Hypothermic Machine Perfusion in Liver Transplantation - A Randomized Trial

BACKGROUND

Transplantation of livers obtained from donors after circulatory death is associated with an increased risk of nonanastomotic biliary strictures. Hypothermic oxygenated machine perfusion of livers may reduce the incidence of biliary complications, but data from prospective, controlled studies are limited.

METHODS

In this multicenter, controlled trial, we randomly assigned patients who were undergoing transplantation of a liver obtained from a donor after circulatory death to receive that liver either after hypothermic oxygenated machine perfusion (machine-perfusion group) or after conventional static cold storage alone (control group). The primary end point was the incidence of nonanastomotic biliary strictures within 6 months after transplantation. Secondary end points included other graft-related and general complications.

RESULTS

A total of 160 patients were enrolled, of whom 78 received a machine-perfused liver and 78 received a liver after static cold storage only (4 patients did not receive a liver in this trial). Nonanastomotic biliary strictures occurred in 6% of the patients in the machine-perfusion group and in 18% of those in the control group (risk ratio, 0.36; 95% confidence interval [CI], 0.14 to 0.94; P = 0.03). Postreperfusion syndrome occurred in 12% of the recipients of a machine-perfused liver and in 27% of those in the control group (risk ratio, 0.43; 95% CI, 0.20 to 0.91). Early allograft dysfunction occurred in 26% of the machine-perfused livers, as compared with 40% of control livers (risk ratio, 0.61; 95% CI, 0.39 to 0.96). The cumulative number of treatments for nonanastomotic biliary strictures was lower by a factor of almost 4 after machine perfusion, as compared with control. The incidence of adverse events was similar in the two groups.

CONCLUSIONS

Hypothermic oxygenated machine perfusion led to a lower risk of nonanastomotic biliary strictures following the transplantation of livers obtained from donors after circulatory death than conventional static cold storage. (Funded by Fonds NutsOhra; DHOPE-DCD ClinicalTrials.gov number, NCT02584283.).

Transplantation of High-risk Donor Livers After Ex Situ Resuscitation and Assessment Using Combined Hypo- and Normothermic Machine Perfusion: A Prospective Clinical Trial

OBJECTIVE

The aim of this study was to evaluate sequential hypothermic and normothermic machine perfusion (NMP) as a tool to resuscitate and assess viability of initially declined donor livers to enable safe transplantation.

SUMMARY BACKGROUND DATA

Machine perfusion is increasingly used to resuscitate and test the function of donor livers. Although (dual) hypothermic oxygenated machine perfusion ([D]HOPE) resuscitates livers after cold storage, NMP enables assessment of hepatobiliary function.

METHODS

In a prospective clinical trial, nationwide declined livers were subjected to ex situ NMP (viability assessment phase), preceded by 1-hour DHOPE (resuscitation phase) and 1 hour of controlled oxygenated rewarming (COR), using a perfusion fluid containing an hemoglobin-based oxygen carrier. During the first 2.5 hours of NMP, hepatobiliary viability was assessed, using predefined criteria: perfusate lactate <1.7 mmol/L, pH 7.35 to 7.45, bile production >10 mL, and bile pH >7.45. Livers meeting all criteria were accepted for transplantation. Primary endpoint was 3-month graft survival.

RESULTS

Sixteen livers underwent DHOPE-COR-NMP. All livers were from donors after circulatory death, with median age of 63 (range 42-82) years and median Eurotransplant donor risk index of 2.82. During NMP, all livers cleared lactate and produced sufficient bile volume, but in 5 livers bile pH remained <7.45. The 11 (69%) livers that met all viability criteria were successfully transplanted, with 100% patient and graft survival at 3 and 6 months. Introduction of DHOPE-COR-NMP increased the number of deceased donor liver transplants by 20%.

CONCLUSIONS

Sequential DHOPE-COR-NMP enabled resuscitation and safe selection of initially declined high-risk donor livers, thereby increasing the number of transplantable livers by 20%.

TRIAL REGISTRATION

www.trialregister.nl; NTR5972.

Pretransplant sequential hypo- and normothermic machine perfusion of suboptimal livers donated after circulatory death using a hemoglobin-based oxygen carrier perfusion solution

Ex situ dual hypothermic oxygenated machine perfusion (DHOPE) and normothermic machine perfusion (NMP) of donor livers may have a complementary effect when applied sequentially. While DHOPE resuscitates the mitochondria and increases hepatic adenosine triphosphate (ATP) content, NMP enables hepatobiliary viability assessment prior to transplantation. In contrast to DHOPE, NMP requires a perfusion solution with an oxygen carrier, for which red blood cells (RBC) have been used in most series. RBC, however, have limitations and cannot be used cold. We, therefore, established a protocol of sequential DHOPE, controlled oxygenated rewarming (COR), and NMP using a new hemoglobin-based oxygen carrier (HBOC)-based perfusion fluid (DHOPE-COR-NMP trial, NTR5972). Seven livers from donation after circulatory death (DCD) donors, which were initially declined for transplantation nationwide, underwent DHOPE-COR-NMP. Livers were considered transplantable if perfusate pH and lactate normalized, bile production was ≥10 mL and biliary pH > 7.45 within 150 minutes of NMP. Based on these criteria five livers were transplanted. The primary endpoint, 3-month graft survival, was a 100%. In conclusion, sequential DHOPE-COR-NMP using an HBOC-based perfusion fluid offers a novel method of liver machine perfusion for combined resuscitation and viability testing of suboptimal livers prior to transplantation.

Sequential hypothermic and normothermic machine perfusion enables safe transplantation of high-risk donor livers

Ex situ normothermic machine perfusion (NMP) is increasingly used for viability assessment of high-risk donor livers, whereas dual hypothermic oxygenated machine perfusion (DHOPE) reduces ischemia-reperfusion injury. We aimed to resuscitate and test the viability of initially-discarded, high-risk donor livers using sequential DHOPE and NMP with two different oxygen carriers: an artificial hemoglobin-based oxygen carrier (HBOC) or red blood cells (RBC). In a prospective observational cohort study of 54 livers that underwent DHOPE-NMP, the first 18 procedures were performed with a HBOC-based perfusion solution and the subsequent 36 procedures were performed with an RBC-based perfusion solution for the NMP phase. All but one livers were derived from extended criteria donation after circulatory death donors, with a median donor risk index of 2.84 (IQR 2.52-3.11). After functional assessment during NMP, 34 livers (63% utilization), met the viability criteria and were transplanted. One-year graft and patient survival were 94% and 100%, respectively. Post-transplant cholangiopathy occurred in 1 patient (3%). There were no significant differences in utilization rate and post-transplant outcomes between the HBOC and RBC group. Ex situ machine perfusion using sequential DHOPE-NMP for resuscitation and viability assessment of high-risk donor livers results in excellent transplant outcomes, irrespective of the oxygen carrier used.

Hypothermic oxygenated machine perfusion reduces bile duct reperfusion injury after transplantation of donation after circulatory death livers

Dual hypothermic oxygenated machine perfusion (DHOPE) of the liver has been advocated as a method to reduce ischemia/reperfusion injury (IRI). This study aimed to determine whether DHOPE reduces IRI of the bile ducts in donation after circulatory death (DCD) liver transplantation. In a recently performed phase 1 trial, 10 DCD livers were preserved with DHOPE after static cold storage (SCS; www.trialregister.nl NTR4493). Bile duct biopsies were obtained at the end of SCS (before DHOPE; baseline) and after graft reperfusion in the recipient. Histological severity of biliary injury was graded according to an established semiquantitative grading system. Twenty liver transplantations using DCD livers not preserved with DHOPE served as controls. Baseline characteristics and the degree of bile duct injury at baseline (end of SCS) were similar between both groups. In controls, the degree of stroma necrosis (P = 0.002) and injury of the deep peribiliary glands (PBG; P = 0.02) increased after reperfusion compared with baseline. In contrast, in DHOPE-preserved livers, the degree of bile duct injury did not increase after reperfusion. Moreover, there was less injury of deep PBG (P = 0.04) after reperfusion in the DHOPE group compared with controls. In conclusion, this study suggests that DHOPE reduces IRI of bile ducts after DCD liver transplantation. Liver Transplantation 24 655-664 2018 AASLD.

A multicentre outcome analysis to define global benchmarks for donation after circulatory death liver transplantation

BACKGROUND & AIMS

The concept of benchmarking is established in the field of transplant surgery; however, benchmark values for donation after circulatory death (DCD) liver transplantation are not available. Thus, we aimed to identify the best possible outcomes in DCD liver transplantation and to propose outcome reference values.

METHODS

Based on 2,219 controlled DCD liver transplantations, collected from 17 centres in North America and Europe, we identified 1,012 low-risk, primary, adult liver transplantations with a laboratory MELD score of ≤20 points, receiving a DCD liver with a total donor warm ischemia time of ≤30 minutes and asystolic donor warm ischemia time of ≤15 minutes. Clinically relevant outcomes were selected and complications were reported according to the Clavien-Dindo-Grading and the comprehensive complication index (CCI). Corresponding benchmark cut-offs were based on median values of each centre, where the 75th-percentile was considered.

RESULTS

Benchmark cases represented between 19.7% and 75% of DCD transplantations in participating centres. The 1-year retransplant and mortality rates were 4.5% and 8.4% in the benchmark group, respectively. Within the first year of follow-up, 51.1% of recipients developed at least 1 major complication (≥Clavien-Dindo-Grade III). Benchmark cut-offs were ≤3 days and ≤16 days for ICU and hospital stay, ≤66% for severe recipient complications (≥Grade III), ≤16.8% for ischemic cholangiopathy, and ≤38.9 CCI points 1 year after transplant. Comparisons with higher risk groups showed more complications and impaired graft survival outside the benchmark cut-offs. Organ perfusion techniques reduced the complications to values below benchmark cut-offs, despite higher graft risk.

CONCLUSIONS

Despite excellent 1-year survival, morbidity in benchmark cases remains high. Benchmark cut-offs targeting morbidity parameters offer a valid tool to assess the protective value of new preservation technologies in higher risk groups and to provide a valid comparator cohort for future clinical trials.

LAY SUMMARY

The best possible outcomes after liver transplantation of grafts donated after circulatory death (DCD) were defined using the concept of benchmarking. These were based on 2,219 liver transplantations following controlled DCD donation in 17 centres worldwide. Donor and recipient combinations with higher risk had significantly worse outcomes. However, the use of novel organ perfusion technology helped high-risk patients achieve similar outcomes as the benchmark cohort.

The Emerging Role of Viability Testing During Liver Machine Perfusion

The transplant community continues to be challenged by the disparity between the need for liver transplantation and the shortage of suitable donor organs. At the same time, the number of unused donor livers continues to increase, most likely attributed to the worsening quality of these organs. To date, there is no reliable marker of liver graft viability that can predict good posttransplant outcomes. Ex situ machine perfusion offers additional data to assess the viability of donor livers before transplantation. Hence, livers initially considered unsuitable for transplantation can be assessed during machine perfusion in terms of appearance and consistency, hemodynamics, and metabolic and excretory function. In addition, postoperative complications such as primary nonfunction or posttransplant cholangiopathy may be predicted and avoided. A variety of viability criteria have been used in machine perfusion, and to date there is no widely accepted composition of criteria for clinical use. This review discusses potential viability markers for hepatobiliary function during machine perfusion, describes current limitations, and provides future recommendations for the use of viability criteria in clinical liver transplantation.

Extended hypothermic oxygenated machine perfusion enables ex situ preservation of porcine livers for up to 24 hours

Background & Aims

End-ischemic hypothermic oxygenated machine perfusion (HOPE) of the donor liver for 1-2 h mitigates ischemia-reperfusion injury during subsequent liver transplantation. Extended preservation time may be preferred to facilitate difficult recipient hepatectomy or to optimize logistics. We therefore investigated whether end-ischemic dual HOPE (DHOPE) could extend preservation time for up to 24 h using a porcine liver reperfusion model.

Methods

Following 30 min warm ischemia, porcine livers were subjected to 2 h static cold storage (SCS), followed by 2 h, 6 h, or 24 h DHOPE (n = 6 per group). Subsequent normothermic reperfusion was performed for 4 h using autologous blood. Two livers preserved by 24 h SCS served as additional controls. A proof of principle confirmation was carried out in 2 discarded human livers subjected to extended DHOPE. Hepatocellular and cholangiocyte injury and function were assessed. Oxidative stress levels and histology were compared between groups.

Results

Perfusion flows remained stable during DHOPE, regardless of duration. After normothermic reperfusion, livers perfused for 24 h by DHOPE had similar lactate clearance, blood pH, glucose, and alanine aminotransferase levels, and biliary pH, bicarbonate, and LDH levels, as livers perfused for 2 h and 6 h. Levels of malondialdehyde and high-mobility group box 1 in serum and liver parenchyma were similar for all groups. Histological analysis of bile ducts and liver parenchyma revealed no differences between the groups. Extended DHOPE in discarded human livers preserved hepatocellular and cholangiocyte function and histology after reperfusion. In contrast, livers preserved by 24 h SCS were non-functioning.

Conclusion

Extended end-ischemic DHOPE enabled successful preservation of porcine and discarded human donor livers for up to 24 h. Extended DHOPE enables safe extension of preservation time, which may facilitate allocation and transplantation from a logistical perspective, and further expand the donor pool.

Lay summary

It has been suggested that preserving liver grafts with a technique called (dual) hypothermic oxygenated machine perfusion ([D]HOPE) leads to better outcomes after transplantation than if livers are stored on ice, especially if an organ is of lesser quality. In this study, we showed that DHOPE could be used to preserve liver grafts for up to 24 h. This extended procedure could be used globally to facilitate transplantation and expand the donor pool.

Repopulating the biliary tree from the peribiliary glands

The larger ducts of the biliary tree contain numerous tubulo-alveolar adnexal glands that are lined with biliary epithelial cells and connected to the bile duct lumen via small glandular canals. Although these peribiliary glands (PBG) were already described in the 19th century, their exact function and role in the pathophysiology and development of cholangiopathies have not become evident until recently. While secretion of serous and mucinous components into the bile was long considered as the main function of PBG, recent studies have identified PBG as an important source for biliary epithelial cell proliferation and renewal. Activation, dilatation, and proliferation of PBG (or the lack thereof) have been associated with various cholangiopathies. Moreover, PBG have been identified as niches of multipotent stem/progenitor cells with endodermal lineage traits. This has sparked research interest in the role of PBG in the pathogenesis of various cholangiopathies as well as bile duct malignancies. Deeper understanding of the regenerative capacity of the PBG may contribute to the development of novel regenerative therapeutics for previously untreatable hepatobiliary diseases. This article is part of a Special Issue entitled: Cholangiocytes in Health and Disease edited by Jesus Banales, Marco Marzioni, Nicholas LaRusso and Peter Jansen.

Evaluation of Liver Graft Donation After Euthanasia

Importance

The option of donating organs after euthanasia is not well known. Assessment of the results of organ transplants with grafts donated after euthanasia is essential to justify the use of this type of organ donation.

Objectives

To assess the outcomes of liver transplants (LTs) with grafts donated after euthanasia (donation after circulatory death type V [DCD-V]), and to compare them with the results of the more commonly performed LTs with grafts from donors with a circulatory arrest after the withdrawal of life-supporting treatment (type III [DCD-III]).

Design, Setting, and Participants

This retrospective multicenter cohort study analyzed medical records and LT data for most transplant centers in the Netherlands and Belgium. All LTs with DCD-V grafts performed from the start of the donation after euthanasia program (September 2012 for the Netherlands, and January 2005 for Belgium) through July 1, 2018, were included in the analysis. A comparative cohort of patients who received DCD-III grafts was also analyzed. All patients in both cohorts were followed up for at least 1 year. Data analysis was performed from September 2019 to December 2019.

Exposures

Liver transplant with either a DCD-V graft or DCD-III graft.

Main Outcomes and Measures

Primary outcomes were recipient and graft survival rates at years 1, 3, and 5 after the LT. Secondary outcomes included postoperative complications (early allograft dysfunction, hepatic artery thrombosis, and nonanastomotic biliary strictures) within the first year after the LT.

Results

Among the cohort of 47 LTs with DCD-V grafts, 25 organ donors (53%) were women and the median (interquartile range [IQR]) age was 51 (44-59) years. Among the cohort of 542 LTs with DCD-III grafts, 335 organ donors (62%) were men and the median (IQR) age was 49 (37-57) years. Median (IQR) follow-up was 3.8 (2.1-6.3) years. In the DCD-V cohort, 30 recipients (64%) were men, and the median (IQR) age was 56 (48-64) years. Recipient survival in the DCD-V cohort was 87% at 1 year, 73% at 3 years, and 66% at 5 years after LT. Graft survival among recipients was 74% at 1 year, 61% at 3 years, and 57% at 5 years after LT. These survival rates did not differ statistically significantly from those in the DCD-III cohort. Incidence of postoperative complications did not differ between the groups. For example, the occurrence of early allograft dysfunction after the LT was found to be 13 (31%) in the DCD-V cohort and 219 (45%) in the DCD-III cohort. The occurrence of nonanastomotic biliary strictures after the LT was found to be 7 (15%) in the DCD-V cohort and 83 (15%) in the DCD-III cohort.

Conclusions and Relevance

The findings of this cohort study suggest that LTs with DCD-V grafts yield similar outcomes as LTs with DCD-III grafts; therefore, grafts donated after euthanasia may be a justifiable option for increasing the organ donor pool. However, grafts from these donations should be considered high-risk grafts that require an optimal donor selection process and logistics.

Transplantation of high-risk donor livers after resuscitation and viability assessment using a combined protocol of oxygenated hypothermic, rewarming and normothermic machine perfusion: study protocol for a prospective, single-arm study (DHOPE-COR-NMP trial)

INTRODUCTION

Extended criteria donor (ECD) livers are increasingly accepted for transplantation in an attempt to reduce the gap between the number of patients on the waiting list and the available number of donor livers. ECD livers; however, carry an increased risk of developing primary non-function (PNF), early allograft dysfunction (EAD) or post-transplant cholangiopathy. Ischaemia-reperfusion injury (IRI) plays an important role in the development of these complications. Machine perfusion reduces IRI and allows for reconditioning and subsequent evaluation of liver grafts. Single or dual hypothermic oxygenated machine perfusion (DHOPE) (4°C-12°C) decreases IRI by resuscitation of mitochondria. Controlled oxygenated rewarming (COR) may further reduce IRI by preventing sudden temperature shifts. Subsequent normothermic machine perfusion (NMP) (37°C) allows for ex situ viability assessment to facilitate the selection of ECD livers with a low risk of PNF, EAD or post-transplant cholangiopathy.

METHODS AND ANALYSIS

This prospective, single-arm study is designed to resuscitate and evaluate initially nationwide declined ECD livers. End-ischaemic DHOPE will be performed for the initial mitochondrial and graft resuscitation, followed by COR of the donor liver to a normothermic temperature. Subsequently, NMP will be continued to assess viability of the liver. Transplantation into eligible recipients will proceed if all predetermined viability criteria are met within the first 150 min of NMP. To facilitate machine perfusion at different temperatures, a perfusion solution containing a haemoglobin-based oxygen carrier will be used. With this protocol, we aim to transplant extra livers. The primary endpoint is graft survival at 3 months after transplantation.

ETHICS AND DISSEMINATION

This protocol was approved by the medical ethical committee of Groningen, METc2016.281 in August 2016 and registered in the Dutch Trial registration number TRIAL REGISTRATION NUMBER: NTR5972, NCT02584283.

The First Case of Ischemia-Free Kidney Transplantation in Humans

Background: Ischemia-reperfusion injury (IRI) has been considered an inevitable event in organ transplantation since the first successful kidney transplant was performed in 1954. To avoid IRI, we have established a novel procedure called ischemia-free organ transplantation. Here, we describe the first case of ischemia-free kidney transplantation (IFKT). Materials and Methods: The kidney graft was donated by a 19-year-old brain-dead donor. The recipient was a 47-year-old man with end-stage diabetic nephropathy. The graft was procured, preserved, and implanted without cessation of blood supply using normothermic machine perfusion. Results: The graft appearance, perfusion flow, and urine production suggested that the kidney was functioning well-during the whole procedure. The creatinine dropped rapidly to normal range within 3 days post-transplantation. The levels of serum renal injury markers were low post-transplantation. No rejection or vascular or infectious complications occurred. The patient had an uneventful recovery. Conclusion: This paper marks the first case of IFKT in humans. This innovation may offer a unique solution to optimizing transplant outcomes in kidney transplantation.

First report of successful transplantation of a pediatric donor liver graft after hypothermic machine perfusion

One of the main limiting factors in pediatric liver transplantation is donor availability. For adults, DCD liver grafts are increasingly used to expand the donor pool. To improve outcome after DCD liver transplantation, ex situ machine perfusion is used as an alternative organ preservation strategy, with the supplemental value of providing oxygen to the graft during preservation. We here report the first successful transplantation of a pediatric DCD liver graft after hypothermic oxygenated machine perfusion. The full-size liver graft was derived from a 13-year-old, female DCD donor and was end-ischemic pretreated with dual hypothermic oxygenated machine perfusion. Arterial and portal pressures were set at 18 and 4 mm Hg, slightly lower than protocolized settings for adult livers. During 2 hours of machine perfusion, portal and arterial flows increased from 100 to 210 mL/min and 30 to 63 mL/min, respectively. The pretreated liver graft was implanted in a 16-year-old girl with progressive familial intrahepatic cholestasis type 2. Postoperative AST, ALT, and prothrombin time normalized within a week. The recipient quickly recovered and was discharged from the hospital after 18 days. One year after transplantation, she is in excellent condition with a completely normal liver function and histology. This case is the first report of successful transplantation of a pediatric DCD liver graft after hypothermic oxygenated machine perfusion and illustrates the potential role of ex situ machine perfusion in expanding the donor pool and improving outcome after pediatric liver transplantation.

Bile proteome reveals biliary regeneration during normothermic preservation of human donor livers

Normothermic machine perfusion (NMP) after static cold storage is increasingly used for preservation and assessment of human donor livers prior to transplantation. Biliary viability assessment during NMP reduces the risk of post-transplant biliary complications. However, understanding of molecular changes in the biliary system during NMP remains incomplete. We performed an in-depth, unbiased proteomics analysis of bile collected during sequential hypothermic machine perfusion, rewarming and NMP of 55 human donor livers. Longitudinal analysis during NMP reveals proteins reflective of cellular damage at early stages, followed by upregulation of secretory and immune response processes. Livers with bile chemistry acceptable for transplantation reveal protein patterns implicated in regenerative processes, including cellular proliferation, compared to livers with inadequate bile chemistry. These findings are reinforced by detection of regenerative gene transcripts in liver tissue before machine perfusion. Our comprehensive bile proteomics and liver transcriptomics data sets provide the potential to further evaluate molecular mechanisms during NMP and refine viability assessment criteria.

Ex Situ Machine Perfusion of Human Donor Livers via the Surgically Reopened Umbilical Vein: A Proof of Concept

BACKGROUND

Machine perfusion of donor livers is typically performed via the portal vein main stem. Instead, cannulation of a reopened umbilical vein could allow machine perfusion during organ procurement and subsequent implantation in the recipient without interruption of the portal venous circulation. We aimed to assess the feasibility of portal venous machine perfusion via the umbilical vein.

METHODS

During back table inspection of 5 human livers declined for transplantation, the umbilical vein was surgically reopened, dilated, and cannulated. Hypothermic and normothermic oxygenated machine perfusion (NMP) were performed using the umbilical vein for portal inflow. Three livers were perfused with hypothermic machine perfusion, 1 full liver graft underwent NMP for 4 hours, and 1 left lateral split procedure was performed under continuous NMP with portal perfusion via the umbilical vein.

RESULTS

In all livers, access to the portal venous system via the umbilical vein was successfully achieved with good portal flows and macroscopically homogeneous perfusion. The full liver graft that underwent NMP via the umbilical vein for 4 hours showed good lactate clearance, normalized pH, and achieved good bile production with pH >7.55. During the split procedure under continuous NMP via the umbilical vein, the left lateral segment and extended right lobe remained equally perfused, as demonstrated by Doppler ultrasound.

CONCLUSIONS

Machine perfusion with portal perfusion via the umbilical vein is feasible. Portal venous flows were similar to those obtained after cannulation of the portal vein main stem. This technique enables continuous oxygenated perfusion of liver grafts during procurement, splitting, and implantation.

Restoration of Bile Duct Injury of Donor Livers During Ex Situ Normothermic Machine Perfusion

BACKGROUND

End-ischemic ex situ normothermic machine perfusion (NMP) enables assessment of donor livers prior to transplantation. The objective of this study was to provide support for bile composition as a marker of biliary viability and to investigate whether bile ducts of high-risk human donor livers already undergo repair during NMP.

METHODS

Forty-two livers that were initially declined for transplantation were included in our NMP clinical trial. After NMP, livers were either secondary declined (n = 17) or accepted for transplantation (n = 25) based on the chemical composition of bile and perfusate samples. Bile duct biopsies were taken before and after NMP and assessed using an established histological injury severity scoring system and a comprehensive immunohistochemical assessment focusing on peribiliary glands (PBGs), vascular damage, and regeneration.

RESULTS

Bile ducts of livers that were transplanted after viability testing during NMP showed better preservation of PBGs, (micro)vasculature, and increased cholangiocyte proliferation, compared with declined livers. Biliary bicarbonate, glucose, and pH were confirmed as accurate biomarkers of bile duct vitality. In addition, we found evidence of PBG-based progenitor cell differentiation toward mature cholangiocytes during NMP.

CONCLUSIONS

Favorable bile chemistry during NMP correlates well with better-preserved biliary microvasculature and PBGs, with a preserved capacity for biliary regeneration. During NMP, biliary tree progenitor cells start to differentiate toward mature cholangiocytes, facilitating restoration of the ischemically damaged surface epithelium.

Donor hepatectomy time influences ischemia-reperfusion injury of the biliary tree in donation after circulatory death liver transplantation

BACKGROUND

Donor hepatectomy time is associated with graft survival after liver transplantation. The aim of this study was to identify the impact of donor hepatectomy time on biliary injury during donation after circulatory death liver transplantation.

METHODS

First, bile duct biopsies of livers included in (pre)clinical machine perfusion research were analyzed. Secondly, of the same livers, bile samples were collected during normothermic machine perfusion. Lastly, a nationwide retrospective cohort study was performed including 273 adult patients undergoing donation after circulatory death liver transplantation between January 1, 2002 and January 1, 2017. Primary endpoint was development of non-anastomotic biliary strictures within 2 years of donation after circulatory death liver transplantation. Cox proportional-hazards regression analyses were used to assess the influence of hepatectomy time on the development of non-anastomotic biliary strictures.

RESULTS

Livers with severe histological bile duct injury had a higher median hepatectomy time (P = .03). During normothermic machine perfusion, livers with a hepatectomy time >50 minutes had lower biliary bicarbonate and bile pH levels. In the nationwide retrospective study, donor hepatectomy time was an independent risk factor for non-anastomotic biliary strictures after donation after circulatory death liver transplantation (Hazard Ratio 1.18 per 10 minutes increase, 95% Confidence Interval 1.06-1.30, P value = .002).

CONCLUSION

Donor hepatectomy time negatively influences histological bile duct injury before normothermic machine perfusion and bile composition during normothermic machine perfusion. Additionally, hepatectomy time is a significant independent risk factor for the development of non-anastomotic biliary strictures after donation after circulatory death liver transplantation.

Selected liver grafts from donation after circulatory death can be safely used for retransplantation - a multicenter retrospective study

Due to the growing number of liver transplantations (LTs), there is an increasing number of patients requiring retransplantation (reLT). Data on the use of grafts from extended criteria donors (ECD), especially donation after circulatory death (DCD), for reLT are lacking. We aimed to assess the outcome of patients undergoing reLT using a DCD graft in the Netherlands between 2001 and July 2018. Propensity score matching was used to match each DCD-reLT with three DBD-reLT cases. Primary outcomes were patient and graft survival. Secondary outcome was the incidence of biliary complications, especially nonanastomotic strictures (NAS). 21 DCD-reLT were compared with 63 matched DBD-reLTs. Donors in the DCD-reLT group had a significantly lower BMI (22.4 vs. 24.7 kg/m² , P-value = 0.02). Comparison of recipient demographics and ischemia times yielded no significant differences. Patient and graft survival rates were comparable between the two groups. However, the occurrence of nonanastomotic strictures after DCD-reLT was significantly higher (38.1% vs. 12.7%, P-value = 0.02). ReLT with DCD grafts does not result in inferior patient and graft survival compared with DBD grafts in selected patients. Therefore, DCD liver grafts should not routinely be declined for patients awaiting reLT.

Oxygenated versus non-oxygenated flush out and storage of donor livers-An experimental study

Background

During donor organ procurement and subsequent static cold storage (SCS), hepatic adenosine triphosphate (ATP) levels are progressively depleted, which contributes to ischemia‐reperfusion injury (IRI). We sought to investigate a simple approach to prevent ATP depletion and IRI using a porcine donation after circulatory death (DCD) liver reperfusion model.

Methods

After 30 min warm ischemia, porcine livers were flushed via the portal vein with cold (4°C) non‐oxygenated University of Wisconsin (UW) preservation solution (n = 6, control group) or with oxygenated UW (n = 6, OxyFlush group). Livers were then subjected to 4 h SCS in non‐oxygenated (control) or oxygenated (OxyFlush) UW, followed by 4 h normothermic reperfusion using whole blood. Hepatic ATP levels were compared, and hepatobiliary function and injury were assessed.

Results

At the end of SCS, ATP was higher in the OxyFlush group compared to controls (delta ATP of +0.26 vs. −0.68 µmol/g protein, p = 0.04). All livers produced bile and metabolized lactate, and there were no differences between the groups. Grafts in the OxyFlush group had lower blood glucose levels after reperfusion (p = 0.04). Biliary pH, glucose and bicarbonate were not different between the groups. Injury markers including liver transaminases, lactate dehydrogenase, malondialdehyde, cell‐free DNA and flavin mononucleotide in the SCS solution and during reperfusion were also similar. Histological assessment of the parenchyma and bile ducts did not reveal differences between the groups.

Conclusion

Oxygenated flush out and storage of DCD porcine livers prevents ATP depletion during ischemia, but this does not seem sufficient to mitigate early signs of IRI.

Viability assessment of the liver during ex-situ machine perfusion prior to transplantation

PURPOSE OF REVIEW

In an attempt to reduce waiting list mortality in liver transplantation, less-than-ideal quality donor livers from extended criteria donors are increasingly accepted. Predicting the outcome of these organs remains a challenge. Machine perfusion provides the unique possibility to assess donor liver viability pretransplantation and predict postreperfusion organ function.

RECENT FINDINGS

Assessing liver viability during hypothermic machine perfusion remains challenging, as the liver is not metabolically active. Nevertheless, the levels of flavin mononucleotide, transaminases, lactate dehydrogenase, glucose and pH in the perfusate have proven to be predictors of liver viability. During normothermic machine perfusion, the liver is metabolically active and in addition to the perfusate levels of pH, transaminases, glucose and lactate, the production of bile is a crucial criterion for hepatocyte viability. Cholangiocyte viability can be determined by analyzing bile composition. The differences between perfusate and bile levels of pH, bicarbonate and glucose are good predictors of freedom from ischemic cholangiopathy.

SUMMARY

Although consensus is lacking regarding precise cut-off values during machine perfusion, there is general consensus on the importance of evaluating both hepatocyte and cholangiocyte compartments. The challenge is to reach consensus for increased organ utilization, while at the same time pushing the boundaries by expanding the possibilities for viability testing.