PRONLONGED HYPOTHERMIC MACHINE PERFUSION PRESERVES HEPATOCELLULAR FUNCTION BUT POTENTIATES ENDOTHELIAL CELL DYSFUNCTION IN RAT LIVERS

Cryopreservation of Whole Rat Livers by Vitrification and Nanowarming

Liver cryopreservation has the potential to enable indefinite organ banking. This study investigated vitrification-the ice-free cryopreservation of livers in a glass-like state-as a promising alternative to conventional cryopreservation, which uniformly fails due to damage from ice formation or cracking. Our unique "nanowarming" technology, which involves perfusing biospecimens with cryoprotective agents (CPAs) and silica-coated iron oxide nanoparticles (sIONPs) and then, after vitrification, exciting the nanoparticles via radiofrequency waves, enables rewarming of vitrified specimens fast enough to avoid ice formation and uniformly enough to prevent cracking from thermal stresses, thereby addressing the two main failures of conventional cryopreservation. This study demonstrates the ability to load rat livers with both CPA and sIONPs by vascular perfusion, cool them rapidly to an ice-free vitrified state, and rapidly and homogenously rewarm them. While there was some elevation of liver enzymes (Alanine Aminotransferase) and impaired indocyanine green (ICG) excretion, the nanowarmed livers were viable, maintained normal tissue architecture, had preserved vascular endothelium, and demonstrated hepatocyte and organ-level function, including production of bile and hepatocyte uptake of ICG during normothermic reperfusion. These findings suggest that cryopreservation of whole livers via vitrification and nanowarming has the potential to achieve organ banking for transplant and other biomedical applications.

A Review of Machine Perfusion Strategies in Liver Transplantation

The acceptance of liver transplantation as the standard of care for end-stage liver diseases has led to a critical shortage of donor allografts. To expand the donor organ pool, many countries have liberalized the donor criteria including extended criteria donors and donation after circulatory death. These marginal livers are at a higher risk of injury when they are preserved using the standard static cold storage (SCS) preservation techniques. In recent years, research has focused on optimizing organ preservation techniques to protect these marginal livers. Machine perfusion (MP) of the expanded donor liver has witnessed considerable advancements in the last decade. Research has showed MP strategies to confer significant advantages over the SCS techniques, such as longer preservation times, viability assessment and the potential to recondition high risk allografts prior to implantation. In this review article, we address the topic of MP in liver allograft preservation, with emphasis on current trends in clinical application. We discuss the relevant clinical trials related to the techniques of hypothermic MP, normothermic MP, hypothermic oxygenated MP, and controlled oxygenated rewarming. We also discuss the potential applications of ex vivo therapeutics which may be relevant in the future to further optimize the allograft prior to transplantation.

Abdominal Organ Preservation Solutions in the Age of Machine Perfusion

The past decade has been the foreground for a radical revolution in the field of preservation in abdominal organ transplantation. Perfusion has increasingly replaced static cold storage as the preferred and even gold standard preservation method for marginal-quality organs. Perfusion is dynamic and offers several advantages in comparison with static cold storage. These include the ability to provide a continuous supply of new metabolic substrates, clear metabolic waste products, and perform some degree of organ viability assessment before actual transplantation in the recipient. At the same time, the ongoing importance of static cold storage cannot be overlooked, in particular when it comes to logistical and technical convenience and cost, not to mention the fact that it continues to work well for the majority of transplant allografts. The present review article provides an overview of the fundamental concepts of organ preservation, providing a brief history of static cold preservation and description of the principles behind and basic components of cold preservation solutions. An evaluation of current evidence supporting the use of different preservation solutions in abdominal organ transplantation is provided. As well, the range of solutions used for machine perfusion of abdominal organs is described, as are variations in their compositions related to changing metabolic needs paralleling the raising of the temperature of the perfusate from hypothermic to normothermic range. Finally, appraisal of new preservation solutions that are on the horizon is provided.

Hypothermic oxygenated perfusion with defatting cocktail further improves steatotic liver grafts in a transplantation rat model

In this study, we evaluated the restoring and defatting effect of hypothermic oxygenated perfusion (HOPE) on severe steatotic liver grafts with a defatting cocktail (DF) in a rat model. Severe (≥60%) hepatic macrosteatosis was induced by a high-fat diet (HFD) for 6 weeks, after which the rats were randomly divided into four following groups: Control group, with lean livers being preserved in static cold storage (SCS) at 0°C-4°C for 45 minutes; SCS group, with a steatotic liver graft (SLG) being preserved in SCS at 0°C-4°C for 4 hours; HOPE group, where SLG was perfused with 3-hours HOPE followed by 1-hours SCS; and HOPE + DF group, HOPE with the addition of DF. Graft function after orthotopic liver transplantation was assessed in terms of mitochondrial function (adenosine triphosphate [ATP], Glycogen), endoplasmic reticulum stress (PPY, GRP78, CHOP, and ATF-6), cell apoptosis (Tunel assay, Caspase-3), inflammatory level (HMGB1, TLR4, IL-1β, IL-6. TNF-α, Factor V), and posttransplantation survival. HOPE protected steatotic liver grafts from microcirculation disturbance and endoplasmic reticulum stress and then promoted ATP and glycogen synthesis that improved mitochondrial function. Meanwhile, under conditions of ischemia-reperfusion injury, it prevented nuclear injury and endothelial damage by suppressing the release of an inflammatory mediator. The high efficacy of HOPE was enhanced after the addition of the DF. DF agents cannot promote the lipid decomposition of the steatotic liver graft at 0°C-4°C, but they can further improve steatotic liver and postoperative survival compared to the HOPE. The defatted steatotic liver grafts can be safely used in rat orthotopic liver transplantation.

Extended hypothermic oxygenated machine perfusion enables ex situ preservation of porcine livers for up to 24 hours

Background & Aims

End-ischemic hypothermic oxygenated machine perfusion (HOPE) of the donor liver for 1-2 h mitigates ischemia-reperfusion injury during subsequent liver transplantation. Extended preservation time may be preferred to facilitate difficult recipient hepatectomy or to optimize logistics. We therefore investigated whether end-ischemic dual HOPE (DHOPE) could extend preservation time for up to 24 h using a porcine liver reperfusion model.

Methods

Following 30 min warm ischemia, porcine livers were subjected to 2 h static cold storage (SCS), followed by 2 h, 6 h, or 24 h DHOPE (n = 6 per group). Subsequent normothermic reperfusion was performed for 4 h using autologous blood. Two livers preserved by 24 h SCS served as additional controls. A proof of principle confirmation was carried out in 2 discarded human livers subjected to extended DHOPE. Hepatocellular and cholangiocyte injury and function were assessed. Oxidative stress levels and histology were compared between groups.

Results

Perfusion flows remained stable during DHOPE, regardless of duration. After normothermic reperfusion, livers perfused for 24 h by DHOPE had similar lactate clearance, blood pH, glucose, and alanine aminotransferase levels, and biliary pH, bicarbonate, and LDH levels, as livers perfused for 2 h and 6 h. Levels of malondialdehyde and high-mobility group box 1 in serum and liver parenchyma were similar for all groups. Histological analysis of bile ducts and liver parenchyma revealed no differences between the groups. Extended DHOPE in discarded human livers preserved hepatocellular and cholangiocyte function and histology after reperfusion. In contrast, livers preserved by 24 h SCS were non-functioning.

Conclusion

Extended end-ischemic DHOPE enabled successful preservation of porcine and discarded human donor livers for up to 24 h. Extended DHOPE enables safe extension of preservation time, which may facilitate allocation and transplantation from a logistical perspective, and further expand the donor pool.

Lay summary

It has been suggested that preserving liver grafts with a technique called (dual) hypothermic oxygenated machine perfusion ([D]HOPE) leads to better outcomes after transplantation than if livers are stored on ice, especially if an organ is of lesser quality. In this study, we showed that DHOPE could be used to preserve liver grafts for up to 24 h. This extended procedure could be used globally to facilitate transplantation and expand the donor pool.

Graft glycocalyx degradation in human liver transplantation

OBJECTIVE

Ischaemia/reperfusion-injury degrades endothelial glycocalyx. Graft glycocalyx degradation was studied in human liver transplantation.

METHODS

To assess changes within the graft, blood was drawn from portal and hepatic veins in addition to systemic samples in 10 patients. Plasma syndecan-1, heparan sulfate and chondroitin sulfate, were measured with enzyme-linked immunosorbent assay.

RESULTS

During reperfusion, syndecan-1 levels were higher in graft caval effluent [3118 (934-6141) ng/ml, P = 0.005] than in portal venous blood [101 (75-121) ng/ml], indicating syndecan-1 release from the graft. Concomitantly, heparan sulfate levels were lower in graft caval effluent [96 (32-129) ng/ml, P = 0.037] than in portal venous blood [112 (98-128) ng/ml], indicating heparan sulfate uptake within the graft. Chondroitin sulfate levels were equal in portal and hepatic venous blood. After reperfusion arterial syndecan-1 levels increased 17-fold (P < 0.001) and heparan sulfate decreased to a third (P < 0.001) towards the end of surgery.

CONCLUSION

Syndecan-1 washout from the liver indicates extensive glycocalyx degradation within the graft during reperfusion. Surprisingly, heparan sulfate was taken up by the graft during reperfusion. Corroborating previous experimental reports, this suggests that endogenous heparan sulfate might be utilized within the graft in the repair of damaged glycocalyx.

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.

Machine perfusion and long-term kidney transplant recipient outcomes across allograft risk strata

Background

The use of machine perfusion (MP) in kidney transplantation lowers delayed graft function (DGF) and improves 1-year graft survival in some, but not all, grafts. These associations have not been explored in grafts stratified by the Kidney Donor Profile index (KDPI).

Methods

We analyzed 78 207 deceased-donor recipients using the Scientific Registry of Transplant Recipients data from 2006 to 2013. The cohort was stratified using the standard criteria donor/expanded criteria donor (ECD)/donation after cardiac death (DCD)/donation after brain death (DBD) classification and the KDPI scores. In each subgroup, MP use was compared with cold storage.

Results

The overall DGF rate was 25.4% and MP use was associated with significantly lower DGF in all but the ECD-DCD donor subgroup. Using the donor source classification, the use of MP did not decrease death-censored graft failure (DCGF), except in the ECD-DCD subgroup from 0 to 1 year {adjusted hazard ratio [aHR] 0.56 [95% confidence interval (CI) 0.32-0.98]}. In the ECD-DBD subgroup, higher DCGF from 1 to 5 years was noted [aHR 1.15 (95% CI 1.01-1.31)]. Also, MP did not lower all-cause graft failure except in the ECD-DCD subgroup from 0 to 1 year [aHR = 0.59 (95% CI 0.38-0.91)]. Using the KDPI classification, MP did not lower DCGF or all-cause graft failure, but in the ≤70 subgroup, higher DCGF [aHR 1.16 (95% CI 1.05-1.27)] and higher all-cause graft failure [aHR 1.10 (95% CI 1.02-1.18)] was noted. Lastly, MP was not associated with mortality in any subgroup.

Conclusions

Overall, MP did not lower DCGF. Neither classification better risk-stratified kidneys that have superior graft survival with MP. We question their widespread use in all allografts as an ideal approach to organ preservation.

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.

Oxygenated hypothermic machine perfusion after static cold storage improves endothelial function of extended criteria donor livers

BACKGROUND

Lack of oxygen and biomechanical stimulation during static cold storage (SCS) of donor livers compromises endothelial cell function. We investigated the effect of end-ischemic oxygenated hypothermic machine perfusion (HMP) on endothelial cell function of extended criteria donor (ECD) livers.

METHODS

Eighteen livers, declined for transplantation, were transported to our center using static cold storage (SCS). After SCS, 6 livers underwent two hours of HMP, and subsequent normothermic machine perfusion (NMP) to assess viability. Twelve control livers underwent NMP immediately after SCS. mRNA expression of transcription factor Krüppel-like-factor 2 (KLF2), endothelial nitric oxide synthase (eNOS), and thrombomodulin (TM) was quantified by RT-PCR. Endothelial cell function and injury were assessed by nitric oxide (NO) production and release of TM into the perfusate.

RESULTS

In HMP livers, mRNA expression of KLF2 (p = 0.043), eNOS (p = 0.028), and TM (p = 0.028) increased significantly during NMP. In parallel, NO levels increased during NMP in HMP livers but not in controls. At the end of NMP cumulative TM release was significantly lower HMP livers, compared to controls (p = 0.028).

CONCLUSION

A short period of two hours oxygenated HMP restores endothelial cell viability after SCS and subsequent normothermic reoxygenation of ECD livers.

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.

Subnormothermic Machine Perfusion Preservation With Rewarming for Donation After Cardiac Death Liver Grafts in Pigs

BACKGROUND

The use of grafts from donors after cardiac death (DCD) would greatly contribute to the expansion of the donor organ pool. However, the implementation of such a strategy requires the development of novel preservation methods to recover from changes owing to warm ischemia. The aim of this study was to evaluate the effectiveness of subnormothermic machine perfusion (MP) preservation with rewarming for porcine DCD liver grafts for transplantation.

METHODS

Porcine livers were perfused with newly developed MP system. The livers were perfused for 4 hours with modified University of Wisconsin gluconate solution. Group 1 grafts were preserved with no warm ischemia time (WIT) and hypothermic MP (HMP) for 4 hours. Group 2 grafts were preserved with WIT 60 minutes and HMP for 4 hours. Group 3 grafts were preserved with WIT 60 minutes and rewarming up to 25°C by MP (RMP) for 4 hours.

RESULTS

The aspartate aminotransferase and lactate dehydrogenase in the effluent maintained at lower level in group 3 compared with group 2. However, tissue ATP levels did not recover in groups 2 and 3. Histologically, the fatty degenerate and swelling of the hepatocyte was slightly seen in all groups. The normal structure of the hepatocellular cords, the bile duct and the sinusoid endothelium were preserved in all groups.

CONCLUSIONS

Potentially, subnormothermic preservation with rewarming is expected to help the recovery of function for DCD liver grafts.

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.

Protective Mechanisms of Hypothermia in Liver Surgery and Transplantation

Hepatic ischemia/reperfusion (I/R) injury is a side effect of major liver surgery that often cannot be avoided. Prolonged periods of ischemia put a metabolic strain on hepatocytes and limit the tolerable ischemia and preservation times during liver resection and transplantation, respectively. In both surgical settings, temporarily lowering the metabolic demand of the organ by reducing organ temperature effectively counteracts the negative consequences of an ischemic insult. Despite its routine use, the application of liver cooling is predicated on an incomplete understanding of the underlying protective mechanisms, which has limited a uniform and widespread implementation of liver-cooling techniques. This review therefore addresses how hypothermia-induced hypometabolism modulates hepatocyte metabolism during ischemia and thereby reduces hepatic I/R injury. The mechanisms underlying hypothermia-mediated reduction in energy expenditure during ischemia and the attenuation of mitochondrial production of reactive oxygen species during early reperfusion are described. It is further addressed how hypothermia suppresses the sterile hepatic I/R immune response and preserves the metabolic functionality of hepatocytes. Lastly, a summary of the clinical status quo of the use of liver cooling for liver resection and transplantation is provided.

Normothermic extracorporeal liver perfusion for donation after cardiac death (DCD) livers

BACKGROUND

The susceptibility of extended criteria livers to ischemia reperfusion injury is a major obstacle in organ cold preservation. Normothermic extracorporeal liver perfusion (NELP) has been investigated to reduce ischemic damage, restore physiologic function, and assess viability of the liver prior to transplant. The goal of this study is to compare physiological parameters of livers maintained continuously on NELP to those preserved in cold solution.

METHODS

Livers from 9 female landrace pigs were subjected to either 20 minutes (W20-NELP), 40 minutes (W40-NELP), or 60 minutes (W60-NELP) of warm ischemia followed by 6 hours of NELP followed by a 2-hour NELP evaluation phase. This was compared with 3 livers subjected to 40 minutes of warm ischemia time followed by 6 hours of cold storage (W40-Cold) and a 2-hour NELP evaluation phase. Groups were compared with the 2-way analysis of variance test.

RESULTS

NELP stabilized transaminases accompanied by significant improvement in bile production and decline in lactate and INR values in all W-NELP groups. Histologic analysis demonstrated significant improvement from 0 hour (mild-to-moderate sinusoidal dilation and zone 3 necrosis) to the end of the NELP run (minimal necrosis and mild IRI). Comparison of W40-NELP and W40-Cold revealed greater bile production and oxygen extraction ratio in W40-NELP. In contrast, markers of cellular and functional damage were increased in the W40-Cold group.

CONCLUSION

NELP improves metabolic and functional parameters of livers with either short or extended warm ischemia times compared with livers subjected to comparable cold ischemia times.

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.

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.

Organomatics and organometrics: Novel platforms for long-term whole-organ culture

Organ culture systems are instrumental as experimental whole-organ models of physiology and disease, as well as preservation modalities facilitating organ replacement therapies such as transplantation. Nevertheless, a coordinated system of machine perfusion components and integrated regulatory control has yet to be fully developed to achieve long-term maintenance of organ function ex vivo. Here we outline current strategies for organ culture, or organomatics, and how these systems can be regulated by means of computational algorithms, or organometrics, to achieve the organ culture platforms anticipated in modern-day biomedicine.

Challenges in machine perfusion preservation for liver grafts from donation after circulatory death

Donation after circulatory death (DCD) is a promising solution to the critical shortage of donor graft tissue. Maintaining organ viability after donation until transplantation is essential for optimal graft function and survival. To date, static cold storage is the most widely used form of preservation in clinical practice. However, ischemic damage present in DCD grafts jeopardizes organ viability during cold storage, and whether static cold storage is the most effective method to prevent deterioration of organ quality in the increasing numbers of organs from DCD is unknown. Here we describe the historical background of DCD liver grafts and a new preservation method for experimental and clinical transplantation. To prevent ischemia-reperfusion injury in DCD liver grafts, a hypothermic machine perfusion (HMP) technique has recently been developed and may be superior to static cold preservation. We present evidence supporting the need for improving liver perfusion performance and discuss how doing so will benefit liver transplantation recipients.

Controlled oxygenated rewarming of cold stored liver grafts by thermally graduated machine perfusion prior to reperfusion

The quality of cold-stored livers declines with the extension of ischemic time, increasing the risk of primary dys or nonfunction. A new concept to rescue preserved marginal liver grafts by gentle oxygenated warming-up prior to blood reperfusion was investigated. Porcine livers were preserved by cold storage (CS) in modified HTK-solution for 18 h. Some grafts were subsequently subjected to 90 min of controlled oxygenated rewarming (COR) by machine perfusion with gradual increase of perfusate temperature up to 20°C or simple oxygenated machine perfusion in hypothermia (HMP) or subnormothermia (SNP). Graft viability was assessed thereafter by 4 h of normothermic blood reperfusion ex vivo. Endischemic tissue energetics were significantly improved by COR or SNP and to a notably lesser extent by HMP. COR significantly reduced cellular enzyme loss, gene expression and perfusate activities of TNF-alpha, radical mediated lipid peroxidation (LPO) and increase of portal vascular perfusion resistance upon reperfusion, while HMP or SNP were less protective. Only COR resulted in significantly more bile production than after CS. Histological injury score and caspase 3-activation were significantly lower after COR than after CS. Oxygenated rewarming prior to reperfusion seems to be a promising technique to improve subsequent organ recovery upon reperfusion of long preserved liver grafts.

Extracorporeal machine liver perfusion: are we warming up?

PURPOSE OF REVIEW

Recently, considerable focus has been placed on the use of hypothermic perfusion ex vivo in abdominal organ transplant. Herein, we discuss the appropriateness of using this modality to preserve livers, in particular those of suboptimal quality, and whether perfusing at warmer temperatures in this context may, in fact, be better.

RECENT FINDINGS

Hypothermic perfusion (0-4°C) appears to improve the hepatocellular energy charge and achieve adequate results in normal livers. However, its use for the preservation of suboptimal grafts may lead to significant endothelial and Kupffer cell injury that is incompatible with survival. Studies on the perfusion of suboptimal livers at higher temperatures, on the contrary, indicate that results improve as temperatures approach 37°C, provided that the oxygen supply during perfusion is adequate.

SUMMARY

Normothermic perfusion provides oxygen and other metabolic substrates under physiological conditions; in liver transplant, it appears to be the best option to improve the viability of suboptimal organs.

Preservation methods for kidney and liver

With the successful testing of the immunosuppressive effects of cyclosporine in transplant patients in 1978, the field of organ transplants began an exponential growth. With that, the field of organ preservation became increasingly important as the need to increase preservation time and improve graft function became paramount. However, for every patient that receives a transplanted organ, there are four more on the waiting list. In addition, a patient dies from the lack of a transplant almost every 1(1/2) hour. To alleviate this donor crisis, there is a need to expand the donor pool to marginal donor organs. The main reason these organs are underutilized is because the current method of static preservation, simple cold storage, is ineffective. This article will provide a general review of the methods of preservation including simple cold storage, hypothermic machine perfusion, normothermic machine perfusion, and oxygen persufflation. In addition, the article will provide a review of how these dynamic preservation methods have improved the recovery and preservation of marginal donor organs including Donation after Cardiac Death and Fatty livers.

Donation after cardio-circulatory death liver transplantation

The renewed interest in donation after cardio-circulatory death (DCD) started in the 1990s following the limited success of the transplant community to expand the donation after brain-death (DBD) organ supply and following the request of potential DCD families. Since then, DCD organ procurement and transplantation activities have rapidly expanded, particularly for non-vital organs, like kidneys. In liver transplantation (LT), DCD donors are a valuable organ source that helps to decrease the mortality rate on the waiting lists and to increase the availability of organs for transplantation despite a higher risk of early graft dysfunction, more frequent vascular and ischemia-type biliary lesions, higher rates of re-listing and re-transplantation and lower graft survival, which are obviously due to the inevitable warm ischemia occurring during the declaration of death and organ retrieval process. Experimental strategies intervening in both donors and recipients at different phases of the transplantation process have focused on the attenuation of ischemia-reperfusion injury and already gained encouraging results, and some of them have found their way from pre-clinical success into clinical reality. The future of DCD-LT is promising. Concerted efforts should concentrate on the identification of suitable donors (probably Maastricht category III DCD donors), better donor and recipient matching (high risk donors to low risk recipients), use of advanced organ preservation techniques (oxygenated hypothermic machine perfusion, normothermic machine perfusion, venous systemic oxygen persufflation), and pharmacological modulation (probably a multi-factorial biologic modulation strategy) so that DCD liver allografts could be safely utilized and attain equivalent results as DBD-LT.

A basic consideration for porcine liver preservation using a novel continuous machine perfusion device

INTRODUCTION

The aims of this study were to compare extracellular and intracellular-type University of Wisconsin (UW) solutions for liver grafts and to assess oxygenation in this perfusion system.

MATERIALS AND METHODS

The organ preservation system consisted of 3 circulating systems for the portal vein, hepatic artery, and maintenance of the perfusion solution. The portal vein or hepatic artery system had a roller pump, a flow meter, and a pressure sensor. In this study, we perfused livers with UW or extracellular type UW-gluconate at 4°C-6°C for 4 hours. The flow rates at the entrance were 0.5 mL/min/g liver in the portal vein and 0.2 mL/min/liver in the hepatic artery. Orthotopic liver transplantation was performed in pigs: group 1-a, grafts procured after acute hemorrhagic shock were preserved by a solution without O(2); group 1-b, grafts were preserved with O(2); group 2-a, grafts were perfused using intracellular type solution (UW); and group 2-b, grafts were perfused using extracellular-type solution (UW-gluconate).

RESULTS

Effluent aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) levels in group 1-b were lower than those in group 1-a. Survival rates in group 2-a and group 2-b were 1/4 and 3/3, respectively. Effluent AST and LDH levels in the perfusate of group 2-b were lower than group 2-a. Histological study revealed necrosis of hepatocytes and sinusoidal congestion in group 2-a.

CONCLUSION

A beneficial effect of extracellular-type solution with oxygenation in a novel continuous machine preservation system yielded well-preserved liver graft function.

A fitness index for transplantation of machine-perfused cadaveric rat livers

Background

The 110,000 patients currently on the transplant waiting list reflect the critical shortage of viable donor organs. However, a large pool of unused organs, from donors after cardiac death (DCD) that are disqualified because of extensive ischemic injury, may prove transplantable after machine perfusion treatment, fundamentally impacting the availability of treatment for end-stage organ failure. Machine perfusion is an ex-vivo organ preservation and treatment procedure that has the capacity to quantitatively evaluate and resuscitate cadaveric organs for transplantation.

Methods

To diagnose whether an organ was fresh or ischemic, an initial assessment of liver quality was conducted via dynamic discriminant analysis. Subsequently, to determine whether the organs were sufficiently viable for successful implantation, fitness indices for transplantation were calculated based on squared prediction errors (SPE) for fresh and ischemic livers.

Results

With just three perfusate metabolites, glucose, urea and lactate, the developed MPLSDA model distinguished livers as fresh or ischemic with 90% specificity. The SPE analyses revealed that fresh livers with SPE_F < 10.03 and WI livers with SPE_WI < 3.92 yield successful transplantation with 95% specificity.

Conclusions

The statistical methods used here can discriminate between fresh and ischemic livers based on simple metabolic indicators measured during perfusion. The result is a predictive fitness index for transplantation of rat livers procured after cardiac death. The translational implications of this study are that any donor organ procured from controlled, but most especially from uncontrolled cardiac death donors, will be objectively assessed and its recovery monitored over time, minimizing the critical loss of otherwise viable organs.

A simplified subnormothermic machine perfusion system restores ischemically damaged liver grafts in a rat model of orthotopic liver transplantation

Background

Liver donor shortages stimulate the development of strategies that incorporate damaged organs into the donor pool. Herein we present a simplified machine perfusion system without the need for oxygen carriers or temperature control, which we validated in a model of orthotopic liver transplantation.

Methods

Rat livers were procured and subnormothermically perfused with supplemented Williams E medium for 3 hours, then transplanted into healthy recipients (Fresh-SNMP group). Outcome was compared with static cold stored organs (UW-Control group). In addition, a rat liver model of donation after cardiac death was adapted using a 60-minute warm ischemic period, after which the grafts were either transplanted directly (WI group) or subnormothermically perfused and transplanted (WI-SNMP group).

Results

One-month survival was 100% in the Fresh-SNMP and UW-Control groups, 83.3% in the WI-SNMP group and 0% in the WI group. Clinical parameters, postoperative blood work and histology did not differ significantly between survivors.

Conclusion

This work demonstrates for the first time in an orthotopic transplantation model that ischemically damaged livers can be regenerated effectively using practical subnormothermic machine perfusion without oxygen carriers.

An innovative hyperbaric hypothermic machine perfusion protects the liver from experimental preservation injury

Purpose. Hypothermic machine perfusion systems seem more effective than the current static storage to prevent cold ischemic liver injury. Thus, we test an innovative hyperbaric hypothermic machine perfusion (HHMP), which combines hyperbaric oxygenation of the preservation solution and continuous perfusion of the graft. Methods. Rat livers were preserved with Celsior solution according to 4 different modalities: normobaric static preservation; hyperbaric static preservation at 2 atmosphere absolute (ATA); normobaric dynamic preservation, with continuous perfusion; hyperbaric dynamic preservation, with continuous perfusion at 2 ATA. After 24 h cold preservation, we assessed different parameters. Results. Compared to baseline, livers preserved with the current static storage showed severe ultrastructural damage, glycogen depletion and an increased oxidative stress. Normobaric perfused livers showed improved hepatocyte ultrastructure and ameliorated glycogen stores, but they still suffered a significant oxidative damage. The addition of hyperbaric oxygen produces an extra benefit by improving oxidative injury and by inducing endothelial NO synthase (eNOS) gene expression. Conclusions. Preservation by means of the present innovative HHMP reduced the liver injury occurring after the current static cold storage by lowering glycogen depletion and oxidative damage. Interestingly, only the use of hyperbaric oxygen was associated to a blunted oxidative stress and an increased eNOS gene expression.

Energetic recovery in porcine grafts by minimally invasive liver oxygenation

BACKGROUND

Gaseous insufflation of oxygen via the venous vascular system has proven to be an effective tool for preventing anoxic tissue injury after extended time periods of ischemic liver preservation. Most experimental studies so far have been undertaken in rat models and include a series of pinpricks into postsinusoidal venules as an outlet for the insufflated gas. Here, we describe a simplified technique for minimally invasive liver oxygenation in porcine grafts, representing a hassle-free access to organ oxygenation without vascular lesions.

METHODS

We retrieved livers from Landrace pigs and cold-stored them in histidine-tryptophan-ketoglutarate solution. Subsequent to 18 h preservation, we treated some livers for an additional 2 h with gaseous oxygen, insufflated via silicone tubing inserted into the suprahepatic caval vein. Gas pressure was limited to 18 mm Hg. We occluded the infrahepatic caval vein with a bulldog clamp. Gas bubbles left the graft via the portal vein. We assessed liver integrity by energetic tissue status and by controlled in vitro reperfusion with autologous blood.

RESULTS

Magnetic resonance imaging demonstrated homogeneous gas distribution in the persufflated tissue without major shunting. Biochemical analyses revealed effective and homogeneous restoration of energetic homeostasis in the ischemic graft before reperfusion. Sinusoidal endothelial clearance of hyaluronic acid was significantly improved upon reperfusion, as was hepatic arterial flow. Parenchymal enzyme loss was concordantly mitigated after minimally invasive liver oxygenation.

CONCLUSIONS

Our results indicate that gaseous oxygen persufflation of the porcine liver is possible without tissue trauma, and significantly enhances post-preservation recovery of the graft.

Superior preservation of DCD livers with continuous normothermic perfusion

OBJECTIVE

Unexpected donation after cardiac death (DCD) donors suffer cardiac arrest suddenly and are maintained with normothermic extracorporeal membrane oxygenation (NECMO) while consent for donation is obtained. The objective of this study was to determine whether ex vivo normothermic machine perfusion (NMP) improves upon the benefits of NECMO in a large-animal model of unexpected DCD liver transplant.

METHODS

Donor pigs underwent 90-minute cardiac arrest and were divided in to 3 groups. In the first, livers were preserved immediately with cold storage (CS, n = 6). In the other 2 groups, donors underwent 60-minute NECMO followed by CS (NECMO+CS, n = 6) or NMP (NECMO+NMP, n = 6). After 4-hour preservation, livers were transplanted into recipient pigs.

RESULTS

Five-day survival was 0 in CS, 83% in NECMO+CS, and 100% in NECMO+NMP. After reperfusion, injury, and inflammatory markers rose significantly among CS grafts, all of which developed primary nonfunction. Sixty minutes of NECMO, however, resulted in only 1 death, whereas NECMO followed by NMP led to no deaths and significant improvements in injury, inflammation, and synthetic function in comparison to NECMO and CS.

CONCLUSION

Although 60 minutes recuperative NECMO is better than CS alone, NMP improves further on NECMO and may have a role in preserving DCD livers in the clinical setting.

A metabolic index of ischemic injury for perfusion-recovery of cadaveric rat livers

With over 110,000 patients waiting for organ transplantation, the current crisis in organ transplantation is based on a lack of donors after brain-death (DBD). A very large alternative pool of donor organs that remain untapped are the donors after cardiac death (DCD), recovered after cardiac activity has ceased and therefore sustained some ischemic injury. Machine perfusion has been proposed as a novel modality of organ preservation and treatment to render such cadaveric organs, and in particular livers, transplantable. Two key issues that remain unaddressed are how to assess whether a DCD liver is damaged beyond repair, and whether machine perfusion has rendered an injured organ sufficiently viable for transplantation. In this work, we present a metabolic analysis of the transient responses of cadaveric rat livers during normothermic machine perfusion (NMP), and develop an index of ischemia that enables evaluation of the organ ischemic injury level. Further, we perform a discriminant analysis to construct a classification algorithm with >0.98 specificity to identify whether a given perfused liver is ischemic or fresh, in effect a precursor for an index of transplantability and a basis for the use of statistical process control measures for automated feedback control of treatment of ischemic injury in DCD livers. The analyses yield an index based on squared prediction error (SPE) as log(SPE) >1.35 indicating ischemia. The differences between metabolic functions of fresh and ischemic livers during perfusion are outlined and the metabolites that varied significantly for ischemic livers are identified as ornithine, arginine, albumin and tyrosine.

Hypothermic reconditioning by gaseous oxygen improves survival after liver transplantation in the pig

The quality of cold-stored livers declines with the extension of ischemic time and the risk of primary dys- or nonfunction increases. Here, we provide in vivo evidence for the efficacy of the previously developed end-ischemic gaseous oxygen persufflation technique to resuscitate liver grafts after extended storage times. Porcine livers were recovered according to standard multiorgan procurement protocol. Control livers were cold stored in histidine tryptophan ketoglutarate solution for 10 h (cold storage [CS]; n = 6) at 4°C. In the treatment group (n = 6), livers were additionally subjected to hypothermic reconditioning (HR) by gaseous oxygen persufflation via the caval vein for 2 h before transplantation. Viability was assessed by orthotopic liver transplantation and 1 week follow-up. HR significantly improved pretransplant energy charge and initial graft function after transplantation. One week survival after CS was 0% whereas five of six pigs (83%) survived in the HR group. At that time, coagulation parameters were in the normal range and histological analysis disclosed healthy liver tissue with normal trabecular architecture in the treated grafts. Molecular analyses identify the prevention of ischemia-induced decline of cellular autophagy and mitigation of innate immune machinery (high-mobility group protein B1, interferon-β) as operative mechanisms among the protective effects provided by HR.

Hypothermic machine perfusion ameliorates ischemia-reperfusion injury in rat lungs from non-heart-beating donors

BACKGROUND

The use of non-heart-beating donors (NHBD) has come into practice to resolve the shortage of donor lungs. This study investigated whether hypothermic machine perfusion (HMP) can improve the quality of NHBD lungs.

METHODS

An uncontrolled NHBD model was achieved in male Lewis rats. Ninety minutes after cardiac arrest, HMP was performed for 60 min at 6°C to 10°C. The first study investigated the physiological lung functions during HMP and the lung tissue energy levels before and after HMP. The second study divided the rats into three groups (n=6 each): no ischemia group; 90-min warm ischemia+60-min HMP+120-min static cold storage (SCS) (HMP group); and 90-min warm ischemia+180-min SCS group. All lungs were reperfused for 60 min at 37°C. Lung functions were evaluated at given timings throughout the experiments. Oxidative damage during reperfusion was evaluated immunohistochemically with a monoclonal antibody against 8-hydroxy-2'-deoxyguanosine.

RESULTS

The first study revealed that lung functions were stable during HMP. Lung tissue energy levels decreased during warm ischemia but were significantly increased by HMP (P<0.05). The second study confirmed that HMP significantly decreased pulmonary vascular resistance, increased pulmonary compliance, and improved pulmonary oxygenation. The ratio of 8-hydroxy-2'-deoxyguanosine positive cells to total cells significantly increased in the SCS group (P<0.01).

CONCLUSIONS

Short-term HMP improved lung tissue energy levels that decreased during warm ischemia and ameliorated ischemia-reperfusion injury with decreased production of reactive oxygen species.

Protective effects of hypothermic ex vivo perfusion on ischemia/reperfusion injury and transplant outcomes

Hypothermic machine preservation (HMP) has been used in renal transplantation since the late 1960s with recent robust prospective, multicenter data showing lower rates of delayed graft function and improved graft survival. Although now clearly beneficial for renal transplantation, extrarenal machine perfusion has remained predominantly in preclinical investigations. Pancreatic HMP has drawn little clinical interest because HMP has been suggested to cause graft edema and congestion, which is associated with early venous thrombosis and graft failure. Early investigation showed no benefit of HMP in whole-organ pancreas transplant. One report did show that HMP increases islet cell yield after isolation. Preclinical work in liver HMP has been promising. Short- and long-term HMP has been shown to improve graft viability and reduce preservation injury, even in animal models of steatotic and donation after cardiac death. The first clinical study of liver HMP using a centrifugal dual perfusion technique showed excellent results with lower hepatocellular injury markers and no adverse perfusion-related outcomes. In addition, a dramatic attenuation of proinflammatory cytokine expression was observed. Further studies of liver HMP are planned with focus on developing a reproducible and standard protocol that will allow the widespread availability of this technology. Future research and clinical trials of novel organ preservation techniques, solutions, and interventions are likely to bring about developments that will allow further reduction of preservation-related ischemia/reperfusion injury and improved outcomes and allow safer utilization of the precious and limited resource of donor organs.

Hepatocyte viability and adenosine triphosphate content decrease linearly over time during conventional cold storage of rat liver grafts

INTRODUCTION

The gold standard in organ preservation is static cold storage (SCS) using University of Wisconsin solution (UW). Although it is well-known that there is a finite limit to SCS preservation, and that there is a correlation between the adenosine triphosphate (ATP) levels and organ function post-preservation, a quantitative relationship has not been established, which is important in understanding the fundamental limitations to preservation, minimizing cold ischemic injury, and hence maximizing use of the donor organ pool.

AIM

This study determines the time limits of cellular viability and metabolic function during SCS, and characterizes the relationship between cellular viability and energetic state using clinically relevant techniques in organ preservation.

METHODS

Rat livers were procured and stored using conventional storage in UW solution at 4 °C. Viability was assessed by determining the amount of viable hepatocytes and intracellular ATP content after 0, 24, 48, 72, and 120 hours of storage.

RESULTS

Numbers of viable hepatocytes that were isolated from these livers decreased steadily during SCS. After 5 days, viable hepatocytes decreased from 25.95 × 10(6) to 0.87 × 10(6) cells/gram tissue. Intracellular ATP content decreased from 9.63 to 0.93 moles/g tissue. Statistical analysis of variance established a linear relation for both parameters as a function of time (P < .05).

CONCLUSION

The linear correlation between hepatocyte viability, ATP content, and storage time suggests a shared physiological foundation. These findings confirm ATP as direct predictor for organ quality in the context of liver preservation, which will aid quantitative assessment of donor organs for various applications.

Subnormothermic machine perfusion at both 20°C and 30°C recovers ischemic rat livers for successful transplantation

BACKGROUND

Utilizing livers from donors after cardiac death could significantly expand the donor pool. We have previously shown that normothermic (37°C) extracorporeal liver perfusion significantly improves transplantation outcomes of ischemic rat livers. Here we investigate whether recovery of ischemic livers is possible using sub-normothermic machine perfusion at 20°C and 30°C.

METHODS

Livers from male Lewis rats were divided into five groups after 1 h of warm ischemia (WI): (1) WI only, (2) 5 h of static cold storage (SCS), or 5 h of MP at (3) 20°C, (4) 30°C, and (5) 37°C. Long-term graft performance was evaluated for 28 d post-transplantation. Acute graft performance was evaluated during a 2 h normothermic sanguineous reperfusion ex vivo. Fresh livers with 5 h of SCS were positive transplant controls while fresh livers were positive reperfusion controls.

RESULTS

Following machine perfusion (MP) (Groups 3, 4, and 5), ischemically damaged livers could be orthotopically transplanted into syngeneic recipients with 100% survival (N ≥ 4) after 4 wk. On the other hand, animals from WI only, or WI + SCS groups all died within 24 h of transplantation. Fresh livers preserved using SCS had the highest alanine aminotransferase (ALT), aspartate aminotransferase (AST), and the lowest bile production during reperfusion, while at 28 d post-transplantation, livers preserved at 20°C and 30°C had the highest total bilirubin values.

CONCLUSIONS

MP at both 20°C and 30°C eliminated temperature control in perfusion systems and recovered ischemically damaged rat livers. Postoperatively, low transaminases suggest a beneficial effect of sub-normothermic perfusion, while rising total bilirubin levels suggest inadequate prevention of ischemia- or hypothermia-induced biliary damage.

Machine perfusion of the liver: past, present and future

PURPOSE OF REVIEW

This review considers the potential of machine perfusion to preserve livers for clinical transplantation, including steatotic or ischaemically damaged grafts and aims to go over the most significant achievements in liver machine perfusion over the last year. To reach acceptance in liver preservation, machine perfusion will need to improve outcomes compared with simple cold storage (SCS), provide objective measures of graft viability, and resuscitate less-than-ideal grafts before transplantation.

RECENT FINDINGS

Current machine perfusion protocols comprise both hypothermic (HMP) and normothermic (NMP) approaches. HMP increases energy stores compared to SCS, and NMP shows additional resuscitative potential. Dutkowski transplanted ischaemically damaged pig livers after HMP following SCS, which avoided graft failure observed after SCS alone. Guarrera performed 20 clinical transplants after 4-7 h HMP. Friend has performed porcine transplantations after NMP of 4-20 h and univocally demonstrated the significant resuscitative effects on ischaemically damaged grafts otherwise destined to fail. Whereas NMP promises resuscitative effects, it demands challenging, near-physiologic conditions. Subnormothermic perfusion is being tested as a promising medium in between.

SUMMARY

Despite recent substantial improvements, liver preservation by machine perfusion remains limited and in contrast to the global revival of kidney machine perfusion. However, liver machine perfusion may be close to returning to clinical practice if it has not already done so. History shows that superiority alone does not guarantee immediate clinical use. Further clear-cut benefits of machine perfusion such as viability assessment will have to be accompanied by usability and human factors, and innovative and improved perfusion solutions applied in novel perfusion protocols.

A comparison of hypothermic machine perfusion versus static cold storage in an experimental model of renal ischemia reperfusion injury

INTRODUCTION

There is increasing support for the use of hypothermic machine perfusion (HMP) in an attempt to reduce preservation injury. However, experimental evidence is needed to further examine the effects of HMP on renal ischemia reperfusion injury.

METHODS

Porcine kidneys were subjected to 10 min of warm ischemia followed by 18 hr of static cold storage with hyperosomolar citrate (HOC), histidine-tryptophan-ketoglutarate (HTK), or University of Wisconsin (UW) solutions or 18 hr HMP with Kidney Perfusion Solution using the Lifeport perfusion system. Renal function, oxidative damage, and morphology were assessed during 3 hr of reperfusion with autologous blood using an isolated organ perfusion system.

RESULTS

During reperfusion, intrarenal resistance was significantly lower in the HMP group compared with HOC and UW (area under the curve; HMP 3.8+/-1.7, HOC 9.1+/-4.3, UW 7.7+/-2.2, HTK 5.6+/-1.9 mm Hg/min; P=0.006), and creatinine clearance was significantly higher compared with the UW group (area under the curve creatinine clearance; HMP 9.8+/-7.3, HOC 2.2+/-1.7, UW 1.8+/-1.0, HTK 2.1+/-1.8 mL/min/100 g; P=0.004). Tubular function was significantly improved in the HMP group (P<0.05); however, levels of lipid peroxidation were significantly higher (P=0.005).

CONCLUSION

HMP demonstrated a reduced level of preservation injury compared with the static techniques resulting in improved renal and tubular function and less tubular cell inflammation during reperfusion.

One hour hypothermic oxygenated perfusion (HOPE) protects nonviable liver allografts donated after cardiac death

OBJECTIVES

To test, in a large animal model, the efficacy of machine perfusion to rescue livers after prolonged ischemic injury.

BACKGROUND

Our group previously showed in various rodent models the benefit of endischemic hypothermic oxygenated perfusion (HOPE) in protecting liver injury from donation after cardiac death (DCD). Convincing results are needed in large animal models before application in human.

METHODS

A new model of DCD liver transplantation in large pigs was developed. Pig livers (1300 +/- 210 g each) were harvested 60 minutes after induction of cardiac death (respirator withdrawal). In situ flush and organ procurement were initiated without heparin pretreatment. Then, livers were preserved for 7 hours in cold Celsior (DCD-group) prior to orthotopic transplantation (OLT). Some livers were treated by 1 hour HOPE prior to implantation (HOPE-group). In a first step, animals were kept under anesthesia for 6 hours after orthotopic transplantation. Endpoints included serum (AST) and tissue (ATP, glutathione) markers of injury, bile flow, and histology. In a second step, survival experiments were performed.

RESULTS

Livers from the DCD group displayed diffuse necrosis of hepatocytes, increased adhesion of platelets, high AST release, absence of bile flow, depletion of glutathione, and ATP. In contrast, livers treated with HOPE showed dramatic reduction of necrosis, platelet adhesion, while bile flow, ATP recovery and glutathione were improved. Importantly, untreated DCD livers caused graft failure and death of all recipients within 6 hours of reperfusion, whereas HOPE treated DCD livers remained hemodynamically stable.

CONCLUSIONS

This is the first study in a reliable large animal transplant model demonstrating the efficacy of a simple cold oxygenated machine perfusion system to rescue, otherwise lethal, ischemic injured DCD liver grafts.

Liver transplantation: Issues for the next 20 years

The growing numbers of potential transplant recipients on waiting lists is increasingly disproportionate to the supply of cadaveric donor organs. The hope for the next 20 years is that supply will satisfy demand. This requires both a reduction in indications for the procedure and an increase in the transplants performed. A multi-pronged approach is needed to increase cadaveric organ donation, generating enthusiasm for donation among both the general public and hospital staff. Accurate assessment of marginal grafts with stringent criteria known to predict graft function will diminish wastage of organs. Methods of rehabilitating marginal grafts during extracorporeal perfusion will increase organ availability. Supply of non-heart beating donors can be greatly expanded and protocols developed with ethical consent to optimize their initial function despite warm ischemia. Splitting livers that fulfill selection criteria, thus providing for two recipients, should be universally applied with acceptable incentives to those units who do not directly benefit. A proportion of recipients, though not those transplanted for autoimmune disease, will be spared the side-effects of immunosuppression thanks to immune tolerance. Protocols for close monitoring of those patients for rejection during treatment withdrawal must be carefully observed. In addition to gene therapy, it is highly likely that hepatocyte transplantation will replace orthotopic grafting in patients without cirrhosis, especially for inherited metabolic diseases. It is much more difficult to envisage that heterologous stem cell transplantation or xenotransplantation will have clinical impact in the next 20 years, although research in those areas has obvious long-term potential.

Amiodarone pretreatment of organ donors exerts anti-oxidative protection but induces excretory dysfunction in liver preservation and reperfusion

The continuous shortage of organs necessitates the use of marginal organs from donors with various diseases, including arrhythmia-associated cardiac failure. One of the most frequently used anti-arrhythmic drugs is amiodarone (AM), which is given in particular in emergency situations. Apart from its anti-arrhythmic actions, AM provides anti-oxidative properties in cardiomyocytes. Thus, we were interested in whether AM donor pretreatment affects the organ quality and function of livers procured for preservation and transplantation. Donor rats were pretreated with AM (5 mg/kg of body weight) 10 minutes before flush-out of the liver with a cold (4 degrees C) histidine-tryptophan-ketoglutarate solution (n = 8). Livers were then stored for 24 hours at 4 degrees C before ex situ reperfusion with a 37 degrees C Krebs-Henseleit solution for 60 minutes in a nonrecirculating system. At the end of reperfusion, tissue samples were taken for histology and Western blot analysis. Animals with vehicle only (0.9% NaCl) served as ischemia/reperfusion controls (n = 8). Additionally, livers of untreated animals (n = 8) not subjected to 24 hours of cold ischemia served as sham controls. AM pretreatment effectively attenuated lipid peroxidation, stress protein expression, and apoptotic cell death. This was indicated by an AM-mediated reduction of malondialdehyde, heme oxygenase-1, and caspase-3 activation. However, AM treatment also induced mitochondrial damage and hepatocellular excretory dysfunction, as indicated by a significantly increased glutamate dehydrogenase concentration in the effluate and decreased bile production. In conclusion, AM donor pretreatment exerts anti-oxidative actions in liver preservation and reperfusion. However, these protective AM actions are counteracted by an induction of mitochondrial damage and hepatocellular dysfunction. Accordingly, AM pretreatment of donors for anti-arrhythmic therapy should be performed with caution.

Recovery of warm ischemic rat liver grafts by normothermic extracorporeal perfusion

Liver transplantation is currently the only established treatment of end-stage liver disease, but it is limited by a severe shortage of viable donor livers. Donors after cardiac death (DCD) are an untapped source that could significantly increase the pool of available livers. Preservation of these DCD livers by conventional static cold storage (SCS) is associated with an unacceptable risk of primary nonfunction and delayed graft failure. Normothermic extracorporeal liver perfusion (NELP) has been suggested as an improvement over SCS. Livers recovered from male Lewis rats were subjected to 1 hr of warm ischemia and preserved with 5 hr of SCS or NELP, and transplanted into syngeneic recipients. As additional controls, non-ischemic livers preserved with 6 hr of SCS or NELP and unpreserved ischemic livers were transplanted. After NELP, ischemically damaged livers could be orthotopically transplanted into syngeneic recipients with 92% survival (n=13) after 4 weeks, which was comparable with control animals that received healthy livers preserved by SCS (n=9) or NELP (n=11) for 6 hr. On the other hand, animals from ischemia/SCS control group all died within 12 hr postoperatively (n=6). Similarly, animals that received ischemic livers without preservation all died within 24 hr after transplantation (n=6). These results suggest that NELP has the potential to reclaim warm ischemic livers that would not be transplantable otherwise. The rat model in this study is a useful platform to further optimize NELP as a method of recovery and preservation of DCD livers.