Oxygenated versus non-oxygenated flush out during deceased donor liver procurement: The first proof-of-concept study in humans.

BACKGROUND: Liver transplantation is used for treating end-stage liver disease, fulminant hepatitis, and oncological malignancies and organ shortage is a major limiting factor worldwide. The use of grafts based on extended donor criteria have become internationally accepted. Oxygenated machine perfusion technologies are the most recent advances in organ transplantation; however, it is only applied after a period of cold ischemia. Due to its high cost, we aimed to use a novel device, OxyFlush®, based on oxygenation of the preservation solution, applied during liver procurement targeting the maintenance of ATP during static cold storage (SCS). METHODS: Twenty patients were randomly assigned to the OxyFlush or control group based on a 1:1 ratio. In the OxyFlush group, the perfusion solution was oxygenated with OxyFlush® device while the control group received a non-oxygenated solution. Liver and the common bile duct (CBD) biopsies were obtained at three different time points. The first was at the beginning of the procedure, the second during organ preparation, and the third after total liver reperfusion. Biopsies were analyzed, and adenosine triphosphate (ATP) levels and histological scores of the liver parenchyma and CBD were assessed. Postoperative laboratory tests were performed. RESULTS: OxyFlush® was able to maintain ATP levels during SCS and improved the damage caused by the lack of oxygen in the CBD. However, OxyFlush® did not affect laboratory test results and histological findings of the parenchyma. CONCLUSION: We present a novel low-cost device that is feasible and could represent a valuable tool in organ preservation during SCS.

Rare case of an acute liver torsion.

Torsion of an abdominal organ often leads to an acute abdomen requiring emergency surgery. This report describes the rare case of an acute liver torsion in a 76-year-old man. Surgery revealed dislocation of the left liver lobe, which was flipped over to the right upper abdomen. There was a hypermobile and long falciform ligament and absence of the triangular ligaments. The liver was manually flipped back with subsequent fixation of the umbilical ligament to the diaphragm to prevent reoccurrence. The patient had an uneventful recovery and is doing well 3 months after surgery with good liver function.

Prolonged preservation by hypothermic machine perfusion facilitates logistics in liver transplantation: A European observational cohort study.

A short period (1-2 h) of hypothermic oxygenated machine perfusion (HOPE) after static cold storage is safe and reduces ischemia-reperfusion injury-related complications after liver transplantation. Machine perfusion time is occasionally prolonged for logistical reasons, but it is unknown if prolonged HOPE is safe and compromises outcomes. We conducted a multicenter, observational cohort study of patients transplanted with a liver preserved by prolonged (≥4 h) HOPE. Postoperative biochemistry, complications, and survival were evaluated. The cohort included 93 recipients from 12 European transplant centers between 2014-2021. The most common reason to prolong HOPE was the lack of an available operating room to start the transplant procedure. Grafts underwent HOPE for a median (range) of 4:42 h (4:00-8:35 h) with a total preservation time of 10:50 h (5:50-20:50 h). Postoperative peak ALT was 675 IU/L (interquartile range 419-1378 IU/L). The incidence of postoperative complications was low, and 1-year graft and patient survival were 94% and 88%, respectively. To conclude, good outcomes are achieved after transplantation of donor livers preserved with prolonged (median 4:42 h) HOPE, leading to a total preservation time of almost 21 h. These results suggest that simple, end-ischemic HOPE may be utilized for safe extension of the preservation time to ease transplantation logistics.

Sequential hypothermic and normothermic machine perfusion enables safe transplantation of high-risk donor livers.

Ex situ normothermic machine perfusion (NMP) is increasingly used for viability assessment of high-risk donor livers, whereas dual hypothermic oxygenated machine perfusion (DHOPE) reduces ischemia-reperfusion injury. We aimed to resuscitate and test the viability of initially-discarded, high-risk donor livers using sequential DHOPE and NMP with two different oxygen carriers: an artificial hemoglobin-based oxygen carrier (HBOC) or red blood cells (RBC). In a prospective observational cohort study of 54 livers that underwent DHOPE-NMP, the first 18 procedures were performed with a HBOC-based perfusion solution and the subsequent 36 procedures were performed with an RBC-based perfusion solution for the NMP phase. All but one livers were derived from extended criteria donation after circulatory death donors, with a median donor risk index of 2.84 (IQR 2.52-3.11). After functional assessment during NMP, 34 livers (63% utilization), met the viability criteria and were transplanted. One-year graft and patient survival were 94% and 100%, respectively. Post-transplant cholangiopathy occurred in 1 patient (3%). There were no significant differences in utilization rate and post-transplant outcomes between the HBOC and RBC group. Ex situ machine perfusion using sequential DHOPE-NMP for resuscitation and viability assessment of high-risk donor livers results in excellent transplant outcomes, irrespective of the oxygen carrier used.

The Emerging Role of Viability Testing During Liver Machine Perfusion.

The transplant community continues to be challenged by the disparity between the need for liver transplantation and the shortage of suitable donor organs. At the same time, the number of unused donor livers continues to increase, most likely attributed to the worsening quality of these organs. To date, there is no reliable marker of liver graft viability that can predict good posttransplant outcomes. Ex situ machine perfusion offers additional data to assess the viability of donor livers before transplantation. Hence, livers initially considered unsuitable for transplantation can be assessed during machine perfusion in terms of appearance and consistency, hemodynamics, and metabolic and excretory function. In addition, postoperative complications such as primary nonfunction or posttransplant cholangiopathy may be predicted and avoided. A variety of viability criteria have been used in machine perfusion, and to date there is no widely accepted composition of criteria for clinical use. This review discusses potential viability markers for hepatobiliary function during machine perfusion, describes current limitations, and provides future recommendations for the use of viability criteria in clinical liver transplantation.

Oxygenated versus non-oxygenated flush out and storage of donor livers: An experimental study.

BACKGROUND: During donor organ procurement and subsequent static cold storage (SCS), hepatic adenosine triphosphate (ATP) levels are progressively depleted, which contributes to ischemia-reperfusion injury (IRI). We sought to investigate a simple approach to prevent ATP depletion and IRI using a porcine donation after circulatory death (DCD) liver reperfusion model. METHODS: After 30 min warm ischemia, porcine livers were flushed via the portal vein with cold (4°C) non-oxygenated University of Wisconsin (UW) preservation solution (n = 6, control group) or with oxygenated UW (n = 6, OxyFlush group). Livers were then subjected to 4 h SCS in non-oxygenated (control) or oxygenated (OxyFlush) UW, followed by 4 h normothermic reperfusion using whole blood. Hepatic ATP levels were compared, and hepatobiliary function and injury were assessed. RESULTS: At the end of SCS, ATP was higher in the OxyFlush group compared to controls (delta ATP of +0.26 vs. -0.68 µmol/g protein, p = 0.04). All livers produced bile and metabolized lactate, and there were no differences between the groups. Grafts in the OxyFlush group had lower blood glucose levels after reperfusion (p = 0.04). Biliary pH, glucose and bicarbonate were not different between the groups. Injury markers including liver transaminases, lactate dehydrogenase, malondialdehyde, cell-free DNA and flavin mononucleotide in the SCS solution and during reperfusion were also similar. Histological assessment of the parenchyma and bile ducts did not reveal differences between the groups. CONCLUSION: Oxygenated flush out and storage of DCD porcine livers prevents ATP depletion during ischemia, but this does not seem sufficient to mitigate early signs of IRI.

The economic impact of machine perfusion technology in liver transplantation.

INTRODUCTION: Several clinical studies have demonstrated the safety, feasibility, and efficacy of machine perfusion in liver transplantation, although its economic outcomes are still underexplored. This review aimed to examine the costs related to machine perfusion and its associated outcomes. METHODS: Expert opinion of several groups representing different machine perfusion modalities. Critical analysis of the published literature reporting the economic outcomes of the most used techniques of machine perfusion in liver transplantation (normothermic and hypothermic ex situ machine perfusion and in situ normothermic regional perfusion). RESULTS: Machine perfusion costs include disposable components of the perfusion device, perfusate components, personnel and facility fees, and depreciation of the perfusion device or device lease fee. The limited current literature suggests that although this upfront cost varies between perfusion modalities, its use is highly likely to be cost-effective. Optimization of the donor liver utilization rate, local conditions of transplant programs (long waiting list times and higher MELD scores), a decreased rate of complications, changes in logistics, and length of hospital stay are potential cost savings points that must highlight the expected benefits of this intervention. An additional unaccounted factor is that machine perfusion optimizing donor organ utilization allows patients to be transplanted earlier, avoiding clinical deterioration while on the waiting list and the costs associated with hospital admissions and other required procedures. CONCLUSION: So far, the clinical benefits have guided machine perfusion implementation in liver transplantation. Albeit there is data suggesting the economic benefit of the technique, further investigation of its costs to healthcare systems and society and associated outcomes is needed.

The Liver Retransplantation Risk Score: a prognostic model for survival after adult liver retransplantation.

High-risk combinations of recipient and graft characteristics are poorly defined for liver retransplantation (reLT) in the current era. We aimed to develop a risk model for survival after reLT using data from the European Liver Transplantation Registry, followed by internal and external validation. From 2006 to 2016, 85 067 liver transplants were recorded, including 5581 reLTs (6.6%). The final model included seven predictors of graft survival: recipient age, model for end-stage liver disease score, indication for reLT, recipient hospitalization, time between primary liver transplantation and reLT, donor age, and cold ischemia time. By assigning points to each variable in proportion to their hazard ratio, a simplified risk score was created ranging 0-10. Low-risk (0-3), medium-risk (4-5), and high-risk (6-10) groups were identified with significantly different 5-year survival rates ranging 56.9% (95% CI 52.8-60.7%), 46.3% (95% CI 41.1-51.4%), and 32.1% (95% CI 23.5-41.0%), respectively (P < 0.001). External validation showed that the expected survival rates were closely aligned with the observed mortality probabilities. The Retransplantation Risk Score identifies high-risk combinations of recipient- and graft-related factors prognostic for long-term graft survival after reLT. This tool may serve as a guidance for clinical decision-making on liver acceptance for reLT.

Donor diabetes mellitus is a risk factor for diminished outcome after liver transplantation: a nationwide retrospective cohort study.

With the growing incidence of diabetes mellitus (DM), an increasing number of organ donors with DM can be expected. We sought to investigate the association between donor DM with early post-transplant outcomes. From a national cohort of adult liver transplant recipients (1996-2016), all recipients transplanted with a liver from a DM donor (n = 69) were matched 1:2 with recipients of livers from non-DM donors (n = 138). The primary end-point included early post-transplant outcome, such as the incidence of primary nonfunction (PNF), hepatic artery thrombosis (HAT), and 90-day graft survival. Cox regression analysis was used to analyze the impact of donor DM on graft failure. PNF was observed in 5.8% of grafts from DM donors versus 2.9% of non-DM donor grafts (P = 0.31). Recipients of grafts derived from DM donors had a higher incidence of HAT (8.7% vs. 2.2%, P = 0.03) and decreased 90-day graft survival (88.4% [70.9-91.1] vs. 96.4% [89.6-97.8], P = 0.03) compared to recipients of grafts from non-DM donors. The adjusted hazard ratio for donor DM on graft survival was 2.21 (1.08-4.53, P = 0.03). In conclusion, donor DM is associated with diminished outcome early after liver transplantation. The increased incidence of HAT after transplantation of livers from DM donors requires further research.

RNA interference therapeutics in organ transplantation: The dawn of a new era.

RNA interference (RNAi) is a natural process through which double-stranded RNA molecules can silence the gene carrying the same code as the particular RNA of interest. In 2006, the discovery of RNAi was awarded the Nobel Prize in Medicine and its success has accumulated since. Gene silencing through RNAi has been used successfully in a broad range of diseases, and, more recently, this technique has gained interest in the field of organ transplantation. Here, genes related to ischemia-reperfusion injury (IRI) or graft rejection may be silenced to improve organ quality after transplantation. Several strategies have been used to deliver siRNA, and pretransplant machine perfusion presents a unique opportunity to deliver siRNA to the target organ during ex situ preservation. In this review, the potential of RNAi in the field of organ transplantation will be discussed. A brief overview on the discovery of RNAi, its mechanism, and limitations are included. In addition, studies using RNAi to target genes related to IRI in liver, kidney, lung, and heart transplantation are discussed.

Hyperthermia-induced changes in liver physiology and metabolism: a rationale for hyperthermic machine perfusion.

Liver transplantation is the standard treatment for end-stage liver disease. However, due to the ongoing disparity between supply and demand for optimal donor organs, there is increasing usage of extended criteria donor organs, including steatotic liver grafts. To mitigate the increased risks associated with extended criteria donor livers, ex situ oxygenated machine perfusion (MP) has received increasing attention in recent years as an emerging platform for dynamic preservation, reconditioning, and viability assessment to increase organ utilization. MP can be applied at different temperatures. During hypothermic MP (4-12°C), liver metabolism is reduced, while oxygenation restores the intracellular levels of adenosine triphosphate. The liver is quickly "recharged" to support metabolism when at normothermia (35-37°C) and to ameliorate the detrimental effects of ischemia/reperfusion injury during transplantation. During normothermia, MP can be applied to assess hepatocellular and cholangiocellular viability. MP at hyperthermic (>38°C) temperatures (HyMP), however, remains relatively understudied. The liver is an important component in the regulation of core body temperature and, as such, displays significant physiological and metabolic changes in response to different temperatures. Hyperthermia may promote vasodilation, increase aerobic metabolism and induce production of protective molecules such as heat shock proteins. Therefore, HyMP could provide an attractive reconditioning strategy for steatotic livers. In this review, we describe current literature on the physiological and metabolic effects of the liver at hyperthermia for human, rodents, and pigs and provide a rationale for using therapeutic HyMP during isolated liver machine perfusion to recondition extended criteria donor livers, including steatotic livers, before transplantation.

Bile Composition as a Diagnostic and Prognostic Tool in Liver Transplantation.

Bile secretion and composition reflects the functional status of hepatocytes and cholangiocytes. Bile composition can have a role in the assessment of donor grafts before implantation in the recipient. In addition, changes in bile composition after liver transplantation can serve as a diagnostic and prognostic tool to predict posttransplant complications, such as primary nonfunction, acute cellular rejection, or nonanastomotic biliary strictures. With the popularization of liver machine perfusion preservation in the clinical setting, there is a revisited interest in biliary biomarkers to assess graft viability before implantation. This review discusses current literature on biliary biomarkers that could predict or assess liver graft and bile duct viability. Bile composition offers an exciting and novel perspective in the search for reliable hepatocyte and cholangiocyte viability biomarkers.

Gene Silencing With siRNA (RNA Interference): A New Therapeutic Option During Ex Vivo Machine Liver Perfusion Preservation

RNA interference (RNAi) is a natural process of posttranscriptional gene regulation that has raised a lot of attention culminating with the Nobel Prize in Medicine in 2006. RNAi-based therapeutics have been tested in experimental transplantation to reduce ischemia/reperfusion injury (IRI) with success. Modulation of genes of the innate immune system, as well as apoptotic genes, and those involved in the nuclear factor kappa B pathways can reduce liver injury in rodent liver pedicle clamping and transplantation models of IRI. However, in vivo use of RNAi faces limitations regarding the method of administration, uptake, selectivity, and stability. Machine perfusion preservation, a more recent alternative approach for liver preservation showing superior results to static cold preservation, could be used as a platform for gene interference therapeutics. Our group was the first to demonstrate uptake of small interfering RNA (siRNA) during liver machine preservation under both normothermic and hypothermic perfusion. Administering siRNA in the perfusion solution during ex vivo machine preservation has several advantages, including more efficient delivery, lower doses and cost-saving, and none/fewer side effects to other organs. Recently, the first RNAi drug was approved by the US Food and Drug Administration for clinical use, opening a new avenue for new drugs with different clinical applications. RNAi has the potential to have transformational therapeutic applications in several areas of medicine including transplantation. We believe that machine preservation offers great potential to be the ideal delivery method of siRNA to the liver graft, and future studies should be initiated to improve the clinical applicability of RNAi in solid organ transplantation.

Renal temperature reduction progressively favors mitochondrial ROS production over respiration in hypothermic kidney preservation.

BACKGROUND: Hypothermia, leading to mitochondrial inhibition, is widely used to reduce ischemic injury during kidney preservation. However, the exact effect of hypothermic kidney preservation on mitochondrial function remains unclear. METHODS: We evaluated mitochondrial function [i.e. oxygen consumption and production of reactive oxygen species (ROS)] in different models (porcine kidney perfusion, isolated kidney mitochondria, and HEK293 cells) at temperatures ranging 7-37 °C. RESULTS: Lowering temperature in perfused kidneys and isolated mitochondria resulted in a rapid decrease in oxygen consumption (65% at 27 °C versus 20% at 7 °C compared to normothermic). Decreased oxygen consumption at lower temperatures was accompanied by a reduction in mitochondrial ROS production, albeit markedly less pronounced and amounting only 50% of normothermic values at 7 °C. Consequently, malondialdehyde (a marker of ROS-induced lipid peroxidation) accumulated in cold stored kidneys. Similarly, low temperature incubation of kidney cells increased lipid peroxidation, which is due to a loss of ROS scavenging in the cold. CONCLUSIONS: Lowering of temperature highly affects mitochondrial function, resulting in a progressive discrepancy between the lowering of mitochondrial respiration and their production of ROS, explaining the deleterious effects of hypothermia in transplantation procedures. These results highlight the necessity to develop novel strategies to decrease the formation of ROS during hypothermic organ preservation.

The Risk of Microbial Transmission in Recipients of Donor Livers That Underwent Hypothermic or Normothermic Machine Perfusion.

Background: Ex situ machine perfusion is increasingly used to preserve and assess donor livers before transplantation. Compared with traditional static cold storage (SCS), machine perfusion exposes livers to an additional risk of microbial contamination. However, information on the risk of microbial transmission during machine perfusion is lacking. Methods: All livers that underwent either hypothermic oxygenated machine perfusion (HOPE) or normothermic machine perfusion (NMP) in our center between September 2021 and September 2023, and during which samples were taken from SCS fluid and/or machine perfusion solution for microbiological examination, were included in this retrospective, observational clinical study. Microbial transmission was examined from SCS fluid to machine perfusion solution fluid and, subsequently, to recipients of these livers. Results: A total of 90 cases of liver machine perfusion were included: 59 HOPE and 31 NMP. SCS preservation fluid cultures before HOPE or NMP were positive for at least 1 microorganism in 52% of the cases. After HOPE, there were no cases of positive machine perfusion fluid or evidence of microbial transmission to the recipients. After NMP, in 1 (3%) patient Escherichia coli was grown from abdominal drain fluid, the same bacterial strain that was also grown from the SCS preservation fluid before NMP. This E coli was resistant to the antibiotics that are routinely added to the NMP perfusion fluid. Conclusions: The risk of microbial transmission after machine perfusion is very low but not absent. We recommend routine sampling of machine perfusion fluid at the end of the procedure for microbiological analysis.

Prolonged hypothermic machine perfusion enables daytime liver transplantation - an IDEAL stage 2 prospective clinical trial.

Background: Liver transplantation is traditionally performed around the clock to minimize organ ischemic time. However, the prospect of prolonging preservation times holds the potential to streamline logistics and transform liver transplantation into a semi-elective procedure, reducing the need for nighttime surgeries. Dual hypothermic oxygenated machine perfusion (DHOPE) of donor livers for 1-2 h mitigates ischemia-reperfusion injury and improves transplant outcomes. Preclinical studies have shown that DHOPE can safely extend the preservation of donor livers for up to 24 h. Methods: We conducted an IDEAL stage 2 prospective clinical trial comparing prolonged (≥4 h) DHOPE to conventional (1-2 h) DHOPE for brain-dead donor livers, enabling transplantation the following morning. Liver allocation to each group was based on donor hepatectomy end times. The primary safety endpoint was a composite of all serious adverse events (SAE) within 30 days after transplantation. The primary feasibility endpoint was defined as the number of patients assigned and successfully receiving a prolonged DHOPE-perfused liver graft. Trial registration at: WHO International Clinical Trial Registry Platform, number NL8740. Findings: Between November 1, 2020 and July 16, 2022, 24 patients were enrolled. The median preservation time was 14.5 h (interquartile range [IQR], 13.9-15.5) for the prolonged group (n = 12) and 7.9 h (IQR, 7.6-8.6) for the control group (n = 12; p = 0.01). In each group, three patients (25%; 95% CI 3.9-46%, p = 1) experienced a SAE. Markers of ischemia-reperfusion injury and oxidative stress in both perfusate and recipients were consistently low and showed no notable discrepancies between the two groups. All patients assigned to either the prolonged group or control group successfully received a liver graft perfused with either prolonged DHOPE or control DHOPE, respectively. Interpretation: This first-in-human clinical trial demonstrates the safety and feasibility of DHOPE in prolonging the preservation time of donor livers to enable daytime transplantation. The ability to extend the preservation window to up to 20 h using hypothermic oxygenated machine preservation at a 10 °C temperature has the potential to reshape the landscape of liver transplantation. Funding: University Medical Center Groningen, the Netherlands.

What Is Hot and New in Basic and Translational Science in Liver Transplantation in 2023? Report of the Basic and Translational Research Committee of the International Liver Transplantation Society.

The 2023 Joint Annual Congress of the International Liver Transplantation Society, European Liver and Intestine Transplant Association, and Liver Intensive Care Group of Europe were held in Rotterdam, the Netherlands, from May 3 to 6, 2023. This year, all speakers were invited to attend the Congress in person for the first time since the COVID-19 pandemic. The congress was attended by 1159 registered delegates from 54 countries representing 5 continents, with the 10 countries comprising the bulk of the delegates. Of the 647 abstracts initially submitted, 542 were eventually presented at the meeting, coming from 38 countries (mainly North America, Europe, and Asia) and 85% of them (462 abstracts) came from only 10 countries. Fifty-three (9.8%) abstracts, originated from 17 countries, were submitted under the Basic/Translational Scientific Research category, a similar percentage as in 2022. Abstracts presented at the meeting were classified as (1) ischemia and reperfusion injury, (2) machine perfusion, (3) bioengineering and liver regeneration, (4) transplant oncology, (5) novel biomarkers in liver transplantation, (6) liver immunology (rejection and tolerance), and (7) artificial intelligence and machine learning. Finally, we evaluated the number of abstracts commented in the Basic and Translational Research Committee-International Liver Transplantation Society annual reports over the past 5 y that resulted in publications in peer-reviewed journals to measure their scientific impact in the field of liver transplantation.

Heat Stroke as a Cause of Liver Failure and Evaluation of Liver Transplant.

Heat stroke is a multiple organ dysfunction syndrome of poorly understood pathogenesis. Exertional heat stroke with acute liver failure is a rarely reported condition. Liver transplant has been recommended as treatment in cases of severe liver dysfunction; however, there are only 5 described cases of long-term survival after this procedure in patients with heat stroke. Here, we present 2 cases of young athletes who developed heat stroke. Both patients developed acute liver failure and were listed for liver transplant. Liver function tests of one patient improved, and he was discharged on postoperative day 13. The other patient showed no signs of improvement and liver biopsy showed massive necrosis. The patient underwent combined kidney-liver transplant and was discharged on postoperative day 17. After a follow-up of longer than 6 years, both patients are doing well with normal liver function and no neurologic sequelae. We also reviewed all published cases of hepatic failure associated with heat stroke and found 9 published cases of liver transplant for heat stroke in the English literature. Conservative management appears to be justified in heat stroke-associated liver failure, even in the presence of accepted criteria for emergency liver transplant. If the liver does not show signs of recovery and hepatic decompensation progresses, liver transplant should be performed.