"Resuscitation" of marginal liver allografts for transplantation with machine perfusion technology

Evaluation of Minimum-to-Severe Global and Macrovesicular Steatosis in Human Liver Specimens: A Portable Ambient Light-Compatible Spectroscopic Probe

BACKGROUND AND AIMS

Hepatic steatosis (HS), particularly macrovesicular steatosis (MaS), influences transplant outcomes. Accurate assessment of MaS is crucial for graft selection. While traditional assessment methods have limitations, non-invasive spectroscopic techniques like Raman and reflectance spectroscopy offer promise. This study aimed to evaluate the efficacy of a portable ambient light-compatible spectroscopic system in assessing global HS and MaS in human liver specimens.

METHODS

A two-stage approach was employed on thawed snap-frozen human liver specimens under ambient room light: biochemical validation involving a comparison of fat content from Raman and reflectance intensities with triglyceride (TG) quantifications and histopathological validation, contrasting Raman-derived fat content with evaluations by an expert pathologist and a "Positive Pixel Count" algorithm. Raman and reflectance intensities were combined to discern significant (≥ 10%) discrepancies in global HS and MaS.

RESULTS

The initial set of 16 specimens showed a positive correlation between Raman and reflectance-derived fat content and TG quantifications. The Raman system effectively differentiated minimum-to-severe global and macrovesicular steatosis in the subsequent 66 specimens. A dual-variable prediction algorithm was developed, effectively classifying significant discrepancies (> 10%) between algorithm-estimated global HS and pathologist-estimated MaS.

CONCLUSION

Our study established the viability and reliability of a portable spectroscopic system for non-invasive HS and MaS assessment in human liver specimens. The compatibility with ambient light conditions and the ability to address limitations of previous methods marks a significant advancement in this field. By offering promising differentiation between global HS and MaS, our system introduces an innovative approach to real-time and quantitative donor HS assessments. The proposed method holds the promise of refining donor liver assessment during liver recovery and ultimately enhancing transplantation outcomes.

Cross-species metabolomic profiling reveals phosphocholine-mediated liver protection from cold and ischemia/reperfusion

Cold and ischemia/reperfusion (IR)-associated injuries are seemingly inevitable during liver transplantation and hepatectomy. Because Syrian hamsters demonstrate intrinsic tolerance to transplantation-like stimuli, cross-species comparative metabolomic analyses were conducted with hamster, rat, and donor liver samples to seek hepatic cold and IR-adaptive mechanisms. Lower hepatic phosphocholine contents were found in recipients with early graft-dysfunction and with virus-caused cirrhosis or high model for end-stage liver disease scores (≥30). Choline/phosphocholine deficiency in cultured human THLE-2 hepatocytes and animal models weakened hepatocellular cold tolerance and recovery of glutathione and ATP production, which was rescued by phosphocholine supplements. Among the biological processes impacted by choline/phosphocholine deficiency, 3 lipid-related metabolic processes were downregulated, whereas phosphocholine elevated the expression of genes in methylation processes. Consistently, in THLE-2, phosphocholine enhanced the overall RNA m6A methylation, among which the transcript stability of fatty acid desaturase 6 (FADS6) was improved. FADS6 functioned as a key phosphocholine effector in the production of polyunsaturated fatty acids, which may facilitate the hepatocellular recovery of energy and redox homeostasis. Thus, our study reveals the choline-phosphocholine metabolism and its downstream FADS6 functions in hepatic adaptation to cold and IR, which may inspire new strategies to monitor donor liver quality and improve recipient recovery from the liver transplantation process.

Development of a Large Animal Model of Ischemia-free Liver Transplantation in Pigs

Background

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.

Methods

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.

Results

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.

Conclusions

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.

Video analysis of ex vivo beating hearts during preservation on the TransMedics® organ care system

Background

Reliable biomarkers for assessing the viability of the donor hearts undergoing ex vivo perfusion remain elusive. A unique feature of normothermic ex vivo perfusion on the TransMedics® Organ Care System (OCS™) is that the donor heart is maintained in a beating state throughout the preservation period. We applied a video algorithm for an in vivo assessment of cardiac kinematics, video kinematic evaluation (Vi.Ki.E.), to the donor hearts undergoing ex vivo perfusion on the OCS™ to assess the feasibility of applying this algorithm in this setting.

Methods

Healthy donor porcine hearts (n = 6) were procured from Yucatan pigs and underwent 2 h of normothermic ex vivo perfusion on the OCS™ device. During the preservation period, serial high-resolution videos were captured at 30 frames per second. Using Vi.Ki.E., we assessed the force, energy, contractility, and trajectory parameters of each heart.

Results

There were no significant changes in any of the measured parameters of the heart on the OCS™ device over time as judged by linear regression analysis. Importantly, there were no significant changes in contractility during the duration of the preservation period (time 0-30 min, 918 ± 430 px/s; time 31-60 min, 1,386 ± 603 px/s; time 61-90 min, 1,299 ± 617 px/s; time 91-120 min, 1,535 ± 728 px/s). Similarly, there were no significant changes in the force, energy, or trajectory parameters. Post-transplantation echocardiograms demonstrated robust contractility of each allograft.

Conclusion

Vi.Ki.E. assessment of the donor hearts undergoing ex vivo perfusion is feasible on the TransMedics OCS™, and we observed that the donor hearts maintain steady kinematic measurements throughout the duration.

Transplantation of a human liver following 3 days of ex situ normothermic preservation

Current organ preservation methods provide a narrow window (usually <12 hours) to assess, transport and implant donor grafts for human transplantation. Here we report the transplantation of a human liver discarded by all centers, which could be preserved for several days using ex situ normothermic machine perfusion. The transplanted liver exhibited normal function, with minimal reperfusion injury and the need for only a minimal immunosuppressive regimen. The patient rapidly recovered a normal quality of life without any signs of liver damage, such as rejection or injury to the bile ducts, according to a 1-year follow up. This inaugural clinical success opens new horizons in clinical research and promises an extended time window of up to 10 days for assessment of viability of donor organs as well as converting an urgent and highly demanding surgery into an elective procedure.

Pre-Ischemic Hypothermic Oxygenated Perfusion Alleviates Protective Molecular Markers of Ischemia-Reperfusion Injury in Rat Liver

To expand the pool of organs, hypothermic oxygenated perfusion (HOPE), one of the most promising perfusion protocols, is currently performed after cold storage (CS) at transplant centers (HOPE-END). We investigated a new timing for HOPE, hypothesizing that performing HOPE before CS (HOPE-PRE) could boost mitochondrial protection allowing the graft to better cope with the accumulation of oxidative stress during CS. We analyzed liver injuries at 3 different levels. Histologic analysis demonstrated that, compared to classical CS (CTRL), the HOPE-PRE group showed significantly less ischemic necrosis compared to CTRL vs HOPE-END. From a biochemical standpoint, transaminases were lower after 2 hours of reperfusion in the CTRL vs HOPE-PRE group, which marked decreased liver injury. qPCR analysis on 37 genes involved in ischemia-reperfusion injury revealed protection in HOPE-PRE and HOPE-END compared to CTRL mediated through similar pathways. However, the CTRL vs HOPE-PRE group demonstrated an increased transcriptional level for protective genes compared to the CTRL vs HOPE-END group. This study provides insights on novel biomarkers that could be used in the clinic to better characterize graft quality improving transplantation outcomes.

Utilization of dielectric properties for assessment of liver ischemia-reperfusion injury in vivo and during machine perfusion

There is a shortage of donor livers and patients consequently die on waiting lists worldwide. Livers are discarded if they are clinically judged to have a high risk of non-function following transplantation. With the aim of extending the pool of available donor livers, we assessed the condition of porcine livers by monitoring the microwave dielectric properties. A total of 21 livers were divided into three groups: control with no injury (CON), biliary injury by hepatic artery occlusion (AHEP), and overall hepatic injury by static cold storage (SCS). All were monitored for four hours in vivo, followed by ex vivo plurithermic machine perfusion (PMP). Permittivity data was modeled with a two-pole Cole–Cole equation, and dielectric properties from one-hour intervals were analyzed during in vivo and normothermic machine perfusion (NMP). A clear increasing trend in the conductivity was observed in vivo in the AHEP livers compared to the control livers. After four hours of NMP, separations in the conductivity were observed between the three groups. Our results indicate that dielectric relaxation spectroscopy (DRS) can be used to detect and differentiate liver injuries, opening for a standardized and reliable point of evaluation for livers prior to transplantation.

The Effect of Early Retransplantation on Early and Late Survival After Liver Transplantation

BACKGROUND

Early liver retransplantation after liver transplantation (LT) is the ultimate salvage procedure for irreversible graft failure. The aim of this study was to assess the impact of early retransplantation on 90-day and 5-year patient survival.

METHODS

This retrospective cohort study included 2185 patients after LT in the period between 1997 and 2019. First, the patients undergoing first retransplantation within 6 months after initial LT were compared with naïve LT patients for early mortality (within 90 days). Second, to assess late survival, the patients who had retransplantation and survived at least 90 days post LT were compared with naïve LT patients for 5-year overall survival. The patients undergoing late retransplantation (>6 months) were excluded from analyses. Fisher's exact test was used to compare groups for early survival and log-rank test for late survival.

RESULTS

The cumulative 1-, 3-, and 5-year overall survival was 87.0%, 79.9%, 75.0%, respectively, and did not differ significantly between the groups. The patients undergoing early retransplantation had lower 90-day survival rate of 89.2% as compared to 95.7% for naïve LT patients (P < .001).

CONCLUSIONS

The early liver retransplantation has profound impact on post-LT 90-day survival; however, patients who survive that period can achieve long overall survival comparable with naïve LT patients.

Controlled DCD Liver Transplantation Is Not Associated With Increased Hyperfibrinolysis and Blood Loss After Graft Reperfusion

BACKGROUND

The specific effect of donation after circulatory death (DCD) liver grafts on fibrinolysis, blood loss, and transfusion requirements after graft reperfusion is not well known. The aim of this study was to determine whether transplantation of controlled DCD livers is associated with an elevated risk of hyperfibrinolysis, increased blood loss, and higher transfusion requirements upon graft reperfusion, compared with livers donated after brain death (DBD).

METHODS

A retrospective single-center analysis of all adult recipients of primary liver transplantation between 2000 and 2019 was performed (total cohort n = 628). Propensity score matching was used to balance baseline characteristics for DCD and DBD liver recipients (propensity score matching cohort n = 218). Intraoperative and postoperative hemostatic variables between DCD and DBD liver recipients were subsequently compared. Additionally, in vitro plasma analyses were performed to compare the intraoperative fibrinolytic state upon reperfusion.

RESULTS

No significant differences in median (interquartile range) postreperfusion blood loss (1.2 L [0.5-2.2] versus 1.3 L [0.6-2.2]; P = 0.62), red blood cell transfusion (2 units [0-4] versus 1.1 units [0-3]; P = 0.21), or fresh frozen plasma transfusion requirements (0 unit [0-2.2] versus 0 unit [0-0.9]; P = 0.11) were seen in DCD compared with DBD recipients, respectively. Furthermore, plasma fibrinolytic potential was similar in both groups.

CONCLUSIONS

Transplantation of controlled DCD liver grafts does not result in higher intraoperative blood loss or more transfusion requirements, compared with DBD liver transplantation. In accordance with this, no evidence for increased hyperfibrinolysis upon reperfusion in DCD compared with DBD liver grafts was found.

Machine perfusion of the liver: Putting the puzzle pieces together

The realm of extended criteria liver transplantation created the 'adjacent possible' for dynamic organ preservation. Machine perfusion of the liver greatly expanded donor organ preservation possibilities, reaching before unattainable goals, including the mitigation of ischemia-reperfusion injury, viability assessment, and organ reconditioning prior to transplantation. However, current scientific evidence lacks uniformity between studies, perfusion protocols, and acceptance criteria. Construction of collaborative research networks for sharing knowledge should, therefore, enable the development of high-level evidence and guidelines for machine perfusion utilization, including donor acceptance criteria. Finally, this approach shall guarantee conditions for further progress to occur.

A marginal liver graft with hyperbilirubinemia transplanted successfully by ischemia-free liver transplantation

The shortage of transplant organs remains a serious issue worldwide, and using liver grafts from extended criteria donors could expand the donor pool. Extended criteria donor liver allografts have a high chance of complications such as primary nonfunction, early allograft dysfunction, and ischemic-type biliary lesions. How to employ these extended criteria donors safely and effectively warrants further investigation. Herein, we report the successful use of a marginal donor liver with hyperbilirubinemia to save the life of an acute-on-chronic liver failure recipient using a new surgical technique: ischemia-free liver transplantation (IFLT). The graft was retrieved for transplantation due to the following reasons: (I) the recipient was in a life-threatening situation and no living donor donation candidate was available; (II) the graft was considered transplantable except for cholestasis; and (III) IFLT could reduce ischemia/reperfusion injury (IRI), resuscitate the allograft ex situ, and maintain organ viability before transplantation. The graft was transplanted successfully using the IFLT procedure. Although anatomic biliary stricture occurred after surgery, no IRI-related complications were found during the follow-up. The use of liver grafts from extended criteria donors is safe and effective under IFLT. Additional IFLT clinical studies need to be performed, particularly concerning donor management, graft selection, and ex situ resuscitation.

Viability Assessment in Liver Transplantation-What Is the Impact of Dynamic Organ Preservation?

Based on the continuous increase of donor risk, with a majority of organs classified as marginal, quality assessment and prediction of liver function is of utmost importance. This is also caused by the notoriously lack of effective replacement of a failing liver by a device or intensive care treatment. While various parameters of liver function and injury are well-known from clinical practice, the majority of specific tests require prolonged diagnostic time and are more difficult to assess ex situ. In addition, viability assessment of procured organs needs time, because the development of the full picture of cellular injury and the initiation of repair processes depends on metabolic active tissue and reoxygenation with full blood over several hours or days. Measuring injury during cold storage preservation is therefore unlikely to predict the viability after transplantation. In contrast, dynamic organ preservation strategies offer a great opportunity to assess organs before implantation through analysis of recirculating perfusates, bile and perfused liver tissue. Accordingly, several parameters targeting hepatocyte or cholangiocyte function or metabolism have been recently suggested as potential viability tests before organ transplantation. We summarize here a current status of respective machine perfusion tests, and report their clinical relevance.

Preventing Tumour Recurrence after Liver Transplantation: The Role of Machine Perfusion

Tumour recurrence is currently a hot topic in liver transplantation. The basic mechanisms are increasingly discussed, and, for example, recurrence of hepatocellular carcinoma is often described in pre-injured donor livers, which frequently suffer from significant ischemia/reperfusion injury. This review article highlights the underlying mechanisms and describes the specific tissue milieu required to promote tumour recurrence after liver transplantation. We summarise the current literature in this field and show risk factors that contribute to a pro-tumour-recurrent environment. Finally, the potential role of new machine perfusion technology is discussed, including the most recent data, which demonstrate a protective effect of hypothermic oxygenated perfusion before liver transplantation.

Pattern Recognition Receptor-reactivity Screening of Liver Transplant Patients: Potential for Personalized and Precise Organ Matching to Reduce Risks of Ischemia-reperfusion Injury

OBJECTIVE AND BACKGROUND

Pattern recognition receptors (PRRs) on immune and parenchymal cells can detect danger-associated molecular patterns (DAMPs) released from cells damaged during ischemia-reperfusion injury (IRI), in heart attack or stroke settings, but also as an unavoidable consequence of solid organ transplantation. Despite IRI being a significant clinical problem across all solid organ transplants, there are limited therapeutics and patient-specific diagnostics currently available.

METHODS

We screened portal blood samples obtained from 67 human liver transplant recipients both pre- [portal vein (PV) sample] and post-(liver flush; LF) reperfusion for their ability to activate a panel of PRRs, and analyzed this reactivity in relation to biopsy-proven IRI.

RESULTS

PV samples from IRI+ orthotopic liver transplantation (OLT) patients (n = 35) decreased activation of hTLR4- and hTLR9-transfected cells, whereas PV from IRI- patients (n = 32) primarily increased hTLR7 and hNOD2 activation. LF samples from OLT-IRI patients significantly increased activation of hTLR4 and hTLR9 over IRI- LF. In addition, the change from baseline reactivity to hTLR4/9/NOD2 was significantly higher in IRI+ than IRI- OLT patients.

CONCLUSIONS

These results demonstrate that TLR4/7/9 and NOD2 are involved in either promoting or attenuating hepatic IRI, and suggest a diagnostic screening of portal blood for reactivity to these PRRs might prove useful for prediction and/or therapeutic intervention in OLT patients before transplantation.

Risk Factors for No Valid Liver Graft. Multivariate Study Based on the Variables Included in the Donation Protocol of the National Trasplant Organisation

INTRODUCTION

Among the strategies designed to optimize the number of existing liver grafts for transplantation, the implementation of the graft assessment process is one of the least explored. The main objective is to identify the risk factors presented by liver donors for «NO validity». Secondly, we analyzed the coincidence between the surgeon's assessment and that of the anatomo-pathologist in the invalid donors.

MATERIAL AND METHOD

Retrospective study conducted from a prospective database that analyzes 190 liver donors, 95 valid and 95 NOT valid. The variables of each of them corresponding to the donation protocol of the National Transplant Organization are studied. Through a multivariate study we determine the independent risk factors of NO validity. We checked the causes of NO validity argued with the histopathological findings of these grafts.

RESULTS

The independent risk factors of non-validity in the multivariate study (P < .05) were: dyslipidemia, personal medical history other than cardiovascular and abdominal surgical risk factors, GGT, BrT, and the result of previous liver ultrasound. The 3 most frequent causes of NO validity were: steatosis, fibrosis and macroscopic appearance of the organ. 78% of the biopsies confirmed the NO validity of the graft (in 57.9% of the cases the histological findings coincided with those described by the surgeon). The 22.1% of the biopsies hadńt pathological findings.

CONCLUSIONS

The determination of the risk factors of NO validity will contribute to the design of future assessment scores that are useful tools in the process of liver graft assessment.).

Use of machine perfusion in livers showing steatosis prior to transplantation: a systematic review

BACKGROUND

The role of machine perfusion (MP) in the evaluation of liver grafts with macrovesicular steatosis (MaS) remains ill-defined as only a limited number of studies has been reported. The objective of the current study was to provide a systematic review to evaluate the role of MP in the setting of MaS livers.

METHODS

A systematic review, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines was performed. Eligible articles published up to April 2019 were included using the MEDLINE, Scopus, and Google Scholar databases.

RESULTS

Among the 422 articles screened, only 16 papers met the inclusion criteria. A total of 54 cases of MP use before liver transplantation were included. Sixteen (29.6%) grafts were from donors after circulatory death. In 22 (40.7%) cases, hypothermic machine perfusion was performed. Normothermic machine perfusion was done in the remaining 32 (59.3%) cases. According to the histological results of the donor core biopsy, a MaS value < 30% was observed in 41 (75.9%) cases, whereas 13 (24.1%) patients had moderate-to-severe (≥ 30%) MaS. Following categorization of the pooled population according to the presence of moderate-to-severe (≥ 30%) MaS in the donor graft, no differences were noted in terms of post-transplant death or severe complications following MP. There was no correlation between the proportion of MaS in the donor graft relative to post-transplant peak ALT among patients treated with MP. Among the entire pooled cohort, there was also no correlation between MaS values and ALT peak (R = 0.13; P = 0.42).

CONCLUSIONS

MP appears to be feasible and safe in MaS livers. Experience to date has been very limited, and the benefit of MP remains not determined. Prospective studies will need to define better the potential effect of "defatting" drugs used during the perfusion process on MaS.

Leveraging the zebrafish to model organ transplantation

PURPOSE OF REVIEW

The availability of organs for transplant fails to meet the demand and this shortage is growing worse every year. As the cost of not getting a suitable donor organ can mean death for patients, new tools and approaches that allows us to make advances in transplantation faster and provide a different vantage point are required. To address this need, we introduce the concept of using the zebrafish (Danio rerio) as a new model system in organ transplantation. The zebrafish community offers decades of research experience in disease modeling and a rich toolbox of approaches for interrogating complex pathological states. We provide examples of how already existing zebrafish assays/tools from cancer, regenerative medicine, immunology, and others, could be leveraged to fuel new discoveries in pursuit of solving the organ shortage.

RECENT FINDINGS

Important innovations have enabled several types of transplants to be successfully performed in zebrafish, including stem cells, tumors, parenchymal cells, and even a partial heart transplant. These innovations have been performed against a backdrop of an expansive and impressive list of tools designed to uncover the biology of complex systems that include a wide array of fluorescent transgenic fish that label specific cell types and mutant lines that are transparent, immune-deficient. Allogeneic transplants can also be accomplished using immune suppressed and syngeneic fish. Each of these innovations within the zebrafish community would provide several helpful tools that could be applied to transplant research.

SUMMARY

We highlight some examples of existing tools and assays developed in the zebrafish community that could be leveraged to overcome barriers in organ transplantation, including ischemia-reperfusion, short preservation durations, regeneration of marginal grafts, and acute and chronic rejection.

Top Papers in Liver Transplantation 2017-2018

Organ shortage remains a major limitation in liver transplantation, and there has been a significant effort over the past decade to increase the existing deceased donor pool. Recent advances have included better selection and management of donors after circulatory arrest, application of hypothermic and normothermic perfusion, minimization of standard immunosuppression, and use of new immunosuppressive medications. Additionally, there has been renewed emphasis and understanding of liver immunology and the impact of antibody-mediated rejection. Together, these advances have allowed for expansion of the donor pool with concurrent improved patient outcomes. Furthermore, direct-acting antiviral agents for the treatment of hepatitis C virus infection has been management of this infection. These changes have affected the practice of solid organ transplantation by altering the framework by which patients with end-stage organ disease are managed and receive organ transplants. In this article, we analyze some of the top papers published in 2017-2018 dealing with these issues.

Machine perfusion strategies in liver transplantation

Machine perfusion is a hot topic in liver transplantation and several new perfusion concepts are currently developed. Prior to introduction into routine clinical practice, however, such perfusion approaches need to demonstrate their impact on liver function, post-transplant complications, utilization rates of high-risk organs, and cost benefits. Therefore, based on results of experimental and clinical studies, the community has to recognize the limitations of this technology. In this review, we summarize current perfusion concepts and differences between protective mechanisms of ex- and in-situ perfusion techniques. Next, we discuss which graft types may benefit most from perfusion techniques, and highlight the current understanding of liver viability testing. Finally, we present results from recent clinical trials involving machine liver perfusion, and analyze the value of different outcome parameters, currently used as endpoints for randomized controlled trials in the field.

Analysis of Data from the Oxygen Persufflation in Liver Transplantation (OPAL) Study to Determine the Role of Factors Affecting the Hepatic Microcirculation and Early Allograft Dysfunction

Background

Adequate microcirculatory perfusion is essential for the provision of oxygen to the liver following transplantation. Data from the Oxygen Persufflation in Liver Transplantation (OPAL) study (ISRCTN00167887) were analyzed from liver transplants performed at a single center to determine the role of factors affecting the hepatic microcirculation and early allograft dysfunction (EAD).

Material/Methods

Retrospective data from 116 patients from the Oxygen Persufflation as Adjunction in Liver Transplantation (OPAL) study who underwent liver transplantation at a single center were analyzed. Oxygen saturation of hemoglobin (SO₂), relative capillary hemoglobin concentration (rHb), relative tissue blood flow (rBF) using laser Doppler flow measurements, and the Oxygen-to-See (O2C) spectrometry were measured and with post-transplant allograft function were analyzed using univariate and multivariate logistic regression statistics.

Results

Livers donors had a median donor risk index of 1.8. Most liver transplant recipients were men (60.3%), with a median age of 54 years (IQR, 23–68 years). Mean post-transplant 3-month survival was 90.5%. The EAD rate was 22.4%, the median SO₂ was 78% (IQR, 29.5–95.8%), the median rHb was 55.6 AU (IQR, 16.8–74.8 AU), and the median rBF was 110.1 AU (IQR, 35.8–406.8 AU). Multivariate logistic regression analysis showed that tissue SO₂ (p=0.01), body mass index (BMI) of the transplant recipient (p=0.002), serum alanine transaminase (ALT) of the donor (p=0.02), and portal blood flow (p=0.01) were predictive factors for EAD.

Conclusions

Non-invasive investigations of the liver microcirculation and hemoglobin oxygenation were shown to be predictive factors for EAD following liver transplantation.

Biofabrication of Autologous Human Hepatocytes for Transplantation: How Do We Get There?

Directed differentiation of hepatocytes from induced pluripotent stem cells (iPSCs) holds promise as source material for treating some liver disorders. The unlimited availability of perfectly differentiated iPSC-derived hepatocytes will dramatically facilitate cell therapies. While systems to manufacture large quantities of iPSC-derived cells have been developed, we have been unable to generate and maintain stable and mature adult liver cells ex vivo. This short review highlights important challenges and possible solutions to the current state of hepatocyte biofabrication for cellular therapies to treat liver diseases. Successful cell transplantation will require optimizing the best cell function, overcoming limitations to cell numbers and safety, as well as a number of other challenges. Collaboration among scientists, clinicians, and industry is critical for generating new autologous stem cell-based therapies to treat liver diseases.

Liver graft preservation methods during cold ischemia phase and normothermic machine perfusion

The growing demand for donor organs requires measures to expand donor pool. Those include extended criteria donors, such as elderly people, steatotic livers, donation after cardiac death, etc. Static cold storage to reduce metabolic requirements developed by Collins in late 1960s is the mainstay and the golden standard for donated organ protection. Hypothermic machine perfusion provides dynamic organ preservation at 4°C with protracted infusion of metabolic substrates to the graft during the ex vivo period. It has been used instead of static cold storage or after it as short perfusion in transplant center. Normothermic machine perfusion (NMP) delivers oxygen, and nutrition at physiological temperature mimicking regular environment in order to support cellular function. This would minimize effects of ischemia/reperfusion injury. Potentially, NMP may help to estimate graft functionality before implantation into a recipient. Clinical studies demonstrated at least its non-inferiority or better outcomes vs static cold storage. Regular grafts donated after brain death could be safely preserved with convenient static cold storage. Except for prolonged ischemia time where hypothermic machine perfusion started in transplant center could be estimated to provide possible positive reconditioning effect. Use of hypothermic machine perfusion in regular donation instead of static cold storage or in extended criteria donors requires further investigation. Multicenter randomized clinical trial supposed to be completed in December 2021. Extended criteria donors need additional measures for graft storage and assessment until its implantation. NMP is actively evaluating promising method for this purpose. Future studies are necessary for precise estimation and confirmation to issue clinical practice recommendations.

Evaluation of a micro-spectrometer for the real-time assessment of liver graft with mild-to-moderate macrosteatosis: A proof of concept study

BACKGROUND & AIMS

Liver macrosteatosis (MS) is a major predictor of graft dysfunction after transplantation. However, frozen section techniques to quantify steatosis are often unavailable in the context of procurements, and the findings of preoperative imaging techniques correlate poorly with those of permanent sections, so that the surgeon is ultimately responsible for the decision. Our aim was to assess the accuracy of a non-invasive pocket-sized micro-spectrometer (PSM) for the real-time estimation of MS.

METHODS

We prospectively evaluated a commercial PSM by scanning the liver capsule. A double pathological quantification of MS was performed on permanent sections. Initial calibration (training cohort) was performed on 35 livers (MS ≤60%) and an algorithm was created to correlate the estimated (PSM) and known (pathological) MS values. A second assessment (validation cohort) was then performed on 154 grafts.

RESULTS

Our algorithm achieved a coefficient of determination R2 = 0.81. Its validation on the second cohort demonstrated a Lin's concordance coefficient of 0.78. Accuracy reached 0.91%, with reproducibility of 86.3%. The sensitivity, specificity, positive and negative predictive values for MS ≥30% were 66.7%, 100%, 100% and 98%, respectively. The PSM could predict the absence (<30%)/presence (≥30%) of MS with a kappa coefficient of 0.79. Neither graft weight nor height, donor body mass index nor the CT-scan liver-to-spleen attenuation ratio could accurately predict MS.

CONCLUSION

We demonstrated that a PSM can reliably and reproducibly assess mild-to-moderate MS. Its low cost and the immediacy of results may offer considerable added-value decision support for surgeons. This tool could avoid the detrimental and prolonged ischaemia caused by the pathological examination of (potentially) marginal grafts. This device now needs to be assessed in the context of a large-scale multicentre study.

LAY SUMMARY

Macro-vacuolar liver steatosis is a major prognostic factor for outcomes after liver transplantation. However, it is often difficult for logistical reasons to get this estimation during procurement. Therefore, we developed an algorithm for a commercial, portable and affordable spectrometer to accurately estimate this content in a real-time fashion. This device could be of great interest for clinical decision-making to accept or discard a potential human liver graft.

The efficacy of extracorporeal membrane oxygenation in liver transplantation from non-heart-beating donors: A systemic review and meta-analysis

BACKGROUND

A systematic review and meta-analysis was made to see whether extracorporeal membrane oxygenation (ECMO) in liver transplantation could improve non-heart-beating donors (NHBDs) recipients' outcomes compared with donors after brain death (DBDs) recipients.

METHODS

We searched MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials for eligible studies. The study eligible criteria are cohort or case-control studies using ECMO in all NHBDs; studies involved a comparison group of DBDs; and studies evaluated 1-year graft and patient survival rate in NHBDs and DBDs groups.

RESULTS

Four studies with 704 patients fulfilled the inclusion criteria. The pooled odds ratio (OR) of 1-year patient survival rate in NHBDs recipients compared with DBDs recipients was 0.8 (95% confidence interval [CI], 0.41-1.55). The pooled OR of 1-year graft survival rate in NHBDs recipients compared with DBDs recipients was 0.46 (95% CI, 0.26-0.81). NHBDs recipients were at greater risks to the occurrence of primary nonfunction (PNF) (OR = 7.12, 95% CI, 1.84-27.52) and ischemic cholangiopathy (IC) (OR = 9.46, 95% CI, 2.76-32.4) than DBDs recipients.

CONCLUSIONS

ECMO makes 1-year patient survival acceptable in NHBDs recipients. One-year graft survival rate was lower in NHBDs recipients than in DBDs recipients. Compared with DBDs recipients, the risks to develop PNF and IC were increased among NHBDs recipients.

Liver transplantation for critically ill cirrhotic patients: Overview and pragmatic proposals

Liver transplantation for critically ill cirrhotic patients with acute deterioration of liver function associated with extrahepatic organ failures is controversial. While transplantation has been shown to be beneficial on an individual basis, the potentially poorer post-transplant outcome of these patients taken as a group can be held as an argument against allocating livers to them. Although this issue concerns only a minority of liver transplants, it calls into question the very heart of the allocation paradigms in place. Indeed, most allocation algorithms have been centered on prioritizing the sickest patients by using the model for end-stage liver disease score. This has led to allocating increasing numbers of livers to increasingly critically ill patients without setting objective or consensual limits on how sick patients can be when they receive an organ. Today, finding robust criteria to deem certain cirrhotic patients too sick to be transplanted seems urgent in order to ensure the fairness of our organ allocation protocols. This review starts by fleshing out the argument that finding such criteria is essential. It examines five types of difficulties that have hindered the progress of recent literature on this issue and identifies various strategies that could be followed to move forward on this topic, taking into account the recent discussion on acute on chronic liver failure. We move on to review the literature along four axes that could guide clinicians in their decision-making process regarding transplantation of critically ill cirrhotic patients.

Normothermic ex-vivo liver perfusion: where do we stand and where to reach?

Nowadays liver transplantation is considered as the treatment of choice, however, the scarcity of suitable donor organs limits the delivery of care to the end-stage liver disease patients leading to the death while on the waiting list. The advent of ex-situ normothermic machine perfusion (NMP) has emerged as an alternative to the standard organ preservation technique, static cold storage (SCS). The newer technique promises to not only restore the normal metabolic activity but also attempt to recondition the marginal livers back to the pristine state, which are otherwise more susceptible to ischemic injury and foster the poor post-transplant outcomes. Areas covered: An extensive search of all the published literature describing the role of NMP based device in liver transplantation as an alternative to SCS was made on MEDLINE, EMBASE, Cochrane, BIOSIS, Crossref, Scopus databases and clinical trial registry on 10 May 2018. Expert commentary: The main tenet of NMP is the establishment of the physiological milieu, which permits aerobic metabolism to continue through out the period of preservation and limits the effects of ischemia-reperfusion (I/R) injury. In addition, by assessing the various metabolic and synthetic parameters the viability and suitability of donor livers for transplantation can be determined. This important technological advancement has scored satisfactorily on the safety and efficacy parameters in preliminary clinical studies. The present review suggests that NMP can offer the opportunity to assess and safely utilize the marginal donor livers if deemed appropriate for the transplantation. However, ongoing trials will determine its full potential and further adoption.

High-Mobility Group Box 1 Protein Regulates Autophagy in LO2 Cells Following Anoxia-Reoxygenation Injury

The mechanisms of autophagy during liver ischemia-reperfusion injury are not completely understood. This study aimed to assess the role of high-mobility group box 1 protein (HMGB1) in autophagy in LO2 cells following anoxia-reoxygenation injury. LO2 cells were pretreated with the HMGB1 inhibitor ammonium glycyrrhizinate (1000 μmol/L) or the HMGB1 agonist recombinant HMGB1 (rHMGB1, 10 ng/mL) at proper concentrations before induction of anoxia-reoxygenation injury. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels and cell viability were evaluated. Then, the expression levels of LC3 and Beclin-1, which are classical autophagy markers, were assessed by Western blot. Autophagosomes were detected by electron microscopy. Our results showed that rHMGB1-treated cells had increased AST and ALT levels in the culture medium, aggravated cell injury, enhanced expression of beclin-1 and LC3 proteins, and increased number of autophagosomes. However, glycyrrhizinate treatment alleviated ALT and AST levels in culture medium, relieved cell injury, reduced beclin-1 and LC3 protein expression levels, and decreased autophagosome number. These findings indicated that HMGB1 likely regulates autophagy in LO2 cells exposed to anoxia-reoxygenation injury.

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

The pervasive shortage of deceased donor liver allografts contributes to significant waitlist mortality despite efforts to increase organ donation. Ex vivo liver perfusion appears to enhance preservation of donor organs, extending viability and potentially evaluating function in organs previously considered too high risk for transplant. These devices pose novel challenges for organ allocation, safety, training, and finances. This white paper describes the American Society of Transplant Surgeons' belief that organ preservation technology is a vital advance, but its use should not change fundamental aspects of organ allocation. Additional data elements need to be collected, made available for organ assessment by transplant professionals to allow determination of organ suitability in the case of reallocation and incorporated into risk adjustment methodology. Finally, further work is needed to determine the optimal strategy for management and oversight of perfused organs prior to transplantation.

Evaluation of Graft Effluent High Mobility Group Box-1 (HMGB-1) for Prediction of Outcome After Liver Transplantation

BACKGROUND Pre-transplant assessment of the graft for liver transplantation is crucial. Based on experimental data, this study was designed to assess both nuclear high mobility group box-1 (HMGB-1) protein and arginine-specific proteolytic activity (ASPA) in the graft effluent. MATERIAL AND METHODS In a non-interventional trial, both HMGB-1 and ASPA were measured in the effluent of 30 liver grafts after cold storage before transplantation. Values of HMGB-1 and ASPA levels were compared with established prognostic parameters such as the donor risk index, balance of risk score, and Donor-Model for End-Stage Liver Disease. RESULTS The early allograft dysfunction (EAD) was best predicted by recipient age (p=0.026) and HMGB-1 (p=0.031). HMGB -1 thresholds indicated the likelihood for initial non-function (1608 ng/ml, p=0.004) and EAD (580 ng/ml, p=0.017). The multivariate binary regression analysis showed a 21-fold higher (95% CI: 1.6-284.5, p=0.022) risk for EAD in cases with levels exceeding 580 ng/ml. The ASPA was lower in cases of initial non-function (p=0.028) but did not correlate with the rate of EAD (p=0.4). CONCLUSIONS This study demonstrates the feasibility of HMGB-1 detection in the graft effluent after cold storage. Along with conventional prognostic scores, it may be helpful to predict the early fate of a graft in human liver transplantation.

Preliminary Experience With Hypothermic Oxygenated Machine Perfusion in an Italian Liver Transplant Center

BACKGROUND

Machine perfusion is increasingly utilized in liver transplantation to face the detrimental consequences of the use of extended-criteria donors. Hypothermic oxygenated machine perfusion (HOPE) appears to be more protective relative to static cold storage. Conversely, normothermic machine perfusion (NMP) allows a better graft evaluation. We describe a pilot prospective study on machine perfusion in selected grafts.

METHODS

HOPE was executed for all the grafts procured from donors after cardiac death (DCDs) and for livers from donors after brain death (DBDs) requiring prolonged preservation time. NMP was used when a more precise evaluation was needed. Both HOPE and NMP were performed through the portal vein and hepatic artery.

RESULTS

From July 2016 to November 2017, we performed 7 HOPE procedures: 5 for DCD and 2 for DBD grafts. Two livers presented with macrovesicular steatosis >30% (1 DCD and 1 DBD). HOPE lasted 240 minutes (180-320 min) with a total ischemia time of 575 minutes (410-810 min). Six grafts were successfully transplanted. One DCD graft required additional evaluation using NMP. The graft was then discarded due to extensive hepatocellular necrosis. In the post-transplant course, acute and chronic renal failure were the main complications affecting 3 and 2 recipients, respectively. In our series, steatosis was the main risk factor for kidney injury. Patient and graft survival rate was 100% and no ischemic cholangiopathies were observed after 270 days (106-582 days).

CONCLUSIONS

Our study confirms HOPE safety and efficacy for DCD and DBD grafts. These data are particularly significant for DCD management in the Italian setting where the mandatory 20-minute hands-off interval before death declaration further prolongs warm ischemia time.

Hypothermic oxygenated perfusion (HOPE) attenuates ischemia/reperfusion injury in the liver through inhibition of the TXNIP/NLRP3 inflammasome pathway in a rat model of donation after cardiac death

Hypothermic oxygenated perfusion (HOPE) is a relatively new dynamic preservation procedure that has not been widely implemented in liver transplantation despite its advantages. Improved graft protection is one such advantage offered by HOPE and has been attributed to multiple mechanisms, one of which may be the modulation of the thioredoxin-interacting protein (TXNIP)/NOD-like receptor protein 3 (NLRP3) inflammasome pathway. The TXNIP/NLRP3 inflammasome pathway plays a critical role in sterile inflammation under oxidative stress as a result of ischemia/reperfusion injury (IRI). In the current study, we aimed to investigate the graft protection offered by HOPE and its impact on the TXNIP/NLRP3 inflammasome pathway. To simulate conditions of donation after cardiac death (DCD) liver transplantation, rat livers were exposed to 30 min of warm ischemia after cardiac arrest. Livers were then preserved under cold storage (CS) or with HOPE for 3 h. Livers were then subjected to 1 h of isolated reperfusion. Liver injuries were assessed on the isolated perfusion rat liver model system before and after reperfusion. Compared with the CS group, the HOPE group had a significant reduction in liver injury and improvement in liver function. Our findings also revealed that reperfusion injury induced liver damage and activated the TXNIP/NLRP3 inflammasome pathway in DCD rat livers. Pretreatment of DCD rat livers with HOPE inhibited the TXNIP/NLRP3 inflammasome pathway and attenuated liver IRI. Attenuation of oxidative stress as a result of HOPE led to the down-regulation of the TXNIP/NLRP3 inflammasome pathway and thus offered superior protection compared with the traditional CS method of organ preservation.-He, W., Ye, S., Zeng, C., Xue, S., Hu, X., Zhang, X., Gao, S., Xiong, Y., He, X., Vivalda, S., Li, L., Wang, Y., Ye, Q. Hypothermic oxygenated perfusion (HOPE) attenuates ischemia/reperfusion injury in the liver through inhibition of the TXNIP/NLRP3 inflammasome pathway in a rat model of donation after cardiac death.

The Role of Normothermic Perfusion in Liver Transplantation (TRaNsIT Study): A Systematic Review of Preliminary Studies

INTRODUCTION

The success of liver transplantation has been limited by the unavailability of suitable donor livers. The current organ preservation technique, i.e., static cold storage (SCS), is not suitable for marginal organs. Alternatively, normothermic machine perfusion (NMP) promises to recreate the physiological environment and hence holds promise for the better organ preservation. The objective of this systematic review is to provide an overview of the safety, benefits, and insight into the other potential useful parameters of NMP in the liver preservation.

MATERIAL AND METHODS

We searched the current literature following registration in the International Prospective Register of Systematic Reviews (PROSPERO) with registration number CRD42018086034 for prospective trials comparing the role of NMP device to SCS in liver transplant by searching the PubMed, EMBASE, Cochrane, BIOSIS, Crossref, and Scopus databases and clinical trial registry.

RESULTS

The literature search identified five prospective clinical trials (four being early phase single institutional and single randomized multi-institutional) comparing 187 donor livers on NMP device to 273 donor livers on SCS. The primary outcome of interest was to assess the safety and graft survival at day 30 after transplant following NMP of the donor liver. Secondary outcomes included were early allograft dysfunction (EAD) in the first seven days; serum measures of liver functions as bilirubin, aspartate aminotransferase (AST), alanine amino transferase (ALT), alkaline phosphatase (ALP), and international normalized ratio (INR) on days 1-7; major complications as defined by a Clavien-Dindo score ≥ 3; and patient and graft survival and biliary complications at six months. The peaked median AST level between days 1 and 7 in the five trials was 417-1252 U/L (range 84-15009 U/L) while on NMP and 839-1474 U/L (range 153-8786 U/L) in SCS group. The median bilirubin level on day 7 ranged within 25-79 µmol/L (range 8-344 µmol/l) and 30-47.53 µmol/l (range 9-340 µmol/l) in NMP and SCS groups, respectively. A single case of PNF was reported in NMP group in the randomized trial while none of the other preliminary studies reported any in either group. There was intertrial variability in EAD which ranged within 15-56% in NMP group while being within 23-37% in SCS group. Biliary complications observed in NMP group ranged from 0 to 20%. Single device malfunction was reported in randomized controlled trial leading to renouncement of transplant while none of the other trials reported any machine failure, although two user related device errors inadvertent were reported.

CONCLUSION

This review outlines that NMP not only demonstrated safety and efficacy but also provided the favourable environment of organ preservation, repair, and viability assessment to donor liver prior to the transplantation with low rate of posttransplantation complication as PNF, EAD, and biliary complication; however further studies are needed to broaden our horizon.

Does Ischemia Free Liver Procurement Under Normothermic Perfusion Benefit the Outcome of Liver Transplantation?

Background

In contrast to conventional static cold preservation, normothermic machine perfusion (NMP) provides a beneficial alternative preservation of donor livers. However, the liver still suffered cold ischemic injury before attaching to the perfusion device.

Material/Methods

To prevent cold ischemic injury during procurement, we describe a novel procedure called ischemia-free liver procurement (IFLP) under NMP. Two liver grafts were procured from brain death donor under NMP and underwent 2-hour ex vivo NMP followed by 3 and 6 hours of static cold preservation. From procurement to post-transplantation course, evidence was collected to prove that IFLP is safe and benefits recipients.

Results

The post-transplantation course was uneventful, and the liver function tests and histological study revealed minimal hepatocyte and biliary epithelium injury during the preservation.

Conclusions

This preliminary experience demonstrates the clinical feasibility and safety of IFLP under NMP which offering opportunities to increase the number of donor livers and to improve the organ function.

Impact of real-time metabolomics in liver transplantation: Graft evaluation and donor-recipient matching

BACKGROUND & AIMS

There is an emerging need to assess the metabolic state of liver allografts especially in the novel setting of machine perfusion preservation and donor in cardiac death (DCD) grafts. High-resolution magic-angle-spinning nuclear magnetic resonance (HR-MAS-NMR) could be a useful tool in this setting as it can extemporaneously provide untargeted metabolic profiling. The purpose of this study was to evaluate the potential value of HR-MAS-NMR metabolomic analysis of back-table biopsies for the prediction of early allograft dysfunction (EAD) and donor-recipient matching.

METHOD

The metabolic profiles of back-table biopsies obtained by HR-MAS-NMR, were compared according to the presence of EAD using partial least squares discriminant analysis. Network analysis was used to identify metabolites which changed significantly. The profiles were compared to native livers to identify metabolites for donor-recipient matching.

RESULTS

The metabolic profiles were significantly different in grafts that caused EAD compared to those that did not. The constructed model can be used to predict the graft outcome with excellent accuracy. The metabolites showing the most significant differences were lactate level >8.3 mmol/g and phosphocholine content >0.646 mmol/g, which were significantly associated with graft dysfunction with an excellent accuracy (AUROC_lactates = 0.906; AUROC_{phosphocholine} = 0.816). Native livers from patients with sarcopenia had low lactate and glycerophosphocholine content. In patients with sarcopenia, the risk of EAD was significantly higher when transplanting a graft with a high-risk graft metabolic score.

CONCLUSION

This study underlines the cost of metabolic adaptation, identifying lactate and choline-derived metabolites as predictors of poor graft function in both native livers and liver grafts. HR-MAS-NMR seems a valid technique to evaluate graft quality and the consequences of cold ischemia on the graft. It could be used to assess the efficiency of graft resuscitation on machine perfusion in future studies.

LAY SUMMARY

Real-time metabolomic profiles of human grafts during back-table can accurately predict graft dysfunction. High lactate and phosphocholine content are highly predictive of graft dysfunction whereas low lactate and phosphocholine content characterize patients with sarcopenia. In these patients, the cost of metabolic adaptation may explain the poor outcomes.

Hypothermic Machine Preservation of the Liver: State of the Art

PURPOSE OF REVIEW

In this review, we highlight which livers may benefit from additional treatment before implantation and describe the concept of hypothermic machine liver perfusion. Furthermore, we explain why cold oxygenated perfusion concepts could potentially lead to a breakthrough in this challenging field of transplantation. Accordingly, we summarize recent clinical applications of different hypothermic perfusion approaches.

RECENT FINDINGS

The impact of end-ischemic, hypothermic liver perfusion in liver transplantation is currently assessed by two multicenter, randomized controlled trials. Recently, new applications of hypothermic perfusion showed promising results and recipients were protected from severe intrahepatic biliary complications, despite the use of very extended criteria grafts including donation after circulatory death livers.

SUMMARY

Hypothermic machine liver perfusion is beneficial for high-risk livers and protects recipients from most feared complications. Importantly, such easy approach is currently implemented in several European centers and new markers obtained from perfusate may improve the prediction of liver function in the future.

Hypothermic machine perfusion in liver transplantation

PURPOSE OF THE REVIEW

The purpose of the review is to report recent human application of hypothermic machine liver perfusion, and to discuss potential protective mechanisms.

RECENT FINDINGS

Human application of hypothermic machine liver perfusion is still very limited. Currently, three transplant centers apply this novel treatment in donation after cardiac death (DCD) or donation after brain death (DBD) liver grafts. In all cases, endischemic perfusion was performed after initial cold storage for organ transport. Perfusion conditions differ slightly in terms of oxygenation (pO2 15-60 kPa), perfusion route (dual vs. portal), perfusion time (2-4 h), and perfusate.

SUMMARY

The current data support the hypothesis that applying endischemic hypothermic machine liver perfusion protects extended criteria DBD and DCD livers from initial reperfusion injury, with better graft function and less biliary complications. Hypothermic machine perfusion may therefore offer revitalization of liver grafts before implantation by a simple and practical perfusion technique with a high impact on enlarging the donor pool. Multicentric phase III randomized control trials in DBD and DCD liver transplantation have been initiated to further test this strategy, which may establish machine liver perfusion in the clinical setting.

Perfusion machines and hepatocellular carcinoma: a good match between a marginal organ and an advanced disease?

Hepatocellular carcinoma (HCC) accounts for 90% of primary liver cancers, is the second leading cause of cancer-related deaths and the leading cause of death in patients with cirrhosis. Liver transplantation (LT) represents the ideal treatment for selected patients as it removes both the tumor and the underlying cirrhotic liver with 5-year survival rates higher than 70%. Unfortunately, due to tumor characteristics, patient co-morbidities or shortage of organs available for transplant, only 20% of patients can undergo curative treatment. Ex situ machine perfusion (MP) is a technology recently introduced that might potentially improve organ preservation, allow graft assessment and increase the pool of available organs. The purpose of this review is to provide an update on the current role of ex situ liver MP in liver transplantation for HCC patients.

The Use of an Acellular Oxygen Carrier in a Human Liver Model of Normothermic Machine Perfusion

BACKGROUND

Normothermic machine perfusion of the liver (NMP-L) is a novel technique that preserves liver grafts under near-physiological conditions while maintaining their normal metabolic activity. This process requires an adequate oxygen supply, typically delivered by packed red blood cells (RBC). We present the first experience using an acellular hemoglobin-based oxygen carrier (HBOC) Hemopure in a human model of NMP-L.

METHODS

Five discarded high-risk human livers were perfused with HBOC-based perfusion fluid and matched to 5 RBC-perfused livers. Perfusion parameters, oxygen extraction, metabolic activity, and histological features were compared during 6 hours of NMP-L. The cytotoxicity of Hemopure was also tested on human hepatic primary cell line cultures using an in vitro model of ischemia reperfusion injury.

RESULTS

The vascular flow parameters and the perfusate lactate clearance were similar in both groups. The HBOC-perfused livers extracted more oxygen than those perfused with RBCs (O2 extraction ratio 13.75 vs 9.43 % ×10 per gram of tissue, P = 0.001). In vitro exposure to Hemopure did not alter intracellular levels of reactive oxygen species, and there was no increase in apoptosis or necrosis observed in any of the tested cell lines. Histological findings were comparable between groups. There was no evidence of histological damage caused by Hemopure.

CONCLUSIONS

Hemopure can be used as an alternative oxygen carrier to packed red cells in NMP-L perfusion fluid.

Opportunities for Therapeutic Intervention During Machine Perfusion

PURPOSE OF REVIEW

There is a vast discrepancy between the number of patients waiting for organ transplantation and the available donor organs. Ex vivo machine perfusion (MP) has emerged in an effort to expand the donor pool, by improving organ preservation, providing diagnostic information, and more recently, acting as a platform for organ improvement. This article reviews the current status of MP with a focus on its role in organ preconditioning and therapeutic interventions prior to transplantation.

RECENT FINDINGS

MP has allowed longer organ preservation compared to conventional static cold storage and allowed the use of organs that might otherwise have been discarded. Moreover, experimental studies have investigated the role of MP in reducing ischemia reperfusion injury of lungs, kidneys and livers by applying mesenchymal stem cells (MSCs), anti-inflammatory agents, cytotopic anticoagulants, and defatting cocktails.

SUMMARY

MP has opened a new era in the field of organ transplantation and tissue medication.

The postoperative Model for End stage Liver Disease score as a predictor of short-term outcome after transplantation of extended criteria donor livers

BACKGROUND

Recently, the postoperative Model for End stage Liver Disease score (POPMELD) was suggested as a definition of postoperative graft dysfunction and a predictor of outcome after liver transplantation (LT).

AIM

The aim of the present study was to validate this concept in the context of extended criteria donor (ECD) organs.

PATIENTS AND METHODS

Single-center prospectively collected data (OPAL study/01/11-12/13) of 116 ECD LTs were utilized. For each recipient, the Model for End stage Liver Disease (MELD) score was calculated for 7 postoperative days (PODs). The ability of international normalized ratio, bilirubin, aspartate aminotransferase, Donor Risk Index, a recent definition of early allograft dysfunction, and the POPMELD was compared to predict 90-day graft loss. Predictive abilities were compared by receiver operating characteristic curves, sensitivity and specificity, and positive and negative predictive values.

RESULTS

The median Donor Risk Index was 1.8. In all, 60.3% of recipients were men [median age of 54 (23-68) years]. The median POD1-7 peak-aspartate aminotransferase value was 1052 (194-17 577) U/l. The rate of early allograft dysfunction was 22.4%. The 90-day graft survival was 89.7%. Out of possible predictors of the 90-day graft loss MELD on POD5 was the best predictor of outcome (area under the curve=0.84). A MELD score of 16 or more on POD5 predicted the 90-day graft loss with a specificity of 80.8%, a sensitivity of 81.8%, and a positive and negative predictive value of 31 and 97.7%.

CONCLUSION

A MELD score of 16 or more on POD5 is an excellent predictor of outcome in ECD donor LT. Routine evaluation of POPMELD scores might support clinical decision-making and should be reported routinely in clinical trials.

Impact of Subnormothermic Machine Perfusion Preservation in Severely Steatotic Rat Livers: A Detailed Assessment in an Isolated Setting

The current drastic shortage of donor organs has led to acceptance of extended-criteria donors for transplantation, despite higher risk of primary nonfunction. Here, we report the impact of subnormothermic machine perfusion (SMP) preservation on the protection of >50% macrosteatotic livers. Dietary hepatic steatosis was induced in Wistar rats via 2-day fasting and subsequent 3-day re-feeding with a fat-free, carbohydrate-rich diet. This protocol induces 50-60% macrovesicular steatosis, which should be discarded when preserved via cold storage (CS). The fatty livers were retrieved and preserved for 4 h using either CS in histidine-tryptophan-ketoglutarate or SMP in polysol solution. Graft functional integrity was evaluated via oxygenated ex vivo reperfusion for 2 h at 37°C. SMP resulted in significant reductions in not only parenchymal alanine aminotransferase (p < 0.001), but also mitochondrial glutamate dehydrogenase (p < 0.001) enzyme release. Moreover, portal venous pressure (p = 0.047), tissue adenosine triphosphate (p = 0.001), bile production (p < 0.001), high-mobility group box protein-1 (p < 0.001), lipid peroxidation, and tissue glutathione were all significantly improved by SMP. Electron microscopy revealed that SMP alleviated deleterious alterations of sinusoidal microvasculature and hepatocellular mitochondria, both of which are characteristic disadvantages associated with steatosis. SMP could protect 50-60% macrosteatotic livers from preservation/reperfusion injury, and may thus represent a new means for expanding available donor pools.

Hypo- and normothermic perfusion of the liver: Which way to go?

The demand of donor livers for transplantation exceeds the supply. In an attempt to maximize the number of potentially usable donor livers, several centers are exploring the role of machine perfusion. This review provides an update on machine perfusion strategies and basic concepts, based on current clinical issues, and discuss challenges, including currently used biomarkers for assessing the quality and viability of perfused organs. The potential benefits of machine perfusion on immunogenicity and the consequences on post-operative immunosuppression management are discussed.

Preconditioning methods in the management of hepatic ischemia reperfusion- induced injury: Update on molecular and future perspectives

Hepatic IR (ischemia reperfusion) injury is a commonly encountered obstacle in the post-operative management of hepatic surgery. Hepatic IR occurs during 'Pringle maneuver' for reduction of blood loss or during a brief period of cold storage followed by reperfusion of liver grafts. The stress induced during hepatic IR, triggers a spectrum of cellular responses leading to the varying degrees of hepatic complications which in turn affect the post operative care. Different preconditioning methods either activate or subdue different sets of molecular signals, resulting in varied levels of protection against hepatic IR injury. Yet, there is a serious lacuna in the knowledge regarding the choice of preconditioning methods and the resulting molecular changes in order to assess the efficiency and choice of these methods correctly. This review provides an update on the various preconditioning approaches such as surgical/ischemic, antioxidant, pharmaceutical and genetic preconditioning strategies published during last six years (2009-2015). Further, we discuss the attenuation or inhibition of specific inflammatory, apoptotic and necrotic markers in the various experimental models of liver IR subjected to different preconditioning strategies. While enlisting the controversies in the ischemic preconditioning strategy, we bring out the uncertainties in the existing molecular targets and their reliability in the attenuation of hepatic IR injury. Future research studies would include the novel preconditioning strategies employ i) the targeted gene silencing of key molecular targets inducing IR, ii) hyper expression of beneficial molecular signals against IR via gene transfer techniques. The above studies would see the combination of these latest techniques with the established preconditioning strategies for better post-operative hepatic management.

Efficacy of hydrodynamic interleukin 10 gene transfer in human liver segments with interest in transplantation

Different diseases lead, during their advanced stages, to chronic or acute liver failure, whose unique treatment consists in organ transplantation. The success of intervention is limited by host immune response and graft rejection. The use of immunosuppressant drugs generally improve organ transplantation, but they cannot completely solve the problem. Also, their management is delicate, especially during the early stages of treatment. Thus, new tools to set an efficient modulation of immune response are required. The local expression of interleukin (IL) 10 protein in transplanted livers mediated by hydrodynamic gene transfer could improve the organ acceptance by the host because it presents the natural ability to modulate the immune response at different levels. In the organ transplantation scenario, IL10 has already demonstrated positive effects on graft tolerance. Hydrodynamic gene transfer has been proven to be safe and therapeutically efficient in animal models and could be easily moved to the clinic. In the present work, we evaluated efficacy of human IL10 gene transfer in human liver segments and the tissue natural barriers for gene entry into the cell, employing gold nanoparticles. In conclusion, the present work shows for the first time that hydrodynamic IL10 gene transfer to human liver segments ex vivo efficiently delivers a human gene into the cells. Indexes of tissue protein expression achieved could mediate local pharmacological effects with interest in controlling the immune response triggered after liver transplantation. On the other hand, the ultrastructural study suggests that the solubilized plasmid could access the hepatocyte in a passive manner mediated by the hydric flow and that an active mechanism of transportation could facilitate its entry into the nucleus. Liver Transplantation 23:50-62 2017 AASLD.