Hypothermic Oxygenated Machine Perfusion in Porcine Donation After Circulatory Determination of Death Liver Transplant

Ex Vivo Liver Machine Perfusion: Comprehensive Review of Common Animal Models

The most common preservation technique for liver grafts is static cold storage. Due to the organ shortage for liver transplantation (LT), extended criteria donor (ECD) allografts are increasingly used-despite the higher risk of inferior outcome after transplantation. Ex vivo liver machine perfusion (MP) has been developed to improve the outcome of transplantation, especially with ECD grafts, and is currently under evaluation in clinical trials. We performed a literature search on PubMed and ISI Web of Science to assemble an overview of rodent and porcine animal models of ex vivo liver MP for transplantation, which is essential for the present and future development of clinical liver MP. Hypothermic, subnormothermic, and normothermic MP systems have been successfully used for rat and pig LT. In comparison with hypothermic systems, normothermic perfusion often incorporates a dialysis unit. Moreover, it enables metabolic assessment of liver grafts. Allografts experiencing warm ischemic time have a superior survival rate after MP compared with cold storage alone, irrespective of the temperature used for perfusion. Furthermore, ex vivo MP improves the outcome of regular and ECD liver grafts in animal models. Small and large animal models of ex vivo liver MP are available to foster the further development of this new technology. Impact Statement Ex vivo machine perfusion is an important part of current research in the field of liver transplantation. While evidence for improve storage is constantly rising, the development of future applications such as quality assessment and therapeutic interventions necessitates robust animal models. This review is intended to provide an overview of this technology in common large and small animal models and to give an outlook on future applications. Moreover, we describe developmental steps that can be followed by others, and which can help to decrease the number of animals used for experiments based on the replace, reduce, refine concept.

Cold but not too cold: advances in hypothermic and normothermic organ perfusion

Transplantation is the method of choice and, in many cases, the only method of treatment for patients with end-stage organ disease. Excellent results have been achieved, and the main focus today is to extend the number of available donors. The use of extended-criteria donors or donors after circulatory death is standard, but is accompanied by an increased risk of ischemia reperfusion injury. This review presents newly developed machine perfusion techniques using hypothermic, subnormothermic, or normothermic conditions, with or without oxygenation. Possibilities for treatment and quality assessment in decision-making about organ acceptability are also discussed.

Transcriptomic profiles of human livers undergoing rewarming machine perfusion before transplantation-first insights

Machine perfusion by controlled oxygenated rewarming (COR) is feasible and safe in clinical application and result in a promising outcome. This study utilizes next-generation sequencing (NGS) to investigate the transcriptome of human liver tissue undergoing COR before liver transplantation. Cold-stored livers were subjected to machine-assisted slow COR for ~120 min before transplantation. Biopsies were taken before (preCOR) and after COR (postCOR) and 1 h after reperfusion (postRep). The samples were sequenced, using RNA-seq to analyze differential transcriptional changes between the different stages and treatments of the grafts. Comparison of differential gene expression preCOR and postCOR demonstrated 10 upregulated genes. postRep 97 and 178 genes were upregulated and 7 and 13 downregulated compared to preCOR and postCOR, respectively. A shift of gene expressions by machine perfusion to the TGF-beta pathway was observed. The present study demonstrates distinct transcriptome profiles associated with machine perfusion by COR and transplantation of human livers. Such data provide a deeper understanding of the molecular mechanisms of machine perfusion technology in human liver transplantation.

Evaluation of the ex vivo liver viability using a nuclear magnetic resonance relaxation time-based assay in a porcine machine perfusion model

There is a dearth of effective parameters for selecting potentially transplantable liver grafts from expanded-criteria donors. In this study, we used a nuclear magnetic resonance (NMR) relaxation analyzer-based assay to assess the viability of ex vivo livers obtained via porcine donation after circulatory death (DCD). Ex situ normothermic machine perfusion (NMP) was utilized as a platform for viability test of porcine DCD donor livers. A liver-targeted contrast agent, gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA), was injected into the perfusate during NMP, and the dynamic biliary excretion of the Gd-EOB-DTPA was monitored by measuring the longitudinal relaxation time (T1). The longitudinal relaxation rate (R1) of the bile was served as a parameter. The delay of increase in biliary R1 during early stage of NMP indicated the impaired function of liver grafts in both warm and cold ischemia injury, which was correlated with the change of alanine aminotransferase. The preservative superiority in cold ischemia of dual hypothermic oxygenated machine perfusion could also be verified by assessing biliary R1 and other biochemical parameters. This study allows for the dynamic assessment of the viability of porcine DCD donor livers by combined usage of ex situ NMP and NMR relaxation time based assay, which lays a foundation for further clinical application.

Hemorheological and Microcirculatory Factors in Liver Ischemia-Reperfusion Injury-An Update on Pathophysiology, Molecular Mechanisms and Protective Strategies

Hepatic ischemia-reperfusion injury (IRI) is a multifactorial phenomenon which has been associated with adverse clinical outcomes. IRI related tissue damage is characterized by various chronological events depending on the experimental model or clinical setting. Despite the fact that IRI research has been in the spotlight of scientific interest for over three decades with a significant and continuous increase in publication activity over the years and the large number of pharmacological and surgical therapeutic attempts introduced, not many of these strategies have made their way into everyday clinical practice. Furthermore, the pathomechanism of hepatic IRI has not been fully elucidated yet. In the complex process of the IRI, flow properties of blood are not neglectable. Hemorheological factors play an important role in determining tissue perfusion and orchestrating mechanical shear stress-dependent endothelial functions. Antioxidant and anti-inflammatory agents, ischemic conditioning protocols, dynamic organ preservation techniques may improve rheological properties of the post-reperfusion hepatic blood flow and target endothelial cells, exerting a potent protection against hepatic IRI. In this review paper we give a comprehensive overview of microcirculatory, rheological and molecular–pathophysiological aspects of hepatic circulation in the context of IRI and hepatoprotective approaches.

Heme oxygenase-1-modified bone marrow mesenchymal stem cells combined with normothermic machine perfusion to protect donation after circulatory death liver grafts

BACKGROUND

Donation after circulatory death (DCD) liver grafts have a poor prognosis after transplantation. We investigated whether the outcome of DCD donor organs can be improved by heme oxygenase 1 (HO-1)-modified bone marrow-derived mesenchymal stem cells (BMMSCs) combined with normothermic machine perfusion (NMP), and explored its underlying mechanisms.

METHODS

BMMSCs were isolated, cultured, and transduced with the HO-1 gene. An NMP system was established. DCD rat livers were obtained, preserved by different methods, and the recipients were divided into 5 groups: sham operation, static cold storage (SCS), NMP, BMMSCs combined with NMP, and HO-1/BMMSCs combined with NMP (HBP) groups. Rats were sacrificed at 1, 7, and 14 days after surgery; their blood and liver tissue samples were collected; and liver enzyme and cytokine levels, liver histology, high-mobility group box 1 (HMGB1) levels in monocytes and liver tissues, and expression of Toll-like receptor 4 (TLR4) pathway-related molecules were evaluated.

RESULTS

After liver transplantation, the SCS group showed significantly increased transaminase levels, liver tissue damage, and shorter survival time. The HBP group showed lower transaminase levels, intact liver morphology, prolonged survival time, and decreased serum and liver proinflammatory cytokine levels. In the NMP and SCS groups, HMGB1 expression in the serum, monocytes, and liver tissues and TLR4 pathway-related molecule expression were significantly decreased.

CONCLUSIONS

HO-1/BMMSCs combined with NMP exerted protective effects on DCD donor liver and significantly improved recipient prognosis. The effect of HO-1/BMMSCs was greater than that of BMMSCs and was mediated via HMGB1 expression and TLR4 pathway inhibition.

Effects of Short-Term Normothermic and Subnormothermic Perfusion After Cold Preservation on Liver Transplantation From Donors After Cardiac Death

BACKGROUND

Liver transplantation from donors after cardiac death (DCD) could increase the pool of organs. We previously reported that oxygenated subnormothermic (20°C-25°C) ex vivo liver perfusion (SELP) improved the graft viability in rats. This study aimed to compare the effectiveness of SELP and normothermic (37°C) ex vivo liver perfusion (NELP) after cold storage (CS) in DCD liver grafts.

METHODS

Male Wistar rats were used, and grafts were retrieved 30 minutes after cardiac arrest. We performed oxygenated NELP and SELP with a Krebs-Henseleit buffer for different time points and durations: Group 0, donation performed from heart-beating donors (control); Group 1 (DCD group), donation performed from DCD donors with no treatments; Group 2, NELP performed before CS (30 minutes); Group 3, NELP performed after CS (30 minutes); Group 4, SELP performed after CS (30 minutes); Group 5, SELP performed after CS (60 minutes); and Group 6, SELP performed after CS (90 minutes). After 15 minutes of incubation at room temperature, the grafts were reperfused under normothermic conditions for 60 minutes as a model of liver transplantation.

RESULTS

No significant differences in body and liver weight were observed between all groups. In the SELP after CS groups, even 30 minutes of perfusion improved bile production, tumor necrosis factor-α, and interleukin-1β significantly compared with the DCD group (P < .05), comparable with NELP groups.

CONCLUSION

SELP rescued DCD livers from ischemia-reperfusion injury the same as the normothermic perfusion before or after CS groups. SELP after CS is more convenient than normothermic perfusion; hence, this technique may increase the organ pool.

A novel and simple formula to predict liver mass in porcine experimental models

A primary limitation in hepatic surgery is leaving a remnant liver of adequate size and function. Experimental models have been designed to study processes of liver injury and regeneration in this context, yet a formula to accurately calculate liver mass in an animal model is lacking. This study aims to create a novel and simple formula to estimate the mass of the native liver in a species of pigs commonly used in experimental liver surgery protocols. Using data from 200 male weanling Landrace-Large White hybrid pigs, multiple linear regression analysis is used to generate the formula. Clinical features used as variables for the predictive model are body mass and length. The final formula for pig liver mass is as follows: Liver mass (g) = 26.34232 * Body mass (kg) - 1.270629 * Length (cm) + 163.0076; R² = 0.7307. This formula for porcine liver mass is simple to use and may be helpful in studies using animals of similar characteristics to evaluate restoration of liver mass following major hepatectomy.

First report of successful transplantation of a pediatric donor liver graft after hypothermic machine perfusion

One of the main limiting factors in pediatric liver transplantation is donor availability. For adults, DCD liver grafts are increasingly used to expand the donor pool. To improve outcome after DCD liver transplantation, ex situ machine perfusion is used as an alternative organ preservation strategy, with the supplemental value of providing oxygen to the graft during preservation. We here report the first successful transplantation of a pediatric DCD liver graft after hypothermic oxygenated machine perfusion. The full-size liver graft was derived from a 13-year-old, female DCD donor and was end-ischemic pretreated with dual hypothermic oxygenated machine perfusion. Arterial and portal pressures were set at 18 and 4 mm Hg, slightly lower than protocolized settings for adult livers. During 2 hours of machine perfusion, portal and arterial flows increased from 100 to 210 mL/min and 30 to 63 mL/min, respectively. The pretreated liver graft was implanted in a 16-year-old girl with progressive familial intrahepatic cholestasis type 2. Postoperative AST, ALT, and prothrombin time normalized within a week. The recipient quickly recovered and was discharged from the hospital after 18 days. One year after transplantation, she is in excellent condition with a completely normal liver function and histology. This case is the first report of successful transplantation of a pediatric DCD liver graft after hypothermic oxygenated machine perfusion and illustrates the potential role of ex situ machine perfusion in expanding the donor pool and improving outcome after pediatric liver transplantation.

Machine perfusion for liver transplantation in the era of marginal organs-New kids on the block

In the face of a critical organ shortage in the Western world, various strategies are employed to expand the donor pool for orthotopic liver transplantation (OLT). Among them is the transplantation of organs from extended criteria donors, a valuable source of liver allografts, however, characterized by potential risks for post-OLT complications and inferior outcomes. In recent years, machine perfusion (MP) of the explanted donor liver as well as regional perfusion techniques has witnessed significant advancements. Here, we aim to discuss different modes of dynamic organ preservation in OLT. These include hypothermic and normothermic MP, hypothermic oxygenated machine perfusion (HOPE), controlled oxygenated rewarming as well as regional perfusion protocols. Over recent years, multiple feasibility trials have demonstrated the clinical prospects of MP. In the context of OLT using organs from extended criteria donors, MP has numerous advantages compared to conventional cold storage, some of which include the preservation and reconditioning of borderline transplantable organs and the viability assessment of high-risk donor allografts. This review aims to address the topic of liver allograft MP, highlighting particularly the current trends in clinical applications and future perspectives. Furthermore, different approaches of liver storage and reconditioning are reviewed in the context of ongoing research.

Optimizing Livers for Transplantation Using Machine Perfusion versus Cold Storage in Large Animal Studies and Human Studies: A Systematic Review and Meta-Analysis

Background

Liver allograft preservation frequently involves static cold storage (CS) and machine perfusion (MP). With its increasing popularity, we investigated whether MP was superior to CS in terms of beneficial outcomes.

Methods

Human studies and large animal studies that optimized livers for transplantation using MP versus CS were assessed (PubMed/Medline/EMBASE). Meta-analyses were conducted for comparisons. Study quality was assessed according to the Newcastle-Ottawa quality assessment scale and SYRCLE's risk of bias tool.

Results

Nineteen studies were included. Among the large animal studies, lower levels of lactate dehydrogenase (SMD -3.16, 95% CI -5.14 to -1.18), alanine transferase (SMD -2.46, 95% CI -4.03 to -0.90), and hyaluronic acid (SMD -2.48, 95% CI -4.21 to -0.74) were observed in SNMP-preserved compared to CS-preserved livers. NMP-preserved livers showing lower level of hyaluronic acid (SMD -3.97, 95% CI -5.46 to -2.47) compared to CS-preserved livers. Biliary complications (RR 0.45, 95% CI 0.28 to 0.73) and early graft dysfunction (RR 0.56, 95% CI 0.34 to 0.92) also significantly reduced with HMP preservation in human studies. No evidence of publication bias was found.

Conclusions

MP preservation could improve short-term outcomes after transplantation compared to CS preservation. Additional randomized controlled trials (RCTs) are needed to develop clinical applications of MP preservation.

Ex situ liver perfusion: Organ preservation into the future

In recent years, remarkable progress has occurred in the development of technologies to support ex situ liver perfusion. Building upon extensive preclinical studies in large animal models, pilot and randomized clinical trials have been initiated, and preliminary outcomes suggest more optimal protection of both standard and extended criteria liver grafts. There currently exists an incredible opportunity and need to further refine this technology, determine appropriate viability measures to predict usable liver grafts, and to explore potent protective additive strategies to further optimize the quality of extended criteria organs. These findings will have major bearing in expanding the limited liver donor pool, and may save lives where up to a quarter of listed patients die on wait-lists. Herein we offer a brief overview of the history and current status of ex situ liver perfusion, and discuss future directions that will likely have major impact on the practice of clinical liver transplantation.

Combined liver-kidney perfusion enhances protective effects of normothermic perfusion on liver grafts from donation after cardiac death

It has been shown that combined liver-kidney normothermic machine perfusion (NMP) is able to better maintain the circuit's biochemical milieu. Nevertheless, whether the combined perfusion is superior to liver perfusion alone in protecting livers from donation after circulatory death (DCD) is unclear. We aimed to test the hypothesis and explored the mechanisms. Livers from 15 DCD pig donors were subjected to either static cold storage (group A), liver-alone NMP (group B), or combined liver-kidney NMP (group C). Livers were preserved for 6 hours and reperfused ex vivo for 2 hours to simulate transplantation or were transplanted in situ. During perfusion, group C showed an improved acid-base and biochemical environment in the circuit over group B. After reperfusion, the architecture of the liver grafts was best preserved in group C, followed by group B, then group A, as shown by the histology and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling staining of both hepatocytes and biliary epithelium. Ki-67 staining showed substantial hepatocyte proliferation and biliary epithelial regeneration after perfusion in group B and group C. Group C produced more bile in the reperfusion phase than those in group A and group B, with more physiological bile composition and less severe biliary epithelium injury. Von Willebrand factor-positive endothelial cells and E-selectin expression decreased in both group B and group C. Combined liver-kidney NMP not only produced more adenosine triphosphate, protected the nitric oxide signaling pathway, but also diminished oxidative stress (high mobility group box-1 protein and 8-hydroxy-2-deoxy guanosine levels) and inflammatory cytokine (IL6 and IL8) release when compared with liver-alone NMP and CS. In addition, the 7-day survival rate of liver transplant recipients was higher in group C than that in groups A and B. In conclusion, combined liver-kidney NMP can better protect DCD livers from warm ischemia and reperfusion injury probably by maintaining the stability of the internal environment and by abolishing oxidative stress injury. Liver Transplantation 24 67-79 2018 AASLD.

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.

An Oxygenated and Transportable Machine Perfusion System Fully Rescues Liver Grafts Exposed to Lethal Ischemic Damage in a Pig Model of DCD Liver Transplantation

BACKGROUND

Control of warm ischemia (WI) lesions that occur with donation after circulatory death (DCD) would significantly increase the donor pool for liver transplantation. We aimed to determine whether a novel, oxygenated and hypothermic machine perfusion device (HMP Airdrive system) improves the quality of livers derived from DCDs using a large animal model.

METHODS

Cardiac arrest was induced in female large white pigs by intravenous injection of potassium chloride. After 60 minutes of WI, livers were flushed in situ with histidine-tryptophan-ketoglutarate and subsequently preserved either by simple cold storage (WI-SCS group) or HMP (WI-HMP group) using Belzer-MPS solution. Liver grafts procured from heart-beating donors and preserved by SCS served as controls. After 4 hours of preservation, all livers were transplanted.

RESULTS

All recipients in WI-SCS group died within 6 hours after transplantation. In contrast, the HMP device fully protected the liver against lethal ischemia/reperfusion injury, allowing 100% survival rate. A postreperfusion syndrome was observed in all animals of the WI-SCS group but none of the control or WI-HMP groups. After reperfusion, HMP-preserved livers functioned better and showed less hepatocellular and endothelial cell injury, in agreement with better-preserved liver histology relative to WI-SCS group. In addition to improved energy metabolism, this protective effect was associated with an attenuation of inflammatory response, oxidative load, endoplasmic reticulum stress, mitochondrial damage, and apoptosis.

CONCLUSIONS

This study demonstrates for the first time the efficacy of the HMP Airdrive system to protect liver grafts from lethal ischemic damage before transplantation in a clinically relevant DCD model.

Implantation of healthy matrix-embedded endothelial cells rescues dysfunctional endothelium and ischaemic tissue in liver engraftment

OBJECTIVE

Liver transplantation is limited by ischaemic injury which promotes endothelial cell and hepatocyte dysfunction and eventually organ failure. We sought to understand how endothelial state determines liver recovery after hepatectomy and engraftment.

DESIGN

Matrix-embedded endothelial cells (MEECs) with retained healthy phenotype or control acellular matrices were implanted in direct contact with the remaining median lobe of donor mice undergoing partial hepatectomy (70%), or in the interface between the remaining median lobe and an autograft or isograft from the left lobe in hepatectomised recipient mice. Hepatic vascular architecture, DNA fragmentation and apoptosis in the median lobe and grafts, serum markers of liver damage and phenotype of macrophage and lymphocyte subsets in the liver after engraftment were analysed 7 days post-op.

RESULTS

Healthy MEECs create a functional vascular splice in donor and recipient liver after 70% hepatectomy in mouse protecting these livers from ischaemic injury, hepatic congestion and inflammation. Macrophages recruited adjacent to the vascular nodes into the implants switched to an anti-inflammatory and regenerative profile M2. MEECs improved liver function and the rate of liver regeneration and prevented apoptosis in donor liver lobes, autologous grafts and syngeneic engraftment.

CONCLUSIONS

Implants with healthy endothelial cells rescue liver donor and recipient endothelium and parenchyma from ischaemic injury after major hepatectomy and engraftment. This study highlights endothelial-hepatocyte crosstalk in hepatic repair and provides a promising new approach to improve regenerative medicine outcomes and liver transplantation.

Practical Recommendations for Long-term Management of Modifiable Risks in Kidney and Liver Transplant Recipients: A Guidance Report and Clinical Checklist by the Consensus on Managing Modifiable Risk in Transplantation (COMMIT) Group

Short-term patient and graft outcomes continue to improve after kidney and liver transplantation, with 1-year survival rates over 80%; however, improving longer-term outcomes remains a challenge. Improving the function of grafts and health of recipients would not only enhance quality and length of life, but would also reduce the need for retransplantation, and thus increase the number of organs available for transplant. The clinical transplant community needs to identify and manage those patient modifiable factors, to decrease the risk of graft failure, and improve longer-term outcomes.COMMIT was formed in 2015 and is composed of 20 leading kidney and liver transplant specialists from 9 countries across Europe. The group's remit is to provide expert guidance for the long-term management of kidney and liver transplant patients, with the aim of improving outcomes by minimizing modifiable risks associated with poor graft and patient survival posttransplant.The objective of this supplement is to provide specific, practical recommendations, through the discussion of current evidence and best practice, for the management of modifiable risks in those kidney and liver transplant patients who have survived the first postoperative year. In addition, the provision of a checklist increases the clinical utility and accessibility of these recommendations, by offering a systematic and efficient way to implement screening and monitoring of modifiable risks in the clinical setting.

Liver ex situ machine perfusion preservation: A review of the methodology and results of large animal studies and clinical trials

Ex vivo machine perfusion (MP) is a promising way to better preserve livers prior to transplantation. Currently, no methodology has a verified benefit over simple cold storage. Before becoming clinically feasible, MP requires validation in models that reliably predict human performance. Such a model has been found in porcine liver, whose physiological, anatomical, and immunological characteristics closely resemble the human liver. Since the 1930s, researchers have explored MP as preservation, but only recently have clinical trials been performed. Making this technology clinically available holds the promise of expanding the donor pool through more effective preservation of extended criteria donor (ECD) livers. MP promises to decrease delayed graft function, primary nonfunction, and biliary strictures, which are all common failure modes of transplanted ECD livers. Although hypothermic machine perfusion (HMP) has become the standard for kidney ex vivo preservation, the precise settings and clinical role for liver MP have not yet been established. In research, there are 2 schools of thought: normothermic machine perfusion, closely mimicking physiologic conditions, and HMP, to maximize preservation. Here, we review the literature for porcine ex vivo MP, with an aim to summarize perfusion settings and outcomes pertinent to the clinical establishment of MP. Liver Transplantation 23 679-695 2017 AASLD.

Preliminary Single-Center Canadian Experience of Human Normothermic Ex Vivo Liver Perfusion: Results of a Clinical Trial

After extensive experimentation, outcomes of a first clinical normothermic machine perfusion (NMP) liver trial in the United Kingdom demonstrated feasibility and clear safety, with improved liver function compared with standard static cold storage (SCS). We present a preliminary single-center North American experience using identical NMP technology. Ten donor liver grafts were procured, four (40%) from donation after circulatory death (DCD), of which nine were transplanted. One liver did not proceed because of a technical failure with portal cannulation and was discarded. Transplanted NMP grafts were matched 1:3 with transplanted SCS livers. Median NMP was 11.5 h (range 3.3-22.5 h) with one DCD liver perfused for 22.5 h. All transplanted livers functioned, and serum transaminases, bilirubin, international normalized ratio, and lactate levels corrected in NMP recipients similarly to controls. Graft survival at 30 days (primary outcome) was not statistically different between groups on an intent-to-treat basis (p = 0.25). Intensive care and hospital stays were significantly more prolonged in the NMP group. This preliminary experience demonstrates feasibility as well as potential technical risks of NMP in a North American setting and highlights a need for larger, randomized studies.

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.

Machine perfusion versus cold storage of livers: a meta-analysis

Different organ preservation methods are key factors influencing the results of liver transplantation. In this study, the outcomes of experimental models receiving donation after cardiac death (DCD) livers preserved through machine perfusion (MP) or static cold storage (CS) were compared by conducting a meta-analysis. Standardized mean difference (SMD) and 95% confidence interval (CI) were calculated to compare pooled data from two animal species. Twenty-four studies involving MP preservation were included in the meta-analysis. Compared with CS preservation, MP can reduce the levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), and hyaluronic acid (HA) and the changes in liver weight. By contrast, MP can enhance bile production and portal vein flow (PVF). Alkaline phosphatase (ALP) levels and histological changes significantly differed between the two preservation methods. In conclusion, MP of DCD livers is superior to CS in experimental animals.

Graft Reconditioning before Liver Transplantation

BACKGROUND

The high demand for livers for transplantation has led to organs of limited quality being accepted to expand the donor pool. This is associated with inferior outcomes due to more pronounced preservation injury. Accordingly, recent research has aimed to develop preservation modalities for improved preservation as well as strategies for liver viability assessment and liver reconditioning.

METHODS

The PubMed database was searched using the terms 'perfusion', 'liver', 'preservation', and 'reconditioning' in various combinations, and the according literature was reviewed.

RESULTS

Several perfusion techniques have been developed in recent years with the potential for liver reconditioning. Preclinical and first emerging clinical data suggest feasibility, safety, and superiority over the current gold standard of cold storage.

CONCLUSION

This review outlines current advances in the field of liver preservation with an emphasis on liver reconditioning methods.

Machine Perfusion of Donor Livers for Transplantation: A Proposal for Standardized Nomenclature and Reporting Guidelines

With increasing demand for donor organs for transplantation, machine perfusion (MP) promises to be a beneficial alternative preservation method for donor livers, particularly those considered to be of suboptimal quality, also known as extended criteria donor livers. Over the last decade, numerous studies researching MP of donor livers have been published and incredible advances have been made in both experimental and clinical research in this area. With numerous research groups working on MP, various techniques are being explored, often applying different nomenclature. The objective of this review is to catalog the differences observed in the nomenclature used in the current literature to denote various MP techniques and the manner in which methodology is reported. From this analysis, we propose a standardization of nomenclature on liver MP to maximize consistency and to enable reliable comparison and meta-analyses of studies. In addition, we propose a standardized set of guidelines for reporting the methodology of future studies on liver MP that will facilitate comparison as well as clinical implementation of liver MP procedures.

Development of a normothermic extracorporeal liver perfusion system toward improving viability and function of human extended criteria donor livers

Donor organ shortages have led to an increased interest in finding new approaches to recover organs from extended criteria donors (ECD). Normothermic extracorporeal liver perfusion (NELP) has been proposed as a superior preservation method to reduce ischemia/reperfusion injury (IRI), precondition suboptimal grafts, and treat ECD livers so that they can be successfully used for transplantation. The aim of this study was to investigate the beneficial effects of a modified NELP circuit on discarded human livers. Seven human livers that were rejected for transplantation were placed on a modified NELP circuit for 8 hours. Perfusate samples and needle core biopsies were obtained at hourly intervals. A defatting solution that contained exendin-4 (50 nM) and L-carnitine (10 mM) was added to the perfusate for 2 steatotic livers. NELP provided normal temperature, electrolytes, and pH and glucose levels in the perfusate along with physiological vascular flows and pressures. Functional, biochemical, and microscopic evaluation revealed no additional injuries to the grafts during NELP with an improved oxygen extraction ratio (>0.5) and stabilized markers of hepatic injury. All livers synthesized adequate amounts of bile and coagulation factors. We also demonstrated a mild reduction (10%) of macroglobular steatosis with the use of the defatting solution. Histology demonstrated normal parenchymal architecture and a minimal to complete lack of IRI at the end of NELP. In conclusion, a modified NELP circuit preserved hepatocyte architecture, recovered synthetic functions, and hepatobiliary parameters of ECD livers without additional injuries to the grafts. This approach has the potential to increase the donor pool for clinical transplantation. Liver Transplantation 22 979-993 2016 AASLD.

Ex-vivo liver perfusion for organ preservation: Recent advances in the field

Liver transplantation is the optimal treatment for end-stage liver disease but is limited by the severe shortage of donor organs. This shortage has prompted increased utilization of marginal grafts from DCD and extended criteria donors, which poorly tolerate cold storage in comparison to standard criteria grafts. Ex-vivo liver perfusion (EVLP) technology has emerged as a potential alternative to cold storage for organ preservation, but there is no consensus regarding the optimal temperature or conditions for EVLP. Herein, we review recent advances in both pre-clinical and clinical studies, organized by perfusion temperature (hypothermic, subnormothermic, normothermic).

Machine perfusion enhances hepatocyte isolation yields from ischemic livers

BACKGROUND

High-quality human hepatocytes form the basis of drug safety and efficacy tests, cell-based therapies, and bridge-to-transplantation devices. Presently the only supply of cells derives from an inadequate pool of suboptimal disqualified donor livers. Here we evaluated whether machine perfusion could ameliorate ischemic injury that many of these livers experience prior to hepatocyte isolation.

METHODS

Non-heparinized female Lewis rat livers were exposed to an hour of warm ischemia (34°C) and then perfused for 3h. Five different perfusion conditions that utilized the cell isolation apparatus were investigated, namely: (1) modified Williams Medium E and (2) Lifor, both with active oxygenation (95%O(2)/5%CO(2)), as well as (3) Lifor passively oxygenated with ambient air (21%O(2)/0.04%CO(2)), all at ambient temperatures (20 ± 2°C). At hypothermic temperatures (5 ± 1°C) and under passive oxygenation were (4) University of Wisconsin solution (UW) and (5) Vasosol. Negative and positive control groups comprised livers that had ischemia (WI) and livers that did not (Fresh) prior to cell isolation, respectively.

RESULTS

Fresh livers yielded 32 ± 9 million cells/g liver while an hour of ischemia reduced the cell yield to 1.6 ± 0.6 million cells/g liver. Oxygenated Williams Medium E and Lifor recovered yields of 39 ± 11 and 31 ± 2.3 million cells/g liver, respectively. The passively oxygenated groups produced 15 ± 7 (Lifor), 13 ± 7 (Vasosol), and 10 ± 6 (UW)million cells/g liver. Oxygenated Williams Medium E was most effective at sustaining pH values, avoiding the accumulation of lactate, minimizing edematous weight gain and producing bile during perfusion.

CONCLUSIONS

Machine perfusion results in a dramatic increase in cell yields from livers that have had up to an hour of warm ischemia, but perfusate choice significantly impacts the extent of recovery. Oxygenated Williams Medium E at room temperature is superior to Lifor, UW and Vasosol, largely facilitated by its high oxygen content and low viscosity.

Influence of perfusate on liver viability during hypothermic machine perfusion

AIM: To optimize the perfusates used for hypothermic machine perfusion (HMP).

METHODS: Sprague-Dawley rats were assigned randomly to three groups (n = 12 per group) that received either saline, University of Wisconsin cold-storage solution (UW) or histidine-tryptophan-ketoglutarate solution (HTK) as the perfusate. Each group was divided into two subgroups: static cold storage (SCS) and HMP (n = 6 per subgroup). The liver graft was retrieved according to the method described by Kamada. For the SCS group, the graft was directly placed into cold perfusate (0-4 °C) for 6 h after liver isolation while the portal vein of the graft was connected to the perfusion machine for the HMP group. Then the perfusates were collected at different time points for analysis of aspartate aminotransferase (AST), alanine transaminase (ALT) and lactate dehydrogenase (LDH) levels. Liver tissues were obtained for evaluation of histology, dry/wet weight (D/W) ratio, and malondialdehyde (MDA) and adenosine-triphosphate (ATP) levels. The portal vein pressure and velocity were monitored in real time in all HMP subgroups.

RESULTS: Comparison of HMP and SCS: Regardless of the perfusate, HMP improved the architecture of donor graft in reducing the congestion around sinusoids and central vein and maintaining sinusoid lining in morphology; HMP improved liver function in terms of ALT, AST and LDH, especially during the 3-6 h period (SCS vs HMP using saline: ALT3, 225.00 ± 105.62 vs 49.50 ± 18.50, P = 0.047; LDH3, 1362.17 ± 563.30 vs 325.75 ± 147.43, P = 0.041; UW: LDH6, 2880.14 ± 948.46 vs 2135.00 ± 174.27, P = 0.049; HTK, AST6, 307.50 ± 52.95 vs 185.20 ± 20.46, P = 0.041); HMP decreased MDA level (saline, 2.79 ± 0.30 vs 1.09 ± 0.09, P = 0.008; UW, 3.01 ± 0.77 vs 1.23 ± 0.68, P = 0.005; HTK, 3.30 ± 0.52 vs 1.56 ± 0.22, P = 0.006). Comparison among HMP subgroups: HTK showed less portal vein resistance than UW and saline (vs saline, 3.41 ± 0.49 vs 5.00 ± 0.38, P < 0.001; vs UW, 3.41 ± 0.49 vs 4.52 ± 0.63, P = 0.007); UW reduced edema most efficiently (vs saline, 0.68 ± 0.02 vs 0.79 ± 0.05, P = 0.013), while HTK maintained ATP levels best (vs saline, 622.60 ± 29.11 vs 327.43 ± 44.66, P < 0.001; vs UW, 622.60 ± 29.11 vs 301.80 ± 37.68, P < 0.001).

CONCLUSION: HMP is superior to SCS in maintaining both architecture and function of liver grafts. Further, HTK was found to be the optimal perfusate for HMP.

Hypothermic Oxygenated Liver Perfusion: Basic Mechanisms and Clinical Application

Dynamic preservation strategies such as hypothermic machine perfusion are increasingly discussed to improve liver graft quality before transplantation. This review summarizes current knowledge of this perfusion technique for liver preservation. We discuss optimization of perfusion conditions and current strategies to assess graft quality during cold perfusion. Next, we provide an overview of possible pathways of protection from ischemia-reperfusion injury. Finally, we report on recent clinical applications of human hypothermic machine liver perfusion.

Liver protection strategies in liver transplantation

BACKGROUND

Liver transplantation is the therapy of choice for patients with end-stage liver diseases. However, the gap between the low availability of organs and high demand is continuously increasing. Innovative strategies for organ protection are necessary to expand donor pool and to achieve better outcomes for liver transplantation. The present review analyzed and compared various strategies of liver protection.

DATA SOURCES

Databases such as PubMed, Embase and Ovid were searched for the literature related to donor liver protection strategies using following key words: "ischemia reperfusion injury", "graft preservation", "liver transplantation", "machine perfusion" and "conditioning". Of the 146 studies identified, only those with cutting edge strategies were analyzed.

RESULTS

A variety of therapeutic approaches were proposed to alleviate graft ischemia/reperfusion injury, which included static cold storage, machine perfusion (hypothermic, normothermic and subnormothermic), manual conditioning (pre, post and remote), and pharmacological conditioning. Evidences from animal experiments and clinical trials suggested that all these strategies could potentially protect liver graft; however, their clinical applications are limited partially due to their own disadvantages.

CONCLUSIONS

There are a plenty of methods suggested to decrease the degree of donor liver transplantation-related injury. However, none of these approaches is perfect in clinical practice. More translational researches (molecular and clinical studies) are needed to improve the techniques in liver graft protection.

Criteria for viability assessment of discarded human donor livers during ex vivo normothermic machine perfusion

Although normothermic machine perfusion of donor livers may allow assessment of graft viability prior to transplantation, there are currently no data on what would be a good parameter of graft viability. To determine whether bile production is a suitable biomarker that can be used to discriminate viable from non-viable livers we have studied functional performance as well as biochemical and histological evidence of hepatobiliary injury during ex vivo normothermic machine perfusion of human donor livers. After a median duration of cold storage of 6.5 h, twelve extended criteria human donor livers that were declined for transplantation were ex vivo perfused for 6 h at 37 °C with an oxygenated solution based on red blood cells and plasma, using pressure controlled pulsatile perfusion of the hepatic artery and continuous portal perfusion. During perfusion, two patterns of bile flow were identified: (1) steadily increasing bile production, resulting in a cumulative output of ≥ 30 g after 6 h (high bile output group), and (2) a cumulative bile production <20 g in 6 h (low bile output group). Concentrations of transaminases and potassium in the perfusion fluid were significantly higher in the low bile output group, compared to the high bile output group. Biliary concentrations of bilirubin and bicarbonate were respectively 4 times and 2 times higher in the high bile output group. Livers in the low bile output group displayed more signs of hepatic necrosis and venous congestion, compared to the high bile output group. In conclusion, bile production could be an easily assessable biomarker of hepatic viability during ex vivo machine perfusion of human donor livers. It could potentially be used to identify extended criteria livers that are suitable for transplantation. These ex vivo findings need to be confirmed in a transplant experiment or a clinical trial.

Donation after circulatory determination of death: the university of michigan experience with extracorporeal support

BACKGROUND

Extracorporeal support (ECS) during organ procurement from donors after circulatory determination of death (DCDD) could increase the number of donor organs and decrease posttransplant complications. This study reports the experience of a large transplant center with controlled DCDD.

METHODS

A retrospective review of all potential controlled-DCDD cases between October 1, 2000 and July 31, 2013 was performed. We focused on methods, ethical and practical issues, and recipient outcome data of organs procured and transplanted in our institution using ECS-assisted DCDD (E-DCDD).

RESULTS

ECS was used for organ procurement in 37 controlled DCDD. The number of organs procured per donor was 2.59, and the number of organs transplanted per donor was 1.68. Delayed graft function occurred in 31% of renal grafts. In three donors (8%), organ donation was not completed because of surgeon judgment. Forty-eight renal grafts (65.8%), thirteen livers (61.9%), and one pancreas (50%) were successfully transplanted.

CONCLUSIONS

ECS can be routinely implemented in controlled DCDD. In our experience, the organs provided per donor was 2.59. Widely applied, EDCDD could result in more donor organs, especially when applied to DCDD in uncontrolled conditions.

Biomarkers to assess graft quality during conventional and machine preservation in liver transplantation

A global rising organ shortage necessitates the use of extended criteria donors (ECD) for liver transplantation (LT). However, poor preservation and extensive ischemic injury of ECD grafts have been recognized as important factors associated with primary non-function, early allograft dysfunction, and biliary complications after LT. In order to prevent for these ischemia-related complications, machine perfusion (MP) has gained interest as a technique to optimize preservation of grafts and to provide the opportunity to assess graft quality by screening for extensive ischemic injury. For this purpose, however, objective surrogate biomarkers are required which can be easily determined at time of graft preservation and the various techniques of MP. This review provides an overview and evaluation of biomarkers that have been investigated for the assessment of graft quality and viability testing during different types of MP. Moreover, studies regarding conventional graft preservation by static cold storage (SCS) were screened to identify biomarkers that correlated with either allograft dysfunction or biliary complications after LT and which could potentially be applied as predictive markers during MP. The pros and cons of the different biomaterials that are available for biomarker research during graft preservation are discussed, accompanied with suggestions for future research. Though many studies are currently still in the experimental setting or of low evidence level due to small cohort sizes, the biomarkers presented in this review provide a useful handle to monitor recovery of ECD grafts during clinical MP in the near future.

Subnormothermic machine perfusion for preservation of porcine kidneys in a donation after circulatory death model

Machine perfusion for preservation led to compelling success for the outcome of renal transplantation. Further refinements of methods to decrease preservation injury remain an issue of high interest. This study investigates functional and morphological aspects of kidneys preserved by subnormothermic (20 °C) machine perfusion (SNTM) compared with oxygenated hypothermic machine perfusion (HMPox) and cold storage (CS) in a donation after circulatory death (DCD) model. After 30 min of warm ischaemia, porcine kidneys were randomly assigned to preservation for 7 h by CS, HMPox or SNTM. Afterwards, kidneys were reperfused for 2 h with autologous blood in vitro for assessment of function and integrity. Application of SNTM for preservation led to significantly higher blood flow and urine output compared with both other groups. SNTM led to a twofold increased creatinine clearance compared with HMPox and 10-fold increased creatinine clearance compared with CS. Structural integrity was best preserved by SNTM. In conclusion, this is the first study on SNTM for kidneys from DCD donors. SNTM seems to be a promising preservation method with the potential to improve functional parameters of kidneys during reperfusion.

Technique of subnormothermic ex vivo liver perfusion for the storage, assessment, and repair of marginal liver grafts

The success of liver transplantation has resulted in a dramatic organ shortage. In most transplant regions 20-30% of patients on the waiting list for liver transplantation die without receiving an organ transplant or are delisted for disease progression. One strategy to increase the donor pool is the utilization of marginal grafts, such as fatty livers, grafts from older donors, or donation after cardiac death (DCD). The current preservation technique of cold static storage is only poorly tolerated by marginal livers resulting in significant organ damage. In addition, cold static organ storage does not allow graft assessment or repair prior to transplantation.

These shortcomings of cold static preservation have triggered an interest in warm perfused organ preservation to reduce cold ischemic injury, assess liver grafts during preservation, and explore the opportunity to repair marginal livers prior to transplantation. The optimal pressure and flow conditions, perfusion temperature, composition of the perfusion solution and the need for an oxygen carrier has been controversial in the past.

In spite of promising results in several animal studies, the complexity and the costs have prevented a broader clinical application so far. Recently, with enhanced technology and a better understanding of liver physiology during ex vivo perfusion the outcome of warm liver perfusion has improved and consistently good results can be achieved.

This paper will provide information about liver retrieval, storage techniques, and isolated liver perfusion in pigs. We will illustrate a) the requirements to ensure sufficient oxygen supply to the organ, b) technical considerations about the perfusion machine and the perfusion solution, and c) biochemical aspects of isolated organs.

Role of hypothermic machine perfusion in liver transplantation

Machine liver perfusion has significantly evolved during the last ten years to optimize extended criteria liver grafts and to address the worldwide organ shortage. This review gives an overview on available ex vivo and in vivo data on hypothermic machine liver perfusion. We discuss also possible protective pathways and show most recent clinical applications of hypothermic machine liver perfusion in human.

Hypothermic or normothermic abdominal regional perfusion in high-risk donors with extended warm ischemia times: impact on outcomes?

Donation after circulatory determination of death (DCD) has the potential to increase the applicability of transplantation as a treatment for end-stage organ disease; its use is limited, however, by the warm ischemic damage suffered by potential grafts. Abdominal regional perfusion (ARP) has been employed in this setting to not only curtail the deleterious effects of cardiac arrest by re-establishing oxygenated flow but also test and even improve the viability of the kidneys and liver prior to transplantation. In the present review article, we discuss experimental and clinical studies that have been published to date on the use of ARP in DCD, differentiating between its application under hypothermic and normothermic conditions. In addition to describing results that have been achieved thus far, we describe the major obstacles limiting the broader implementation of ARP in this context as well as potential means for improving the effectiveness of this modality in the future.

Improving outcomes in DCDD liver transplantation: there can only be strength in numbers

In the United States, liver transplantation using donation after circulatory determination of death (DCDD) donors is challenged by persistently inferior graft survival compared with donation after neurological death (DND), along with declining rates of liver transplantation relative to the total number of DCDD donors. Advances in adult-to-adult living donor liver transplantation graft survival temporally related to the Adult-to-Adult Living Donor Liver Transplantation Cohort Study consortium suggest that a similarly focused collaborative effort may serve to stimulate evolution within DCDD liver transplantation. Without a multi-center consortium to support innovative trials, the current state of DCDD liver transplantation is unlikely to progress.

Hypothermic oxygenated machine perfusion prevents arteriolonecrosis of the peribiliary plexus in pig livers donated after circulatory death

Background

Livers derived from donation after circulatory death (DCD) are increasingly accepted for transplantation. However, DCD livers suffer additional donor warm ischemia, leading to biliary injury and more biliary complications after transplantation. It is unknown whether oxygenated machine perfusion results in better preservation of biliary epithelium and the peribiliary vasculature. We compared oxygenated hypothermic machine perfusion (HMP) with static cold storage (SCS) in a porcine DCD model.

Methods

After 30 min of cardiac arrest, livers were perfused in situ with HTK solution (4°C) and preserved for 4 h by either SCS (n = 9) or oxygenated HMP (10°C; n = 9), using pressure-controlled arterial and portal venous perfusion. To simulate transplantation, livers were reperfused ex vivo at 37°C with oxygenated autologous blood. Bile duct injury and function were determined by biochemical and molecular markers, and a systematic histological scoring system.

Results

After reperfusion, arterial flow was higher in the HMP group, compared to SCS (251±28 vs 166±28 mL/min, respectively, after 1 hour of reperfusion; p = 0.003). Release of hepatocellular enzymes was significantly higher in the SCS group. Markers of biliary epithelial injury (biliary LDH, gamma-GT) and function (biliary pH and bicarbonate, and biliary transporter expression) were similar in the two groups. However, histology of bile ducts revealed significantly less arteriolonecrosis of the peribiliary vascular plexus in HMP preserved livers (>50% arteriolonecrosis was observed in 7 bile ducts of the SCS preserved livers versus only 1 bile duct of the HMP preserved livers; p = 0.024).

Conclusions

Oxygenated HMP prevents arteriolonecrosis of the peribiliary vascular plexus of the bile ducts of DCD pig livers and results in higher arterial flow after reperfusion. Together this may contribute to better perfusion of the bile ducts, providing a potential advantage in the post-ischemic recovery of bile ducts.

Effect of cold perfusion and perfluorocarbons on liver graft ischemia in a donation after cardiac death model

BACKGROUND

Effects of two perfluorocarbon (PFC) formulations (perfluorodecalin emulsion and perfluorodecalin liquid) on the quality of liver graft preservation, in a donation after cardiac death (DCD) rat model, were investigated. The significance of continuous graft perfusion during cold preservation was also explored.

MATERIALS AND METHODS

DCD model: 30 min after cardiopulmonary arrest was initiated, livers were excised and flushed with cold University of Wisconsin (UW) solution (± PFC) and preserved in the same solution for 8 h. The study groups were preserved as follows: group 1: no perfusion; group 2: perfusion with UW; group 3: PFC was administered before cardiac arrest and the liver was perfused with UW alone; and groups 4 and 5: perfused with UW + 1 of two PFCs. In a baseline group used only for comparison of gene expression, livers were quick-frozen after cardiac arrest. Microarrays were used to analyze liver messenger RNA transcripts. Histopathologic, immunohistochemical, and ADP/ATP ratio evaluations were performed to assess the quality of graft preservation.

RESULTS

Significant decreases in downregulation and increases in upregulation of hepatic genes (relative to baseline) were demonstrated in all perfusion groups. This trend was most pronounced in the PFC groups. Lower fat content and ADP/ATP ratio and a reduction in Caspase 3 activation were found in all perfusion groups.

CONCLUSION

Hypothermic perfusion of rat DCD liver grafts with oxygenated UW solution (± PFC) produced superior preservation compared with nonperfusion storage. The observed changes in expression of hepatic genes may represent a protective effect in the DCD model.

Machine perfusion in solid organ transplantation: where is the benefit?

BACKGROUND

Machine perfusion (MP) in solid organ transplantation has been a topic of variable importance for decades. At the dawn of organ transplantation, MP was one of the standard techniques for preservation; today's gold standard for organ preservation for transplantation is cold storage (CS). The outcome after transplantation of solid organs has tremendously improved over the last five decades. MP has been continuously under investigation and may be an option for organ preservation in selected cases; however, there is only little evidence from clinical trials that can be used to advocate for MP as a routine organ preservation method.

METHODS

This article reviews the current knowledge on MP in the field of solid organ transplantation with special focus on findings from clinical trials.

CONCLUSION

Especially in heart and lung transplantation, MP seems to be a promising tool to improve postoperative outcome, but a general evidence-based recommendation for or against an application of MP cannot be given due to the lack of the highest level of clinical evidence. Gold standards such as CS should not be left behind without good reason. Randomized clinical trials are desperately needed to further improve outcome and for better understanding of the underlying pathophysiological mechanisms.

Regional perfusion by extracorporeal membrane oxygenation of abdominal organs from donors after circulatory death: a systematic review

Organs from donors after circulatory death (DCDs) are particularly susceptible to the effects of warm ischemia injury. Regional perfusion (RP) by extracorporeal membrane oxygenation (ECMO) is increasingly being advocated as a useful remedy to the effects of ischemia/reperfusion injury, and it has been reported to enable the transplantation of organs from donors previously deemed unsuitable. The MEDLINE, Embase, and Cochrane databases were searched, and articles published between 1997 and 2013 were obtained. A systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Two hundred ten articles were identified, and 11 were eligible for inclusion. Four hundred eighty-two kidneys and 79 livers were transplanted from regional perfusion-supported donor after circulatory death (RP-DCD) sources. One-year graft survival was lower with uncontrolled RP-DCD liver transplantation, whereas 1-year patient survival was similar. Primary nonfunction and ischemic cholangiopathy were significantly more frequent with RP-DCDs versus donors after brain death (DBDs), but there was no difference in postoperative mortality between the 2 groups. The 1-year patient and graft survival rates for RP-DCD kidney transplantation were better than the rates with standard DCDs and were comparable to, if not better than, the rates with DBDs. At experienced centers, delayed graft function (DGF) for kidney transplantation from RP-DCDs was much less frequent in comparison with all other donor types. In conclusion, RP aids the recovery of DCD organs from ischemic injury and enables transplantation with acceptable survival. RP may help to increase the donor pool, but its benefits must still be balanced with the recognition of significantly higher rates of complications in liver transplantation. In kidney transplantation, significant reductions in DGF can be obtained with RP, and there are potentially important implications for long-term outcomes. Significant ethicolegal issues exist, and they are preventing a worldwide consensus on optimum RP protocols and an accurate appreciation of outcomes.

Hypothermic oxygenated perfusion (HOPE) protects from biliary injury in a rodent model of DCD liver transplantation

BACKGROUND & AIMS

The use of livers from donors after cardiac arrest (DCD) is increasing in many countries to overcome organ shortage. Due to additional warm ischemia before preservation, those grafts are at higher risk of failure and bile duct injury. Several competing rescue strategies by machine perfusion techniques have been developed with, however, unclear effects on biliary injury. We analyze the impact of an end-ischemic Hypothermic Oxygenated PErfusion (HOPE) approach applied only through the portal vein for 1h before graft implantation.

METHODS

Rat livers were subjected to 30-min in situ warm ischemia, followed by subsequent 4-h cold storage, mimicking DCD-organ procurement and conventional organ transport. Livers in the HOPE group underwent also passive cold storage for 4h, but were subsequently machine perfused for 1h before implantation. Outcome was tested by liver transplantation (LT) at 12h after implantation (n=10 each group) and after 4 weeks (n=10 each group), focusing on early reperfusion injury, immune response, and later intrahepatic biliary injury.

RESULTS

All animals survived after LT. However, reperfusion injury was significantly decreased by HOPE treatment as tested by hepatocyte injury, Kupffer cell activation, and endothelial cell activation. Recipients receiving non-perfused DCD livers disclosed less body weight gain, increased bilirubin, and severe intrahepatic biliary fibrosis. In contrast, HOPE treated DCD livers were protected from biliary injury, as detected by cholestasis parameter and histology.

CONCLUSIONS

We demonstrate in a DCD liver transplant model that end-ischemic hypothermic oxygenated perfusion is a powerful strategy for protection against biliary injury.