Improved rat liver preservation by hypothermic continuous machine perfusion using polysol, a new, enriched preservation solution

Ergothioneine: new functional factor in fermented foods

Ergothioneine (EGT) is a high-value natural sulfur-containing amino acid and has been shown to possess extremely potent antioxidant and cytoprotective activities. At present, EGT has been widely used in food, functional food, cosmetics, medicine, and other industries, but its low yield is still an urgent problem to overcome. This review briefly introduced the biological activities and functions of EGT, and expounded its specific applications in food, functional food, cosmetic, and medical industries, introduced and compared the main production methods of EGT and respective biosynthetic pathways in different microorganisms. Furthermore, the use of genetic and metabolic engineering methods to improve EGT production was discussed. In addition, the incorporation of some food-derived EGT-producing strains into fermentation process will allow the EGT to act as a new functional factor in the fermented foods.

The role of normothermic machine perfusion (NMP) in the preservation of ex-vivo liver before transplantation: A review

The discrepancy between the number of patients awaiting liver transplantation and the number of available donors has become a key issue in the transplant setting. There is a limited access to liver transplantation, as a result, it is increasingly dependent on the use of extended criteria donors (ECD) to increase the organ donor pool and address rising demand. However, there are still many unknown risks associated with the use of ECD, among which preservation before liver transplantation is important in determining whether patients would experience complications survive after liver transplantation. In contrast to traditional static cold preservation of donor livers, normothermic machine perfusion (NMP) may reduce preservation injury, improve graft viability, and potentially ex vivo assessment of graft viability before transplantation. Data seem to suggest that NMP can enhance the preservation of liver transplantation to some extent and improve the early outcome after transplantation. In this review, we provided an overview of NMP and its application in ex vivo liver preservation and pre-transplantation, and we summarized the data from current clinical trials of normothermic liver perfusion.

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.

Modeling energy depletion in rat livers using Nash equilibrium metabolic pathway analysis

The current gold standard of Static Cold Storage (SCS), which is static cold storage on ice (about + 4 °C) in a specialized media such as the University of Wisconsin solution (UW), limits storage to few hours for vascular and metabolically active tissues such as the liver and the heart. The liver is arguably the pinnacle of metabolism in human body and therefore metabolic pathway analysis immediately becomes very relevant. In this article, a Nash Equilibrium (NE) approach, which is a first principles approach, is used to model and simulate the static cold storage and warm ischemia of a proposed model of liver cells. Simulations of energy depletion in the liver in static cold storage measured by ATP content and energy charge are presented along with comparisons to experimental data. In addition, conversion of Nash Equilibrium iterations to time are described along with an uncertainty analysis for the parameters in the model. Results in this work show that the Nash Equilibrium approach provides a good match to experimental data for energy depletion and that the uncertainty in model parameters is very small with percent variances less than 0.1%.

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.

[Modern concepts for the dynamic preservation of the liver and kidneys in the context of transplantation]

The increasing demand on donor grafts has forced experimental research on transplantation medicine to develop more efficient organ preservation strategies. Simple cold storage of grafts rarely offers optimal conditions for extended criteria donor organs. Hypothermic, oxygenated machine perfusion (HMP) is a classical method of dynamic organ preservation, which enables the provision of oxygen and nutrients to the tissue and provides a metabolic recovery of the graft prior to implantation. A more modern approach is normothermic machine perfusion (NMP), which instead simulates physiological conditions and enables an ex vivo evaluation and treatment of organ grafts. However, studies have found that a preceding period of cold storage significantly mitigates the functional advantage of NMP. A strategy to circumvent this phenomenon is controlled oxygenated rewarming (COR). The cold-stored graft is slowly and gradually rewarmed to subnormothermic or normothermic temperatures, providing a gentle adaption of energy metabolism and counteracting events of rewarming injury.

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

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

Evaluation of a Novel System for Hypothermic Oxygenated Pulsatile Perfusion Preservation

Background

Recently, a novel innovative machine perfusion (MP) system for hypothermic oxygenated pulsatile perfusion called the Airdrive (AD) has been developed. The aim of the study was to evaluate the biological safety of the AD system for perfusion preservation of kidney grafts in a porcine autotransplantation model using the low-viscosity perfusion solution Polysol (PS) in comparison with cold storage (CS) using PS or the University of Wisconsin solution (UW). In addition, we evaluated real-time microcirculation parameters. At sacrifice, grafts were retrieved for histological analysis and immunohistochemistry

Methods

After assessment of the microcirculation, left kidneys were retrieved. Following the washout, kidneys were preserved for 20 hr using AD-PS, CS-PS or CS-UW. Thereafter, contralateral kidneys were removed followed by heterotopic autotransplantation of the preserved graft. Seven days after transplantation animals were sacrificed with retrieval of the grafts for histological analysis. Renal function, renal microcirculation and tissue injury including the proliferative response of tubular epithelial cells (TECs) were compared.

Results

Preservation using AD-PS or CS-PS resulted in higher microcirculatory flow compared with CS-UW. Improved recovery of renal function was seen in the AD-PS and CS-PS groups compared with CS-UW. Structural integrity was better preserved using AD-PS compared with both CS groups. Proliferative response of TECs was higher in CS-UW preserved grafts compared to grafts preserved using AD-PS.

Conclusion

This study demonstrates the biological safety of the AD system in a porcine autotransplantation model. Also, the microcirculation was better preserved and less morphological injury was observed after 20 hr MP compared with CS.

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.

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

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

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.

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.

Emerging concepts in liver graft preservation

The urgent need to expand the donor pool in order to attend to the growing demand for liver transplantation has obliged physicians to consider the use of suboptimal liver grafts and also to redefine the preservation strategies. This review examines the different methods of liver graft preservation, focusing on the latest advances in both static cold storage and machine perfusion (MP). The new strategies for static cold storage are mainly designed to increase the fatty liver graft preservation via the supplementation of commercial organ preservation solutions with additives. In this paper we stress the importance of carrying out effective graft washout after static cold preservation, and present a detailed discussion of the future perspectives for dynamic graft preservation using MP at different temperatures (hypothermia at 4 °C, normothermia at 37 °C and subnormothermia at 20 °C-25 °C). Finally, we highlight some emerging applications of regenerative medicine in liver graft preservation. In conclusion, this review discusses the "state of the art" and future perspectives in static and dynamic liver graft preservation in order to improve graft viability.

Impact of machine perfusion preservation of liver grafts from donation after cardiac death

Because of the critical shortage of deceased donor grafts, using a donation after cardiac death (DCD) donor is an important resource. However, the ischemic damage of those DCD grafts jeopardizes organ viability during cold storage. Maintaining organ viability after donation until transplantation is important for optimal graft function and survival. This review describes the effective preservation in transplantation for DCD livers. Concepts and development of machine perfusion for DCD liver grafts to reduce ischemia/reperfusion injury are discussed. Despite the fact that hypothermic machine perfusion might be superior to static cold preservation, DCD livers are exposed to hypothermia-induced damage. Recently, some groups introduced the beneficial effects of normothermic or subnormothermic machine perfusion in DCD liver preservation and transplantation.

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

As the rate of medically suitable donors remains relatively static worldwide, clinicians have looked to novel methods to meet the ever-growing demand of the liver transplant waiting lists worldwide. Accordingly, the transplant community has explored many strategies to offset this deficit. Advances in technology that target the ex vivo "preservation" period may help increase the donor pool by augmenting the utilization and improving the outcomes of marginal livers. Novel ex vivo techniques such as hypothermic, normothermic, and subnormothermic machine perfusion may be useful to "resuscitate" marginal organs by reducing ischemia/reperfusion injury. Moreover, other preservation techniques such as oxygen persufflation are explored as they may also have a role in improving function of "marginal" liver allografts. Currently, marginal livers are frequently discarded or can relegate the patient to early allograft dysfunction and primary non-function. Bench to bedside advances are rapidly emerging and hold promise for expanding liver transplantation access and improving outcomes.

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.

First clinical experience with polysol solution: pilot study in living kidney transplantation

In this study, we assessed the safety of the new organ preservation solution polysol solution in the clinical setting of living kidney transplantation. We conducted a prospective pilot study in nine adult donor-recipient couples using polysol solution for washout and cold storage of kidney grafts. Adverse reactions possibly related to the use of polysol solution as well as renal function at 1, 6, and 12 months after transplantation were monitored. All living kidney transplantation performed in adults in our center within 2002 to 2008 using the University of Winconsin solution served as controls (n = 190). The use of polysol solution was associated with a higher acute rejection rate compared to University of Wisconsin solution at all time points. Also, antibody-mediated rejection occurred more frequently in the polysol group. Renal function at all time points was also comparable between the groups. This pilot study in living kidney transplantation is the first clinical study on the use of polysol solution. Although the study was not powered on the endpoint rejection, we observed a high number of acute rejection and antibody-mediated rejection episodes in recipients of polysol solution preserved grafts as compared to University of Wisconsin solution controls. As a consequence the study was terminated prematurely.

Desferrioxamine in warm reperfusion media decreases liver injury aggravated by cold storage

AIM: To evaluate whether desferrioxamine decreases ischemia and perfusion injury aggravated by cold storage (CS) in a rat liver perfusion model.

METHODS: Isolated rat livers were kept in CS in University of Wisconsin Solution for 20 h at 4 °C, then exposed to 25 min of warm ischemia (WI) at 37 °C followed by 2 h of warm perfusion (WP) at 37 °C with oxygenated (95% oxygen and 5% carbon dioxide) Krebs-Henseleit buffer. Desferrioxamine (DFO), an iron chelator, was added at different stages of storage, ischemia and perfusion: in CS only, in WI only, in WP only, in WI and perfusion, or in all stages. Effluent samples were collected after CS and after WI. Perfusate samples and bile were collected every 30 min (0, 0.5, 1, 1.5 and 2 h) during liver perfusion. Cellular injury was assessed by the determination of lactate dehydrogenase (LDH) and aspartate aminotransferase (AST) in the effluent and perfusate samples. Total iron was analysed in the perfusate samples. After WP, the liver was collected for the determination of liver swelling (wet to dry ratio) and liver morphological examination (hematoxylin and eosin staining).

RESULTS: Increased CS time caused increased liver dysfunction during WP. After 2 h of WP, liver injury was indicated by increased release of AST (0.5 h CS: 9.4 ± 2.2 U/g liver vs 20 h CS: 45.9 ± 10.8 U/g liver, P < 0.05) and LDH (0.5 h CS: 59 ± 14 U/g liver vs 20 h CS: 297 ± 71 U/g liver, P < 0.05). There was an associated increase in iron release into the perfusate (0.5 h CS: 0.11 ± 0.03 μmoL/g liver vs 20 h CS: 0.58 ± 0.10 μmoL/g liver, P < 0.05) and reduction in bile flow (0.5 h CS: 194 ± 12 μL/g vs 20 h CS: 71 ± 8 μL/g liver, P < 0.05). When DFO was added during WI and WP following 20 h of CS, release of iron into the perfusate was decreased (DFO absent 0.58 ± 0.10 μmoL/g liver vs DFO present 0.31 ± 0.06 μmoL/g liver, P < 0.05), and liver function substantially improved with decreased release of AST (DFO absent 45.9 ± 10.8 U/g liver vs DFO present 8.1 ± 0.9 U/g liver, P < 0.05) and LDH (DFO absent 297 ± 71 U/g liver vs DFO present 56 ± 7 U/g liver, P < 0.05), and increased bile flow (DFO absent 71 ± 8 μL/g liver vs DFO present 237 ± 36 μL/g liver, P < 0.05). DFO was also shown to improve liver morphology after WP. Cellular injury (the release of LDH and AST) was significantly reduced with the addition of DFO in CS medium but to a lesser extent compared to the addition of DFO in WP or WI and perfusion. There was no effect on liver swelling or bile flow when DFO was only added to the CS medium.

CONCLUSION: DFO added during WI and perfusion decreased liver perfusion injury aggravated by extended CS.

Improved hypothermic short-term storage of isolated mouse islets by adding serum to preservation solutions

Preserving isolated islets at low temperature appears attractive because it can keep islet quantity comparable to freshly isolated islets. In this study, we evaluated the effect of serum as an additive to preservation solutions on islet quality after short-term hypothermic storage. Isolated mouse islets were preserved at 4°C in University of Wisconsin solution (UW) alone, UW with serum, M-Kyoto solution (MK) alone or MK with serum. We then assessed islet quantity, morphology, viability and function in vitro as well as in vivo. Islet quantity after storage in all four solutions was well maintained for up to 120 h. However, islets functioned for different duration; glucose-stimulated insulin release assay revealed that the duration was 72 h when islets were stored in UW with serum and MK with serum, but only 24 h in UW alone, and the islet function disappeared immediately in MK alone. Viability assay confirmed that more than 70% islet cells survived for up to 48 h when islets are preserved in UW with serum and MK with serum, but the viability decreased rapidly in UW alone and MK alone. In in vivo bioassays using 48-h preserved isogeneic islets, all recipient mice restored normal blood glucose concentrations by transplants preserved in UW with serum or MK with serum, whereas 33.3% recipients and no recipient restored diabetes by transplants preserved in UW alone and in MK alone respectively. Adding serum to both UW and MK improves their capability to store isolated islets by maintaining islet functional viability.

Troubleshooting and improving the mouse and rat isolated perfused liver preparation

INTRODUCTION

Isolated perfused liver (IPL) model is not only widely performed in rats but is also used in mouse liver, although a detailed description of this procedure is absent. A comparison of the different techniques used on rats and mice will be discussed in this article association with a detailed description of the surgical and technical aspects needed to obtain and maintain the integrity of the livers during the organ isolation and perfusion.

METHODS

The surgical procedures, the IPL set-up, and the evaluation of hepatic function and damage will be described in relation to both rats and mice. In particular, the heparin dosage and administration, the portal vein cannulation avoiding portal leakage, the use of suprahepatic caval vein output, and the insertion of a cannula for bile collection will be reported. For the settings, the perfusion circuit, the perfusion solution, the temperature and the flow rate will be described, with particular regard to the balance between perfusion pressure and oxygen delivery. The monitoring of liver integrity by measuring oxygen concentration and calculating oxygen delivery rate and oxygen uptake rate, and recommendations for the collection of perfusate and bile samples will be considered. Accurate pH measurement with normalization, and the perfusion portal pressure assay by a calibrated water manometer will be also reported.

RESULTS AND DISCUSSION

This work analyzes the parameters crucial to performing a correct IPL both in rat and mouse, comparing our experience with the equivalent practice from other laboratories. An updated example of IPL applications in liver toxicology and pharmacology, physiology and pathophysiology, and liver graft preservation will be briefly presented, underlining how this technique provides essential information allowing a more accurate planning of the in vivo studies.

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.

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 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.

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.

Improved preservation and microcirculation with POLYSOL after partial liver transplantation in rats

BACKGROUND

Due to the severe shortage of deceased donors, demand for living-donor liver transplantation (LDLT) has increased worldwide. Here, we compared POLYSOL, a recently developed low-viscosity preservation solution, and histidine-tryptophan-ketoglutarate (HTK) for cold storage of partial liver graft in this study.

METHODS

Partial liver transplantations with 30% of the native liver were performed in Lewis rats. The graft livers were flushed with either HTK or POLYSOL (n = 25, respectively) and stored in the respective solution for 3 h at 5°C. Graft function was evaluated regarding ischemia-reperfusion injury and regeneration at 1, 3, 24, and 168 h after reperfusion.

RESULTS

POLYSOL preservation resulted in improvement of portal venous flow (HTK versus POLYSOL; mean ± SEM: 16.8 ± 2.2 versus 21.6 ± 2.1 mL/min; P = 0.005), microcirculation (383 ± 63 versus 532 ± 64 Flux; P = 0.045), ALT (310.2 ± 56.1 versus 181.8 ± 17.0 IU/L; P = 0.0262), LDH (4052.4 ± 764.4 versus 2494.1 ± 410.0 IU/L; P = 0.0215), total bilirubin (21.6 ± 14.2 versus 4.0 ± 0.6 IU/L; P = 0.0236), malondialdehyde (100.0 ± 4.3 versus 69.2 ± 4.0 nmol/mL; P = 0.0015), as well histologic findings at 24 h. Liver regeneration was improved in POLYSOL with regards to liver weight (4.0 ± 0.2 versus 4.3 ± 0.3 g; P = 0.038) and Ki-67 labeling index (9.67 ± 2.17 versus 1.10 ± 0.14%; P < 0.0001) at 24 h with higher up-regulation of portal VEGF (31.55 ± 5.78 versus 91.94 ± 9.27 pg/mL; P = 0.0052).

CONCLUSIONS

This study showed that POLYSOL improves microcirculation and thus improves the preservation quality of partial liver transplantation.

Inhibition of inducible nitric oxide synthase prevents graft injury after transplantation of livers from rats after cardiac death

This study investigated the roles of inducible nitric oxide synthase (iNOS) in the failure of rat liver grafts from cardiac death donors (GCDD). Livers were explanted after 30-minute aorta clamping and implanted after 4-hour storage in University of Wisconsin solution. The iNOS expression increased slightly in grafts from non-cardiac death donors (GNCDD) but markedly in GCDD. Serum nitrite and nitrate and hepatic 3-nitrotyrosine adducts, indicators of NO and peroxynitrite production, respectively, were substantially higher after transplantation of GCDD than GNCDD. Production of reactive nitrogen species (RNS) was largely blocked by 1400W (N-[1-naphthyl]ethylenediamine dihydrochloride; 5 μM), a specific iNOS inhibitor. Alanine aminotransferase release, bilirubin, necrosis, and apoptosis were 6.4-fold, 6.5-fold, 2.3-fold, and 2.7-fold higher, respectively, after transplantation of GCDD than GNCDD. The inhibitor 1400W effectively blocked these alterations and also increased survival of GCDD to 80% from 33%. Increased RNS production and failure of GCDD were associated with activation of c-Jun-N-terminal kinase (JNK), an effect that was blocked by inhibition of iNOS. Inhibition of JNK also improved the outcome after transplantation of GCDD. Together, the data indicate that iNOS increases substantially in GCDD, leading to RNS overproduction, JNK activation, and more severe graft injury. Inhibitors of iNOS are suggested as effective therapies to improve the outcome after transplantation of GCDD.

Biological modulation of liver ischemia-reperfusion injury

PURPOSE OF REVIEW

This review gives a broad overview of the key factors of ischemic injury to the liver and presents the current modifications of preservation solutions and the few strategies of biological modulation in clinical use today.

RECENT FINDINGS

Protective effects in human-liver transplantation were shown by methylprednisolone treatment in decreased donors, and by inhalation of a nontoxic dose of nitric oxide in recipients. In addition, recent results showed rescue of pig livers, donated after cardiac death by application of a cocktail of substances addressing several previously identified mechanisms of ischemia-reperfusion injury.

SUMMARY

The future of a pharmacological approach attenuating or preventing ischemia-reperfusion injury lies in a combination of drugs acting simultaneously on several steps of the injury cascades. Applying these substances during flush, before, and during implantation appears as an attractive strategy to protect extended criteria liver grafts.

Machine perfusion or cold storage in organ transplantation: indication, mechanisms, and future perspectives

Most organs are currently preserved by cold storage (CS) prior to transplantation. However, as more so called marginal donor organs are utilized, machine perfusion has regained clinical interest. Recent studies have demonstrated advantages of pulsatile perfusion over CS preservation for kidney transplantation. However, it remains unclear whether there is a significant benefit of one preservation method over the other in general, or, whether the utilization of particular preservation approaches needs to be linked to organ characteristics. Proposed protective mechanisms of pulsatile perfusion remain largely obscure. It can be speculated that pulsatile perfusion may not only provide nutrition and facilitate the elimination of toxins but also trigger protective mechanisms leading to the amelioration of innate immune responses. Those aspects may be of particular relevance when utilizing grafts with suboptimal quality which may have an increased vulnerability to ischemia/reperfusion injury and compromised repair mechanisms. This review aims to enunciate the principles of organ perfusion and preservation as they relate to indication, aspects of organ protection and to highlight future developments.

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.

Hypothermic Liver Machine Perfusion With EKPS-1 Solution vs Aqix RS-I Solution: In Vivo Feasibility Study in a Pig Transplantation Model

OBJECTIVE

Hypothermic machine perfusion (HMP) is superior to simple cold storage for kidney preservation. We previous observed in a porcine liver transplantation model increased tumor necrosis factor-alpha (TNF-alpha) production eventually leading to poor recipient survival after HMP using standard kidney perfusion solution (KPS-1) compared with simple cold storage. We compared two solutions for HMP preservation of the liver: enriched KPS-1 (EKPS-1) and Aqix RS-I.

METHODS

Pig livers were obtained after cold flushing with histidine-tryptophan-ketoglutarate solution. Subsequently, the livers were subjected to dual-vessel perfusion with two preservation solutions: EKPS-1 (n = 6) and Aqix RS-I (n = 3). After HMP preservation and transplantation, graft and recipient survival, hepatocellular damage (aspartate aminotransferase concentration), TNF-alpha production, and endothelial cell damage (hyaluronic acid clearance) were recorded.

RESULTS

No primary graft nonfunction was observed. Recipient survival at postoperative day 3 was similar in both groups (33%). Aspartate aminotransferase concentration measured in serum samples after reperfusion was similar in both groups. After reperfusion, TNF-alpha concentration was higher and hyaluronic acid clearance was lower in the EKPS-1 group vs the Aqix RS-I group at 60, 120, and 180 minutes (all P < .05).

CONCLUSION

Hypothermic machine perfusion provided adequate longer term graft survival. After reperfusion, TNF-alpha production seems to be reduced, and endothelial cell dysfunction remains pronounced with Aqix RS-1 solution compared with EKPS-1 solution.

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.

Liver preservation: is there anything new yet?

PURPOSE OF REVIEW

To provide an update on recent developments in liver preservation through a comprehensive review of the literature.

RECENT FINDINGS

Comparisons of the available preservation solutions for liver transplantation based on recent trials suggest clinical equivalence. The debate continues regarding risk of biliary-tract complications. Development of new preservation solutions and agents that target specific mechanisms of steatotic and donors after cardiac death pathophysiology is showing promise in a variety of preclinical and clinical studies. Early clinical results of ischemic preconditioning are conflicting and so there is the need for additional clinical studies. The most important developments have been in the machine perfusion of the liver. New portable perfusion systems have shown promise in preclinical studies and may allow rapid evolution of clinical liver machine perfusion. The first human clinical trial is well underway with results showing safety and improved efficacy of preservation of transplanted human liver allografts.

SUMMARY

Liver preservation is in a period of rapid advance. In the future, a multifaceted liver-preservation strategy that integrates pharmacologic agents and hypothermic machine perfusion is likely to minimize organ injury and maximize patient outcomes. An ongoing challenge is to increase the number of innovations entering prospective and randomized clinical trials.

Artificial circulation of the liver: machine perfusion as a preservation method in liver transplantation

Due to the sharp increase in liver transplant candidates and the subsequent shortage of suitable donor livers, an extension of the current donor criteria is necessary. Simple cold storage, the current standard in organ preservation has proven to be insufficient to preserve extended criteria donor livers. Therefore a renewed interest grew toward alternative methods for liver preservation, such as hypothermic machine perfusion and normothermic machine perfusion. These "new" preservation methods were primarily assessed in rat models, and only a few clinically relevant large animal models have been described so far. This review will elaborate on these alternative preservation methods.

Perspectives in organ preservation

Maintaining organ viability after donation until transplantation is critically important for optimal graft function and survival. To date, static cold storage is the most widely used form of preservation in every day clinical practice. Although simple and effective, it is questionable whether this method is able to prevent deterioration of organ quality in the present era with increasing numbers of organs retrieved from older, more marginal, and even non-heart-beating donors. This review describes principles involved in effective preservation and focuses on some basic components and methods of abdominal organ preservation in clinical and experimental transplantation. Concepts and developments to reduce ischemia related injury are discussed, including hypothermic machine perfusion. Despite the fact that hypothermic machine perfusion might be superior to static cold storage preservation, organs are still exposed to hypothermia induced damage. Therefore, recently some groups have pointed at the beneficial effects of normothermic machine perfusion as a new perspective in organ preservation and transplantation.

Preservation of steatotic livers: a comparison between cold storage and machine perfusion preservation

Liver grafts are frequently discarded due to steatosis. Steatotic livers can be classified as suboptimal and deteriorate rapidly during hypothermic static preservation, often resulting in graft nonfunction. Hypothermic machine perfusion (MP) has been introduced for preservation of donor livers instead of cold storage (CS), resulting in superior preservation outcomes. The aim of this study was to compare CS and MP for preservation of the steatotic donor rat liver. Liver steatosis was induced in male Wistar rats by a choline-methionine-deficient diet. After 24 hours hypothermic CS using the University of Wisconsin solution (UW) or MP using UW-Gluconate (UW-G), liver damage (liver enzymes, perfusate flow, and hyaluronic acid clearance) and liver function (bile production, ammonia clearance, urea production, oxygen consumption, adenosine triphosphate [ATP] levels) were assessed in an isolated perfused rat liver model. Furthermore, liver biopsies were visualized by hematoxylin and eosin staining. Animals developed 30 to 60% steatosis. Livers preserved by CS sustained significantly more damage as compared to MP. Bile production, ammonia clearance, urea production, oxygen consumption, and ATP levels were significantly higher after MP as compared to CS. These results were confirmed by histology. In conclusion, MP improves preservation results of the steatotic rat liver, as compared to CS.

Hypothermic perfusion preservation: the future of organ preservation revisited?

Hypothermic perfusion preservation (HPP) was an integral step in the development of early clinical transplantation programmes, and considerable progress was made in understanding the basic principles underlying the technique. In subsequent years, the development of better preservation solutions for cold hypoxic storage, along with pragmatic choices made on grounds of costs and logistics, saw a fall in the application of HPP. More recently, the acute shortage of suitable organ donors and the inevitable pressure to use organs from sub-optimal (or expanded criteria) donors, has forced a re-evaluation of HPP, and the development of a new generation of HPP machines and associated perfusion solutions. This review sets out the historical development of HPP across the range of organs in which the method was originally investigated, describes the biological benefits and drawbacks associated with HPP, and sets out the most recent literature on the topic (including comments on the interest in use of higher temperatures in organ perfusion).

Impact of polysol, a newly developed preservation solution, on cold storage of steatotic rat livers

Chronic shortage of donor organs has led to acceptance of steatotic livers as grafts, although there is a higher risk of primary graft dysfunction. We herein report the beneficial impact of Polysol, a newly developed preservation solution, on cold storage of steatotic rat livers. Dietary hepatic steatosis was induced in Wistar rats by 2-day fasting and subsequent 3-day re-feeding with a fat-free, carbohydrate-rich diet. Fatty livers were retrieved, flushed and then stored at 4 degrees C for 24 hours with either HTK or Polysol. Functional integrity of the grafts was evaluated by isolated reperfusion with oxygenated Krebs-Henseleit buffer at 37 degrees C for 45 minutes in both groups. Polysol preservation resulted in significant reductions of not only parenchymal (AST (IU/L); 6728+/-824 in HTK vs. 3107+/-718 in Polysol; P < 0.001) but also mitochondrial (GLDH (IU/L); 3189+/-773 vs. 1282+/-365; P < 0.01) enzyme release throughout reperfusion. Moreover, PVP (16.9+/-2.7 vs. 7.8+/-1.5 mmHg; P < 0.05), hepatic O2 consumption (0.291+/-0.047 vs. 1.056+/-0.053 micromol/g liver/min; P < 0.001), tissue ATP content (0.695+/-0.086 vs. 1.340+/-0.157 micromol/g dry-liver; P < 0.005), bile production (0.79+/-0.11 vs. 4.08+/-0.66 microL/g liver/45-min; P < 0.001), malondialdehyde into the perfusate (1.922+/-0.198 vs. 0.573+/-0.094 nmol/L; P < 0.0001) and wet/dry-weight ratio of the liver tissues (5.20+/-0.31 vs. 3.85+/-0.15; P < 0.005) were all better preserved by Polysol. In line with these benefits, electron microscopy revealed that Polysol preservation substantially suppressed deleterious mitochondrial alterations in steatotic livers. In conclusion, cold storage using Polysol resulted in significantly better integrity and function of steatotic livers. Polysol, therefore, may be a new alternative especially for "marginal" organs.

Novel short-term hypothermic oxygenated perfusion (HOPE) system prevents injury in rat liver graft from non-heart beating donor

OBJECTIVE

To assess a machine perfusion system in rescuing liver grafts from non-heart-beating donors (NHBD).

SUMMARY BACKGROUND DATA

The introduction of extracorporeal liver perfusion systems in the clinical routine depends on feasibility. Conceivably, perfusion could be performed during recipient preparation. We investigated whether a novel rat liver machine perfusion applied after in situ ischemia and cold storage can rescue NHBD liver grafts.

METHODS

We induced cardiac arrest in male Brown Norway rats by phrenotomy and ligation of the subcardial aorta. We studied 2 experimental groups: 45 minutes of warm in situ ischemia + 5 hours cold storage versus 45 minutes of warm in situ ischemia + 5 hours cold storage followed by 1 hour hypothermic oxygenated extracorporeal perfusion (HOPE). In both groups, livers were reperfused in a closed sanguineous isolated liver perfusion device for 3 hours at 37 degrees C. To test the benefit of HOPE on survival, we performed orthotopic liver transplantation in both experimental groups.

RESULTS

After cold storage and reperfusion, NHBD livers showed necrosis of hepatocytes, increased release of AST, and decreased bile flow. HOPE improved NHBD livers significantly with a reduction of necrosis, less AST release, and increased bile flow. ATP was severely depleted in cold-stored NHBD livers but restored in livers treated by HOPE. After orthotopic liver transplantation, grafts treated by HOPE demonstrated a significant extension on animal survival.

CONCLUSIONS

We demonstrate a beneficial effect of HOPE by preventing reperfusion injury in a clinically relevant NHBD model.

Wash-out of the non-heart-beating donor liver: a matter of flush solution and temperature?

BACKGROUND AND AIMS

Ischemically damaged donor livers are prone to graft non-function. This can in part be explained by a suboptimal wash-out during procurement. An enriched machine perfusion (MP) preservation solution for livers, named Polysol, was developed. The aim of this study was to investigate the type of flush solution, temperature and anticoagulant content on the wash-out of the non-heart-beating donor (NHBD) rat liver.

METHODS

Rat livers were flushed after 30 min warm ischemia. After excision, livers were reperfused at 37 degrees C, with analysis of damage and function, concerning (1) solutions (University of Wisconsin (UW), histidine-tryptophan-ketoglutarate (HTK) and Polysol); (2) temperature (4 degrees C, 18 degrees C and 37 degrees C); (3) addition of heparin and (4) wash-out followed by 24 h MP.

RESULTS

(1) Reperfusion results were inferior in the UW group; (2) less damage and improved function were seen after wash-out using Polysol at 37 degrees C; (3) No effects were seen of the addition of heparin to Polysol; (4) MP after wash-out using HTK resulted in more liver damage and decreased liver function as compared with wash-out using Polysol.

CONCLUSIONS

Polysol is applicable as a flush solution for the NHBD liver, resulting in equal to better wash-out as compared with UW and HTK. The best temperature for this NHBD wash-out is 37 degrees C.