Preservation and reperfusion injuries in liver allografts. An overview and synthesis of current studies

Extracorporeal therapies for post-liver transplant recipient: The road less traveled

Extracorporeal therapies have a definite role in patients with acute liver failure, acute on-chronic liver failure, and progressive chronic liver disease. They act as a bridge-to-transplant in these patients. With the increasing success of liver transplantation, the immediate postoperative complication spectrum continues to expand. Extracorporeal therapies can play an important role in managing these complications. However, the literature on extracorporeal therapies in the post-liver transplant period is limited. This review article discussed various extracorporeal therapies that are still evolving or marred by limited evidence but can improve patient outcomes. These extracorporeal therapies can be divided into two subgroups: (1) Therapies for infective complications. Endotoxin and cytokine adsorption columns; and (2) Therapies for noninfective complications like small for size syndrome, primary allograft nonfunction, early allograft dysfunction, hyperacute rejection, hepatopulmonary syndrome, etc. (plasma exchange, double plasma molecular adsorption, molecular adsorbent recirculation system, and extracorporeal membrane oxygenation, among others).

Upper limit of normothermic machine preservation of liver grafts from donation after circulatory death yet to be defined

BACKGROUND

The normothermic machine perfusion pump (NMPP) could shape the future of transplantation. Providing ex-vivo optimization, NMPP attenuates ischemic insult while replenishing energy. An understanding of machine perfusion time (MPT) impact and potential clinical benefits is paramount and necessitates exploration.

AIM

To investigate the relationship between MPT and post-transplant graft function.

METHODS

Retrospective review of the first 50 donation after circulatory death (DCD) grafts preserved using NMPP in a tertiary institution was performed. Essential preservation time points, graft parameters, recipient information, and postoperative outcomes were prospectively recorded. Early allograft dysfunction (EAD), L-Graft₇ score and 90-day outcomes were collected for all grafts. The first 20 recipients were allocated into the early group, considered the learning curve population for the center. The subsequent 30 were allocated into the late group. Recipients were also stratified into cohorts depending on MPT, i.e., short (< 8 hours), medium (8-16 hours) and long (> 16 hours).

RESULTS

NMPP operational parameters were not predictive of EAD, L-GrAFT₇ or 90-day outcomes. The early group had significantly less MPT and cold ischemia time than the late group (553 minutes vs 850 minutes, P < 0.001) and (127.5 minutes vs 154 minutes, P = 0.025), respectively. MPT had no impact in either group.

CONCLUSION

Increased MPT of DCD liver grafts had no adverse recipient results for the times utilized in this population, indicating its upper limits, likely beyond 24 hours, are not demonstrated within this study. Future studies are necessary to determine whether longer MPT is beneficial or detrimental to graft function and, if the latter, what is the maximum safe duration. Further studies of the effect of normothermic machine perfusion pump duration on long-term outcomes are also needed.

Inflammatory Monocytes Are Rapidly Recruited to the Post-Ischaemic Liver in Patients Undergoing Liver Transplantation and Cytokines Associated with Their Activation Correlate with Graft Outcomes

Liver ischaemia-reperfusion (IR) injury remains a major cause of morbidity and mortality following liver transplantation and resection. CD4+ T cells have been shown to play a key role in murine models; however, there is currently a lack of data that support their role in human patients. Methods: Data on clinical outcomes and complications were documented prospectively in 28 patients undergoing first elective liver transplant surgery. Peripheral blood samples were collected at baseline (pre-op), 2 h post graft reperfusion, immediately post-op, and 24 h post-op. A post-reperfusion biopsy was analysed in all patients, and in five patients, a donor liver biopsy was available pre-implantation. Circulating cytokines were measured, and T cells were analysed for activation markers and cytokine production. Results: Circulating levels of cytokines associated with innate immune cell recruitment and activation were significantly elevated in the peri-transplant period. High circulating IL-10 levels corresponded with the development of graft-specific complications. The proportion of CD4+ T cells in the peripheral circulation fell throughout the peri-operative period, suggesting CD4+ T cell recruitment to the graft. Although TNFα was the predominant cytokine produced by CD4+ T cells in the intrahepatic environment, the production of IFNγ was significantly upregulated by circulating CD4+ T cells. Furthermore, we demonstrated clear recruitment of inflammatory monocytes in the peri-operative period. In donor-and-recipient pairs with a mismatch at the HLA-A2 or A3 allele, we demonstrated that inflammatory monocytes in the liver are recipient-derived. Discussion: This is the first study to our knowledge that tracks early immune cell responses in humans undergoing liver transplantation. The recruitment of inflammatory monocytes from the recipient and their cytokine release is associated with liver-specific complications. Inflammatory monocytes would be an attractive target to ameliorate ischaemia-reperfusion injury.

The Role of Fibrinogen and Platelets in Mouse Liver Ischemia-Reperfusion Injury: Distribution and Pathophysiological Insights

Liver ischemia-reperfusion (I/R) injury is a critical issue in clinical settings, particularly in liver transplantation and resection, leading to severe hepatocellular dysfunction and organ failure. This study investigates the role of fibrinogen and platelets in liver I/R injury, focusing on their distribution and pathophysiological impact within liver lobules. Using a mouse model, we examined the expression and localization of fibrinogen and platelets at various time points postreperfusion. In normal liver, fibrinogen is predominantly expressed in hepatic sinusoids near the portal vein, with sparse platelet distribution. Following I/R injury, fibrinogen expression significantly increases in hepatic sinusoids and hepatocytes, accompanied by substantial platelet aggregation and embolization, particularly in Zone 1 of the liver lobules. These findings highlight the zonal heterogeneity of fibrinogen distribution and its regulatory function in platelet adhesion and microthrombi formation. This study provides crucial insights for developing therapeutic strategies targeting fibrinogen and platelet interactions to mitigate liver I/R injury.

Normothermic Machine Perfusion Is Associated With Improvement in Mortality and Graft Failure in Donation After Cardiac Death Liver Transplant Recipients in the United States

Background

Use of normothermic machine perfusion (NMP) may help to expand the liver transplantation (LT) donor pool by potentially increasing the utilization of donation after circulatory death (DCD) organs. The aim of this study was to assess the impact of NMP on LT from DCD organs.

Methods

Data among DCD adult LT recipients in the United Network for Organ Sharing between January 2016 and December 2022 were analyzed. Outcomes were compared between 2 groups: NMP versus non-MP using propensity score matching.

Results

During the study period, 4217 DCD LT recipients (NMP: 257 and non-MP: 3960) were identified. compared with non-MP, DCD LT recipients in NMP group were older (median recipient age: 61 versus 59 y, P = 0.013), had lower model for the end-stage liver disease score, longer wait time (126 versus 107 d, P = 0.028), and received organs from older donors (median age: 42 versus 38 y, P < 0.01) with longer preservation time (9.9 versus 5.3 h, P < 0.001). Two-year overall survival (NMP 94.4% versus non-MP 89.7%, P = 0.040) and 2-y graft survival (NMP 91.3% versus non-MP 84.6%, P = 0.017) were better in the NMP group. After propensity score matching, 2-y overall survival (NMP 94.2% versus non-MP 88.0%, P = 0.023) and graft survival (NMP 91.3% versus non-MP 81.6%, P = 0.004) were better in the NMP group. On multivariable cox regression analysis, NMP was an independent factor of protection against mortality (hazard ratio, 0.43; 95% confidence interval: 0.20-0.91; P = 0.029) and against graft failure (hazard ratio, 0.26; 95% confidence interval: 0.11-0.61; P = 0.002).

Conclusions

Use of NMP for LT from DCD donors was associated with improved posttransplant patient and graft survival.

The Effect of Pringle Maneuver Applied during Living Donor Hepatectomy on the Ischemia-Reperfusion Injury Observed in the Donors and Recipients

Background and Objectives: The aim of this study is to evaluate the clinical and laboratory changes of ischemia and reperfusion injury in the remnant livers of donors with and without Pringle maneuver. Furthermore, we evaluated the recipients who have been transplanted with liver grafts from these donors. Methods and Materials: A total of 108 patients (54 living liver donors and 54 liver recipients) who underwent donor hepatectomy and recipients who living donor liver transplantation, were included in this randomized double-blind study between February 2021 and June 2021. The donors were divided into two groups: Pringle maneuver applied (n = 27) and Pringle maneuver not applied (n = 27). Similarly, recipients with implanted liver obtained from these donors were divided into two groups as the Pringle maneuver was performed (n = 27) and not performed (n = 27). Blood samples from donors and recipients were obtained on pre-operative, post-operative 0 h day (day of surgery), post-operative 1st day, post-operative 2nd day, post-operative 3rd day, post-operative 4th day, post-operative 5th day, and liver tissue was taken from the graft during the back table procedures. Liver function tests and complete blood count, coagulation tests, IL-1, IL-2, IL-6, TNF-α, and β-galactosidase measurements, and histopathological findings were examined. Results: There was no statistically significant difference in the parameters of biochemical analyses for ischemia-reperfusion injury at all periods in the donors with and without the Pringle maneuver. Similarly, there was no statistically significant difference between in the recipients in who received liver grafts harvested with and without the Pringle maneuver. There was no statistically significant difference between the two recipient groups in terms of perioperative bleeding and early bile duct complications (p = 0.685). In the histopathological examinations, hepatocyte damage was significantly higher in the Pringle maneuver group (p = 0.001). Conclusions: Although the histological scoring of hepatocyte damage was found to be higher in the Pringle maneuver group, the Pringle maneuver did not augment ischemia-reperfusion injury in donors and recipients that was evaluated by clinical and laboratory analyses.

Assessing Liver Viability: Insights From Mitochondrial Bioenergetics in Ischemia-Reperfusion Injury

Orthotopic liver transplantation remains the definitive treatment for patients with end-stage liver disease. Unfortunately, the increasing demand for donor livers and the limited supply of viable organs have both led to a critical need for innovative strategies to expand the pool of transplantable organs. The mitochondrion, central to hepatic cellular function, plays a pivotal role in hepatic ischemic injury, with impaired mitochondrial function and oxidative stress leading to cell death. Mitochondrial protection strategies have shown promise in mitigating IRI and resuscitating marginal organs for transplant. Machine perfusion (MP) has been proven a valuable tool for reviving marginal organs with very promising results. Evaluation of liver viability during perfusion traditionally relies on parameters including lactate clearance, bile production, and transaminase levels. Nevertheless, the quest for more comprehensive and universally applicable viability markers persists. Normothermic regional perfusion has gained robust attention, offering extended recovery time for organs from donation after cardiac death donors. This approach has shown remarkable success in improving organ quality and reducing ischemic injury using the body's physiological conditions. The current challenge lies in the absence of a reliable assessment tool for predicting graft viability and post-transplant outcomes. To address this, exploring insights from mitochondrial function in the context of ischemia-reperfusion injury could offer a promising path toward better patient outcomes and graft longevity. Indeed, hypoxia-induced mitochondrial injury may serve as a surrogate marker of organ viability following oxygenated resuscitation techniques in the future.

Viability assessment and transplantation of fatty liver grafts using end-ischemic normothermic machine perfusion

End-ischemic viability testing by normothermic machine perfusion (NMP) represents an effective strategy to recover liver grafts having initially been discarded for liver transplantation (LT). However, its results in the setting of significant (≥30%) macrovesicular steatosis (MaS) have not been specifically assessed. Prospectively maintained databases at two high-volume LT centers in Northern Italy were searched to identify cases of end-ischemic NMP performed to test the viability of livers with MaS ≥ 30% in the period from January 2019 to January 2022. A total of 14 cases were retrieved, representing 57.9% of NMP and 5.7% of all machine perfusion procedures. Of those patients, 10 (71%) received transplants. Two patients developed primary nonfunction (PNF) and required urgent re-LT, and both were characterized by incomplete or suboptimal lactate clearance during NMP. PNF cases were also characterized by higher perfusate transaminases, lower hepatic artery and portal vein flows at 2 h, and a lack of glucose metabolism in one case. The remaining eight patients showed good liver function (Liver Graft Assessment Following Transplantation risk score, -1.9 [risk, 13.6%]; Early Allograft Failure Simplified Estimation score, -3.7 [risk, 2.6%]) and had a favorable postoperative course. Overall, NMP allowed successful transplantation of 57% of livers with moderate-to-severe MaS. Our findings suggest that prolonged observation (≥6 h) might be required for steatotic livers and that stable lactate clearance is a fundamental prerequisite for their use.

Methane Admixture Protects Liver Mitochondria and Improves Graft Function after Static Cold Storage and Reperfusion

Mitochondria are targets of cold ischemia-reperfusion (IR), the major cause of cell damage during static cold preservation of liver allografts. The bioactivity of methane (CH₄) has recently been recognized in various hypoxic and IR conditions as having influence on many aspects of mitochondrial biology. We therefore hypothesized that cold storage of liver grafts in CH₄-enriched preservation solution can provide an increased defence against organ dysfunction in a preclinical rat model of liver transplantation. Livers were preserved for 24 h in cold histidine-tryptophan-ketoglutarate (HTK) or CH₄-enriched HTK solution (HTK-CH₄) (n = 24 each); then, viability parameters were monitored for 60 min during normothermic isolated reperfusion and perfusate and liver tissue were collected. The oxidative phosphorylation capacity and extramitochondrial Ca²⁺ movement were measured by high resolution respirometry. Oxygen and glucose consumption increased significantly while hepatocellular damage was decreased in the HTK-CH₄ grafts compared to the HTK group. Mitochondrial oxidative phosphorylation capacity was more preserved (128.8 ± 31.5 pmol/s/mL vs 201.3 ± 54.8 pmol/s/mL) and a significantly higher Ca²⁺ flux was detected in HTK-CH₄ storage (2.9 ± 0.1 mV/s) compared to HTK (2.3 ± 0.09 mV/s). These results demonstrate the direct effect of CH₄ on hepatic mitochondrial function and extramitochondrial Ca²⁺ fluxes, which may have contributed to improved graft functions and a preserved histomorphology after cold IR.

Outcomes of Liver Transplantation Using Machine Perfusion in Donation after Cardiac Death vs Brain Death in the US

BACKGROUND

Liver transplant (LT) outcomes using machine perfusion (MP) in donation after brain death (DBD) is promising, but the LT outcomes of MP in donation after cardiac death (DCD) is limited in the US. The aim of this study was to compare LT outcomes of MP between DCD and DBD.

STUDY DESIGN

We analyzed data from the United Network for Organ Sharing between 2016 and 2021 among adult LT recipients. Propensity score matching was performed to assess the outcomes between DCD and DBD.

RESULTS

A total of 380 LTs (295 from DBD and 85 from DCD) were performed using MP. When compared with DBD, DCD group had older median recipient age (61 vs 58 years, p = 0.03), higher prevalence of diabetes (41% vs 28%, p = 0.02), lower model for end-stage liver disease score (17 vs 22, p < 0.01), longer wait time (276 vs 143 days, p < 0.01) and younger median donor age (40 vs 51 years, p < 0.01). The most common primary diagnosis was alcohol-related liver disease, and hepatocellular carcinoma was more common in the DCD group (22% vs 13%). On survival analysis, 1-year overall/graft survivals (DCD 95.4% vs DBD 92.1%, p = 0.54; DCD 91.7% vs DBD 89.8%, p = 0.86) were the same. After propensity score matching, overall/graft survivals were the same. In Cox regression analysis, DCD was not an independent risk factor of mortality (hazard ratio 0.80; 95% CI 0.25 to 2.52; p = 0.70) and graft failure (hazard ratio 0.58; 95% CI 0.17 to 1.97; p = 0.38).

CONCLUSIONS

In transplant recipients who underwent LT using MP, posttransplant outcomes of overall and graft survival were similar among DCD and DBD cohorts.

Application of polymerized porcine hemoglobin in the ex vivo normothermic machine perfusion of rat livers

Background: In contrast to traditional static cold preservation of donor livers, normothermic machine perfusion (NMP) may reduce preservation injury, improve graft viability and potentially allows ex vivo assessment of graft viability before transplantation. The polymerized porcine hemoglobin is a kind of hemoglobin oxygen carrier prepared by crosslinking porcine hemoglobin by glutaraldehyde to form a polymer. The pPolyHb has been proved to have the ability of transporting oxygen which could repair the organ ischemia-reperfusion injury in rats. Objective: In order to evaluate the effectiveness of rat liver perfusion in vitro based on pPolyHb, we established the NMP system, optimized the perfusate basic formula and explored the optimal proportion of pPolyHb and basal perfusate. Methods: The liver was removed and perfused for 6 h at 37°C. We compared the efficacy of liver perfusion with different ratios of pPolyHb. Subsequently, compared the perfusion effect using Krebs Henseleit solution and pPolyHb perfusate of the optimal proportion, and compared with the liver preserved with UW solution. At 0 h, 1 h, 3 h and 6 h after perfusion, appropriate samples were collected for blood gas analysis and liver injury indexes detection. Some tissue samples were collected for H&E staining and TUNEL staining to observe the morphology and detect the apoptosis rate of liver cells. And we used Western Blot test to detect the expression of Bcl-2 and Bax in the tissues. Results: According to the final results, the optimal addition ratio of pPolyHb was 24%. By comparing the values of Bcl-2/Bax, the apoptosis rate of pPolyHb group was significantly reduced. Under this ratio, the results of H&E staining and TUNEL staining showed that the liver morphology was well preserved without additional signs of hepatocyte ischemia, biliary tract injury, or hepatic sinusoid injury, and hepatocyte apoptosis was relatively mild. Conclusion: Through the above-mentioned study we show that within 6 h of perfusion based on pPolyHb, liver physiological and biochemical activities may essentially be maintained in vitro. This study demonstrates that a pPolyHb-based perfusate is feasible for NMP of rat livers. This opens up a prospect for further research on NMP.

Transplantation of a human liver following 3 days of ex situ normothermic preservation

Current organ preservation methods provide a narrow window (usually <12 hours) to assess, transport and implant donor grafts for human transplantation. Here we report the transplantation of a human liver discarded by all centers, which could be preserved for several days using ex situ normothermic machine perfusion. The transplanted liver exhibited normal function, with minimal reperfusion injury and the need for only a minimal immunosuppressive regimen. The patient rapidly recovered a normal quality of life without any signs of liver damage, such as rejection or injury to the bile ducts, according to a 1-year follow up. This inaugural clinical success opens new horizons in clinical research and promises an extended time window of up to 10 days for assessment of viability of donor organs as well as converting an urgent and highly demanding surgery into an elective procedure.

How useful is the machine perfusion in liver transplantation? An answer from a national survey

Machine perfusion (MP) has been shown worldwide to offer many advantages in liver transplantation, but it still has some gray areas. The purpose of the study is to evaluate the donor risk factors of grafts, perfused with any MP, that might predict an ineffective MP setting and those would trigger post-transplant early allograft dysfunction (EAD). Data from donors of all MP-perfused grafts at six liver transplant centers have been analyzed, whether implanted or discarded after perfusion. The first endpoint was the negative events after perfusion (NegE), which is the number of grafts discarded plus those that were implanted but lost after the transplant. A risk factor analysis for NegE was performed and marginal grafts for MP were identified. Finally, the risk of EAD was analyzed, considering only implanted grafts. From 2015 to September 2019, 158 grafts were perfused with MP: 151 grafts were implanted and 7 were discarded after the MP phase because they did not reach viability criteria. Of 151, 15 grafts were lost after transplant, so the NegE group consisted of 22 donors. In univariate analysis, the donor risk index >1.7, the presence of hypertension in the medical history, static cold ischemia time, and the moderate or severe macrovesicular steatosis were the significant factors for NegE. Multivariate analysis confirmed that macrosteatosis >30% was an independent risk factor for NegE (odd ratio 5.643, p = 0.023, 95% confidence interval, 1.27-24.98). Of 151 transplanted patients, 34% experienced EAD and had worse 1- and 3-year-survival, compared with those who did not face EAD (NoEAD), 96% and 96% for EAD vs. 89% and 71% for NoEAD, respectively (p = 0.03). None of the donor/graft characteristics was associated with EAD even if the graft was moderately steatotic or fibrotic or from an aged donor. For the first time, this study shows that macrovesicular steatosis >30% might be a warning factor involved in the risk of graft loss or a cause of graft discard after the MP treatment. On the other hand, the MP seems to be useful in reducing the donor and graft weight in the development of EAD.

Necroptosis in Solid Organ Transplantation: A Literature Overview

Ischemia-reperfusion injury (IRI) is encountered in various stages during solid organ transplantation (SOT). IRI is known to be a multifactorial inflammatory condition involving hypoxia, metabolic stress, leukocyte extravasation, cellular death (including apoptosis, necrosis and necroptosis) and an activation of immune response. Although the cycle of sterile inflammation during IRI is consistent among different organs, the underlying mechanisms are poorly understood. Receptor-interacting protein kinase 3 (RIPK3) and mixed-lineage kinase domain-like pseudokinase (MLKL) are thought to be crucial in the implementation of necroptosis. Moreover, apart from "silent" apoptotic death, necrosis also causes sterile inflammation-necroinflammation, which is triggered by various damage-associated molecular patterns (DAMPs). Those DAMPs activate the innate immune system, causing local and systemic inflammatory responses, which can result in graft failure. In this overview we summarize knowledge on mechanisms of sterile inflammation processes during SOT with special focus on necroptosis and IRI and discuss protective strategies.

Ex vivo normothermic preservation of amputated limbs with a hemoglobin-based oxygen carrier perfusate

BACKGROUND

Ex vivo normothermic limb perfusion (EVNLP) preserves amputated limbs under near-physiologic conditions. Perfusates containing red blood cells (RBCs) have shown to improve outcomes during ex vivo normothermic organ perfusion, when compared with acellular perfusates. To avoid limitations associated with the use of blood-based products, we evaluated the feasibility of EVNLP using a polymerized hemoglobin-based oxygen carrier-201 (HBOC-201).

METHODS

Twenty-four porcine forelimbs were procured from Yorkshire pigs. Six forelimbs underwent EVNLP with an HBOC-201-based perfusate, six with an RBC-based perfusate, and 12 served as static cold storage (SCS) controls. Ex vivo normothermic limb perfusion was terminated in the presence of systolic arterial pressure of 115 mm Hg or greater, fullness of compartments, or drop of tissue oxygen saturation by 20%. Limb contractility, weight change, compartment pressure, tissue oxygen saturation, oxygen uptake rates (OURs) were assessed. Perfusate fluid-dynamics, gases, electrolytes, metabolites, methemoglobin, creatine kinase, and myoglobin concentration were measured. Uniformity of skin perfusion was assessed with indocyanine green angiography and infrared thermography.

RESULTS

Warm ischemia time before EVNLP was 35.50 ± 8.62 minutes (HBOC-201), 30.17 ± 8.03 minutes (RBC) and 37.82 ± 10.45 (SCS) (p = 0.09). Ex vivo normothermic limb perfusion duration was 22.5 ± 1.7 hours (HBOC-201) and 28.2 ± 7.3 hours (RBC) (p = 0.04). Vascular flow (325 ± 25 mL·min-1 vs. 444.7 ± 50.6 mL·min-1; p = 0.39), OUR (2.0 ± 1.45 mL O2·min-1·g-1 vs. 1.3 ± 0.92 mL O2·min-1·g-1 of tissue; p = 0.80), lactate (14.66 ± 4.26 mmol·L-1 vs. 13.11 ± 6.68 mmol·L-1; p = 0.32), perfusate pH (7.53 ± 0.25 HBOC-201; 7.50 ± 0.23 RBC; p = 0.82), flexor (28.3 ± 22.0 vs. 27.5 ± 10.6; p = 0.99), and extensor (31.5 ± 22.9 vs. 28.8 ± 14.5; p = 0.82) compartment pressures, and weight changes (23.1 ± 3.0% vs. 13.2 ± 22.7; p = 0.07) were not significantly different between HBOC-201 and RBC groups, respectively. In HBOC-201 perfused limbs, methemoglobin levels increased, reaching 47.8 ± 12.1% at endpoint. Methemoglobin saturation did not affect OUR (ρ = -0.15, r2 = 0.022; p = 0.45). A significantly greater number of necrotic myocytes was found in the SCS group at endpoint (SCS, 127 ± 17 cells; HBOC-201, 72 ± 30 cells; RBC-based, 56 ± 40 cells; vs. p = 0.003).

CONCLUSION

HBOC-201- and RBC-based perfusates similarly support isolated limb physiology, metabolism, and function.

Impact of Portable Normothermic Blood-Based Machine Perfusion on Outcomes of Liver Transplant: The OCS Liver PROTECT Randomized Clinical Trial

Question

Can oxygenated portable normothermic perfusion of deceased donor livers for transplant improve outcomes compared with the current standard of care using ischemic cold storage?

Findings

In this multicenter randomized clinical trial of 300 recipients of liver transplants with the donor liver preserved by either normothermic perfusion or conventional ischemic cold storage, normothermic machine perfusion resulted in decreased early liver graft injury and ischemic biliary complications and greater organ utilization.

Meaning

In this study, portable normothermic oxygenated machine perfusion of donor liver grafts resulted in improved outcomes after liver transplant and in more livers being transplanted.

Importance

Ischemic cold storage (ICS) of livers for transplant is associated with serious posttransplant complications and underuse of liver allografts.

Objective

To determine whether portable normothermic machine perfusion preservation of livers obtained from deceased donors using the Organ Care System (OCS) Liver ameliorates early allograft dysfunction (EAD) and ischemic biliary complications (IBCs).

Design, Setting, and Participants

This multicenter randomized clinical trial (International Randomized Trial to Evaluate the Effectiveness of the Portable Organ Care System Liver for Preserving and Assessing Donor Livers for Transplantation) was conducted between November 2016 and October 2019 at 20 US liver transplant programs. The trial compared outcomes for 300 recipients of livers preserved using either OCS (n = 153) or ICS (n = 147). Participants were actively listed for liver transplant on the United Network of Organ Sharing national waiting list.

Interventions

Transplants were performed for recipients randomly assigned to receive donor livers preserved by either conventional ICS or the OCS Liver initiated at the donor hospital.

Main Outcomes and Measures

The primary effectiveness end point was incidence of EAD. Secondary end points included OCS Liver ex vivo assessment capability of donor allografts, extent of reperfusion syndrome, incidence of IBC at 6 and 12 months, and overall recipient survival after transplant. The primary safety end point was the number of liver graft–related severe adverse events within 30 days after transplant.

Results

Of 293 patients in the per-protocol population, the primary analysis population for effectiveness, 151 were in the OCS Liver group (mean [SD] age, 57.1 [10.3] years; 102 [67%] men), and 142 were in the ICS group (mean SD age, 58.6 [10.0] years; 100 [68%] men). The primary effectiveness end point was met by a significant decrease in EAD (27 of 150 [18%] vs 44 of 141 [31%]; P = .01). The OCS Liver preserved livers had significant reduction in histopathologic evidence of ischemia-reperfusion injury after reperfusion (eg, less moderate to severe lobular inflammation: 9 of 150 [6%] for OCS Liver vs 18 of 141 [13%] for ICS; P = .004). The OCS Liver resulted in significantly higher use of livers from donors after cardiac death (28 of 55 [51%] for the OCS Liver vs 13 of 51 [26%] for ICS; P = .007). The OCS Liver was also associated with significant reduction in incidence of IBC 6 months (1.3% vs 8.5%; P = .02) and 12 months (2.6% vs 9.9%; P = .02) after transplant.

Conclusions and Relevance

This multicenter randomized clinical trial provides the first indication, to our knowledge, that normothermic machine perfusion preservation of deceased donor livers reduces both posttransplant EAD and IBC. Use of the OCS Liver also resulted in increased use of livers from donors after cardiac death. Together these findings indicate that OCS Liver preservation is associated with superior posttransplant outcomes and increased donor liver use.

Trial Registration

ClinicalTrials.gov Identifier: NCT02522871

Liver regeneration biology: Implications for liver tumour therapies

The liver has remarkable regenerative potential, with the capacity to regenerate after 75% hepatectomy in humans and up to 90% hepatectomy in some rodent models, enabling it to meet the challenge of diverse injury types, including physical trauma, infection, inflammatory processes, direct toxicity, and immunological insults. Current understanding of liver regeneration is based largely on animal research, historically in large animals, and more recently in rodents and zebrafish, which provide powerful genetic manipulation experimental tools. Whilst immensely valuable, these models have limitations in extrapolation to the human situation. In vitro models have evolved from 2-dimensional culture to complex 3 dimensional organoids, but also have shortcomings in replicating the complex hepatic micro-anatomical and physiological milieu. The process of liver regeneration is only partially understood and characterized by layers of complexity. Liver regeneration is triggered and controlled by a multitude of mitogens acting in autocrine, paracrine, and endocrine ways, with much redundancy and cross-talk between biochemical pathways. The regenerative response is variable, involving both hypertrophy and true proliferative hyperplasia, which is itself variable, including both cellular phenotypic fidelity and cellular trans-differentiation, according to the type of injury. Complex interactions occur between parenchymal and non-parenchymal cells, and regeneration is affected by the status of the liver parenchyma, with differences between healthy and diseased liver. Finally, the process of termination of liver regeneration is even less well understood than its triggers. The complexity of liver regeneration biology combined with limited understanding has restricted specific clinical interventions to enhance liver regeneration. Moreover, manipulating the fundamental biochemical pathways involved would require cautious assessment, for fear of unintended consequences. Nevertheless, current knowledge provides guiding principles for strategies to optimise liver regeneration potential.

Role of eicosanoids in liver repair, regeneration and cancer

Eicosanoids are lipid signaling molecules derived from the oxidation of ω-6 fatty acids, usually arachidonic acid. There are three major pathways, including the cyclooxygenase (COX), lipoxygenase (LOX), and P450 cytochrome epoxygenase (CYP) pathway. Prostanoids, which include prostaglandins (PG) and thromboxanes (Tx), are formed via the COX pathway, leukotrienes (LT) and lipoxins (LX) by the action of 5-LOX, and hydroxyeicosatetraenoic acids (HETEs) and epoxyeicosatrienoic acids (EETs) by CYP. Although eicosanoids are usually associated with pro-inflammatory responses, non-classic eicosanoids, as LX, have anti-inflammatory and pro-resolving properties. Eicosanoids like PGE₂, LTB₄ and EETs have been involved in promoting liver regeneration after partial hepatectomy. PGE₂ and LTB₄ have also been reported to participate in the regenerative phase after ischemia and reperfusion (I/R), while cysteinyl leukotrienes (Cys-LT) contribute to the inflammatory process associated with I/R and are also involved in liver fibrosis and cirrhosis. However, LX, another product of 5-LOX, have the opposite effect, acting as pro-resolving mediators in these pathologies. In liver cancer, most studies show that eicosanoids, with the exception of LX, promote the proliferation of hepatocellular carcinoma cells and favor metastasis. This review summarizes the synthesis of different eicosanoids in the liver and discusses key findings from basic research linking eicosanoids to liver repair, regeneration and cancer and the impact of targeting eicosanoid cascade. In addition, studies in patients are presented that explore the potential use of eicosanoids as biomarkers and show correlations between eicosanoid production and the course and prognosis of liver disease.

DUSP12 acts as a novel endogenous protective signal against hepatic ischemia-reperfusion damage by inhibiting ASK1 pathway

Ischemia–reperfusion injury (IRI) consequent to major liver surgery is a still unmet clinical problem. The activation of endogenous systems of hepatoprotection can prevent the damaging effects of ischemia–reperfusion (IR) as shown by the phenomenon known as ‘ischemic preconditioning’. The identification of endogenous signal mediators of hepatoprotection is of main interest since they could be targeted in future therapeutic interventions. Qiu et al. recently reported in Clin. Sci. (Lond.) (2020) 134(17), 2279–2294, the discovery of a novel protective molecule against hepatic IR damage: dual-specificity phosphatase 12 (DUSP12). IR significantly decreased DUSP12 expression in liver whereas DUSP12 overexpression in hepatocytes protected IRI and DUSP12 deletion in DUSP12 KO mice exacerbated IRI. The protective effects of DUSP12 depended on apoptosis signal-regulating kinase 1 (ASK1) and acted through the inhibition of the ASK1-dependent kinases c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK). These results enlighten DUSP12 as a novel intermediate negative regulator of the pro-inflammatory and pro-apoptotic ASK1/JNK-p38 MAPK pathway activated during hepatic IR and identify DUSP12 as potential therapeutic target for IRI.

An oxygenated perfluorocarbon emulsion improves liver graft preservation evaluated in DCD livers of male sprague dawley rats

The application of perfluorocarbons, which can carry large quantities of oxygen, in organ preservation was limited by their poor solubility in water. A stable form of perfluorocarbon dispersed in suitable buffers is urgently needed. Perfluorocarbon emulsion was designed and characterized with respect to size distribution, rheology, stability, and oxygen-carrying capacity. The state of DCD rat donor livers preserved by the oxygenated perfluorocarbon emulsion was studied after ex vivo reperfusion by using biochemistry, pathology, and immunohistochemistry methods. Perfluorocarbon emulsion was successfully prepared by high-pressure homogenization. Optimized perfluorocarbon emulsion showed nanoscale size distribution, good stability, and higher oxygen loading capacity than that of HTK solution or water. The state of preserved livers after cardiac death rat liver was improved significantly after static cold storage for 48 hours in this oxygenated perfluorocarbon emulsion. The ATP content and down-regulation of HIF-1a expression after preservation of the liver graft by the oxygenated perfluorocarbon emulsion suggested the advantage of adequate oxygen supply for adequate time. This perfluorocarbon emulsion reported here might be considered a promising system for oxygenated donor liver storage by attenuation of hypoxia.

Role of Dietary Nutritional Treatment on Hepatic and Intestinal Damage in Transplantation with Steatotic and Non-Steatotic Liver Grafts from Brain Dead Donors

Herein, we investigate whether: (1) the administration of glucose or a lipid emulsion is useful in liver transplantation (LT) using steatotic (induced genetically or nutritionally) or non-steatotic livers from donors after brain death (DBDs); and (2) any such benefits are due to reductions in intestinal damage and consequently to gut microbiota preservation. In recipients from DBDs, we show increased hepatic damage and failure in the maintenance of ATP, glycogen, phospholipid and growth factor (HGF, IGF1 and VEGFA) levels, compared to recipients from non-DBDs. In recipients of non-steatotic grafts from DBDs, the administration of glucose or lipids did not protect against hepatic damage. This was associated with unchanged ATP, glycogen, phospholipid and growth factor levels. However, the administration of lipids in steatotic grafts from DBDs protected against damage and ATP and glycogen drop and increased phospholipid levels. This was associated with increases in growth factors. In all recipients from DBDs, intestinal inflammation and damage (evaluated by LPS, vascular permeability, mucosal damage, TLR4, TNF, IL1, IL-10, MPO, MDA and edema formation) was not shown. In such cases, potential changes in gut microbiota would not be relevant since neither inflammation nor damage was evidenced in the intestine following LT in any of the groups evaluated. In conclusion, lipid treatment is the preferable nutritional support to protect against hepatic damage in steatotic LT from DBDs; the benefits were independent of alterations in the recipient intestine.

Metabolic Profiling of Skeletal Muscle During Ex-Vivo Normothermic Limb Perfusion

INTRODUCTION

Ex vivo normothermic limb perfusion (EVNLP) provides several advantages for the preservation of limbs following amputation: the ability to maintain oxygenation and temperature of the limb close to physiological values, a perfusion solution providing all necessary nutrients at optimal concentrations, and the ability to maintain physiological pH and electrolytes. However, EVNLP cannot preserve the organ viability infinitely. We identified evidence of mitochondrial injury (swelling, elongation, and membrane disruption) after 24 hours of EVNLP of human upper extremities. The goal of this study was to identify metabolic derangements in the skeletal muscle during EVNLP.

MATERIALS AND METHODS

Fourteen human upper extremities were procured from organ donors after family consent. Seven limbs underwent EVNLP for an average of 41.6 ± 9.4 hours, and seven contralateral limbs were preserved at 4°C for the same amount of time. Muscle biopsies were performed at 24 hours of perfusion, both from the EVNLP and control limbs. Perturbations in the metabolic profiles of the muscle during EVNLP were determined via untargeted liquid chromatography-mass spectrometry (MS) operated in positive and negative electrospray ionization modes, over a mass range of 50 to 750 Da. The data were deconvoluted using the XCMS software and further statistically analyzed using the in-house statistical package, MetaboLyzer. Putative identification of metabolites using exact mass within ±7 ppm mass error and MS/MS spectral matching to the mzCloud spectral library were performed via Compound Discoverer v.2.1 (Thermo Scientific, Fremont, CA, USA). We further validated the identity of candidate metabolites by matching the fragmentation pattern of these metabolites to those of their reference pure chemicals. A nonparametric Mann-Whitney U-test was used to compare EVNLP and control group spectral features. Differences were considered significantly different when P-value < 0.05.

RESULTS

We detected over 13,000 spectral features of which 58 met the significance criteria with biologically relevant putative identifications. Furthermore we were able to confirm the identities of the ions taurine (P-value: 0.002) and tryptophan (P-value: 0.002), which were among the most significantly perturbed ions at 24 hours between the experimental and control groups. Metabolites belonging to the following pathways were the most perturbed at 24 hours: neuroactive ligand-receptor interaction (P-values: 0.031 and 0.036) and amino acid metabolism, including tyrosine and tryptophan metabolism (P-values: 0.015, 0.002, and 0.017). Taurine abundance decreased and tryptophan abundance increased at 24 hours. Other metabolites also identified at 24 hours included phenylalanine, xanthosine, and citric acid (P-values: 0.002, 0.002, and 0.0152).

DISCUSSION

This study showed presence of active metabolism during EVNLP and metabolic derangement toward the end of perfusion, which correlated with detection of altered mitochondrial structure, swelling, and elongation.

Beyond Ice and the Cooler: Machine Perfusion Strategies in Liver Transplantation

Machine perfusion (MP) has emerged as a promising preservation technique to reduce the risks associated with transplant of high risk (steatotic, elderly, and donation after circulatory death) hepatic allografts. Multiple strategies for MP are under investigation. MP facilitates assessment of organ viability and enables liver-directed therapy before transplant. Clinical trials suggest MP may improve the use of hepatic allografts, mitigate ischemia-reperfusion injury, and reduce the incidences of early allograft dysfunction, biliary complications, and ischemic cholangiopathy. As MP sees more widespread use outside of trial settings, more investigation will be needed to establish optimal application of this technology.

Use of natural anti-oxidants in experimental animal models of hepatic ischemia-reperfusion injury

Background

Ischemia-reperfusion injury (IRI) remains a clinical challenge in liver surgery, trauma and transplantation, contributing to morbidity and mortality worldwide. Thus, its impact, not only on the liver itself but also on remote tissues, has been studied during the last years. Different natural anti-oxidant substances have been researched in animal models, implementing different times of ischemia, aiming to test new therapeutic interventions.

Objective

A literature review has been conducted with two goals: (1) to identify different natural anti-oxidants studied in experimental models; and (2) to summarize the various times of ischemia employed.

Methods

Scientific papers published in PubMed for the period 2000–2020 were searched and reviewed.

Results

More than 30 natural anti-oxidants have been tested. The time of ischemia ranged from 15 to 90 min with 60 min used most frequently, followed by 45 min. No studies were found with time exceeding 90 min.

Conclusions

A significant number of research has been conducted on the use and protective effect of natural anti-oxidants in experimental animal models. Based on the published papers, 45–60 min seems to be the optimal duration of ischemia.

•

Liver IRI is a multifactorial and complex process, involving many mechanisms, cells and mediators. Even though, most of these mechanisms have not been completely understood, several substances have been tested in experimental models in order to determine their protective or destructive role.

•

Antioxidant therapy is a promising therapeutic pathway that can ameliorate the impact of liver ischemia-reperfusion injury.

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Non-pharmaceutical, natural extracts are increasingly gaining their place into the therapeutic options of physicians, in an attempt to avoid various adverse effects that the chemical drugs can cause.

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New unexplored research areas may include different strains of rats, more studies in larger mammals of comparable anatomy to humans, experiments on different liver diseases, publishing negative results regarding toxic doses of natural antioxidants, and testing different ischemia times.

Organ Restoration With Normothermic Machine Perfusion and Immune Reaction

Liver transplantation is the only recognized effective treatment for end-stage liver disease. However, organ shortages have become the main challenge for patients and physicians within the transplant community. Waiting list mortality remains an issue with around 10% of patients dying whilst waiting for an available organ. The post-transplantation period is also associated with an adverse complication rate for these specific cohorts of high-risk patients, particularly regarding patient and graft survival. Ischaemia reperfusion injury (IRI) has been highlighted as the mechanism of injury that increases parenchymal damage, which eventually lead to significant graft dysfunction and other poor outcome indicators. The consequences of IRI in clinical practice such as reperfusion syndrome, primary non-function of graft, allograft dysfunction, ischaemic biliary damage and early biliary complications can be life-threatening. IRI dictates the development of a significant inflammatory response that drives the pathway to eventual cell death. The main mechanisms of IRI are mitochondrial damage due to low oxygen tension within the hepatic micro-environment and severe adenosine triphosphate (ATP) depletion during the ischaemic period. After the restoration of normal blood flow, this damage is further enhanced by reoxygenation as the mitochondria respond to reperfusion by releasing reactive oxygen species (ROS), which in turn activate Kupffer cells within the hepatic micro-environment, leading to a pro-inflammatory response and eventual parenchymal cell apoptosis and associated tissue degradation. Machine perfusion (MP) is one emergent strategy considered to be one of the most important advances in organ preservation, restoration and transplantation. Indeed, MP has the potential to rescue frequently discarded organs and has been shown to limit the extent of IRI, leading to suppression of the deleterious pro-inflammatory response. This immunomodulation reduces the prevalence of allograft rejection, the use of immunosuppression therapy and minimizes post-transplant complications. This review aims to update the current knowledge of MP with a focus on normothermic machine liver perfusion (NMLP) and its potential role in immune response pathways.

Necroptosis in Hepatosteatotic Ischaemia-Reperfusion Injury

While liver transplantation remains the sole treatment option for patients with end-stage liver disease, there are numerous limitations to liver transplantation including the scarcity of donor livers and a rise in livers that are unsuitable to transplant such as those with excess steatosis. Fatty livers are susceptible to ischaemia-reperfusion (IR) injury during transplantation and IR injury results in primary graft non-function, graft failure and mortality. Recent studies have described new cell death pathways which differ from the traditional apoptotic pathway. Necroptosis, a regulated form of cell death, has been associated with hepatic IR injury. Receptor-interacting protein kinase 3 (RIPK3) and mixed-lineage kinase domain-like pseudokinase (MLKL) are thought to be instrumental in the execution of necroptosis. The study of hepatic necroptosis and potential therapeutic approaches to attenuate IR injury will be a key factor in improving our knowledge regarding liver transplantation with fatty donor livers. In this review, we focus on the effect of hepatic steatosis during liver transplantation as well as molecular mechanisms of necroptosis and its involvement during liver IR injury. We also discuss the immune responses triggered during necroptosis and examine the utility of necroptosis inhibitors as potential therapeutic approaches to alleviate IR injury.

Role of Remote Ischemic Preconditioning in Hepatic Ischemic Reperfusion Injury

The effect of remote ischemic preconditioning (RIPC) has been proposed that mediates the protective response in ischemia reperfusion injury (IRI) of various organs. In this study, we investigated the effect of RIPC in hepatic IRI, by assessing biomarker of oxidative stress and inflammatory cytokines. Moreover, we intended to demonstrate any such protective effect through nitric oxide (NO). Twenty-five rats were divided into the 5 groups: (1) Sham; (2) RIPC; (3) hepatic IRI; (4) RIPC + hepatic IRI; (5) C-PTIO, 2-(4-carboxyphenyl)-4,5dihydro-4,4,5,5-tetramethyl-1H-imidazolyl-1-oxy-3oxide, + RIPC + hepatic IRI. RIPC downregulated the level of aspartate aminotransferase (AST), alanine aminotransferase (ALT), histologic damage, and activity of Malondialdehyde (MDA). However, there was no significant reduction in the level of tumor necrosis factor-alpha (TNF-α) and nuclear factor kappa B (NF-κB). AST and ALT levels, and hepatic tissue morphology in the C-PTIO group showed a significant improvement compared to those of the RIPC + hepatic IRI group. The application of RIPC before hepatic ischemia downregulated the oxidative stress, not the inflammatory cytokines. Moreover, these protective effect of RIPC would be mediated through the activation of NO as well as anti-oxidant effect.

Advances in Limb Preservation: From Replantation to Transplantation

Over the course of the last 60 years, microsurgical techniques, instrumentation, operating microscopes, and suture materials have all been perfected. Microsurgery training became part of the standard curriculum in plastic, orthopedic, and hand surgery programs. Despite those advances, limb replantation and transplantation are still surgical emergencies owing to limits in composite tissue viability under ischemia. Amputated parts, particularly containing large volumes of muscle, have to be revascularized within 4 hours in order to prevent permanent tissue damage. Static cold storage is the current standard to prolong ischemia time with limited success. Our research for the last 7 years has focused on extending ischemia time prior to revascularization. Our long-term goal is to make replantation and transplantation procedures elective. The following essay is the summary of our efforts.

Rescue Hepatectomy and Anhepatic Phase Management After Primary Nonfunction in a Liver Transplant

Primary nonfunction is a rare but lethal complication that occurs in a small number of liver transplants. When primary nonfunction occurs, the only definite treatment is retransplant; however, another liver might not be readily available at that time. Hence, a surgeon should be aware of the various options available at hand for patient care during the time interval between the primary nonfunction and retransplant. Here, we describe the management strategy that was devised to take care of an unstable anhepatic patient in the intensive care unit, care of the patient during anhepatic phase, and successful outcome with a second liver transplant. Our index patient was a recipient of a liver donated after cardiac death. While in the operating room, after reperfusion of the liver, the patient had right heart dysfunction leading to hemodynamic instability and congestion of the liver, which culminated in primary nonfunction. Graft hepatectomy had to be done on postoperative day 1 because of deteriorating condition of the patient, and the patient was maintained in anhepatic phase in the intensive care unit for 27 hours.

Effect of Donor Hepatic Steatosis on Ischemia Reperfusion Injury in Liver Transplant Recipient

INTRODUCTION

Ischemia reperfusion injury (IRI) is an important complication of liver transplant (LT). The donor risk index, which does not incorporate steatosis, includes several variables known to impact on allograft survival. The purpose of this study was to report on donor liver allograft steatosis and its association with severity of IRI.

AIM

The aim of this study was to determine the effect of type and grade of donor liver steatosis on the occurrence and severity of IRI in LT recipients.

METHODS

This was an observational study conducted at a single center over a period of 37 months from July 2013 to August 2016. Liver biopsy was performed twice, initially at the time of procurement before graft perfusion for steatosis assessment. Steatosis was classified as microsteatosis (MiS) or macrosteatosis (MaS) with mild, moderate, or severe grade. Second biopsy for IRI assessment was taken before skin closure in death donor LT (DDLT) and at the time of transaminitis in postoperative period (<72 hrs) in living donor LT (LDLT). IRI was graded as per neutrophil infiltrate, apoptosis, and hepatocyte cell dropout. Prevalence of IRI and association steatosis was studied along with other factors.

RESULTS

Among 53 subjects, 35 were DDLTs and 18 were LDLTs. All live donor grafts were restricted to <15% MaS and the deceased liver grafts had different type and degree of steatosis. In DDLTs, the association between occurrence of IRI and MaS was not statistically significant (P = 0.201). In DDLTs, the mild steatosis was not significantly associated with IRI. Death donor and ischemic time were significantly associated with IRI. Child's stage and MELD scores, gender, and age were not associated with risk of IRI. Severity of IRI is significantly associated with 3-month mortality (P = 0.001).

CONCLUSION

In patients with mild steatosis, IRI does not correlate with steatosis. However, more patients with moderate and severe steatosis are needed to define the relationship of the two in this group of patients.

Extended ex vivo normothermic perfusion for preservation of vascularized composite allografts

Ischemia and reperfusion injury remains a significant limiting factor for the successful revascularization of amputated extremities. Ex vivo normothermic perfusion is a novel approach to prolong the viability of the amputated limbs by maintaining physiologic cellular metabolism. This study aimed to evaluate the outcomes of extended ex vivo normothermic limb perfusion (EVNLP) in preserving the viability of amputated limbs for over 24 hours. A total of 10 porcine forelimbs underwent EVNLP. Limbs were perfused using an oxygenated colloid solution at 38°C containing washed RBCs. Five forelimbs (Group A) were perfused for 12 hours and the following 5 (Group B) until the vascular resistance increased. Contralateral forelimbs in each group were preserved at 4°C as a cold storage control group. Limb viability was compared between the 2 groups through assessment of muscle contractility, compartment pressure, tissue oxygen saturation, indocyanine green (ICG) angiography and thermography. EVNLP was performed for 12 hours in group A and up to 44 hours (24-44 hours) in group B. The final weight increase (-1.28 ± 8.59% vs. 7.28 ± 15.05%, P = .548) and compartment pressure (16.50 ± 8.60 vs. 24.00 ± 9.10) (P = .151) were not significantly different between the two groups. Final myoglobin and CK mean values in group A and B were: 875.0 ± 325.8 ng/mL (A) versus 1133.8 ± 537.7 ng/mL (B) (P = .056) and 53 344.0 ± 16 603.0 U/L versus 64 333.3 ± 32 481.8 U/L (P = .286). Tissue oxygen saturation was stable until the end in both groups. Infra-red thermography and ICG-angiography detected variations of peripheral limb perfusion. Our results suggest that extended normothermic preservation of amputated limbs is feasible and that the outcomes of prolonged EVNLP (>24 hours) are not significantly different from short EVNLP (12 hours).

Biliary calprotectin, lactoferrin and dimeric pyruvate kinase after liver transplantation are associated with biliary damage and graft survival in a case-control study

BACKGROUND

After liver transplantation (LT), biliary complications are associated with reduced graft survival. We tested inflammation markers for their association with biliary damage and graft loss in bile.

MATERIAL AND METHODS

The study design was a retrospective case-control study. Calprotectin, lactoferrin and pyruvate kinase were measured in endoscopically retrieved bile with ELISA.

RESULTS

Calprotectin and lactoferrin were significantly higher in bile of ischemic-type biliary lesions and donor duct non-anastomotic strictures than in control, bile leakage, Cytomegalovirus infection, anastomotic stricture or acute cellular rejection patients (p<0.001) independent of serum liver values at endoscopy. Calprotectin (p=0.02) was independently associated with retransplantation free survival in multivariate analysis, as was γGT (p=0.03) but not ERC radiographic classification of the bile duct or cold ischemia time.

CONCLUSION

Calprotectin and lactoferrin are bile markers for biliary damage and are associated with re-transplantation free survival. They can differentiate progressive biliary damage from non-biliary liver value alterations after LT.

An integrated perfusion machine preserves injured human livers for 1 week

The ability to preserve metabolically active livers ex vivo for 1 week or more could allow repair of poor-quality livers that would otherwise be declined for transplantation. Current approaches for normothermic perfusion can preserve human livers for only 24 h. Here we report a liver perfusion machine that integrates multiple core physiological functions, including automated management of glucose levels and oxygenation, waste-product removal and hematocrit control. We developed the machine in a stepwise fashion using pig livers. Study of multiple ex vivo parameters and early phase reperfusion in vivo demonstrated the viability of pig livers perfused for 1 week without the need for additional blood products or perfusate exchange. We tested the approach on ten injured human livers that had been declined for transplantation by all European centers. After a 7-d perfusion, six of the human livers showed preserved function as indicated by bile production, synthesis of coagulation factors, maintained cellular energy (ATP) and intact liver structure.

Livers are stored long term in a sophisticated perfusion system.

Ex-Vivo Normothermic Limb Perfusion With a Hemoglobin-Based Oxygen Carrier Perfusate

INTRODUCTION

Ex-vivo normothermic limb perfusion (EVNLP) has been proven to preserve limb viability better than standard cold storage. Perfusates containing packed red blood cells (pRBC) improve outcomes when compared to acellular perfusates. Limitations of pRBC-based perfusion include limited availability, need for cross match, mechanical hemolysis, and activation of pro-inflammatory proteins. Hemoglobin-based oxygen carrier (HBOC)-201 (Hemopure) is a solution of polymerized bovine hemoglobin, characterized by low immunogenicity, no risk of hemolytic reaction, and enhanced convective and diffusive oxygen delivery. This is a preliminary study on the feasibility of EVNLP using HBOC-201 as an oxygen carrier.

MATERIALS AND METHODS

Three porcine forelimb perfusions were performed using an established EVNLP model and an HBOC-201-based perfusate. The perfusion circuit included a roller pump, oxygenator, heat exchanger, and reservoir. Electrolytes, limb temperature, weight, compartment pressure, nerve conduction, and perfusion indicated by indocyanine green angiography and infra-red thermography were monitored. Histological evaluation was performed with hematoxylin and eosin and electron microscopy.

RESULTS

Three limbs were perfused for 21.3 ± 2.1 hours. Muscle contractility was preserved for 10.6 ± 2.4 hours. Better preservation of the mitochondrial ultrastructure was evident at 12 hours in contrast to crystallization and destruction features in the cold-storage controls.

CONCLUSIONS

An HBOC-201-EVNLP produced outcomes similar to RBC-EVNLP with preservation of muscle contractility and mitochondrial structure.

Nanocarrier-mediated antioxidant delivery for liver diseases

Liver is the principal detoxifying organ and metabolizes various compounds that produce free radicals (FR) constantly. To maintain the oxidative/antioxidative balance in the liver, antioxidants would scavenge FR by preventing tissue damage through FR formation, scavenging, or by enhancing their decomposition. The disruption of this balance therefore leads to oxidative stress and in turn leads to the onset of various diseases. Supplying the liver with exogeneous antioxidants is an effective way to recreate the oxidative/antioxidative balance in the liver homeostasis. Nevertheless, due to the short half-life and instability of antioxidants in circulation, the methodology for delivering antioxidants to the liver needs to be improved. Nanocarrier mediated delivery of antioxidants proved to be an ingenious way to safely and efficiently deliver a high payload of antioxidants into the liver for circumventing liver diseases. The objective of this review is to provide an overview of the role of reactive oxygen species (oxidant) and ROS scavengers (antioxidant) in liver diseases. Subsequently, current nanocarrier mediated antioxidant delivery methods for liver diseases are discussed.

New Insights into the Liver-Visceral Adipose Axis During Hepatic Resection and Liver Transplantation

In the last decade, adipose tissue has emerged as an endocrine organ with a key role in energy homeostasis. In addition, there is close crosstalk between the adipose tissue and the liver, since pro- and anti-inflammatory substances produced at the visceral adipose tissue level directly target the liver through the portal vein. During surgical procedures, including hepatic resection and liver transplantation, ischemia-reperfusion injury induces damage and regenerative failure. It has been suggested that adipose tissue is associated with both pathological or, on the contrary, with protective effects on damage and regenerative response after liver surgery. The present review aims to summarize the current knowledge on the crosstalk between the adipose tissue and the liver during liver surgery. Therapeutic strategies as well as the clinical and scientific controversies in this field are discussed. The different experimental models, such as lipectomy, to evaluate the role of adipose tissue in both steatotic and nonsteatotic livers undergoing surgery, are described. Such information may be useful for the establishment of protective strategies aimed at regulating the liver-visceral adipose tissue axis and improving the postoperative outcomes in clinical liver surgery.

Avoiding initial hypothermia does not improve liver graft quality in a porcine donation after circulatory death (DCD) model of normothermic perfusion

Background

Normothermic machine perfusion (NMP) of liver grafts donated after circulatory death (DCD) has shown promise in large animal and clinical trials. Following procurement, initial flush with a cold preservation solution is the standard of care. There is concern that initial cooling followed by warming may exacerbate liver injury, and the optimal initial flush temperature has yet to be identified. We hypothesize that avoidance of the initial cold flush will yield better quality liver grafts.

Methods

Twenty-four anaesthetized pigs were withdrawn from mechanical ventilation and allowed to arrest. After 60-minutes of warm ischemia to simulate a DCD procurement, livers were flushed with histidine-tryptophan-ketoglutarate (HTK) at 4°C, 25°C or 35°C (n = 4 per group). For comparison, an adenosine-lidocaine crystalloid solution (AD), shown to have benefit at warm temperatures in heart perfusions, was also used (n = 4 per group). During 12-hours of NMP, adenosine triphosphate (ATP), lactate, transaminase levels, and histological injury were determined. Bile production and hemodynamics were monitored continuously.

Results

ATP levels recovered substantially following 1-hour of NMP reaching pre-ischemic levels by the end of NMP with no difference between groups. There was no difference in peak aspartate aminotransferase (AST) or in lactate dehydrogenase (LDH). Portal vein resistance was lowest in the 4°C group reaching significance after 2 hours (0.13 CI -0.01,0.277, p = 0.025). Lactate levels recovered promptly with no difference between groups. Comparison to AD groups showed no statistical difference in the abovementioned parameters. On electron microscopy the HTK4°C group had the least edema with mean cell thickness of 2.92μm (p = 0.41) while also having the least sinusoidal dilatation with a mean diameter of 5.36μm (p = 0.04). For AD, the 25°C group had the lowest mean cell thickness at 3.14μm (p = 0.09).

Conclusions

Avoidance of the initial cold flush failed to demonstrate added benefit over standard 4°C HTK in this DCD model of liver perfusion.

Peri-transplant lactate levels and delayed lactate clearance as predictive factors for poor outcomes after liver transplantation: A propensity score-matched study

This study aimed to investigate risk factors for early allograft dysfunction (EAD) and outcomes after liver transplantation (LT), focusing on peri-transplant lactate clearance. We reviewed patients who underwent deceased donor LTs between 2011 and 2014. Lactate levels were checked at reperfusion and at the time of intensive care unit admission. Early lactate clearance was defined as reduction rate of lactate between the times of reperfusion and immediately after LT. Patients were categorized into the normal and delayed clearance groups. We used propensity score matching (PSM) between these two groups to estimate an impact of lactate clearance on incidence of EAD and graft survival. A total of 256 recipients were eligible for this study. Cut-off value of lactate clearance to predict occurrence of EAD was determined at 0.2 mmol/L/h. After PSM, 120 patients in the normal clearance and 36 patients in the delayed clearance group were matched. Delayed lactate clearance was considered as an independent risk factor for EAD (Odds ratio 3.49, P = 0.002). The adjusted hazard of one-year graft loss was significantly increased in the delayed clearance group (hazard ratio 6.69, P = 0.001). In conclusion, peri-transplant delayed lactate clearance may be a strong predictor for EAD and poor liver graft outcomes.

Nucleotide-binding oligomerization domain 1 (NOD1) modulates liver ischemia reperfusion through the expression adhesion molecules

BACKGROUND & AIMS

In liver transplantation, organ shortage leads to the use of marginal grafts that are more susceptible to ischemia-reperfusion (IR) injury. We identified nucleotide-binding oligomerization domain 1 (NOD1) as an important modulator of polymorphonuclear neutrophil (PMN)-induced liver injury, which occurs in IR. Herein, we aimed to elucidate the role of NOD1 in IR injury, particularly focusing on its effects on the endothelium and hepatocytes.

METHOD

Nod1 WT and KO mice were treated with NOD1 agonists and subjected to liver IR. Expression of adhesion molecules was analyzed in total liver, isolated hepatocytes and endothelial cells. Interactions between PMNs and hepatocytes were studied in an ex vivo co-culture model using electron microscopy and lactate dehydrogenase levels. We generated NOD1 antagonist-loaded nanoparticles (np ALINO).

RESULTS

NOD1 agonist treatment increased liver injury, PMN tissue infiltration and upregulated ICAM-1 and VCAM-1 expression 20 hours after reperfusion. NOD1 agonist treatment without IR increased expression of adhesion molecules (ICAM-1, VCAM-1) in total liver and more particularly in WT hepatocytes, but not in Nod1 KO hepatocytes. This induction is dependent of p38 and ERK signaling pathways. Compared to untreated hepatocytes, a NOD1 agonist markedly increased hepatocyte lysis in co-culture with PMNs as shown by the increase of lactate dehydrogenase in supernatants. Interaction between hepatocytes and PMNs was confirmed by electron microscopy. In a mouse model of liver IR, treatment with np ALINO significantly reduced the area of necrosis, aminotransferase levels and ICAM-1 expression.

CONCLUSION

NOD1 regulates liver IR injury through induction of adhesion molecules and modulation of hepatocyte-PMN interactions. NOD1 antagonist-loaded nanoparticles reduced liver IR injury and provide a potential approach to prevent IR, especially in the context of liver transplantation.

LAY SUMMARY

Nucleotide-binding oligomerization domain 1 (NOD1) is as an important modulator of polymorphonuclear neutrophil (PMN)-induced liver injury, which occurs in ischemia-reperfusion. Here, we show that the NOD1 pathway targets liver adhesion molecule expression on the endothelium and on hepatocytes through p38 and ERK signaling pathways. The early increase of adhesion molecule expression after reperfusion emphasizes the importance of adhesion molecules in liver injury. In this study we generated nanoparticles loaded with NOD1 antagonist. These nanoparticles reduced liver necrosis by reducing PMN liver infiltration and adhesion molecule expression.

Bioengineering approaches to organ preservation ex vivo

IMPACT STATEMENT

Over the past several decades, ex vivo perfusion has emerged as a promising technology for the assessment, preservation, and recovery of donor organs. Many exciting pre-clinical findings have now been translated to clinical use, and successful transplantation following ex vivo perfusion has been achieved for heart, lung, and liver. While machine perfusion provides distinct advantages over traditional cold preservation, many challenges remain, including that of long-term (multi-day) ex vivo support. Here, we provide an overview of the current status of ex vivo machine perfusion in the pre-clinical and clinical setting and share our perspective on the future direction of the field.

Mitogen Activated Protein Kinases in Steatotic and Non-Steatotic Livers Submitted to Ischemia-Reperfusion

: We analyzed the participation of mitogen-activated protein kinases (MAPKs), namely p38, JNK and ERK 1/2 in steatotic and non-steatotic livers undergoing ischemia-reperfusion (I-R), an unresolved problem in clinical practice. Hepatic steatosis is a major risk factor in liver surgery because these types of liver tolerate poorly to I-R injury. Also, a further increase in the prevalence of steatosis in liver surgery is to be expected. The possible therapies based on MAPK regulation aimed at reducing hepatic I-R injury will be discussed. Moreover, we reviewed the relevance of MAPK in ischemic preconditioning (PC) and evaluated whether MAPK regulators could mimic its benefits. Clinical studies indicated that this surgical strategy could be appropriate for liver surgery in both steatotic and non-steatotic livers undergoing I-R. The data presented herein suggest that further investigations are required to elucidate more extensively the mechanisms by which these kinases work in hepatic I-R. Also, further researchers based in the development of drugs that regulate MAPKs selectively are required before such approaches can be translated into clinical liver surgery.

Control of Ischemia-Reperfusion Injury in Liver Transplantation: Potentials for Increasing the Donor Pool

BACKGROUND

Organ shortage is a growing problem, with a rising number of organs being harvested from extended criteria donors, and this trend will further continue to increase as organ donors are getting older and have more comorbidities. Since this fact is immutable, efforts have been made to reduce the extent of ischemia-reperfusion injury (IRI) as well as of direct and indirect harvest-related graft injury which affects all organs in a more or less distinct way.

METHODS

In liver transplantation (LT), the activation of Kupffer cells during organ reperfusion, thus provoking microcirculatory disturbances, hypoxia, and endothelial cell injury, is one of the key mechanisms causing graft dysfunction. Multiple approaches have been taken in order to find efficient preconditioning methods by pharmacological pretreatment, controlled induction of ischemia, controlled denervation of donor organs, and reconditioning with machine perfusion to prevent IRI, whereas marginal organs (i.e. steatotic grafts) are especially vulnerable.

RESULTS

The above-mentioned approaches have been pursued in experimental and clinical settings. At this time point, however, there is not yet enough clinical evidence available to recommend any particular drug pretreatment or any other intervention for organ preconditioning prior to transplantation.

CONCLUSION

The multifactorial pathophysiology in the setting of IRI in LT requires a multimodal therapeutic approach with the integration of pharmacological and technical means being applied to the donor, the organ per se, and the recipient. Currently, there is no consensus on standardized pretreatment of donor organs in order to improve the transplant outcome.

Investigation of the preventive effect of proanthocyanidin in ischemia-reperfusion injury in lung transplantation: An experimental study

Background

This study aims to investigate the preventive effect of proanthocyanidin against ischemia-reperfusion injury after lung transplantation.

Methods

The study included 12 swines (weighing 35±5 kg) and separated into four groups. Groups 1 and 3 were identified as control groups and left upper lobectomy was performed. Groups 2 and 4 were identified as transplantation groups and left lower lobectomy and heterotransplantation were performed. Proanthocyanidin was only given to groups 3 and 4. Tissue samples were analyzed under light microscope and histopathological findings were recorded.

Results

There was no statistically significant difference between control groups in terms of the numerical values of histopathological findings that include congestion (p=0.565), alveolar edema (p=0.197) and peribronchial inflammation (p=0.444). However, numerical values of acute cellular rejection were statistically significantly different between transplantation groups (p=0.048). Mean oxidative stress enzyme levels were higher in group 2 compared to group 4; however, the difference was not statistically significant (p>0.05).

Conclusion

According to the findings of our experimental study, proanthocyanidin can be safely used in lung transplantation based on its preventive effect in ischemia-reperfusion injury that may lead to morbidity and mortality.