Graft reconditioning with nitric oxide gas in rat liver transplantation from cardiac death donors. Transplantation. 2014;97:618-625. [PMID: 24521773 DOI: 10.1097/tp.0000000000000025]

Impact of aging on peribiliary glands in ischemia-reperfusion injury

BACKGROUND

The detailed mechanisms underlying the development of ischemia-type biliary lesions (ITBLs) in aged donor grafts remain unclear. In the present study we aimed to investigate the impact of aging on the response of the peribiliary gland (PBG) to ischemia-reperfusion injury (IRI) and its temporal changes.

METHODS

Experiments were performed using a 90-min partial warm liver ischemia model in male Wistar rats of two age groups: young (7-8 weeks old) and old (52-60 weeks old). Liver tissues were obtained 24, 72, and 168 h after IRI. Histopathological and immunohistochemical assessments of the perihilar bile duct (PHBD), including the PBG, distal to the clip-clamped site were performed.

RESULTS

Young rats showed little change in the bile duct tissues after IRI. However, old rats showed an increased PBG volume in the PHBD and marked PBG cell proliferation 24 h after IRI. Bile duct wall thickening with narrowing of the lumen peaked 72 h after IRI. Mucus production and oxidative stress in the PBG were significantly higher in old than in young rats after IRI. These findings showed a trend toward improvement 168 h after IRI.

CONCLUSION

Age-dependent differences in the response of the PBG to IRI may be related to differences in ITBL frequency.

Persufflation—Current State of Play

With the ever-increasing disparity between the number of patients waiting for organ transplants and the number organs available, some patients are unable to receive life-saving transplantation in time. The present, widely-used form of preservation is proving to be incapable of maintaining organ quality during long periods of preservation and meeting the needs of an ever-changing legislative and transplantation landscape. This has led to the need for improved preservation techniques. One such technique that has been extensively researched is gaseous oxygen perfusion or Persufflation (PSF). This method discovered in the early 20th century has shown promise in providing both longer term preservation and organ reconditioning capabilities for multiple organs including the liver, kidneys, and pancreas. PSF utilises the organs own vascular network to provide oxygen to the organ tissue and maintain metabolism during preservation to avoid hypoxic damage. This review delves into the history of this technique, its multiple different approaches and uses, as well as in-depth discussion of work published in the past 15 years. Finally, we discuss exciting commercial developments which may help unlock the potential for this technique to be applied at scale.

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

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

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.

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

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

Prediction of rat liver transplantation outcomes using energy metabolites measured by microdialysis

BACKGROUND

Warm ischemia jeopardizes graft quality and recipient survival in donation after cardiac death (DCD) transplantation. Currently, there is no system to objectively evaluate the liver quality from DCD. The present study tried to use energy metabolites to evaluate the donor liver quality.

METHODS

We divided 195 Sprague-Dawley rats into five groups: the control (n = 39), warm ischemic time (WIT) 15 min (n = 39), WIT 30 min (n = 39), WIT 45 min (n = 39), and WIT 60 min (n = 39) groups. Three rats from each group were randomly selected for pretransplant histologic evaluation of warm ischemia-related damage. The remaining 36 rats were randomly divided into donors and recipients of 18 liver transplantations, and were subjected to postoperative liver function and survival analyses. Between cardiac arrest and cold storage, liver energy metabolites including glucose, lactate, pyruvate, and glycerol were measured by microdialysis. The lactate to pyruvate ratio (LPR) was calculated.

RESULTS

The changes in preoperative pathology with warm ischemia were inconspicuous, but the trends in postoperative pathology and aminotransferase levels were consistent with preoperative energy metabolite measurements. The 30-day survival rates of the control and WIT 15, 30, 45, and 60 min groups were 100%, 81.82%, 76.92%, 58.33%, and 25.00%, respectively. The areas under the receiver operating characteristic curves of glucose, lactate, glycerol, and LPR were 0.87, 0.88, 0.88, and 0.92, respectively.

CONCLUSION

Glucose, lactate, glycerol, and LPR are predictors of graft quality and survival outcomes in DCD transplantation.

Postreperfusion microcirculatory derangements after liver transplantation: Relationship to hemodynamics, serum mediators, and outcome

Despite the growing data supporting the role of microcirculation in regulating liver function, little of this knowledge has been translated into clinical practice. The aim of this study is to quantify hepatic microcirculation in vivo using sidestream dark field (SDF) imaging and correlate these findings with hepatic blood flow, hemodynamic parameters, and soluble mediators. Postreperfusion hepatic microcirculation was assessed using SDF imaging. Hepatic microcirculation measurements included functional sinusoidal density (cm/cm² ), sinusoidal diameter (μm), red blood cell velocity (μm/second), volumetric blood flow (pl/second), and flow heterogeneity (FH) index. The serum concentrations of endothelin 1 (ET-1) and other inflammatory markers were analyzed with Luminex technology. Portal venous and hepatic artery flows were measured using a flowmeter. Twenty-eight patients undergoing cadaveric liver transplantations have been included in this study. Early allograft dysfunction (EAD) occurred in 7 (25%) patients and was associated with microcirculatory dysfunction. Low arterial and portal flow, high dose of inotropes, cold ischemia time, steatosis, and high ET-1 levels were all associated with impaired microcirculation. The time interval between portal venous and hepatic arterial reperfusion significantly correlated with the changes of the liver grafts' microcirculation. EAD patients tended to have higher serum levels of ET-1 on postoperative days 1, 2, 5, and 7 (all P < 0.01). Serum levels of ET-1 correlated significantly with microcirculation parameters. In conclusion, postreperfusion hepatic microcirculation is a determinant of organ dysfunction after liver reperfusion and could be used to identify very early patients at risk of EAD. Liver Transplantation 23 527-536 2017 AASLD.

Remote ischemic perconditioning prevents liver transplantation-induced ischemia/reperfusion injury in rats: Role of ROS/RNS and eNOS

AIM

To investigate the underlying mechanisms of the protective role of remote ischemic perconditioning (RIPerC) in rat liver transplantation.

METHODS

Sprague-Dawley rats were subjected to sham, orthotopic liver transplantation (OLT), ischemic postconditioning (IPostC) or RIPerC. After 3 h reperfusion, blood samples were taken for measurement of alanine aminotransferase, aspartate aminotransferase, creatinine (Cr) and creatinine kinase-myocardial band (CK-MB). The liver lobes were harvested for the following measurements: reactive oxygen species (ROS), H₂O₂, mitochondrial membrane potential (ΔΨm) and total nitric oxide (NO). These measurements were determined using an ROS/H₂O₂, JC1 and Total NOx Assay Kit, respectively. Endothelial NO synthase (eNOS) was analyzed by reverse transcription-polymerase chain reaction (RT-PCR) and western blotting, and peroxynitrite was semi-quantified by western blotting of 3-nitrotyrosine.

RESULTS

Compared with the OLT group, the grafts subjected to RIPerC showed significantly improved liver and remote organ functions (P < 0.05). ROS (P < 0.001) including H₂O₂ (P < 0.05) were largely elevated in the OLT group as compared with the sham group, and RIPerC (P < 0.05) reversed this trend. The collapse of ΔΨm induced by OLT ischemia/reperfusion (I/R) injury was significantly attenuated in the RIPerC group (P < 0.001). A marked increase of NO content and phosphoserine eNOS, both in protein and mRNA levels, was observed in liver graft of the RIPerC group as compared with the OLT group (P < 0.05). I/R-induced 3-nitrotyrosine content was significantly reduced in the RIPerC group as compared with the OLT group (P < 0.05). There were no significant differences between the RIPerC and IPostC groups for all the results except Cr. The Cr level was lower in the RIPerC group than in the IPostC group (P < 0.01).

CONCLUSION

Liver graft protection by RIPerC is similar to or better than that of IPostC, and involves inhibition of oxidative stress and up-regulation of the PI3K/Akt/eNOS/NO pathway.

Current Antioxidant Treatments in Organ Transplantation

Oxidative stress is one of the key mechanisms affecting the outcome throughout the course of organ transplantation. It is widely believed that the redox balance is dysregulated during ischemia and reperfusion (I/R) and causes subsequent oxidative injury, resulting from the formation of reactive oxygen species (ROS). Moreover, in order to alleviate organ shortage, increasing number of grafts is retrieved from fatty, older, and even non-heart-beating donors that are particularly vulnerable to the accumulation of ROS. To improve the viability of grafts and reduce the risk of posttransplant dysfunction, a large number of studies have been done focusing on the antioxidant treatments for the purpose of maintaining the redox balance and thereby protecting the grafts. This review provides an overview of these emerging antioxidant treatments, targeting donor, graft preservation, and recipient as well.

Thioredoxin Protects Skin Flaps from Ischemia-Reperfusion Injury: A Novel Prognostic and Therapeutic Target

BACKGROUND

Ischemia-reperfusion injury is inevitable during free-tissue transfer, causing oxidative damage and extensive apoptosis. Thioredoxin is an endogenous protein with antioxidant and antiapoptotic activity in a variety of tissues. This study aims to investigate the protective effects of human thioredoxin-1 on ischemia-reperfusion flaps, and its clinical application value.

METHODS

Sixteen clinical specimens of ischemia-reperfusion flaps were collected and assessed for apoptosis and thioredoxin-1 expression. Eighty mice were administered recombinant human thioredoxin-1 or saline intraperitoneally for 5 days before ischemia-reperfusion. Half of the mice were killed 24 hours after reperfusion. The flap tissues were harvested and detected for the changes of morphology, apoptosis, redox condition, and relative protein expression. The flap survival percentage of the remaining mice was consecutively observed within 7 days of reperfusion.

RESULTS

Thioredoxin-1 abundance was negatively correlated with ischemia-reperfusion-induced apoptosis in human samples and animal models. The survival rate of the ischemia-reperfusion flaps in mice increased significantly following recombinant human thioredoxin-1 pretreatment. Mitigated tissue damage, reduced apoptosis, and more antioxidant activity were observed in recombinant human thioredoxin-1-pretreated flaps. Western blot analysis revealed thioredoxin-1 depletion and a significant increase in apoptosis signal-regulating kinase 1, p-p38, and cleaved caspase-3 abundance in the ischemia-reperfusion flaps, whereas supplementation of recombinant human thioredoxin-1 significantly reduced the apoptosis-related protein expression.

CONCLUSIONS

Thioredoxin-1 exerts its flap-protective role through redox regulation of reactive oxygen species scavenging and antiapoptotic signaling. The authors' research provides evidence that thioredoxin-1 may serve as a potential prognostic and therapeutic target for skin flap ischemia-reperfusion injury.

Oxygenated Static Preservation of Donation after Cardiac Death Liver Grafts Improves Hepatocyte Viability and Function

BACKGROUND

Cell therapy, such as hepatocyte transplantation (HTx), is promising for the treatment of metabolic liver diseases or as a bridge to orthotopic liver transplantation in patients with fulminant liver failure. However, one of the limitations of this therapy is the shortage of donors. The present study aims to investigate whether the two-layer method (TLM) of cold preservation with oxygenation improves the viability and activity of hepatocytes from rat donation after cardiac death (DCD) donors compared with results obtained with the University of Wisconsin (UW) solution. Moreover, we evaluated the hepatocyte function after culture or transplantation into the spleen.

MATERIALS AND METHODS

We used male Sprague-Dawley rats for this study. The DCD model was induced by phrenotomy after injecting heparin. We assigned rats based on warm ischemia times of 15 and 30 min to groups S and L, respectively. Each group (n = 5) was then subdivided as follows: (1) group S: not preserved (S/N), preserved by TLM for 3 h (S/TLM3) and 12 h (S/TLM12), and in the UW solution for 3 h (S/UW3) and 12 h (S/UW12), and (2) group L: not preserved (L/N), preserved by TLM for 3 h (L/TLM3) and 12 h (L/TLM12), and in the UW solution for 3 h (L/UW3) and 12 h (L/UW12). The cell viability and function of isolated DCD hepatocytes were analyzed for culture or HTx into the spleen.

RESULTS

The viability and ATP levels of DCD hepatocytes significantly improved after TLM compared with the values after preservation in cold UW solution in group S/N (p < 0.059). The levels of albumin production and urea synthesis by hepatocytes after culture were significantly higher in groups S/TLM3 and S/TLM12 than in groups S/UW3 and S/UW12 (p < 0.05), respectively. Further, serum albumin levels after HTx were also markedly higher in groups S/TLM3 and S/TLM12 than in groups S/UW3 and S/UW12. The morphological features revealed that cultured and transplanted hepatocytes remained clearly viable and maintained an expression for specific hepatic function, such as the production of albumin and glycogen.

CONCLUSION

This novel method of oxygenated cold preservation of DCD livers can expand the hepatocyte donor pool for HTx and establish a wider application of this developing technique.

Molecular pathways in protecting the liver from ischaemia/reperfusion injury: a 2015 update

Ischaemia/reperfusion injury is an important cause of liver damage during surgical procedures such as hepatic resection and liver transplantation, and represents the main cause of graft dysfunction post-transplantation. Molecular processes occurring during hepatic ischaemia/reperfusion are diverse, and continuously include new and complex mechanisms. The present review aims to summarize the newest concepts and hypotheses regarding the pathophysiology of liver ischaemia/reperfusion, making clear distinction between situations of cold and warm ischaemia. Moreover, the most updated therapeutic strategies including pharmacological, genetic and surgical interventions, as well as some of the scientific controversies in the field are described.

New strategies and concepts in organ preservation

Organ transplantation is still affected by a notable degree of preservation-associated ischemia and reperfusion injury, which can seriously hamper early graft function. The increasing extension of the criteria for donor organ acceptance, especially for organs that have suffered from periods of warm ischemic injury prior to graft retrieval, results in even higher demands on preserving these ischemia-sensitive grafts. Growing attention is thus directed towards more dynamic preservation methods instead of simple static storage. Particularly in grafts that are retrieved after cardiac standstill of the donor, provision of oxygen to enable some kind of regenerative metabolism appears to be desirable, although the optimal temperature for oxygenated preservation/revitalization is still under debate. Hybrid solutions, comprising conventional cold storage for ease of graft procurement and transportation together with more sophisticated 'in-house' reconditioning protocols after arrival at the implantation clinic, might help to minimize graft injury during the critical transition from preservation to reperfusion.