Addition of carvedilol to University Wisconsin solution improves rat steatotic and nonsteatotic liver preservation

Defatting of donor transplant livers during normothermic perfusion-a randomised clinical trial: study protocol for the DeFat study

BACKGROUND

Liver disease is the third leading cause of premature death in the UK. Transplantation is the only successful treatment for end-stage liver disease but is limited by a shortage of suitable donor organs. As a result, up to 20% of patients on liver transplant waiting lists die before receiving a transplant. A third of donated livers are not suitable for transplant, often due to steatosis. Hepatic steatosis, which affects 33% of the UK population, is strongly associated with obesity, an increasing problem in the potential donor pool. We have recently tested defatting interventions during normothermic machine perfusion (NMP) in discarded steatotic human livers that were not transplanted. A combination of therapies including forskolin (NKH477) and L-carnitine to defat liver cells and lipoprotein apheresis filtration were investigated. These interventions resulted in functional improvement during perfusion and reduced the intrahepatocellular triglyceride (IHTG) content. We hypothesise that defatting during NMP will allow more steatotic livers to be transplanted with improved outcomes.

METHODS

In the proposed multi-centre clinical trial, we will randomly assign 60 livers from donors with a high-risk of hepatic steatosis to either NMP alone or NMP with defatting interventions. We aim to test the safety and feasibility of the defatting intervention and will explore efficacy by comparing ex-situ and post-reperfusion liver function between the groups. The primary endpoint will be the proportion of livers that achieve predefined functional criteria during perfusion which indicate potential suitability for transplantation. These criteria reflect hepatic metabolism and injury and include lactate clearance, perfusate pH, glucose metabolism, bile composition, vascular flows and transaminase levels. Clinical secondary endpoints will include proportion of livers transplanted in the two arms, graft function; cell-free DNA (cfDNA) at follow-up visits; patient and graft survival; hospital and ITU stay; evidence of ischemia-reperfusion injury (IRI); non-anastomotic biliary strictures and recurrence of steatosis (determined on MRI at 6 months).

DISCUSSION

This study explores ex-situ pharmacological optimisation of steatotic donor livers during NMP. If the intervention proves effective, it will allow the safe transplantation of livers that are currently very likely to be discarded, thereby reducing waiting list deaths.

TRIAL REGISTRATION

ISRCTN ISRCTN14957538. Registered in October 2022.

Steatotic Donor Transplant Livers: Preservation Strategies to Mitigate against Ischaemia-Reperfusion Injury

Liver transplantation (LT) is the only definitive treatment for end-stage liver disease, yet the UK has seen a 400% increase in liver disease-related deaths since 1970, constrained further by a critical shortage of donor organs. This shortfall has necessitated the use of extended criteria donor organs, including those with evidence of steatosis. The impact of hepatic steatosis (HS) on graft viability remains a concern, particularly for donor livers with moderate to severe steatosis which are highly sensitive to the process of ischaemia-reperfusion injury (IRI) and static cold storage (SCS) leading to poor post-transplantation outcomes. This review explores the pathophysiological predisposition of steatotic livers to IRI, the limitations of SCS, and alternative preservation strategies, including novel organ preservation solutions (OPS) and normothermic machine perfusion (NMP), to mitigate IRI and improve outcomes for steatotic donor livers. By addressing these challenges, the liver transplant community can enhance the utilisation of steatotic donor livers which is crucial in the context of the global obesity crisis and the growing need to expand the donor pool.

Effect of PERLA®, a new cold-storage solution, on oxidative stress injury and early graft function in rat kidney transplantation model

BACKGROUND

The composition of organ preservation solutions is crucial for maintaining graft integrity and early graft function after transplantation. The aim of this study is to compare new organ preservation solution PERLA® with the gold standard preservation solution University of Wisconsin (UW) regarding oxidative stress and early graft injury.

METHODS

In order to assess oxidative stress after cold storage, kidney grafts have been preserved for 18 h at 4° C in either UW solution or PERLA® solution and then assessed for oxidative stress injury (protocol 1). To assess kidney injuries and oxidative stress after reperfusion, rat kidneys were harvested, stored in cold UW or in PERLA® solutions for 18 h at 4 °C and then transplanted heterotopically for 6 h (protocol 2). PERLA® is a high Na+/low K+ solution including PEG-35 (1 g/L), trimetazidine (1 µM), carvedilol (10 µM) and tacrolimus (5 µM).

RESULTS

Our results showed that preservation of kidneys in PERLA® solution significantly attenuates oxidative stress parameters after cold storage and reperfusion. We found a significant decrease in oxidative damage indicators (MDA, CD and CP) and a significant increase in antioxidant indicators (GPx, GSH, CAT, SOD and PSH). Moreover, PERLA® solution decreased kidney injury after reperfusion (creatinine, LDH and uric acid).

CONCLUSION

PERLA® solution was more effective than UW storage solution in preserving rat's kidney grafts.

Modification of Preservative Fluids with Antioxidants in Terms of Their Efficacy in Liver Protection before Transplantation

Transplantation is currently the only effective treatment for patients with end-stage liver failure. In recent years, many advanced studies have been conducted to improve the efficiency of organ preservation techniques. Modifying the composition of the preservation fluids currently used may improve graft function and increase the likelihood of transplantation success. The modified fluid is expected to extend the period of safe liver storage in the peri-transplantation period and to increase the pool of organs for transplantation with livers from marginal donors. This paper provides a literature review of the effects of antioxidants on the efficacy of liver preservation fluids. Medline (PubMed), Scopus, and Cochrane Library databases were searched using a combination of MeSH terms: "liver preservation", "transplantation", "preservation solution", "antioxidant", "cold storage", "mechanical perfusion", "oxidative stress", "ischemia-reperfusion injury". Studies published up to December 2023 were included in the analysis, with a focus on publications from the last 30 years. A total of 45 studies met the inclusion criteria. The chemical compounds analyzed showed mostly bioprotective effects on hepatocytes, including but not limited to multifactorial antioxidant and free radical protective effects. It should be noted that most of the information cited is from reports of studies conducted in animal models, most of them in rodents.

How to Preserve Steatotic Liver Grafts for Transplantation

Liver allograft steatosis is a significant risk factor for postoperative graft dysfunction and has been associated with inferior patient and graft survival, particularly in the case of moderate or severe macrovesicular steatosis. In recent years, the increasing incidence of obesity and fatty liver disease in the population has led to a higher proportion of steatotic liver grafts being used for transplantation, making the optimization of their preservation an urgent necessity. This review discusses the mechanisms behind the increased susceptibility of fatty livers to ischemia-reperfusion injury and provides an overview of the available strategies to improve their utilization for transplantation, with a focus on preclinical and clinical evidence supporting donor interventions, novel preservation solutions, and machine perfusion techniques.

Nanoparticle-Based Interventions for Liver Transplantation

Liver transplantation is the only treatment for hepatic insufficiency as a result of acute and chronic liver injuries/pathologies that fail to recover. Unfortunately, there remains an enormous and growing gap between organ supply and demand. Although recipients on the liver transplantation waitlist have significantly higher mortality, livers are often not allocated because they are (i) classified as extended criteria or marginal livers and (ii) subjected to longer cold preservation time (>6 h) with a direct correlation of poor outcomes with longer cold ischemia. Downregulating the recipient's innate immune response to successfully tolerate a graft having longer cold ischemia times or ischemia-reperfusion injury through induction of immune tolerance in the graft and the host would significantly improve organ utilization and post-transplant outcomes. Broadly, technologies proposed for development aim to extend the life of the transplanted liver through post-transplant or recipient conditioning. In this review, we focus on the potential benefits of nanotechnology to provide unique pre-transplant grafting and recipient conditioning of extended criteria donor livers using immune tolerance induction and hyperthermic pre-conditioning.

A Potential Route to Reduce Ischemia/Reperfusion Injury in Organ Preservation

The pathophysiological process of ischemia and reperfusion injury (IRI), an inevitable step in organ transplantation, causes important biochemical and structural changes that can result in serious organ damage. IRI is relevant for early graft dysfunction and graft survival. Today, in a global context of organ shortages, most organs come from extended criteria donors (ECDs), which are more sensitive to IRI. The main objective of organ preservation solutions is to protect against IRI through the application of specific, nonphysiological components, under conditions of no blood or oxygen, and then under conditions of metabolic reduction by hypothermia. The composition of hypothermic solutions includes osmotic and oncotic buffering components, and they are intracellular (rich in potassium) or extracellular (rich in sodium). However, above all, they all contain the same type of components intended to protect against IRI, such as glutathione, adenosine and allopurinol. These components have not changed for more than 30 years, even though our knowledge of IRI, and much of the relevant literature, questions their stability or efficacy. In addition, several pharmacological molecules have been the subjects of preclinical studies to optimize this protection. Among them, trimetazidine, tacrolimus and carvedilol have shown the most benefits. In fact, these drugs are already in clinical use, and it is a question of repositioning them for this novel use, without additional risk. This new strategy of including them would allow us to shift from cold storage solutions to cold preservation solutions including multitarget pharmacological components, offering protection against IRI and thus protecting today's more vulnerable organs.

Revisiting the Principles of Preservation in an Era of Pandemic Obesity

The current obesity epidemic has caused a significant decline in the health of our donor population. Organs from obese deceased donors are more prone to ischemia reperfusion injury resulting from organ preservation. As a consequence, these donors are more likely to be discarded under the assumption that nothing can be done to make them viable for transplant. Our current methods of organ preservation-which remain relatively unchanged over the last ~40 years-were originally adopted in the context of a much healthier donor population. But methods that are suitable for healthier deceased donors are likely not optimal for organs from obese donors. Naturally occurring models of acute obesity and fasting in hibernating mammals demonstrate that obesity and resilience to cold preservation-like conditions are not mutually exclusive. Moreover, recent advances in our understanding of the metabolic dysfunction that underlies obesity suggest that it may be possible to improve the resilience of organs from obese deceased donors. In this mini-review, we explore how we might adapt our current practice of organ preservation to better suit the current reality of our deceased donor population.

Therapeutics administered during ex vivo liver machine perfusion: An overview

Although the use of extended criteria donors has increased the pool of available livers for transplant, it has also introduced the need to develop improved methods of protection against ischemia-reperfusion injury (IRI), as these "marginal" organs are particularly vulnerable to IRI during the process of procurement, preservation, surgery, and post-transplantation. In this review, we explore the current basic science research investigating therapeutics administered during ex vivo liver machine perfusion aimed at mitigating the effects of IRI in the liver transplantation process. These various categories of therapeutics are utilized during the perfusion process and include invoking the RNA interference pathway, utilizing defatting cocktails, and administering classes of agents such as vasodilators, anti-inflammatory drugs, human liver stem cell-derived extracellular vesicles, and δ-opioid agonists in order to reduce the damage of IRI. Ex vivo machine perfusion is an attractive alternative to static cold storage due to its ability to continuously perfuse the organ, effectively deliver substrates and oxygen required for cellular metabolism, therapeutically administer pharmacological or cytoprotective agents, and continuously monitor organ viability during perfusion. The use of administered therapeutics during machine liver perfusion has demonstrated promising results in basic science studies. While novel therapeutic approaches to combat IRI are being developed through basic science research, their use in clinical medicine and treatment in patients for liver transplantation has yet to be explored.

Ischaemia reperfusion injury in liver transplantation: Cellular and molecular mechanisms

Liver disease causing end organ failure is a growing cause of mortality. In most cases, the only therapy is liver transplantation. However, liver transplantation is a complex undertaking and its success is dependent on a number of factors. In particular, liver transplantation is subject to the risks of ischaemia-reperfusion injury (IRI). Liver IRI has significant effects on the function of a liver after transplantation. The cellular and molecular mechanisms governing IRI in liver transplantation are numerous. They involve multiple cells types such as liver sinusoidal endothelial cells, hepatocytes, Kupffer cells, neutrophils and platelets acting via an interconnected network of molecular pathways such as activation of toll-like receptor signalling, alterations in micro-RNA expression, production of ROS, regulation of autophagy and activation of hypoxia-inducible factors. Interestingly, the cellular and molecular events in liver IRI can be correlated with clinical risk factors for IRI in liver transplantation such as donor organ steatosis, ischaemic times, donor age, and donor and recipient coagulopathy. Thus, understanding the relationship of the clinical risk factors for liver IRI to the cellular and molecular mechanisms that govern it is critical to higher levels of success after liver transplantation. This in turn will help in the discovery of therapeutics for IRI in liver transplantation - a process that will lead to improved outcomes for patients suffering from end-stage liver disease.

Interrelation of liver vascularity to non-alcoholic fatty liver through a comparative study of the vasodilator effect of carvedilol or nicorandil in rats

AIM

An experimental study of the effect of two vasodilators, carvedilol (B blocker with alpha-antagonist) and nicorandil (NO donor) on nonalcoholic fatty liver (NAFLD) induced by hypercholesterolemia and fatty diet in rats through studying the possible anti-inflammatory and antioxidant mechanisms.

MAIN METHODS

The rats were divided into 4 groups (6 rats each): The first (negative control group). The second, third and fourth groups were fed with cholesterol and fat- enriched diet for one month that stopped and continued on the standard diet for another month without treatment in the second group but treated with carvedilol and nicorandil in the third and fourth group respectively.

KEY FINDINGS

They revealed that both improved NAFLD especially nicorandil treated proved by the reduction of liver enzymes (AST, ALT), the fatty infiltration determined histologically and biochemically (decrease liver triglycerides). This may be due to either being antioxidants (reduced malondialdehyde and elevated reduced glutathione) or anti-inflammatory (decreased of TNF-α) together with the reduction of insulin resistance and adiponectin elevation or gene expression (increased liver NF-κB and decreased eNOS expression) and finally maybe by their obvious effect on improvements of lipid parameters.

SIGNIFICANCE

Carvedilol and nicorandil improved NAFLD through the interrelationship between inflammatory cytokines, antioxidants and insulin resistance.

Proteomic Analysis of Liver Preservation Solutions Prior to Liver Transplantation

Material/Methods:

Samples were collected from the pre-transplant preservation mediums of 23 liver donors. For all donors, the cases involved Donation after Brain Death (DBD). 2D-PAGE and LCMSMS methodologies were used to detect the proteins and peptides from the preservation mediums.

Results:

A total of 198 proteins originating from the liver were detected.

Conclusion:

The data provide valuable insights into biomarkers that may be used to evaluate organ injury, functional status, and suitability for transplantation. Additionally, the findings could be valuable for the development of new strategies for effective preservation of solid organs prior to transplantation.

Effect of Prolactin on Biochemical and Morphological Parameters of Rabbit Liver in Warm Ischemia

BACKGROUND

The aim of the study was to assess the degree of liver damage in a rabbit perfused with histidine-tryptophan-ketoglutarate (HTK [Custodiol]) solution with and without the presence of prolactin (PRL) based on biochemical studies in perfundate and ultrastructural analysis of hepatocytes.

MATERIALS AND METHODS

The experiment was carried out on rabbits. Liver ischemia was used in the study, based on Pringle's maneuver. About 70% of the rabbit liver lobes were perfused with HTK with or without the addition of PRL (2.5μg/g liver/h) under ischemic conditions for 2 hours. In the perfundate, the activity of enzymes alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), γ-glutamyl transpeptidase (GGT), and lactate concentration were determined. Liver biopsies were collected for histopathologic evaluation under an electron microscope.

RESULTS

The addition of PRL to the HTK significantly reduced the leakage of enzymes from the liver to perfundate compared with the control group without PRL. The activity of ALT, AST, LDH, and GGT in the perfundates obtained after 2-hour perfusion with HTK-PRL solution was lower when compared with activity of the same parameters determined in perfundates with liver perfused with HTK without PRL. The area under the curve (AUC_0-2h) calculated for GGT, LDH, and lactates was significantly higher after perfusion with the HTK than with HTK with the addition of PRL. In the study group, bile was secreted throughout the whole experiment. The morphological confirmation of these results was obtained by means of transmission microscopy.

CONCLUSION

PRL added to the preservation solution significantly inhibits the process of liver cell cytolysis, which may suggest its hepatoprotective effect.

Donor Hepatic Steatosis Induce Exacerbated Ischemia-Reperfusion Injury Through Activation of Innate Immune Response Molecular Pathways

BACKGROUND

Severe liver steatosis is a known risk factor for increased ischemia-reperfusion injury (IRI) and poor outcomes after liver transplantation (LT). This study aimed to identify steatosis-related molecular mechanisms associated with IRI exacerbation after LT.

METHODS

Paired graft biopsies (n = 60) were collected before implantation (L1) and 90 minutes after reperfusion (L2). The LT recipients (n = 30) were classified by graft macrosteatosis: without steatosis (WS) of 5% or less (n = 13) and with steatosis (S) of 25% or greater (n = 17). Plasma samples were collected at L1, L2, and 1 day after LT (postoperative [POD]1) for cytokines evaluation. Tissue RNA was isolated for gene expression microarrays. Probeset summaries were obtained using robust multiarray average algorithm. Pairwise comparisons were fit using 2-sample t test. P values 0.01 or less were significant (false discovery rate <5%). Molecular pathway analyses were conducted using Ingenuity Pathway Analysis tool.

RESULTS

Significantly differentially expressed genes were identified for WS and S grafts after reperfusion. Comprehensive comparison analysis of molecular profiles revealed significant association of S grafts molecular profile with innate immune response activation, macrophage production of nitric oxide and reactive oxygen species, IL-6, IL-8, IL-10 signaling activation, recruitment of granulocytes, and accumulation of myeloid cells. Postreperfusion histological patterns of S grafts revealed neutrophilic infiltration surrounding fat accumulation. Circulating proinflammatory cytokines after reperfusion and 24 hours after LT concurred with intragraft-deregulated molecular pathways. All tested cytokines were significantly increased in plasma of S grafts recipients after reperfusion when compared with WS group at same time.

CONCLUSIONS

Increases of graft steatosis exacerbate IRI by exacerbation of innate immune response after LT. Preemptive strategies should consider it for safety usage of steatotic livers.

Ankaflavin ameliorates steatotic liver ischemia-reperfusion injury in mice

BACKGROUND

It is well-known that steatotic liver is more susceptible to ischemia-reperfusion (I/R) injury during liver transplantation, liver resection and other liver surgeries. The increasing incidence of non-alcoholic fatty liver disease (NAFLD) decreases the availability of liver donors. Although steatotic liver is now accepted as a source of liver for transplantation, NAFLD exacerbates the liver injury after liver surgery. The present study was to investigate the protective role of ankaflavin in steatotic liver I/R injury.

METHODS

The model of fatty liver mice was induced with high fat diet in four weeks, ankaflavin or vehicle (saline) was administrated by gavage once a day for one week. The animals were subjected to partial hepatic I/R. Blood samples were collected to measure serum aminotransferases. The liver tissues were used to examine liver steatosis, apoptosis of hepatocytes, hepatic oxidative stress, Kupffer cells and inflammatory cytokines. The effects of ankaflavin on inflammatory cytokines were evaluated in isolated Kupffer cells from the steatotic liver.

RESULTS

Ankaflavin reduced liver steatosis in high fat diet mice. Compared with normal mice, I/R induced more damage to the mice with steatosis, such as hepatocyte apoptosis, inflammatory cytokines (TNF-alpha, IL-6 and IL-1 beta), serum aminotransferases and thiobarbituric acid reactive substances. Importantly, ankaflavin administration significantly attenuated these changes. In addition, ankaflavin significantly decreased the proliferation of Kupffer cells and the expression of TNF-alpha, IL-6 and IL-1 beta protein in isolated Kupffer cells stimulated by TNF-alpha.

CONCLUSION

Ankaflavin has protective effects against I/R injury through anti-inflammatory, anti-oxidant and anti-apoptotic mechanisms in fatty livers, these effects are at least partially mediated by inhibiting Kupffer cell functions.

Effects of Institut Georges Lopez-1 and Celsior preservation solutions on liver graft injury

AIM: To compare Institut Georges Lopez (IGL-1) and Celsior preservation solutions for hepatic endothelium relaxation and liver cold ischemia reperfusion injury (IRI).

METHODS: Two experimental models were used. In the first one, acetylcholine-induced endothelium-dependent relaxation (EDR) was measured in isolated ring preparations of rat hepatic arteries preserved or not in IGL-1 or Celsior solutions (24 h at 4 °C). To determine nitric oxide (NO) and cyclooxygenase EDR, hepatic arteries were incubated with L-NG-nitroarginine methyl ester (L-NAME), an inhibitor of endothelium nitric oxide synthase (eNOS), or with L-NAME plus indomethacin, an inhibitor of cyclooxygenase. In the second experiment, rat livers were cold-stored in IGL-1 or Celsior solutions for 24 h at 4 °C and then perfused “ex vivo” for 2 h at 37 °C. Liver injury was assessed by transaminase measurements, liver function by bile production and bromosulfophthalein clearance, oxidative stress by malondialdehyde levels and catalase activity and alterations in cell signaling pathways by pAkt, pAMPK, eNOS and MAPKs proteins level.

RESULTS: After cold storage for 24 h with either Celsior or IGL-1, EDR was only slightly altered. In freshly isolated arteries, EDR was exclusively mediated by NO. However, cold-stored arteries showed NO- and COX-dependent relaxation. The decrease in NO-dependent relaxation after cold storage was significantly more marked with Celsior. The second study indicated that IGL-1 solution obtained better liver preservation and protection against IRI than Celsior. Liver injury was reduced, function was improved and there was less oxidative stress. IGL-1 solution activated Akt and AMPK, which was concomitant with increased eNOS expression and nitrite/nitrate levels. Furthermore, MAPKs kinases were regulated in livers preserved with IGL-1 solution since reductions in p-p38, p-ERK and p-JNK protein levels were observed.

CONCLUSION: IGL-1 solution preserved NO-dependent relaxation better than Celsior storage solution and enhanced liver graft preservation.

CD47 blockade reduces ischemia/reperfusion injury and improves survival in a rat liver transplantation model

Orthotopic liver transplantation (OLT) remains the standard treatment option for nonresponsive liver failure. Because ischemia/reperfusion injury (IRI) is an important impediment to the success of OLT, new therapeutic strategies are needed to reduce IRI. We investigated whether blocking the CD47/thrombospondin-1 inhibitory action on nitric oxide signaling with a monoclonal antibody specific to CD47 (CD47mAb400) would reduce IRI in liver grafts. Syngeneic OLT was performed with Lewis rats. Control immunoglobulin G or CD47mAb400 was administered to the donor organ at procurement or to both the organ and the recipient at the time of transplant. Serum transaminases, histological changes of the liver, and animal survival were assessed. Oxidative stress, inflammatory responses, and hepatocellular damage were also quantified. A significant survival benefit was not achieved when CD47mAb400 was administered to the donor alone. However, CD47mAb400 administration to both the donor and the recipient increased animal survival afterward. The CD47mAb400-treated group showed lower serum transaminases, bilirubin, oxidative stress, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling staining, caspase-3 activity, and proinflammatory cytokine expression of tumor necrosis factor α, interleukin-1β, and interleukin-6. Thus, CD47 blockade with CD47mAb400 administered both to the donor and the recipient reduced liver graft IRI in a rat liver transplantation model. This may translate to decreased liver dysfunction and increased survival of liver transplant recipients.

2-Acetylcyclopentanone, an enolate-forming 1,3-dicarbonyl compound, is cytoprotective in warm ischemia-reperfusion injury of rat liver

We have previously shown that 2-acetylcyclopentanone (2-ACP), an enolate-forming 1,3-dicarbonyl compound, provides protection in cell culture and animal models of oxidative stress. The pathophysiology of ischemia-reperfusion injury (IRI) involves oxidative stress, and, therefore, we determined the ability of 2-ACP to prevent this injury in a rat liver model. IRI was induced by clamping the portal vasculature for 45 minutes (ischemia phase), followed by recirculation for 180 minutes (reperfusion phase). This sequence was associated with substantial derangement of plasma liver enzyme activities, histopathological indices, and markers of oxidative stress. The 2-ACP (0.80-2.40 mmol/kg), administered by intraperitoneal injection 10 minutes prior to reperfusion, provided dose-dependent cytoprotection, as indicated by normalization of the IRI-altered liver histologic and biochemical parameters. The 2-ACP (2.40 mmol/kg) was also hepatoprotective when injected before clamping the circulation (ischemia phase). In contrast, an equimolar dose of N-acetylcysteine (2.40 mmol/kg) was not hepatoprotective when administered prior to reperfusion. Our studies to date suggest that during reperfusion the enolate nucleophile of 2-ACP limits the consequences of mitochondrial-based oxidative stress through scavenging unsaturated aldehyde electrophiles (e.g., acrolein) and chelation of metal ions that catalyze the free radical-generating Fenton reaction. The ability of 2-ACP to reduce IRI when injected prior to ischemia most likely reflects the short duration of this experimental phase (45 minutes) and favorable pharmacokinetics that maintain effective 2-ACP liver concentrations during subsequent reperfusion. These results provide evidence that 2-ACP or an analog might be useful in treating IRI and other conditions that have oxidative stress as a common molecular etiology.

A novel form of the human manganese superoxide dismutase protects rat and human livers undergoing ischaemia and reperfusion injury

Hepatic microcirculatory dysfunction due to cold storage and warm reperfusion (CS+WR) injury during liver transplantation is partly mediated by oxidative stress and may lead to graft dysfunction. This is especially relevant when steatotic donors are considered. Using primary cultured liver sinusoidal endothelial cells (LSECs), liver grafts from healthy and steatotic rats, and human liver samples, we aimed to characterize the effects of a new recombinant form of human manganese superoxide dismutase (rMnSOD) on hepatic CS+WR injury. After CS+WR, the liver endothelium exhibited accumulation of superoxide anion (O2-) and diminished levels of nitric oxide (NO); these detrimental effects were prevented by rMnSOD. CS+WR control and steatotic rat livers exhibited markedly deteriorated microcirculation and acute endothelial dysfunction, together with liver damage, inflammation, oxidative stress, and low NO. rMnSOD markedly blunted oxidative stress, which was associated with a global improvement in liver damage and microcirculatory derangements. The addition of rMnSOD to CS solution maintained its antioxidant capability, protecting rat and human liver tissues. In conclusion, rMnSOD represents a new and highly effective therapy to significantly upgrade liver procurement for transplantation.

Hepatic ischemia and reperfusion injury: effects on the liver sinusoidal milieu

Ischemia-reperfusion injury is an important cause of liver damage occurring during surgical procedures including hepatic resection and liver transplantation, and represents the main underlying cause of graft dysfunction post-transplantation. Cellular and biochemical processes occurring during hepatic ischemia-reperfusion are diverse and complex, and include the deregulation of the healthy phenotype of all liver cellular components. Nevertheless, a significant part of these processes are still unknown or unclear. The present review aims at summarizing the current knowledge in liver ischemia-reperfusion, but specifically focusing on liver cell phenotype and paracrine interaction deregulations. Moreover, the most updated therapeutic strategies including pharmacological, genetic and surgical interventions, as well as some of the scientific controversies in the field will be described. Finally, the importance of considering the subclinical situation of liver grafts when translating basic knowledge to the bedside is discussed.

Strategies to rescue steatotic livers before transplantation in clinical and experimental studies

The shortage of donor livers has led to an increased use of organs from expanded criteria donors. Included are livers with steatosis, a metabolic abnormality that increases the likelihood of graft complications post-transplantation. After a brief introduction on the etiology, pathophysiology, categories and experimental models of hepatic steatosis, we herein review the methods to rescue steatotic donor livers before transplantation applied in clinical and experimental studies. The methods span the spectrum of encouraging donor weight loss, employing drug therapy, heat shock preconditioning, ischemia preconditioning and selective anesthesia on donors, and the treatment on isolated grafts during preservation. These methods work at different stages of transplantation process, although share similar molecular mechanisms including lipid metabolism stimulation through enzymes or nuclear receptor e.g., peroxisomal proliferator-activated receptor, or anti-inflammation through suppressing cytokines e.g., tumor necrosis factor-α, or antioxidant therapies to alleviate oxidative stress. This similarity of molecular mechanisms implies possible future attempts to reinforce each approach by repeating the same treatment approach at several stages of procurement and preservation, as well as utilizing these alternative approaches in tandem.

A luminance-based heart chip assay for assessing the efficacy of graft preservation solutions in heart transplantation in rats

Objective

We developed a novel luciferase-based viability assay for assessing the viability of hearts preserved in different solutions. We examined whether this in vitro system could predict heart damage and survival after transplantation in rats.

Design

By our novel system, preserved heart viability evaluation and transplanted heart-graft functional research study.

Setting

University basic science laboratory.

Interventions

Isolated Luciferase-transgenic Lewis (LEW) rat cardiac-tissue-chips were plated on 96-well tissue-culture plates and incubated in preservation solutions at 4°C. Viability was measured as photon intensity by using a bio-imaging system. Heart-grafts preserved in University of Wisconsin (UW), extracellular-trehalose-Kyoto (ETK), Euro-Collins (EC), histidin-tryptophan-ketoglutarat solution (HTK), lactated Ringer's (LR) or normal saline solution were transplanted cervically by using a cuff-technique or into the abdomens of syngeneic wild-type LEW rats by using conventional microsurgical suture techniques.

Main outcome measures

Imaging an evaluation of preservation heart-graft and functional analysis.

Results

Cardiac-tissue-chips preserved with UW, HTK or ETK solution gave higher luminance than those preserved with EC, LR or normal saline (p<0.03). After 24 h of preservation of hearts in each solution at 4°C, the beating of the isolated hearts was evaluated. The success rate, evaluation of beating, of cervical heart transplants using UW and ETK solution exceeded 70%, but those using other preservation solutions were lower (UW: 100%, ETK: 75%, EC: 42.86%, HTK: 14.29%, normal saline: 0%). Histological analysis of cervical heart-grafts after 3 h preservation by myeloperoxidase (MPO), zona occludens-1(ZO-1), and caspase-3 immunostaining revealed different degrees of preservation damage in all grafts.

Conclusions

Our novel assay system is simple and can test multiple solutions. It should therefore be a powerful tool for developing and improving new heart-graft preservation solutions.

Liver defatting: an alternative approach to enable steatotic liver transplantation

Macrovesicular steatosis in greater than 30% of hepatocytes is a significant risk factor for primary graft nonfunction due to increased sensitivity to ischemia reperfusion (I/R) injury. The growing prevalence of hepatic steatosis due to the obesity epidemic, in conjunction with an aging population, may negatively impact the availability of suitable deceased liver donors. Some have suggested that metabolic interventions could decrease the fat content of liver grafts prior to transplantation. This concept has been successfully tested through nutritional supplementation in a few living donors. Utilization of deceased donor livers, however, requires defatting of explanted organs. Animal studies suggest that this can be accomplished by ex vivo warm perfusion in a time scale of a few hours. We estimate that this approach could significantly boost the size of the donor pool by increasing the utilization of steatotic livers. Here we review current knowledge on the mechanisms whereby excessive lipid storage and macrosteatosis exacerbate hepatic I/R injury, and possible approaches to address this problem, including ex vivo perfusion methods as well as metabolically induced defatting. We also discuss the challenges ahead that need to be addressed for clinical implementation.

Pretreatment with mangafodipir improves liver graft tolerance to ischemia/reperfusion injury in rat

Ischemia/reperfusion injury occurring during liver transplantation is mainly due to the generation of reactive oxygen species (ROS) upon revascularization. Thus, delivery of antioxidant enzymes might reduce the deleterious effects of ROS and improve liver graft initial function. Mangafodipir trisodium (MnDPDP), a contrast agent currently used in magnetic resonance imaging of the liver, has been shown to be endowed with powerful antioxidant properties. We hypothesized that MnDPDP could have a protective effect against liver ischemia reperfusion injury when administrated to the donor prior to harvesting. Livers from Sprague Dawley rats pretreated or not with MnDPDP were harvested and subsequently preserved for 24 h in Celsior® solution at 4°C. Organs were then perfused ex vivo for 120 min at 37°C with Krebs Henseleit solution. In MnDPDP (5 µmol/kg) group, we observed that ATP content was significantly higher at the end of the cold preservation period relative to untreated group. After reperfusion, livers from MnDPDP-treated rats showed better tissue integrity, less hepatocellular and endothelial cell injury. This was accompanied by larger amounts of bile production and higher ATP recovery as compared to untreated livers. The protective effect of MnDPDP was associated with a significant decrease of lipid peroxidation, mitochondrial damage, and apoptosis. Interestingly, MnDPDP-pretreated livers exhibited activation of Nfr2 and HIF-1α pathways resulting in a higher catalase and HO-1 activities. MnDPDP also increased total nitric oxide (NO) production which derived from higher expression of constitutive NO synthase and lower expression of inducible NO synthase. In conclusion, our results show that donor pretreatment with MnDPDP protects the rat liver graft from cold ischemia/reperfusion injury and demonstrate for the first time the potential interest of this molecule in the field of organ preservation. Since MnDPDP is safely used in liver imaging, this preservation strategy holds great promise for translation to clinical liver transplantation.

Phosphoenolpyruvate, a glycolytic intermediate, as a cytoprotectant and antioxidant in ex-vivo cold-preserved mouse liver: a potential application for organ preservation

OBJECTIVES

The aim of this study was to examine the effect of phosphoenolpyruvate (PEP), a glycolytic intermediate, on organ damage during cold preservation of liver.

METHODS

An ex-vivo mouse liver cold-preservation model and an in-vitro liver injury model induced by hydrogen peroxide in HepG2 cells were leveraged.

KEY FINDINGS

PEP attenuated the elevation of aminotransferases and lactate dehydrogenase leakage during organ preservation, histological changes and changes in oxidative stress parameters (measured as thiobarbituric acid reactive substance and glutathione content) induced by 72 h of cold preservation of the liver. The effects were comparable with the University of Wisconsin solution, a gold standard organ preservation agent. The decrease in ATP content in liver during the cold preservation was attenuated by PEP treatment. PEP prevented the cellular injury and increases in intracellular reactive oxygen species in HepG2 cells. In addition, PEP scavenged hydroxyl radicals, but had no effect on superoxide anion as evaluated by an electron paramagnetic resonance spin-trapping technique.

CONCLUSIONS

PEP significantly attenuated the injury, oxidative stress and ATP depletion in liver during cold preservation. The antioxidative potential of PEP was confirmed by in-vitro examination. We suggest that PEP acts as a glycolytic intermediate and antioxidant, and is particularly useful as an organ preservation agent in clinical transplantation.

Implication of mitochondrial cytoprotection in human islet isolation and transplantation

Islet transplantation is a promising therapy for type 1 diabetes mellitus; however, success rates in achieving both short- and long-term insulin independence are not consistent, due in part to inconsistent islet quality and quantity caused by the complex nature and multistep process of islet isolation and transplantation. Since the introduction of the Edmonton Protocol in 2000, more attention has been placed on preserving mitochondrial function as increasing evidences suggest that impaired mitochondrial integrity can adversely affect clinical outcomes. Some recent studies have demonstrated that it is possible to achieve islet cytoprotection by maintaining mitochondrial function and subsequently to improve islet transplantation outcomes. However, the benefits of mitoprotection in many cases are controversial and the underlying mechanisms are unclear. This article summarizes the recent progress associated with mitochondrial cytoprotection in each step of the islet isolation and transplantation process, as well as islet potency and viability assays based on the measurement of mitochondrial integrity. In addition, we briefly discuss immunosuppression side effects on islet graft function and how transplant site selection affects islet engraftment and clinical outcomes.

The use of a reversible proteasome inhibitor in a model of Reduced-Size Orthotopic Liver transplantation in rats

Ischemia/reperfusion injury (IRI), inherent in liver transplantation (LT), is the main cause of initial deficiencies and primary non-function of liver allografts. Living-related LT was developed to alleviate the mortality resulting from the scarcity of suitable deceased grafts. The main problem in using living-related LT for adults is graft size disparity. In this study we propose for the first time that the use of a proteasome inhibitor (Bortezomib) treatment could improve liver regeneration and reduce IRI after Reduced-Size Orthotopic Liver transplantation (ROLT). Rat liver grafts were reduced by removing the left lateral lobe and the two caudate lobes and preserved in UW or IGL-1 preservation solution for 1h liver and then subjected to ROLT with or without Bortezomib treatment. Our results show that Bortezomib reduces IRI after LT and is correlated with a reduction in mitochondrial damage, oxidative stress and endoplasmic reticulum stress. Furthermore, Bortezomib also increased liver regeneration after reduced-size LT and increased the expression of well-known ischemia/reperfusion protective proteins such as nitric oxide synthase, heme oxigenase 1 (HO-1) and Heat Shock Protein 70. Our results open new possibilities for the study of alternative therapeutic strategies aimed at reducing IRI and increasing liver regeneration after LT. It is hoped that the results of our study will contribute towards improving the understanding of the molecular processes involved in IRI and liver regeneration, and therefore help to improve the outcome of this type of LT in the future.

Addition of simvastatin to cold storage solution prevents endothelial dysfunction in explanted rat livers

Pathophysiological alterations in the endothelial phenotype result in endothelial dysfunction. Flow cessation, occurring during organ procurement for transplantation, triggers the endothelial dysfunction characteristic of ischemia/reperfusion injury, partly due to a reduction in the expression of the vasoprotective transcription factor Kruppel-like Factor 2 (KLF2). We aimed at (1) characterizing the effects of flow cessation and cold storage on hepatic endothelial phenotype, and (2) ascertaining if the consequences of cold stasis on the hepatic endothelium can be pharmacologically modulated, improving liver graft function. Expression of KLF2 and its vasoprotective programs was determined in (i) hepatic endothelial cells (HEC) incubated under cold storage conditions with or without the KLF2-inducer simvastatin, and (ii) rat livers not cold stored or preserved in cold University of Wisconsin solution (UWS) supplemented with simvastatin or its vehicle. In addition, upon warm reperfusion hepatic vascular resistance, endothelial function, nitric oxide vasodilator pathway, apoptosis, inflammation, and liver injury were evaluated in not cold stored livers or livers preserved in cold UWS supplemented with simvastatin or vehicle. Expression of KLF2 and its vasoprotective programs decrease in HEC incubated under cold storage conditions. Cold-stored rat livers exhibit a time-dependent decrease in KLF2 and its target genes, liver injury, increased hepatic vascular resistance, and endothelial dysfunction. The addition of simvastatin to the storage solution, maintained KLF2-dependent vasoprotective programs, prevented liver damage, inflammation, and oxidative stress and improved endothelial dysfunction.

CONCLUSION

Our results provide a rationale to evaluate the beneficial effects of a vasoprotective preservation solution on human liver procurement for transplantation.

How to protect liver graft with nitric oxide

Organ preservation and ischemia reperfusion injury associated with liver transplantation play an important role in the induction of graft injury. One of the earliest events associated with the reperfusion injury is endothelial cell dysfunction. It is generally accepted that endothelial nitric oxide synthase (e-NOS) is cell-protective by mediating vasodilatation, whereas inducible nitric oxide synthase mediates liver graft injury after transplantation. We conducted a critical review of the literature evaluating the potential applications of regulating and promoting e-NOS activity in liver preservation and transplantation, showing the most current evidence to support the concept that enhanced bioavailability of NO derived from e-NOS is detrimental to ameliorate graft liver preservation, as well as preventing subsequent graft reperfusion injury. This review deals mainly with the beneficial effects of promoting “endogenous” pathways for NO generation, via e-NOS inducer drugs in cold preservation solution, surgical strategies such as ischemic preconditioning, and alternative “exogenous” pathways that focus on the enrichment of cold storage liquid with NO donors. Finally, we also provide a basic bench-to-bed side summary of the liver physiology and cell signalling mechanisms that account for explaining the e-NOS protective effects in liver preservation and transplantation.

Relevance of epidermal growth factor to improve steatotic liver preservation in IGL-1 solution

AIM

Static preservation solution is critical for liver graft outcomes, especially when steatosis is present. Institut Georges Lopez (IGL)-1 solution protects fatty livers effectively against cold ischemia reperfusion injury. Its benefits are mediated by nitric oxide and prevention of oxidative stress. The supplementation of IGL-1 with epidermal growth factor (EGF) enhances steatotic graft preservation by increasing adenosine triphosphate content, thereby mitigating oxidative stress and mitochondrial damage.

METHODS

After steatotic livers were preserved for 24 hours in IGL-1 solution with or without EGF supplements, they were perfused ex vivo for 2 hours at 37°C. The benefits of EGF were assessed by evidences of hepatic damage and function--transaminases, bile production, and flow rate--as well as by other factors presumably associated with the poor tolerance of fatty livers toward cold ischemia-reperfusion injury (IRI)--energy metabolism, mitochondrial damage, oxidative stress, eNOS activity and proinflammatory interleukin (IL) beta content.

RESULTS

Steatotic livers preserved in IGL-1 solutions supplemented with EGF (10 μg/L) showed lower transaminase levels, greater bile production, and ameliorated flow rates when compared to IGL-1 alone. In addition, energy metabolism deterioration, mitochondrial damage, oxidative stress, and cytokine IL-1 beta release were prevented.

CONCLUSION

EGF addition to IGL-1 increased fatty liver graft preservation, thereby reducing steatotic liver damage against cold IRI.

Melatonin protects steatotic and nonsteatotic liver grafts against cold ischemia and reperfusion injury

Chronic organ-donor shortage has required the acceptance of steatotic livers for transplantation purposes despite the higher risk of graft dysfunction or nonfunction associated with the cold ischemia-reperfusion injury. This study evaluated the use of melatonin as an additive to Institute Georges Lopez (IGL-1) solution for protecting nonsteatotic and steatotic liver grafts against cold ischemia-reperfusion injury. In the current investigation, we used an ex vivo isolated perfused rat liver model. Steatotic and nonsteatotic livers were preserved for 24 hr (4°C) in University of Wisconsin or IGL-1 solutions with or without melatonin, as well as in University of Wisconsin solution alone. Thereafter, livers were subjected to 2-hr reperfusion (37°C). We assessed hepatic injury (transaminases) and function [bile production and sulfobromophthalein (BSP) clearance, vascular resistance], as well as other factors potentially implicated in the high vulnerability of steatotic livers against ischemia-reperfusion injury (oxidative stress and related inflammatory mediators including nitric oxide and cytokines). We also evaluated well-known cytoprotective factors as hemeoxygenase 1 (HO-1). Fatty livers preserved in IGL-1 solution enriched with melatonin showed lower transaminase levels and higher bile production and BSP clearance when compared to those obtained for livers maintained in IGL-1 solution alone. A significant diminution of vascular resistance was also observed when melatonin was added to the IGL-1 solution. The melatonin benefits correlated with the generation of nitric oxide (through constitutive e-NOS activation) and the prevention of oxidative stress and inflammatory cytokine release including tumor necrosis factor and adiponectin, respectively. The addition of melatonin to IGL-1 solution improved nonsteatotic and steatotic liver graft preservation, limiting their risk against cold ischemia-reperfusion injury.

Insulin like growth factor-1 increases fatty liver preservation in IGL-1 solution

AIM: To investigate the benefits of insulin like growth factor-1 (IGF-1) supplementation to serum-free institut georges lopez-1 (IGL-1)^® solution to protect fatty liver against cold ischemia reperfusion injury.

METHODS: Steatotic livers were preserved for 24 h in IGL-1^® solution supplemented with or without IGF-1 and then perfused “ex vivo” for 2 h at 37°C. We examined the effects of IGF-1 on hepatic damage and function (transaminases, percentage of sulfobromophthalein clearance in bile and vascular resistance). We also studied other factors associated with the poor tolerance of fatty livers to cold ischemia reperfusion injury such as mitochondrial damage, oxidative stress, nitric oxide, tumor necrosis factor-α (TNF-α) and mitogen-activated protein kinases.

RESULTS: Steatotic livers preserved in IGL-1^® solution supplemented with IGF-1 showed lower transaminase levels, increased bile clearance and a reduction in vascular resistance when compared to those preserved in IGL-1^® solution alone. These benefits are mediated by activation of AKT and constitutive endothelial nitric oxide synthase (eNOS), as well as the inhibition of inflammatory cytokines such as TNF-α. Mitochondrial damage and oxidative stress were also prevented.

CONCLUSION: IGL-1^® enrichment with IGF-1 increased fatty liver graft preservation through AKT and eNOS activation, and prevented TNF-α release during normothermic reperfusion.