiopathy and rejection, and minimizing ischemia reperfusion injury.

NMP has resulted in increased organ utilization from marginal donors with acceptable outcomes. The added flexibility of prolonged organ storage times has the potential to improve time constraints and transplant logistics. Further research to determine ideal viability criteria and investigate ways to optimize marginal and otherwise nontransplantable liver grafts during NMP is warranted.

In organ transplantation, ischemia, and reperfusion injury (IRI) is considered as an inevitable event and the major contributor to graft failure. Ischemia-free liver transplantation (IFLT) is a novel transplant procedure that can prevent IRI and provide better transplant outcomes. However, a large animal model of IFLT has not been reported. Therefore, we develop a new, reproducible, and stable model of IFLT in pigs for investigating mechanisms of IFLT in IRI.

Ten pigs were subjected to IFLT or conventional liver transplantation (CLT). Donor livers in IFLT underwent 6-h continuous normothermic machine perfusion (NMP) throughout graft procurement, preservation, and implantation, whereas livers in CLT were subjected to 6-h cold storage before implantation. The early reperfusion injury was compared between the 2 groups.

Continuous bile production, low lactate, and liver enzyme levels were observed during NMP in IFLT. All animals survived after liver transplantation. The posttransplant graft function was improved with IFLT when compared with CLT. Minimal histologic changes, fewer apoptotic hepatocytes, less sinusoidal endothelial cell injury, and proinflammatory cytokine (interleukin [IL]-1β, IL-6, and tumor necrosis factor-α) release after graft revascularization were documented in the IFLT group versus the CLT group.

We report that the concept of IFLT is achievable in pigs. This innovation provides a potential strategy to investigate the mechanisms of IRI and provide better transplant outcomes for clinical practice.

Normothermic machine perfusion (NMP) of livers allows for the expansion of the donor pool and minimization of posttransplant complications. Results to date have focused on both donor and recipient outcomes, but there remains potential for NMP to also impact transplant providers.

Using United Network for Organ Sharing Standard Transplant Analysis file data, adult deceased donors who underwent transplantation between January 1, 2016, and December 31, 2022, were identified. Transplanted livers were divided by preservation methods (static cold storage [SCS] and NMP) and case time (day-reperfusion 8 am to 6 pm ). Patient factors, transplant characteristics, and short-term outcomes were analyzed between Mahalanobis-metric-matched groups.

NMP livers represented 742 (1.4%) of 52,132 transplants. NMP donors were more marginal with higher Donor Risk Index scores (1.78 ± 0.50 NMP vs 1.49 ± 0.38 SCS, p < 0.001) and donation after cardiac death frequency (36.9% vs 8.4%, p < 0.001). NMP recipients more often had model for end-stage liver disease (MELD) exception status (29.9% vs 23.4%, p < 0.001), lower laboratory MELD scores (20.7 ± 9.7 vs 24.3 ± 10.9, p < 0.001), and had been waitlisted longer (111.5 [21.0 to 307.0] vs 60.0 [9.0 to 245.0] days, p < 0.001). One-year graft survival (90.2% vs 91.6%, p = 0.505) was similar between groups, whereas length of stay was lower for NMP recipients (8.0 [6.0 to 14.0] vs 10.0 [6.0 to 16.0], p = 0.017) after adjusting for confounders. Notably, peak case volume occurred at 11 am with NMP livers (vs 9 pm with SCS). Overall, a higher proportion of transplants was performed during daytime hours with NMP (51.5% vs 43.0%, p < 0.001).

NMP results in increased use of marginal allografts, which facilitated transplantation in lower laboratory MELD recipients who have been waitlisted longer and often have exception points. Importantly, NMP also appeared to shift peak caseloads from nighttime to daytime, which may have significant effects on the quality of life for the entire liver transplant team.

Liver transplantation (LT) is the only definitive treatment for end-stage liver disease, yet the UK has seen a 400% increase in liver disease-related deaths since 1970, constrained further by a critical shortage of donor organs. This shortfall has necessitated the use of extended criteria donor organs, including those with evidence of steatosis. The impact of hepatic steatosis (HS) on graft viability remains a concern, particularly for donor livers with moderate to severe steatosis which are highly sensitive to the process of ischaemia-reperfusion injury (IRI) and static cold storage (SCS) leading to poor post-transplantation outcomes. This review explores the pathophysiological predisposition of steatotic livers to IRI, the limitations of SCS, and alternative preservation strategies, including novel organ preservation solutions (OPS) and normothermic machine perfusion (NMP), to mitigate IRI and improve outcomes for steatotic donor livers. By addressing these challenges, the liver transplant community can enhance the utilisation of steatotic donor livers which is crucial in the context of the global obesity crisis and the growing need to expand the donor pool.

The last decade has been notable for increasing high-quality research and dramatic improvement in outcomes with dynamic liver preservation. Robust evidence from numerous randomized controlled trials has been pooled by meta-analyses, providing the highest available evidence on the protective effect of machine perfusion (MP) over static cold storage in liver transplantation (LT). Based on a protective effect with less complications and improved graft survival, the field has seen a paradigm shift in organ preservation. This editorial focuses on the role of MP in LT and how it could become the new "gold standard". Strong collaborative efforts are needed to explore its effects on long-term outcomes.

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

Since the advent of University of Wisconsin preservation solution in the 1980s, clinicians have learned to work within its confines. While affording improved outcomes, considerable limitations still exist and contribute to the large number of livers that go unused each year, often for fear they may never work. The last 10 years have seen the widespread availability of new perfusion modalities which provide an opportunity for assessing organ viability and prolonged organ storage. This review will discuss the role of in situ normothermic regional perfusion for livers donated after circulatory death. It will also describe the different modalities of ex situ perfusion, both normothermic and hypothermic, and discuss how they are thought to work and the opportunities afforded by them.

This review discusses recent experimental and clinical findings related to ferroptosis, with a focus on the role of MSCs. Therapeutic efficacy and current applications of MSC-based ferroptosis therapies are also discussed.

Ferroptosis is a type of programmed cell death that differs from apoptosis, necrosis, and autophagy; it involves iron metabolism and is related to the pathogenesis of many diseases, such as Parkinson's disease, cancers, and liver diseases. In recent years, the use of mesenchymal stem cells (MSCs) and MSC-derived exosomes has become a trend in cell-free therapies. MSCs are a heterogeneous cell population isolated from a diverse range of human tissues that exhibit immunomodulatory functions, regulate cell growth, and repair damaged tissues. In addition, accumulating evidence indicates that MSC-derived exosomes play an important role, mainly by carrying a variety of bioactive substances that affect recipient cells. The potential mechanism by which MSC-derived exosomes mediate the effects of MSCs on ferroptosis has been previously demonstrated. This review provides the first overview of the current knowledge on ferroptosis, MSCs, and MSC-derived exosomes and highlights the potential application of MSCs exosomes in the treatment of ferroptotic conditions. It summarizes their mechanisms of action and techniques for enhancing MSC functionality. Results obtained from a large number of experimental studies revealed that both local and systemic administration of MSCs effectively suppressed ferroptosis in injured hepatocytes, neurons, cardiomyocytes, and nucleus pulposus cells and promoted the survival and regeneration of injured organs.

We reviewed the role of ferroptosis in related tissues and organs, focusing on its characteristics in different diseases. Additionally, the effects of MSCs and MSC-derived exosomes on ferroptosis-related pathways in various organs were reviewed, and the mechanism of action was elucidated. MSCs were shown to improve the disease course by regulating ferroptosis.

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.

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

Extended duration of normothermic machine perfusion (NMP) provides opportunities to resuscitate suboptimal donor livers. This intervention requires adequate oxygen delivery typically provided by a blood-based perfusion solution. Methaemoglobin (MetHb) results from the oxidation of iron within haemoglobin and represents a serious problem in perfusions lasting > 24 h. We explored the effects of anti-oxidant, N-acetylcysteine (NAC) on the accumulation of methaemoglobin. NMP was performed on nine human donor livers declined for transplantation: three were perfused without NAC (no-NAC group), and six organs perfused with an initial NAC bolus, followed by continuous infusion (NAC group), with hourly methaemoglobin perfusate measurements. In-vitro experiments examined the impact of NAC (3 mg) on red cells (30 ml) in the absence of liver tissue. The no-NAC group sustained perfusions for an average of 96 (range 87-102) h, universally developing methaemoglobinaemia (≥ 2%) observed after an average of 45 h, with subsequent steep rise. The NAC group was perfused for an average of 148 (range 90-184) h. Only 2 livers developed methaemoglobinaemia (peak MetHb of 6%), with an average onset of 116.5 h. Addition of NAC efficiently limits formation and accumulation of methaemoglobin during NMP, and allows the significant extension of perfusion duration.

With a very long history of setbacks and successes, organ transplantation is one of the greatest medical achievements of the twentieth century. Liver transplantation is currently the most effective method for treating end-stage liver disease. From humble beginnings, improvements in surgical technique, perioperative management, and immunosuppressive therapy have yielded excellent graft and patient outcomes. Most established 'liver transplant' (LT) centres have a 1-year survival rate exceeding 90%, and a 3-year survival rate of over 80%. With immense success, the need for hepatic grafts substantially exceeds their availability. This problem has been partially addressed by using split grafts, living donor liver transplantation (LDLT), and extended criteria grafts (ECG). This article reviews the immense progress made in various aspects of LT including evaluation, increasing donor pool, surgical advances, immunosuppression and anaesthesia related aspects and the way forward. With ongoing cutting edge research in technologies like artificial liver devices, tissue bioengineering and hepatocyte 'farms', the future of LT is more exciting than ever before.

To compare conventional low-temperature storage of transplant donor livers [static cold storage (SCS)] with storage of the organs at physiological body temperature [normothermic machine perfusion (NMP)].

The high success rate of liver transplantation is constrained by the shortage of transplantable organs (eg, waiting list mortality >20% in many centers). NMP maintains the liver in a functioning state to improve preservation quality and enable testing of the organ before transplantation. This is of greatest potential value with organs from brain-dead donor organs (DBD) with risk factors (age and comorbidities), and those from donors declared dead by cardiovascular criteria (donation after circulatory death).

Three hundred eighty-three donor organs were randomized by 15 US liver transplant centers to undergo NMP (n = 192) or SCS (n = 191). Two hundred sixty-six donor livers proceeded to transplantation (NMP: n = 136; SCS: n = 130). The primary endpoint of the study was "early allograft dysfunction" (EAD), a marker of early posttransplant liver injury and function.

The difference in the incidence of EAD did not achieve significance, with 20.6% (NMP) versus 23.7% (SCS). Using exploratory, "as-treated" rather than "intent-to-treat," subgroup analyses, there was a greater effect size in donation after circulatory death donor livers (22.8% NMP vs 44.6% SCS) and in organs in the highest risk quartile by donor risk (19.2% NMP vs 33.3% SCS). The incidence of acute cardiovascular decompensation at organ reperfusion, "postreperfusion syndrome," as a secondary outcome was reduced in the NMP arm (5.9% vs 14.6%).

NMP did not lower EAD, perhaps related to the inclusion of lower-risk liver donors, as higher-risk donor livers seemed to benefit more. The technology is safe in standard organ recovery and seems to have the greatest benefit for marginal donors.

Machine perfusion is increasingly being tested in clinical transplantation. Despite this, the number of large prospective clinical trials remains limited. The aim of this study was to compare the impact of machine perfusion vs. static cold storage (SCS) on outcomes after liver transplantation.

A systematic search of MEDLINE, EMBASE, CINAHL and the Cochrane Central Register of Controlled Trials (CENTRAL) was conducted to identify randomized-controlled trials (RCTs) comparing "post-transplant" outcomes following machine perfusion vs. SCS. Data were pooled using random effect models. Risk ratios (RRs) were calculated for relevant outcomes. The quality of evidence was rated using the GRADE-framework.

Seven RCTs were identified (four on hypothermic oxygenated [HOPE] and three on normothermic machine perfusion [NMP]), including a total number of 1,017 patients. Both techniques were associated with significantly lower rates of early allograft dysfunction (NMP: n = 41/282, SCS: n = 74/253, RR 0.50, 95% CI 0.30-0.86, p = 0.01, I2 = 39%; HOPE: n = 45/241, SCS: n = 97/241, RR 0.48, 95% CI 0.35-0.65, p < 0.00001, I2 = 5%). The HOPE approach led to a significant reduction in major complications (Clavien Grade ≥IIIb; HOPE: n = 90/241; SCS: n = 117/241, RR 0.76, 95% CI 0.63-0.93, p = 0.006, I2 = 0%), "re-transplantation" (HOPE: n = 1/163; SCS: n = 11/163; RR 0.21, 95% CI 0.04-0.96, p = 0.04; I2 = 0%) and graft loss (HOPE: n = 7/163; SCS: n = 19/163; RR 0.40, 95% CI 0.17-0.95, p = 0.04; I2 = 0%). Both perfusion techniques were found to 'likely' reduce overall biliary complications and non-anastomotic strictures.

Although this study provides the highest current evidence on the role of machine perfusion, outcomes remain limited to a 1-year follow-up after liver transplantation. Comparative RCTs and large real-world cohort studies with longer follow-up are required to enhance the robustness of the data further, thereby supporting the introduction of perfusion technologies into routine clinical practice.

CRD42022355252.

For a decade, two dynamic perfusion concepts have increasingly been tested in several transplant centres worldwide. We undertook the first systematic review and meta-analysis and identified seven published RCTs, including 1,017 patients, evaluating the effect of machine perfusion (hypothermic and normothermic perfusion techniques) compared to static cold storage in liver transplantation. Both perfusion techniques were associated with lower rates of early allograft dysfunction in the first week after liver transplantation. Hypothermic oxygenated perfusion led to a reduction in major complications, lower "re-transplantation" rates and better graft survival. Both perfusion strategies were found to 'likely' reduce overall biliary complications and non-anastomotic biliary strictures. This study provides the highest current evidence on the role of machine perfusion. Outcomes remain limited to a 1-year post-transplant follow-up. Larger cohort studies with longer follow-up and clinical trials comparing the perfusion techniques are required. This is especially relevant to provide clarity and optimise implementation processes further to support the commissioning of this technology worldwide.