L-arginine reduces liver and biliary tract damage after liver transplantation from non-heart-beating donor pigs

Treprostinil Supplementation Ameliorates Hepatic Ischemia Reperfusion Injury and Regulates Expression of Hepatic Drug Transporters: An Isolated Perfused Rat Liver (IPRL) Study

Purpose

IR injury is an unavoidable consequence in deceased donor liver transplantation. Cold preservation and warm reperfusion may change the expression and function of drug transporters in the liver due to vasoconstriction, infiltration of neutrophils and release of cytokines. We hypothesize that vasodilation, anti-platelet aggregation and proinflammatory downregulation activities of treprostinil will diminish the IR injury and its associated effects.

Methods

Livers obtained from male SD rats (n = 20) were divided into 1) Control, 2) IR, 3) Treprostinil-1 (preservation only), and 4) Treprostinil-2 (preservation and reperfusion) groups. Control livers were procured and immediately reperfused. Livers in the other groups underwent preservation for 24 h and were reperfused. All the livers were perfused using an Isolated Perfused Rat Liver (IPRL) system. Periodic perfusate, cumulative bile samples and liver tissue at the end of perfusion were collected. Liver injury markers, bile flow rates, m-RNA levels for uptake and efflux transporters (qRT-PCR) were measured.

Results

Cold preservation and warm reperfusion significantly increased the release of AST and ALT in untreated livers. Treprostinil supplementation substantially reduced liver injury. Bile flow rate was significantly improved in treprostinil-2 group. m-RNA levels of Slc10a1, Slc22a1, and Slc22a7 in liver were increased and m-RNA levels of Mdr1a were decreased by IR. Treprostinil treatment increased Abcb11 and Abcg2 m-RNA levels and maintained Slc22a1m-RNA similar to control livers.

Conclusions

Treprostinil treatment significantly reduced liver injury. IR injury changed expression of both uptake and efflux transporters in rat livers. Treprostinil significantly altered the IR injury mediated changes in m-RNA expression of transporters.

HTK-N as a new preservation solution for human kidney preservation: Results of a pilot randomized controlled clinical phase II trial in living donor transplantation

BACKGROUND

HTK-N was developed based on the traditional HTK preservation solution, resulting in stronger protection against reactive oxygen species as well as better tolerance to hypothermia and ischemia. Aim of the present study was to compare HTK-N to HTK in clinical kidney transplantation demonstrating safety and non-inferiority.

METHODS

We performed a randomized controlled single blinded clinical phase II trial in patients undergoing living donor kidney transplantation. After retroperitoneoscopic nephrectomy kidneys were either perfused and stored with classical HTK solution or the new HTK-N solution. Primary endpoint was the glomerular filtration rate (eGFR according to CKD EPI) 3 months after transplantation. Secondary endpoints included graft and patient survival beside others.

RESULTS

The study included 42 patients, of which 22 were randomized in the HTK-N group and 20 in the HTK group. The primary end point showed a mean eGFR of 55.4 ± 14.0 ml/min/1.73 m² in the HTK group compared to a GFR of 57.2 ± 16.7 ml/min/m² in the HTK-N group (P = .72). Regarding secondary endpoints, there were no apparent differences. Posttransplant graft and patient survival was 100%.

CONCLUSION

This study is the first clinical application of HTK-N for kidney preservation and demonstrates non-inferiority compared to HTK in the setting of living donor kidney transplantation.

A prospective, randomized, single-blind, multicentre, phase III study on organ preservation with Custodiol-N solution compared with Custodiol® solution in organ transplantation (kidney, liver and pancreas)

BACKGROUND

Organ preservation before transplantation is still a challenge. Both the University of Wisconsin and Bretschneider's histidine-tryptophan-ketoglutarate (HTK; Custodiol®) solution are standard for liver, kidney and pancreas preservation. Organ preservation with both solutions is comparable; recently, however, Custodiol® solution has been modified to Custodiol-N according to the needs of today. Thus, our study was defined to study its effect in clinical transplantation.

METHODS

Patients undergoing kidney transplantation (n = 412) (including approximately 30 combined kidney-pancreas) or liver transplantation (n = 202) receive grafts that have been cold stored in either Custodiol® or Custodiol-N to demonstrate noninferiority of Custodiol-N regarding both graft function and graft injury after transplantation.

DISCUSSION

Preclinical data have clearly shown that Custodiol-N is superior to Custodiol® in cold static organ preservation via mechanisms including inhibition of hypoxic cell injury, cold-induced cell injury and avoidance of adverse effects during warm exposure to the solution. Further clinical safety data on Custodiol-N for cardioplegia are available. Thus, this study was designed to compare Custodiol® with Custodiol-N for the first time in a prospective, randomized, single-blinded, multicentre, phase III clinical transplantation trial.

TRIAL REGISTRATION

Eudra-CT, 2017-002198-20. Registered on 28 November 2018.

Mesenchymal stem cells improve mouse non-heart-beating liver graft survival by inhibiting Kupffer cell apoptosis via TLR4-ERK1/2-Fas/FasL-caspase3 pathway regulation

Background

Liver transplantation is the optimal treatment option for end-stage liver disease, but organ shortages dramatically restrict its application. Donation after cardiac death (DCD) is an alternative approach that may expand the donor pool, but it faces challenges such as graft dysfunction, early graft loss, and cholangiopathy. Moreover, DCD liver grafts are no longer eligible for transplantation after their warm ischaemic time exceeds 30 min. Mesenchymal stem cells (MSCs) have been proposed as a promising therapy for treatment of certain liver diseases, but the role of MSCs in DCD liver graft function remains elusive.

Methods

In this study, we established an arterialized mouse non-heart-beating (NHB) liver transplantation model, and compared survival rates, cytokine and chemokine expression, histology, and the results of in vitro co-culture experiments in animals with or without MSC infusion.

Results

MSCs markedly ameliorated NHB liver graft injury and improved survival post-transplantation. Additionally, MSCs suppressed Kupffer cell apoptosis, Th1/Th17 immune responses, chemokine expression, and inflammatory cell infiltration. In vitro, PGE2 secreted by MSCs inhibited Kupffer cell apoptosis via TLR4-ERK1/2-caspase3 pathway regulation.

Conclusion

Our study uncovers a protective role for MSCs and elucidates the underlying immunomodulatory mechanism in an NHB liver transplantation model. Our results suggest that MSCs are uniquely positioned for use in future clinical studies owing to their ability to protect DCD liver grafts, particularly in patients for whom DCD organs are not an option according to current criteria.

Mesenchymal stem cells improve mouse non-heart-beating liver graft survival by inhibiting Kupffer cell apoptosis via TLR4-ERK1/2-Fas/FasL-caspase3 pathway regulation

BACKGROUND

Liver transplantation is the optimal treatment option for end-stage liver disease, but organ shortages dramatically restrict its application. Donation after cardiac death (DCD) is an alternative approach that may expand the donor pool, but it faces challenges such as graft dysfunction, early graft loss, and cholangiopathy. Moreover, DCD liver grafts are no longer eligible for transplantation after their warm ischaemic time exceeds 30 min. Mesenchymal stem cells (MSCs) have been proposed as a promising therapy for treatment of certain liver diseases, but the role of MSCs in DCD liver graft function remains elusive.

METHODS

In this study, we established an arterialized mouse non-heart-beating (NHB) liver transplantation model, and compared survival rates, cytokine and chemokine expression, histology, and the results of in vitro co-culture experiments in animals with or without MSC infusion.

RESULTS

MSCs markedly ameliorated NHB liver graft injury and improved survival post-transplantation. Additionally, MSCs suppressed Kupffer cell apoptosis, Th1/Th17 immune responses, chemokine expression, and inflammatory cell infiltration. In vitro, PGE2 secreted by MSCs inhibited Kupffer cell apoptosis via TLR4-ERK1/2-caspase3 pathway regulation.

CONCLUSION

Our study uncovers a protective role for MSCs and elucidates the underlying immunomodulatory mechanism in an NHB liver transplantation model. Our results suggest that MSCs are uniquely positioned for use in future clinical studies owing to their ability to protect DCD liver grafts, particularly in patients for whom DCD organs are not an option according to current criteria.

A systematic review of pharmacological treatment options used to reduce ischemia reperfusion injury in rat liver transplantation

BACKGROUND

Although animal studies models are frequently used for the purpose of attenuating ischemia reperfusion injury (IRI) in liver transplantation (LT), many of pharmacological agents have not become part of clinical routine.

METHODS

A search was performed using the PubMed database to identify agents, from which 58 articles containing 2700 rat LT procedures were selected. The identified pharmacological agents were categorized as follows: I - adenosine agonists, nitric oxide agonists, endothelin antagonists, and prostaglandins, II - Kupffer cell inactivator, III - complement inhibiter, IV - antioxidant, V - neutrophil inactivator, VI -anti-apoptosis agent, VII - heat shock protein and nuclear factor kappa B inducer, VIII - metabolic agent, IX - traditional Chinese medicine, and X - others. Meta-analysis using 7-day-survival rate was also performed with Mantel-Haenszel's Random effects model.

RESULTS

The categorization revealed that the rate of donor-treated experiments in each group was highest for agents from Group II (70%) and VII (71%), whereas it was higher for agents from Group V (83%) in the recipient-treated experiments. Furthermore, 90% of the experiments with agents in Group II provided 7-day-survival benefits. The Risk Ratio (RR) of the meta-analysis was 2.43 [95% CI: 1.88-3.14] with moderate heterogeneity. However, the RR of each of the studies was too model-dependent to be used in the search for the most promising pharmacological agent.

CONCLUSION

With regard to hepatic IRI pathology, the categorization of agents of interest would be a first step in designing suitable multifactorial and pleiotropic approaches to develop pharmacological strategies.

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

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

Graft cholangiopathy: etiology, diagnosis, and therapeutic strategies

BACKGROUND

Graft cholangiopathy has been recognized as a significant cause of morbidity, graft loss, and even mortality in patients after orthotopic liver transplantation. The aim of this review is to analyze the etiology, pathogenesis, diagnosis and therapeutic strategies of graft cholangiopathy after liver transplantation.

DATA SOURCE

A PubMed database search was performed to identify articles relevant to liver transplantation, biliary complications and cholangiopathy.

RESULTS

Several risk factors for graft cholangiopathy after liver transplantation have been identified, including ischemia/reperfusion injury, cytomegalovirus infection, immunological injury and bile salt toxicity. A number of strategies have been attempted to prevent the development of graft cholangiopathy, but their efficacy needs to be evaluated in large clinical studies. Non-surgical approaches may offer good results in patients with extrahepatic lesions. For most patients with complex hilar and intrahepatic biliary abnormalities, however, surgical repair or re-transplantation may be required.

CONCLUSIONS

The pathogenesis of graft cholangiopathy after liver transplantation is multifactorial. In the future, more efforts should be devoted to the development of more effective preventative and therapeutic strategies against graft cholangiopathy.

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

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

The differential tissue expression of inflammatory, oxidative stress, and apoptosis markers in human uncontrolled non-heart-beating donors

BACKGROUND

Uncontrolled non-heart-beating donor (UNHBD) transplantation offers a major opportunity to ameliorate the effects of the donor shortage. However, little is known about the true status of the organs obtained from these donors. UNHBD transplantation is performed under unfavorable conditions and involves exposure to several harmful stimuli that have been identified as triggers for immediate inflammatory response, oxidative stress, and apoptotic phenomena. This adverse scenario could explain the higher rates of graft dysfunction due to primary nonfunction traditionally observed in NHBD. Our aim was to assess the expression of proinflammatory, oxidative, and apoptotic markers in liver, lung, and pancreas tissue samples obtained from UNHBD and to compare these expression levels with those observed in brain-dead donors (BDD).

METHODS

Samples from human type 2 NHBD and BDD were obtained at the end of cold storage. Interleukin (IL)-1β, tumor necrosis factor-α, IL-6, IL-10, endothelial nitric oxide synthase, inducible nitric oxide synthase, type 1 heme oxygenase, type 2 heme oxygenase, Bax, and Bcl-2 protein and mRNA expression, as well as catalase, glutathione peroxidase, and glutathione reductase tissue activity, were determined.

RESULTS

UNHBD showed similar or lower expression of proinflammatory mediators and apoptosis markers in all three organs without modifications to the anti-inflammatory cytokines. Although the major oxidative stress marker levels were also comparable in both types of donors, the type 1 heme oxygenase mRNA expression and antioxidant enzyme activity were slightly diminished in UNHBD.

CONCLUSIONS

The initial tissue damage generated during the UNHB donation process is at least comparable with that observed in BDD. However, although the expression of the immediate immune response and apoptosis markers is similar, a mild impairment of the local antioxidant activity was observed.

The nitric oxide pathway--evidence and mechanisms for protection against liver ischaemia reperfusion injury

Ischaemia reperfusion (IR) injury is a clinical entity with a major contribution to the morbidity and mortality of liver surgery and transplantation. A central pathway of protection against IR injury utilizes nitric oxide (NO). Nitric oxide synthase (NOS) enzymes manufacture NO from L-arginine. NO generated by the endothelial NOS (eNOS) isoform protects against liver IR injury, whereas inducible NOS (iNOS)-derived NO may have either a protective or a deleterious effect during the early phase of IR injury, depending on the length of ischaemia, length of reperfusion and experimental model. In late phase hepatic IR injury, iNOS-derived NO plays a protective role. In addition to NOS consumption of L-arginine during NO synthesis, this amino acid may also be metabolized by arginase, an enzyme whose release is increased during prolonged ischaemia, and therefore diverts L-arginine away from NOS metabolism leading to a drop in the rate of NO synthesis. NO most commonly acts through the soluble guanylyl cyclase-cyclic GMP- protein kinase G pathway to ameliorate hepatic IR injury. Both endogenously generated and exogenously administered NO donors protect against liver IR injury. The beneficial effects of NO on liver IR are not, however, universal, and certain conditions, such as steatosis, may influence the protective effects of NO. In this review, the evidence for, and mechanisms of these protective actions of NO are discussed, and areas in need of further research are highlighted.

Applicability and results of Maastricht type 2 donation after cardiac death liver transplantation

Maastricht type 2 donation after cardiac death (DCD) donors suffer sudden and unexpected cardiac arrest, typically outside the hospital; they have significant potential to expand the donor pool. Herein, we analyze the results of transplanted livers and all potential donors treated under our type 2 DCD protocol. Cardiac arrest was witnessed; potential donors arrived at the hospital after attempts at resuscitation had failed. Death was declared based on the absence of cardiorespiratory activity during a 5-min no-touch period. Femoral vessels were cannulated to establish normothermic extracorporeal membrane oxygenation, which was maintained until organ recovery. From April 2002 to December 2010, there were 400 potential donors; 34 liver transplants were performed (9%). Among recipients, median age, model for end-stage liver disease and cold and reperfusion warm ischemic times were 55 years (49-60), 19 (14-21) and 380 (325-430) and 30 min (26-35), respectively. Overall, 236 (59%) and 130 (32%) livers were turned down due to absolute and relative contraindications to donate, respectively. One-year recipient and graft survivals were 82% and 70%, respectively (median follow-up 24 months). The applicability of type 2 DCD liver transplant was <10%; however, with better preservation technology and expanded transplant criteria, we may be able to improve this figure significantly.

Step-by-step guide for a simplified model of porcine orthotopic liver transplant

BACKGROUND

Based on similar anatomy, physiology, and size to humans, pigs provide an excellent means for studying new therapies related to orthotopic liver transplant (OLT). Techniques that have been described to date, however, are unnecessarily complex and increase the likelihood of morbidity and adverse outcome.

MATERIALS AND METHODS

Male outbred weanling pigs underwent OLT according to our procedure, with a short anhepatic time (<20 min) and without veno-venous bypass or vasoactive substances during the anhepatic phase. Vascular anastomoses were performed identical to the clinical setting, and a simple stented choledochocholedochostomy was created.

RESULTS

The authors have performed this procedure 130 times using four transplant models: standard, whole-liver (n = 10), small-for-size (n = 48), donor after cardiac death (n = 44), and donor adenoviral gene transfection (n = 28). The average cold ischemic and anhepatic times were 302 ± 43 and 17 ± 3 min, respectively. Hypotension was successfully treated with intravenous fluids. In all cases, the recipient survived the operation and was extubated. Survival to the end follow-up varied according to the model and was 56% (73/130) for all cases. At autopsy or euthanasia, no vascular thrombosis or outflow obstruction was found. Survival was 100% for pigs transplanted with standard, whole-liver grafts (n = 10). In this group, AST and bilirubin rose during the first 24 h after graft reperfusion, while the Quick prothrombin time (QPT) fell. By the fifth postoperative day, these parameters had returned to baseline.

CONCLUSIONS

This model is straightforward and reproducible and offers surgeons and researchers the opportunity to perform OLT studies under clinically relevant conditions.

In-vivo normothermic recirculation: an update

PURPOSE OF REVIEW

The use of nonheart-beating donors (NHBD), as a source for liver grafts, is the only way to objectively increase the activity in liver transplantation. Through the use of more strict criteria, 1-year graft survival has increased from 50% in initial series to 84-100%. With respect to type II NHBD (failure of cardiopulmonary resuscitation) we believe that the use of normothermic recirculation provides the possibility to obtain good quality grafts for transplantation. Our recent experience shows a 66% and 73% graft and patient survival respectively.

RECENT FINDINGS

However, the incidence of biliary tract complications (ischemic type), as well as the relative low number of grafts procured that are finally transplanted, makes this methodology difficult to develop. The use of a 'normothermic machine perfusion' (once the liver is procured), added to the already described method, may actually increase the efficacy and safety of the whole procedure. Recent experience by our group as well as others have shown that the liver so perfused is able to recover from the warm ischemic lesion and at the same time the procedure allows the possibility to evaluate the quality of the potential graft.

SUMMARY

NHBD are the only source that may objectively increased the number of liver transplant. The use of normothermic recirculation has proved to be effective and well tolerated. The addition of the 'normothermic machine perfusion' to the whole procedure may significantly increase the number of transplants.

Reduced glutathione in the liver as a potential viability marker in non-heart-beating donors

Although the use of non-heart-beating donors (NHBD) is the oldest type of organ transplantation, the results were and still are disappointing. To consider using a liver from NHBD, it is of importance to assess the graft viability. Our aim was to assess the role of reduced liver glutathione (rGSHL) as a potential predictive marker of liver function before transplantation. Autotransplanted livers were subjected to 0, 60, and 90 minutes of ischemia in 20 pigs. We analyzed systemic cardiocirculatory parameters, bowel ischemia by endotoxin, endotoxin-neutralizing capacity, oxidative stress, hepatic perfusion parameters, liver enzymes, local bowel ischemia, and liver oxidative stress (rGSHL and oxidized glutathione in the liver). Autotransplantation was comparable to donor explantation/recipient transplantation with respect to systemic and hepatic parameters. Liver ischemia for 0, 60, and 90 minutes resulted in survival in 100% (NHBD-0), 71% (NHBD-60), and 57% (NHBD-90) of animals. Of all parameters, only hepatic microperfusion, pHi of the sigmoid colon, and bowel ischemia by endotoxin in the NHBD-90 group showed significant changes compared to NHBD-60 and control animals. Although systemic endotoxin-neutralizing capacity and total glutathione in erythrocytes levels were mainly influenced by cold perfusion, hepatic oxidative stress increased with ischemia time. The cut-off value of 11.5 ng/mmol of rGSHL could distinguish survivors from nonsurvivors, independent of the ischemia time. In conclusion, rGSHL has the potential of becoming an important viability marker, as it could predict survival in autotransplantation NHBD model regardless of the ischemia time. Further investigation to declare reasons for differing rGSHL levels within the liver is required.

Nitric oxide-deficiency regulates hepatic heme oxygenase-1

Nitric oxide plays a crucial role in the maintenance of liver function and integrity. During stress, the inducible heme oxygenase-1 protein and its reaction products, including carbon monoxide, also exert potent hepatoprotective effects. We investigated a potential relationship between endogenous nitric oxide synthesis and the hepatic regulation of heme oxygenase-1. Inhibition of nitric oxide synthesis in vivo by injection of l-NAME led to a dose-dependent induction of heme oxygenase-1 mRNA, protein and activity in the rat liver, whereas did not affect the expression of other heat shock proteins. The effect of l-NAME was demonstrated by hemodynamic changes within the liver circulation as measured by ultrasonic flow probes. Inhibition of nitric oxide synthase led to a decline in hepatic arterial and portal venous blood flow, and subsequently caused liver cell damage. In contrast, the combined administration of l-NAME and the nitric oxide-independent intestinal vasodilator dihydralazine completely restored portal venous flow, abolished the liver cell damage, and prevented the upregulation of heme oxygenase-1, despite inhibition of nitric oxide production. In conclusion, nitric oxide deficiency upregulates hepatic heme oxygenase-1, which is reversible by maintaining hepatic blood flow. This interdependence has important implications for the development of therapeutic strategies aimed at modulating the activity of these hepatoprotective mediator systems.

Gene transduction of an active mutant of akt exerts cytoprotection and reduces graft injury after liver transplantation

Akt is expected to be an effective target for the treatment of ischemia-reperfusion injury (I/R) due to its anti-apoptotic properties and its ability to activate the endothelial nitric oxide synthase (eNOS) enzyme. Therefore, this study was aimed to determine the efficacy of an active mutant of Akt (myr-Akt) to decrease I/R injury in a model of orthotopic liver transplantation in pigs. In addition, we analyzed the contribution of nitric oxide in the Akt-mediated effects by using an eNOS mutant (S1179DeNOS) that mimics the phosphorylation promoted by Akt in the eNOS sequence. Donors were treated with adenoviruses codifying for myr-Akt, S1179DeNOS or beta-galactosidase 24 h before liver harvesting. Then, liver grafts were orthotopically transplanted into their corresponding recipients. Levels of transaminases and lactate dehydrogenase (LDH) increased in all recipients after 24 h of transplant. However, transaminases and LDH levels were significantly lower in the myr-Akt group compared with vehicle. The percentage of apoptotic cells and the amount of activated-caspase 3 protein were also markedly reduced in myr-Akt-treated grafts after 4 days of liver transplant compared with vehicle and S1179DeNOS groups. In conclusion, myr-Akt gene therapy effectively exerts cytoprotection against hepatic I/R injury regardless of the Akt-dependent eNOS activation.

The effect of normothermic recirculation is mediated by ischemic preconditioning in NHBD liver transplantation

We have evaluated the involvement of hepatic preconditioning mediators (adenosine, adenosine A1 and A2 receptors) during normothermic recirculation (NR) in a model of liver transplantation from non-heart-beating donor (NHBD) pigs. Application of NR after 20 min of warm ischemia (WI) reversed the lethal injury associated with transplantation of NHBD livers (achieving 5-day survival and diminishing glutathione S-transferase (GST), aspartate aminotransferase (AST) and hyaluronic acid (HA)). Adenosine administration prior to WI simulated the effect of NR. Measuring adenosine, we found that during NR, hepatic adenosine levels increased and xanthine levels decreased. Then when we blocked A2 receptors the effect of NR was abolished, whereas the blocking of A1 receptors further protected the liver. Furthermore, A2 blocking improved hepatic perfusion during NR whereas A1 blocking reduced it. The study suggests that NR has a preconditioning effect by maintaining adequate adenosine and xanthine levels. During NR, adenosine protects the liver through A2 activation and damages it through A1 activation although simultaneous stimulation of both receptors exerts a clear beneficial effect. The possible relation of NR mechanism with other preconditioning mediators such as cAMP and nitric oxide synthesis are discussed.

Thymoglobulin induction protects liver allografts from ischemia/reperfusion injury

BACKGROUND

Interventions that minimize hepatic ischemia/reperfusion injury (IRI) can expand the donor organ pool. Thymoglobulin (TG) induction therapy has been shown to ameliorate delayed graft function and possibly decrease IRI in cadaver renal transplants recipients. This controlled randomized trial was designated to assess the ability of TG to protect against IRI in liver transplant recipients.

PATIENTS AND METHODS

Twenty-two cadaveric liver transplant recipients were randomized to receive either TG (1.5 mg/kg/dose) during the anhepatic period and QOD x2 doses or no TG. No differences in recipients' demographics were present and donor characteristics were similar in terms of age, cause of death, and cold ischemia time. Maintenance immunosupression consisted of Tacrolimus (or Cyclosporine) and steroids for both groups. Donor biopsies were obtained during organ procurement, cold storage and 1 h after re-vascularization. Post-operative liver function tests were monitored. Early graft function, length of stay, patient and graft survival rates, incidence of primary non-function and rate of rejection were assessed.

RESULTS

Patient and graft survival at 3 months was 100%. There was no incidence of primary graft non-function and no need for re-transplantation. The incidence of acute rejection was similar between the two groups. Patients in the TG group had significant decreases in alanine aminotransferase test at day 1 compared to the control group (p = 0.02). There were also near significant decreases of total bilirubin at day 5 and shorter length of hospitalization. Liver biopsy (at procurement, when cold, and post-reperfusion) of TG group demonstrated a trend for increased central ballooning.

CONCLUSION

The TG allowed for more compromised liver grafts to be transplanted with less clinical evidence of IRI and improved function. Further studies on the degree of apoptosis in the liver biopsy post-reperfusion are underway.

Prevention of meningo/encephalomyelitis due to Sarcocystis neurona infection in mice is mediated by CD8 cells

Immunodeficient CD8 knockout mice were infected with Sarcocystis neurona merozoites, in order to determine the role of CD8 cells in protective immunity. Using a direct agglutination test, all infected mice seroconverted by selected time points. Infected mice developed splenomegaly and bilateral lymphadenopathy. Histological changes included marked follicular development in the spleen, endothelitis and moderate perivascular inflammation in the liver, and meningoencephalitis in the brain. Infected brains were positive for S. neurona by polymerase chain reaction. Corresponding to histopathological changes, there were decreased numbers of B-cells in the spleen. The mice did not have significant memory (CD44hi/CD4) or effector (CD45RBhi/CD4) populations present at the time of euthanasia. Flow cytometry confirmed the lack of CD8 cells. Taken together, these data support previous studies suggesting a critical role for CD8 cells in the prevention of menigoencephalitis in S. neurona-infected mice.

Hepatic ischemia/reperfusion injury can be modulated with thymoglobulin induction therapy

BACKGROUND

Thymoglobulin induction therapy has been shown to ameliorate delayed graft function and possibly decrease ischemia reperfusion injury in cadaver renal transplant recipients. This controlled randomized trial was designed to assess whether thymoglobulin also protects liver transplant recipients from ischemia reperfusion injury.

PATIENTS AND METHODS

Twenty-two cadaver liver transplant recipients were randomized to receive either thymoglobulin (1.5 mg/kg per dose) during the anhepatic period and two doses every other day or no thymoglobulin. No differences in recipient or donor demographics were present. Maintenance immunosupression consisted of tacrolimus (or cyclosporine) and steroids for both groups. Donor biopsies were obtained during organ procurement, cold storage, and 1 hour after revascularization. Postoperative liver function tests were monitored. Early graft function, length of stay, patient and graft survival rates, incidence of primary nonfunction, and rate of rejection were assessed.

RESULTS

Patient and graft survival at 3 months was 100%. There was no incidence of primary graft nonfunction and no need for retransplantation. The incidence of acute rejection was similar between the two groups. Although donor livers randomized to thymoglobulin had less optimal preimplantation biopsies, these recipients had significant decreases in ALT at day 1 compared to the control group (P = .02), near significant decreases of total bilirubin at day 5, and shorter length of hospitalization.

CONCLUSION

Thymoglobulin allowed for more compromised liver grafts to be transplanted with less clinical evidence of ischemia reperfusion injury and improved function.

Liver transplantation from non-heart-beating donors: current status and future prospects

Liver transplantation is the treatment of choice for many patients with acute and chronic liver failure, but its application is limited by a shortage of donor organs. Donor organ shortage is the principal cause of increasing waiting lists, and a number of patients die while awaiting transplantation. Non-heart-beating donor (NHBD) livers are a potential means of expanding the donor pool. This is not a new concept. Prior to the recognition of brainstem death, organs were retrieved from deceased donors only after cardiac arrest. Given the preservation techniques available at that time, this restricted the use of extrarenal organs for transplantation. In conclusion, after establishment of brain death criteria, deceased donor organs were almost exclusively from heart-beating donors (HBDs). To increase organ availability, there is now a resurgence of interest in NHBD liver transplantation. This review explores the basis for this and considers some of the published results.

The utility of marginal donors in liver transplantation

The shortage of organs has led centers to expand their criteria for the acceptance of marginal donors. The combination of multiple marginal factors seems to be additive on graft injury. In this review, the utility of various marginal donors in patients requiring liver transplantation will be described, including older donors, steatotic livers, non-heart-beating donors, donors with viral hepatitis, and donors with malignancies. The pathophysiology of the marginal donor will be discussed, along with strategies for minimizing the ischemia reperfusion injury experienced by these organs. Finally, new strategies for improving the function of the marginal/expanded donor liver will be reviewed.

Hepatic preconditioning after prolonged warm ischemia by means of S-adenosyl-L-methionine administration in pig liver transplantation from non-heart-beating donors

BACKGROUND

This study ascertained the effect of S-adenosyl-L-methionine (SAMe) administration on the ischemia-reperfusion injury associated with pig liver transplantation from non-heart-beating donors (NHBDs) after prolonged warm ischemia.

METHOD

Twenty-five animals underwent transplantation with an allograft from an NHBD. After donor cardiac arrest, cardiopulmonary bypass and normothermic recirculation (NR) were performed for 30 min. Ten animals were given SAMe during NR. Donors were cooled to 15 degrees C, and liver procurement was performed.

RESULTS

SAMe reduced histologic liver damage 5 days after transplantation. The necrotic area affected 15.9%+/-14.5% of the liver biopsies in controls and 7.4%+/-9% in SAMe livers. Six of eight controls and only one of eight survivors in the SAMe group developed ischemic cholangitis. SAMe reduced apoptosis of hepatocytes 5 days after transplantation and apoptosis of sinusoidal endothelial cells at reperfusion and at 5 days. SAMe increased energy charge at the end of NR and favored the balance between adenosine and xanthine. It was also associated with higher portal blood flow (740+/-59.2 vs. 475.2+/-65.0 mL/min-1/m-2), hepatic hyaluronic acid extraction (132+/-72.2 vs. -205.8+/-64.6 microg/L), and lower levels of alpha-glutathione-S-transferase after reperfusion (2,601%+/-581% with respect to baseline vs. 6,488%+/-5,612%).

CONCLUSION

SAMe administration during liver procurement from NHBDs prevents liver endothelial, parenchymal, and biliary tract damage. The protective role of SAMe may be partially mediated by the effect of adenosine during liver procurement.

Liver transplantation from controlled non-heart-beating donors: an increased incidence of biliary complications

BACKGROUND

Hepatic allografts from non-heart-beating donors (NHBD) have been cited as a means to expand the supply of donor livers. Concern exists that donor warm ischemic time in addition to subsequent cold ischemia-reperfusion injury may result in damage to sensitive cell populations within the liver. Because the biliary epithelium is sensitive to ischemia-reperfusion injury, the authors surmised that an increased incidence of biliary complications might occur among recipients of an NHBD allograft.

METHODS

This study was a retrospective evaluation of NHBD recipients compared to a group of heart-beating donor (HBD) recipients from a single institution.

RESULTS

Fifteen patients received a hepatic allograft from a controlled NHBD donor. NHBD and HBD (n=221) graft survival did not differ at 1 (71.8% vs. 85.4%, P=0.23) or 3 years (71.8% vs. 73.9%, P=0.68). Patient survival at 1 (79% vs. 90.9%, P=0.16) and 3 years (79.0% vs. 77.7%, P=0.8) was also similar. Major biliary complications occurred in five (33.3%) NHBD recipients; 66.6% of the NHBD biliary complications consisted of intrahepatic strictures versus 19.2% among HBD recipients (P<0.01). Major biliary complications in the NHBD recipients resulted in multiple interventional procedures, retransplantation, and death.

CONCLUSIONS

Donor warm ischemic time may predispose hepatic allografts to an increased incidence of ischemic type strictures. Although graft and patient survival was similar to a cohort of HBD recipients, caution is urged with the use of these organs.

Long-term dietary L-arginine supplementation attenuates proteinuria and focal glomerulosclerosis in experimental chronic renal transplant failure

Glomerular endothelial nitric oxide synthase expression is decreased in humans during acute rejection and chronic renal transplant failure (CRTF). This may contribute to vascular damage through changes in the renal hemodynamics and enhanced endothelial adhesion of leukocytes and platelets. Dietary supplementation of L-arginine may increase endothelial NO production, thereby protecting the vascular wall and improving renal hemodynamics. We tested the hypothesis that long-term L-arginine supplementation attenuates the development of CRTF in an experimental model for renal transplantation. In the Fisher 344 to Lewis rat model for renal transplantation, renal function and histology of untreated rats was compared with rats receiving L-arginine in the drinking water (10g/L), starting 2 days before transplantation. Every 4 weeks systolic blood pressure was measured and serum and urine were collected for measurement of nitrite and nitrate (NO(x)), creatinine, and proteinuria. At 34 weeks the histological renal damage was assessed by scoring focal glomerulosclerosis and measurement of alpha-smooth muscle actin (alpha-SMA) expression. Urinary NO(x) was significantly increased in treated animals. Proteinuria was significantly lower in L-arginine-treated animals from week 24 onward (p<0.05). Plasma creatinine and creatinine clearance did not differ between the groups. The focal and segmental glomerulosclerosis (FGS) score (max 400) at week 34 was also significantly lower in treated rats arbitrary U (20+/-21 vs 61+/-67 arbitrary U; p<0.05). The expression of alpha-SMA was lower in L-arginine-treated rats than in untreated rats (1.93+/-0.8% area surface vs 3.64+/-2.5% area surface). In conclusion, in this experimental model for CRTF, L-arginine administration significantly reduced FGS and proteinuria, without affecting renal function. Our data suggest that dietary L-arginine supplementation attenuates progression of CRTF and may therefore be an additional therapeutic option in human renal allograft recipients.

Arginine and nitric oxide metabolism in critically ill septic pediatric patients

OBJECTIVE

To investigate whole body, arginine metabolism and nitric oxide synthesis rates in septic, critically ill pediatric patients.

DESIGN

Prospective study.

SETTING

Pediatric intensive care unit at a general hospital.

PATIENTS

Ten consecutive septic patients age 6-16 yrs.

INTERVENTIONS

Septic patients received an 8-hr primed, constant intravenous tracer infusion of L-[guanidino-15N2]arginine, L-[1-13C]leucine, and [13C]urea. A 24-hr urine collection was obtained for determination of [15N]nitrate enrichment (15NO3(-)) and urinary nitrogen. The next day they received an infusion of L-[5-13C]arginine and L-[5-13C-ureido, 5,5, 2H2]citrulline. Blood samples were obtained for determination of plasma isotopic enrichment of the tracers given and of derived [15N]citrulline (nitric oxide synthesis), L-[13C-guanidino 5,5, 2H2]arginine (M+3 arg) (arginine synthesis), and [15N]urea (urea formation). Data are compared with historic controls from studies in healthy young adults.

MEASUREMENTS AND MAIN RESULTS

Plasma arginine fluxes were 67 +/- 21 and 72 +/- 17 micromol x kg(-1) x hr(-1), respectively, for the [15N2 guanidino] and the [13C] arginine labels, which were not different from reported adult values. The rates of arginine oxidation were 22.9 +/- 10.8 micromol x kg(-1) x hr(-1) and were higher than arginine synthesis rates of 9.6 +/- 4.2 micromol x kg(-1) x hr(-1) (p <.01); therefore, these patients were in a negative arginine balance. The rates of nitric oxide synthesis as estimated by the [15N]citrulline method were 1.58 +/- 0.69 micromol x kg(-1) x hr(-1) for septic patients and higher (p <.05) than values of 0.96 +/- 0.1 micromol x kg(-1) x hr(-1) in healthy adults. Septic patients were in a negative protein (leucine) balance of about -1.00 +/- 0.40 g x kg(-1) x day(-1).

CONCLUSIONS

Homeostasis of plasma arginine in septic patients was impaired compared with reported adult values. The rates of arginine oxidation were increased whereas net arginine synthesis was unchanged, leading to a negative arginine balance. The rates of nitric oxide synthesis and the fraction of plasma arginine used for nitric oxide and urea formation were increased. These findings suggest that under condition of sepsis, arginine becomes essential in critically ill children.