Hypothermic oxygenated perfusion (HOPE) protects from biliary injury in a rodent model of DCD liver transplantation

Hypothermic Oxygenated Machine Perfusion Alleviates Donation After Circulatory Death Liver Injury Through Regulating P-selectin-dependent and -independent Pathways in Mice

BACKGROUND

Hypothermic oxygenated machine perfusion (HOPE) has been shown to improve the quality of liver donation after circulatory death (DCD) compared to cold storage (CS). However, the mechanism by which HOPE works is unclear. In this study, a mouse liver HOPE system was developed to characterize the role of P-selectin in the protective effect of HOPE on DCD livers.

METHODS

A warm ischemia model of the liver and an isolated perfused liver system were established to determine a suitable flow rate for HOPE. Perfusate and tissue samples from wild-type and P-selectin knockout (KO) mice were used to determine liver function, apoptosis and necrosis rates, deoxyribonucleic acid injury and oxidative stress levels, leukocyte and endothelial cell activation, and inflammatory reactions.

RESULTS

A mouse liver HOPE system was successfully established. HOPE at flow rates between 0.1 and 0.5 mL/min · g were shown to have a protective effect on the DCD liver. P-selectin KO improved the quality of the DCD liver in the CS group, and reduction of P-selectin expression in the wild-type HOPE group had similar protective effects. Moreover, there was a reduction in the degree of oxidative stress and deoxyribonucleic acid injury in the P-selectin KO HOPE group compared with the P-selectin KO CS group.

CONCLUSIONS

We established a mouse HOPE system and determined its suitable flow. We also proved that P-selectin deficiency alleviated DCD liver injury. HOPE protected the DCD liver through regulating P-selectin-dependent and -independent pathways.

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.

Effect of the Selective NLRP3 Inflammasome Inhibitor mcc950 on Transplantation Outcome in a Pig Liver Transplantation Model With Organs From Donors After Circulatory Death Preserved by Hypothermic Machine Perfusion

BACKGROUND

We investigated whether the outcome of organs from donors after circulatory death (DCD) can be improved by the addition of mcc950 to the perfusate of the hypothermic machine perfusion (HMP) system and intravenous mcc950 injection after transplantation in a pig liver transplantation model.

METHODS

Thirty-six healthy Bama mini pigs randomized into 3 groups. All the DCD livers were preserved in an HMP system after 2 hours of simple cold storage. In HMP-Postop group, mcc950 was added to the perfusate; in the control group and Postop group, the perfusate was normal LPS. After transplantation, the pigs in the Postop group and HMP-Postop group were intravenously administered 3 mg/kg mcc950, at the time of reperfusion and on day 2 and day 3 after transplantation. During the 3-day follow-up period, general operative characteristics, and serological markers and histological features related to ischemia reperfusion injury were examined.

RESULTS

The HMP-Postop group suffer the lightest ischemia reperfusion injury (IRI), and functioned best after transplantation. Model for the Early Allograft Function Score (predictor of long-term survival), degree of injury in the hepatocytes and rate of apoptosis was lowest in the HMP-Postop group. Further, in the HMP-Postop group, the nucleotide-binding domain leucine-rich repeat containing family pyrin domain containing 3 inflammasome pathway activation was lowest, and the level of IL-1β was lowest. Postop group functioned better than control group, but not comparable with HMP-Postop group.

CONCLUSIONS

The outcome of DCD organs can be improved by the addition of mcc950 to the perfusate of the HMP system and intravenous injection of mcc950 after transplantation.

Human Atrial Natriuretic Peptide in Cold Storage of Donation After Circulatory Death Rat Livers: An Old but New Agent for Protecting Vascular Endothelia?

BACKGROUND

Current critical shortage of donor organs has increased the use of donation after circulatory death (DCD) livers for transplantation, despite higher risk for primary nonfunction or ischemic cholangiopathy. Human atrial natriuretic peptide (hANP) is a cardiovascular hormone that possesses protective action to vascular endothelia. We aimed to clarify the therapeutic potential of hANP in cold storage of DCD livers.

METHODS

Male Wistar rats were exposed to 30-minute warm ischemia in situ. Livers were then retrieved and cold-preserved for 6 hours with or without hANP supplementation. Functional and morphological integrity of the livers was evaluated by oxygenated ex vivo reperfusion at 37°C.

RESULTS

hANP supplementation resulted in significant reduction of portal venous pressure (12.2 ± 0.5 versus 22.5 ± 3.5 mm Hg, P < 0.001). As underlying mechanisms, hANP supplementation significantly increased tissue adenosine concentration (P = 0.008), resulting in significant upregulation of endothelial nitric oxide synthase and significant downregulation of endothelin-1 (P = 0.01 and P = 0.004 vs. the controls, respectively). Consequently, hANP significantly decreased transaminase release (P < 0.001) and increased bile production (96.2 ± 18.2 versus 36.2 ± 15.2 μL/g-liver/h, P < 0.001). Morphologically, hepatocytes and sinusoidal endothelia were both better maintained by hANP (P = 0.021). Electron microscopy also revealed that sinusoidal ultrastructures and microvilli formation in bile canaliculi were both better preserved by hANP supplementation. Silver staining also demonstrated that hANP significantly preserved reticulin fibers in Disse space (P = 0.017), representing significant protection of sinusoidal frameworks/architectures.

CONCLUSIONS

Supplementation of hANP during cold storage significantly attenuated cold ischemia/warm reperfusion injury of DCD livers.

Hypothermic oxygenated machine perfusion alleviates liver injury in donation after circulatory death through activating autophagy in mice

Hypothermic oxygenated machine perfusion (HOPE) is a safe and reliable method that could alleviate liver injury in donation after circulatory death (DCD). This study focuses on the role of autophagy in HOPE's protective effect on DCD liver injury. A 30-minute warm ischemic liver model was established in mice. After 4 hours of cold storage (CS), 1 hour of hypothermic machine perfusion (HMP) with 100% O₂ or 100% N₂ was employed. During 2 hours of reperfusion, liver tissue and perfusate were collected to evaluate liver function, oxidative stress level, apoptosis, and necrosis. Western blotting was used to explore the level of autophagy. When the liver experienced warm ischemic injury, LC3B-II expression was significantly enhanced. Compared with the CS, HOPE induced lower release of AST and ALT, as well as lower oxidative stress levels, apoptosis, and necrosis cell numbers, and led to higher tissue ATP content. Meanwhile, expression of autophagy-related proteins, such as ULK1, Atg5, and LC3B-II, increased. When oxygen was completely replaced by nitrogen, the washout effect of HMP did not activate autophagy and did not relieve DCD liver injury. When the autophagy inhibitor 3-methyladenine was used in HOPE, the protective effect of HOPE was attenuated. In conclusion, DCD liver injury activated autophagy compared with healthy liver, while HOPE alleviated DCD liver injury by increasing autophagy levels further in this mouse model. However, HMP with 100% of N₂ had no beneficial effect on DCD liver injury or on autophagy levels compared with CS. The research on autophagy may provide a new strategy for alleviating DCD liver injury in clinical practice.

Hypothermic Oxygenated Machine Perfusion of Liver Grafts from Brain-Dead Donors

Hypothermic oxygenated machine perfusion (HOPE) was introduced in liver transplantation (LT) to mitigate ischemia-reperfusion injury. Available clinical data mainly concern LT with donors after circulatory-determined death, whereas data on brain-dead donors (DBD) are scarce. To assess the impact of end-ischemic HOPE in DBD LT, data on primary adult LTs performed between March 2016 and June 2018 were analyzed. HOPE was used in selected cases of donor age >80 years, apparent severe graft steatosis, or ischemia time ≥10 hours. Outcomes of HOPE-treated cases were compared with those after static cold storage. Propensity score matching (1:2) and Bayesian model averaging were used to overcome selection bias. During the study period, 25 (8.5%) out of 294 grafts were treated with HOPE. After matching, HOPE was associated with a lower severe post-reperfusion syndrome (PRS) rate (4% versus 20%, p = 0.13) and stage 2–3 acute kidney injury (AKI) (16% versus 42%, p = 0.046). Furthermore, Bayesian model averaging showed lower transaminases peak and a lower early allograft dysfunction (EAD) rate after HOPE. A steeper decline in arterial graft resistance throughout perfusion was associated with lower EAD rate. HOPE determines a significant reduction of ischemia reperfusion injury in DBD LT.

TAK242 suppresses the TLR4 signaling pathway and ameliorates DCD liver IRI in rats

Ischemia-reperfusion injury (IRI) is a notable cause of tissue damage during surgical procedures and a major risk factor in graft dysfunction in liver transplantation. Livers obtained from donors after circulatory death (DCD) are prone to IRI and toll-like receptor 4 (TLR4) serves a prominent role in the inflammatory response associated with DCD liver IRI. The present study was designed to investigate whether TAK242, a specific TLR4 inhibitor, improves hepatic IRI following a DCD graft and to investigate its underlying protective mechanisms. Male Sprague-Dawley rats were randomized into 4 groups: Control, TAK242, DCD and DCD+TAK242 groups. Rats were pretreated with TAK242 or its vehicle for 30 min, then the livers were harvested without warm ischemia (control group and TAK242 group) or with warm ischemia in situ for 30 min. The livers were stored in cold University of Wisconsin solution for 24 h and subsequently perfused for 60 min with an isolated perfused rat liver system. Rat liver injury was evaluated thereafter. When compared with the DCD group, DCD livers with TAK242 pretreatment displayed significantly improved hepatic tissue injury and less tissue necrosis (P<0.05). Compared with DCD livers, mechanistic experiments revealed that TAK242 pretreatment alleviated mitochondrial dysfunction, reduced reactive oxygen species and malondialdehyde levels and inhibited apoptosis. Additionally, TAK242 significantly inhibited the IRI-associated inflammatory response, indicated by the decreased expression of TLR4, interleukin (IL)-1β, IL-6 and cyclooxygenase 2 at the mRNA and protein levels (P<0.05). TAK242 ameliorates DCD liver IRI via suppressing the TLR4 signaling pathway in rats. The results of the present study have revealed that TAK242 pretreatment harbors a potential benefit for liver transplantation.

N,N-dimethyltryptamine Prevents Renal Ischemia-Reperfusion Injury in a Rat Model

BACKGROUND

Ischemia reperfusion (I/R) injury remains one of the most challenging fields of organ transplantation. It is highly associated with the use of expanded criteria donors that might conclude to delayed graft function or early or late graft failure.

OBJECTIVE

To investigate the metabolic, microcirculatory parameters, and histologic changes under the effect of N,N-dimethyltryptamine (DMT) in a renal I/R model in rats.

METHOD

In 26 anesthetized rats both kidneys were exposed. In the control group (n = 6) no other intervention happened. In 20 other animals, the right renal vessels were ligated, and after 60 minutes the right kidney was removed. The left renal vessels were clamped for 60 minutes then released, followed by 120 minutes of reperfusion. In the I/R group (n = 10), there was no additive treatment, while in I/R + DMT group (n = 10) DMT was administered 15 minutes before ischemia. Blood samples were taken, laser Doppler measurement was performed, and both kidneys were evaluated histologically.

RESULTS

Microcirculation (blood flux units [BFU]) diminished in all groups, but remarkably so in the I/R + DMT group. This group compensated better after the 30th minute of reperfusion. The control and I/R + DMT groups had similar BFUs after 120 minutes of reperfusion, but in the I/R group BFU was higher. Tubular necrosis developed in the I/R and I/R + DMT groups too; it was moderated under DMT effect, and severe without. Histologic injuries were less in I/R + DMT Group compared to non-treated animals.

CONCLUSION

Histologic changes characteristic to I/R injuries were reversible and microcirculation recovered at the end of 120 minutes reperfusion under the administration of DMT. DMT can be used for renoprotection in kidney transplantation.

Age and liver transplantation

The average age of liver transplant donors and recipients has increased over the years. Independent of the cause of liver disease, older candidates have more comorbidities, higher waitlist mortality and higher post-transplant mortality than younger patients. However, transplant benefit may be similar in older and younger recipients, provided older recipients are carefully selected. The cohort of elderly patients transplanted decades ago is also increasingly raising issues concerning long-term exposure to immunosuppression and aging of the transplanted liver. Excellent results can be achieved with elderly donors and there is virtually no upper age limit for donors after brain death liver transplantation. The issue is how to optimise selection, procurement and matching to ensure good results with elderly donors. The impact of old donor age is more pronounced in younger recipients and patients with a high model for end-stage liver disease score. Age matching between the donor and the recipient should be incorporated into allocation policies with a multistep approach. However, age matching may vary depending on the objectives of different allocation policies. In addition, age matching must be revisited in the era of direct-acting antivirals. More restrictive limits have been adopted in donation after circulatory death. Perfusion machines which are currently under investigation may help expand these limits. In living donor liver transplantation, donor age limit is essentially guided by morbidity related to procurement. In this review we summarise changing trends in recipient and donor age. We discuss the implications of older age donors and recipients. We also consider different options for age matching in liver transplantation that could improve outcomes.

Liver graft preservation methods during cold ischemia phase and normothermic machine perfusion

The growing demand for donor organs requires measures to expand donor pool. Those include extended criteria donors, such as elderly people, steatotic livers, donation after cardiac death, etc. Static cold storage to reduce metabolic requirements developed by Collins in late 1960s is the mainstay and the golden standard for donated organ protection. Hypothermic machine perfusion provides dynamic organ preservation at 4°C with protracted infusion of metabolic substrates to the graft during the ex vivo period. It has been used instead of static cold storage or after it as short perfusion in transplant center. Normothermic machine perfusion (NMP) delivers oxygen, and nutrition at physiological temperature mimicking regular environment in order to support cellular function. This would minimize effects of ischemia/reperfusion injury. Potentially, NMP may help to estimate graft functionality before implantation into a recipient. Clinical studies demonstrated at least its non-inferiority or better outcomes vs static cold storage. Regular grafts donated after brain death could be safely preserved with convenient static cold storage. Except for prolonged ischemia time where hypothermic machine perfusion started in transplant center could be estimated to provide possible positive reconditioning effect. Use of hypothermic machine perfusion in regular donation instead of static cold storage or in extended criteria donors requires further investigation. Multicenter randomized clinical trial supposed to be completed in December 2021. Extended criteria donors need additional measures for graft storage and assessment until its implantation. NMP is actively evaluating promising method for this purpose. Future studies are necessary for precise estimation and confirmation to issue clinical practice recommendations.

Liver repair and regeneration after ischemia-reperfusion injury is associated with prolonged fibrosis

Liver recovery after hepatic ischemia-reperfusion (I/R) injury is characterized by clearance of dead tissue and its replacement with functional liver parenchyma. Previous reports have observed fibrosis after liver I/R. To determine whether liver fibrosis after I/R was a pathologic consequence of the injury response, we assessed the development of liver fibrosis after I/R and its impact on subsequent insult. A murine model of partial I/R was used to induce liver injury and study the reparative response. During liver remodeling after I/R, expression of the profibrotic genes increased in the ischemic liver. Histologically, α-smooth muscle actin (α-SMA)-positive hepatic stellate cells (HSCs)/myofibroblasts increased, and collagen deposition was enhanced along the injured site. Selective staining experiments showed that HSCs, not portal fibroblasts, were the major source of myofibroblasts. During liver repair after I/R, liver fibrosis was readily observed at the interface between necrotic tissue and regenerating liver in association with HSCs/myofibroblasts. The number of HSCs/myofibroblasts decreasing shortly after the full resolution of necrotic injury and restoration are normal liver architecture. However, liver fibrosis persisted for several more weeks before gradually resolving. Resolution of liver fibrosis was accompanied by upregulated expression of matrix metalloproteinase-13. After resolution of fibrosis, the administration of CCl4 did not result in exacerbated liver injury, suggesting that I/R injury does not predispose the liver to future fibrotic insults. The data suggest that liver fibrosis is a component of tissue repair after I/R, is caused by myofibroblasts derived from HSC, and does not increase susceptibility of the liver to subsequent hepatic injury. NEW & NOTEWORTHY This study is the first to assess pathology of liver fibrosis during the reparative process after ischemia-reperfusion (I/R) injury. Here we show that profibrotic gene expression increased in the liver after I/R, and collagen accumulation produced by hepatic stellate cells (HSCs)/myofibroblasts enhanced at the interface between necrotic tissue and regenerating liver. Liver fibrosis gradually resolved concomitant with decreasing activation of HSC and upregulating matrix metalloproteinase-13. After resolution of fibrosis, the liver was not more susceptible to subsequent hepatic injury.

Improvement of Normothermic Ex Vivo Machine Perfusion of Rat Liver Grafts by Dialysis and Kupffer Cell Inhibition With Glycine

Normothermic ex vivo liver machine perfusion might be a superior preservation strategy for liver grafts from extended criteria donors. However, standardized small animal models are not available for basic research on machine perfusion of liver grafts. A laboratory-scaled perfusion system was developed consisting of a custom-made perfusion chamber, a pressure-controlled roller pump, and an oxygenator. Male Wistar rat livers were perfused via the portal vein for 6 hours using oxygenated culture medium supplemented with rat erythrocytes. A separate circuit was connected via a dialysis membrane to the main circuit for plasma volume expansion. Glycine was added to the flush solution, the perfusate, and the perfusion circuit. Portal pressure and transaminase release were stable over the perfusion period. Dialysis significantly decreased the potassium concentration of the perfusate and led to significantly higher bile and total urea production. Hematoxylin-eosin staining and immunostaining for single-stranded DNA and activated caspase 3 showed less sinusoidal dilatation and tissue damage in livers treated with dialysis and glycine. Although Kupffer cells were preserved, tumor necrosis factor α messenger RNA levels were significantly decreased by both treatments. For proof of concept, the optimized perfusion protocol was tested with donation after circulatory death (DCD) grafts, resulting in significantly lower transaminase release into the perfusate and preserved liver architecture compared with baseline perfusion. In conclusion, our laboratory-scaled normothermic portovenous ex vivo liver perfusion system enables rat liver preservation for 6 hours. Both dialysis and glycine treatment were shown to be synergistic for preservation of the integrity of normal and DCD liver grafts.

Outcomes of DCD liver transplantation using organs treated by hypothermic oxygenated perfusion before implantation

BACKGROUND & AIMS

Donation after circulatory death (DCD) liver transplantation is known for potentially worse outcomes because of higher rates of graft non-function or irreversible cholangiopathy. The impact of machine liver perfusion techniques on these complications remains elusive. We aimed to provide data on 5-year outcomes in patients receiving DCD liver transplants, after donor organs had been treated by hypothermic oxygenated perfusion (HOPE).

METHODS

Fifty HOPE-treated DCD liver transplants performed in Zurich between 2012 and 3/2017 were matched with 50 primary donation after brain death (DBD) liver transplants, and with 50 untreated DCD liver transplants in Birmingham. Match factors focussed on short cold ischaemia, comparable recipient age and low recipient laboratory model for end-stage liver disease scores. Primary endpoints were post-transplant complications, and non-tumour-related patient death or graft loss.

RESULTS

Despite extended donor warm ischaemia, HOPE-treated DCD liver transplants achieved similar overall graft survival, compared to standard DBD liver transplants. Particularly, graft loss due to any non-tumour-related causes occurred in 8% (4/50) of cases. In contrast, untreated DCD livers resulted in non-tumour-related graft failure in one-third (16/50) of cases (p = 0.005), despite significantly (p <0.001) shorter functional donor warm ischaemia. Five-year graft survival, censored for tumour death, was 94% for HOPE-treated DCD liver transplants vs. 78% in untreated DCD liver transplants (p = 0.024).

CONCLUSIONS

The 5-year outcomes of HOPE-treated DCD liver transplants were similar to those of DBD primary transplants and superior to those of untreated DCD liver transplants, despite much higher risk. These results suggest that a simple end-ischaemic perfusion approach is very effective and may open the field for safe utilisation of extended DCD liver grafts.

LAY SUMMARY

Machine perfusion techniques are currently being introduced into the clinic, with the aim of optimising injured grafts prior to implantation. While short-term effects of machine liver perfusion have been frequently reported in terms of hepatocellular enzyme release and early graft function, the long-term benefit on irreversible graft loss has been unclear. Herein, we report on 5-year graft survival in donation after cardiac death livers, treated either by conventional cold storage, or by 1-2 h of hypothermic oxygenated perfusion (HOPE) after cold storage. Graft loss was significantly less in HOPE-treated livers, despite longer donor warm ischaemia times. Therefore, HOPE after cold storage appears to be a simple and effective method to treat high-risk livers before implantation.

Combined Hypothermic and Normothermic Machine Perfusion Improves Functional Recovery of Extended Criteria Donor Livers

Hypothermic oxygenated perfusion (HOPE) and normothermic perfusion are seen as distinct techniques of ex situ machine perfusion of the liver. We aimed to demonstrate the feasibility of combining both techniques and whether it would improve functional parameters of donor livers into transplant standards. Ten discarded human donor livers had either 6 hours of normothermic perfusion (n = 5) or 2 hours of HOPE followed by 4 hours of normothermic perfusion (n = 5). Liver function was assessed according to our viability criteria; markers of tissue injury and hepatic metabolic activity were compared between groups. Donor characteristics were comparable. During the hypothermic perfusion phase, livers down-regulated mitochondrial respiration (oxygen uptake, P = 0.04; partial pressure of carbon dioxide perfusate, P = 0.04) and increased adenosine triphosphate levels 1.8-fold. Following normothermic perfusion, those organs achieved lower tissue expression of markers of oxidative injury (4-hydroxynonenal, P = 0.008; CD14 expression, P = 0.008) and inflammation (CD11b, P = 0.02; vascular cell adhesion molecule 1, P = 0.05) compared with livers that had normothermic perfusion alone. All livers in the combined group achieved viability criteria, whereas 40% (2/5) in the normothermic group failed (P = 0.22). In conclusion, this study suggests that a combined protocol of hypothermic oxygenated and normothermic perfusions might attenuate oxidative stress, tissue inflammation, and improve metabolic recovery of the highest-risk donor livers compared with normothermic perfusion alone.

Impact of Machine Perfusion on Biliary Complications after Liver Transplantation

We describe in this review the different types of injuries caused to the biliary tree after liver transplantation. Furthermore, we explain underlying mechanisms and why oxygenated perfusion concepts could not only protect livers, but also repair high-risk grafts to prevent severe biliary complications and graft loss. Accordingly, we summarize experimental studies and clinical applications of machine liver perfusion with a focus on biliary complications after liver transplantation. Key points: (1) Acute inflammation with subsequent chronic ongoing liver inflammation and injury are the main triggers for cholangiocyte injury and biliary tree transformation, including non-anastomotic strictures; (2) Hypothermic oxygenated perfusion (HOPE) protects livers from initial oxidative injury at normothermic reperfusion after liver transplantation. This is a unique feature of a cold oxygenation approach, which is effective also end-ischemically, e.g., after cold storage, due to mitochondrial repair mechanisms. In contrast, normothermic oxygenated perfusion concepts protect by reducing cold ischemia, and are therefore most beneficial when applied instead of cold storage; (3) Due to less downstream activation of cholangiocytes, hypothermic oxygenated perfusion also significantly reduces the development of biliary strictures after liver transplantation.

Graft Dysfunction and Management in Liver Transplantation

Graft dysfunction of the liver allograft manifests across a spectrum in both timing posttransplantation and clinical presentation. This can range from mild transient abnormalities of liver tests to acute liver failure potentially leading to graft failure. The causes of graft dysfunction can be divided into those resulting in early and late graft dysfunction. Although nonspecific, liver biochemistry abnormalities are still the mainstay investigation used in monitoring for dysfunction. This article provides a summary of the main causes and management strategies for liver graft dysfunction in the early through late posttransplant stages.

A Comparative Study of Single and Dual Perfusion During End-ischemic Subnormothermic Liver Machine Preservation

Background

It remains controversial if arterial perfusion in addition to portal vein perfusion during machine preservation improves liver graft quality. Comparative studies using both techniques are lacking. We studied the impact of using single or dual machine perfusion of donation after circulatory death rat livers. In addition, we analyzed the effect of pulsatile versus continuous arterial flow.

Methods

Donation after circulatory death rat livers (n = 18) were preserved by 6 hours cold storage, followed by 1 hour subnormothermic machine perfusion (20°C, pressure of 40/5 mm Hg) and 2 hours ex vivo warm reperfusion (37°C, pressure of 80/11 mm Hg, 9% whole blood). Machine preservation was either through single portal vein perfusion (SP), dual pulsatile (DPP), or dual continuous perfusion (DCP) of the portal vein and hepatic artery. Hydrodynamics, liver function tests, histopathology, and expression of endothelial specific genes were assessed during 2 hours warm reperfusion.

Results

At the end of reperfusion, arterial flow in DPP livers tended to be higher compared to DCP and SP grafts. However, this difference was not significant nor was better flow associated with better outcome. No differences in bile production or alanine aminotransferase levels were observed. SP livers had significantly lower lactate compared to DCP, but not DPP livers. Levels of Caspase-3 and tumor necrosis factor-α were similar between the groups. Expression of endothelial genes Krüppel-like-factor 2 and endothelial nitric oxide synthase tended to be higher in dual perfused livers, but no histological evidence of better preservation of the biliary endothelium or vasculature of the hepatic artery was observed.

Conclusions

This study shows comparable outcomes after using a dual or single perfusion approach during end-ischemic subnormothermic liver machine preservation.

Optimizing Livers for Transplantation Using Machine Perfusion versus Cold Storage in Large Animal Studies and Human Studies: A Systematic Review and Meta-Analysis

Background

Liver allograft preservation frequently involves static cold storage (CS) and machine perfusion (MP). With its increasing popularity, we investigated whether MP was superior to CS in terms of beneficial outcomes.

Methods

Human studies and large animal studies that optimized livers for transplantation using MP versus CS were assessed (PubMed/Medline/EMBASE). Meta-analyses were conducted for comparisons. Study quality was assessed according to the Newcastle-Ottawa quality assessment scale and SYRCLE's risk of bias tool.

Results

Nineteen studies were included. Among the large animal studies, lower levels of lactate dehydrogenase (SMD -3.16, 95% CI -5.14 to -1.18), alanine transferase (SMD -2.46, 95% CI -4.03 to -0.90), and hyaluronic acid (SMD -2.48, 95% CI -4.21 to -0.74) were observed in SNMP-preserved compared to CS-preserved livers. NMP-preserved livers showing lower level of hyaluronic acid (SMD -3.97, 95% CI -5.46 to -2.47) compared to CS-preserved livers. Biliary complications (RR 0.45, 95% CI 0.28 to 0.73) and early graft dysfunction (RR 0.56, 95% CI 0.34 to 0.92) also significantly reduced with HMP preservation in human studies. No evidence of publication bias was found.

Conclusions

MP preservation could improve short-term outcomes after transplantation compared to CS preservation. Additional randomized controlled trials (RCTs) are needed to develop clinical applications of MP preservation.

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.

The UK DCD Risk Score: A new proposal to define futility in donation-after-circulatory-death liver transplantation

BACKGROUND & AIMS

Primary non-function and ischaemic cholangiopathy are the most feared complications following donation-after-circulatory-death (DCD) liver transplantation. The aim of this study was to design a new score on risk assessment in liver-transplantation DCD based on donor-and-recipient parameters.

METHODS

Using the UK national DCD database, a risk analysis was performed in adult recipients of DCD liver grafts in the UK between 2000 and 2015 (n = 1,153). A new risk score was calculated (UK DCD Risk Score) on the basis of a regression analysis. This is validated using the United Network for Organ Sharing database (n = 1,617) and our own DCD liver-transplant database (n = 315). Finally, the new score was compared with two other available prediction systems: the DCD risk scores from the University of California, Los Angeles and King's College Hospital, London.

RESULTS

The following seven strongest predictors of DCD graft survival were identified: functional donor warm ischaemia, cold ischaemia, recipient model for end-stage liver disease, recipient age, donor age, previous orthotopic liver transplantation, and donor body mass index. A combination of these risk factors (UK DCD risk model) stratified the best recipients in terms of graft survival in the entire UK DCD database, as well as in the United Network for Organ Sharing and in our own DCD population. Importantly, the UK DCD Risk Score significantly predicted graft loss caused by primary non-function or ischaemic cholangiopathy in the futile group (>10 score points). The new prediction model demonstrated a better C statistic of 0.79 compared to the two other available systems (0.71 and 0.64, respectively).

CONCLUSIONS

The UK DCD Risk Score is a reliable tool to detect high-risk and futile combinations of donor-and-recipient factors in DCD liver transplantation. It is simple to use and offers a great potential for making better decisions on which DCD graft should be rejected or may benefit from functional assessment and further optimization by machine perfusion.

LAY SUMMARY

In this study, we provide a new prediction model for graft loss in donation-after-circulatory-death (DCD) liver transplantation. Based on UK national data, the new UK DCD Risk Score involves the following seven clinically relevant risk factors: donor age, donor body mass index, functional donor warm ischaemia, cold storage, recipient age, recipient laboratory model for end-stage liver disease, and retransplantation. Three risk classes were defined: low risk (0-5 points), high risk (6-10 points), and futile (>10 points). This new model stratified best in terms of graft survival compared to other available models. Futile combinations (>10 points) achieved an only very limited 1- and 5-year graft survival of 37% and less than 20%, respectively. In contrast, an excellent graft survival has been shown in low-risk combinations (≤5 points). The new model is easy to calculate at the time of liver acceptance. It may help to decide which risk combination will benefit from additional graft treatment, or which DCD liver should be declined for a certain recipient.

Hypothermic machine perfusion in liver transplantation

A finite supply of donor organs has led many transplant centers to accept marginal liver allografts with increasing frequency. These allografts may be at higher risk of primary nonfunction, early allograft dysfunction, and other recipient complications following liver transplantation. Machine perfusion preservation is an emerging technology that limits ischemia/reperfusion injury associated with preservation and may lead to improved outcomes following transplantation. Increased used of machine perfusion in liver preservation may permit an expansion of the donor pool. In this review, we examine the major clinical experience of hypothermic machine perfusion in human liver transplantation.Liver Transplantation 24 276-281 2018 AASLD.

Hypothermic Machine Preservation of the Liver: State of the Art

PURPOSE OF REVIEW

In this review, we highlight which livers may benefit from additional treatment before implantation and describe the concept of hypothermic machine liver perfusion. Furthermore, we explain why cold oxygenated perfusion concepts could potentially lead to a breakthrough in this challenging field of transplantation. Accordingly, we summarize recent clinical applications of different hypothermic perfusion approaches.

RECENT FINDINGS

The impact of end-ischemic, hypothermic liver perfusion in liver transplantation is currently assessed by two multicenter, randomized controlled trials. Recently, new applications of hypothermic perfusion showed promising results and recipients were protected from severe intrahepatic biliary complications, despite the use of very extended criteria grafts including donation after circulatory death livers.

SUMMARY

Hypothermic machine liver perfusion is beneficial for high-risk livers and protects recipients from most feared complications. Importantly, such easy approach is currently implemented in several European centers and new markers obtained from perfusate may improve the prediction of liver function in the future.

Role of temperature in reconditioning and evaluation of cold preserved kidney and liver grafts

Purpose of review

Organ shortage in transplantation medicine forces surgical research toward the development of more efficient approaches in organ preservation to enable the application of ‘less than optimal’ grafts. This review summarizes current techniques aiming to recondition cold-stored organ grafts prior to transplantation to reduce reperfusion-induced tissue injury and improve postimplantation graft function.

Recent findings

End-ischemic reconditioning has classically been attempted by cold oxygenated perfusion. By contrast, evaluation of graft performance prior to transplantation might be facilitated by perfusion at higher temperatures, ideally at normothermia. A drastic temperature shift from cold preservation to warm perfusion, however, has been incriminated to trigger a so-called rewarming injury associated with mitochondrial alterations. A controlled gradual warming up during machine perfusion could enhance the restitution of cellular homeostasis and improve functional outcome upon warm reperfusion.

Summary

Machine perfusion after conventional cold storage is beneficial for ulterior function after transplantation. Cold grafts should be initially perfused at low temperatures allowing for restitution of cellular homeostasis under protective hypothermic limitation of metabolic turnover. Delayed slow rewarming of the organ might further mitigate rewarming injury upon reperfusion and also increases the predictive power of evaluative measures, taken during pretransplant perfusion.

Kidney perfusion: some like it hot others prefer to keep it cool

PURPOSE OF REVIEW

Machine perfusion technologies provide an opportunity for improved preservation, organ assessment, and resuscitation of damaged kidneys. This review summarizes the recent advances in hypothermic and normothermic kidney machine perfusion technologies.

RECENT FINDINGS

Modifications to the perfusion conditions with the addition of oxygen during hypothermic machine perfusion can support a low level of metabolism, which in experimental settings improves graft function. Normothermic machine perfusion technologies are evolving in different directions including short-duration resuscitation, more prolonged periods of perfusion, and the transition between hypothermic and normothermic conditions. Clinical trials are ongoing in both hypothermic and normothermic settings. Functional parameters can be used to assess kidney quality and although normothermic machine perfusion may hold an advantage over hypothermic machine perfusion, new metabolomic, proteomic, and genomic technologies may be applied in the future to both technologies to provide more rigorous information on kidney quality. Promoting recovery by introducing an intervention during perfusion is an attractive area of research and therapies targeting the endothelium are a particular area of interest.

SUMMARY

A great deal of research is still needed to optimize and logistically place hypothermic and normothermic perfusion technologies. In the future, we may progress toward organ-tailored preservation whereby high-risk kidneys can undergo assessment and repair before transplantation.

Pretreatment Donors after Circulatory Death with Simvastatin Alleviates Liver Ischemia Reperfusion Injury through a KLF2-Dependent Mechanism in Rat

Objective

Severe hepatic ischemia reperfusion injury (IRI) can result in poor short- and long-term graft outcome after transplantation. The way to improve the viability of livers from donors after circulatory death (DCD) is currently limited. The aim of the present study was to explore the protective effect of simvastatin on DCD livers and investigate the underlying mechanism.

Methods

24 male rats randomly received simvastatin or its vehicle. 30 min later, rat livers were exposed to warm ischemia in situ for 30 min. Livers were removed and cold-stored in UW solution for 24 h, subsequently reperfused for 60 min with an isolated perfused rat liver system. Liver injury was evaluated during and after warm reperfusion.

Results

Pretreatment of DCD donors with simvastatin significantly decreased IRI liver enzyme release, increased bile output and ATP, and ameliorated hepatic pathological changes. Simvastatin maintained the expression of KLF2 and its protective target genes (eNOS, TM, and HO-1), reduced oxidative stress, inhibited innate immune responses and inflammation, and increased the expression of Bcl-2/Bax to suppress hepatocyte apoptosis compared to DCD control group.

Conclusion

Pretreatment of DCD donors with simvastatin improves DCD livers' functional recovery probably through a KLF2-dependent mechanism. These data suggest that simvastatin may provide a potential benefit for clinical DCD liver transplantation.

Hypothermic machine perfusion in liver transplantation

PURPOSE OF THE REVIEW

The purpose of the review is to report recent human application of hypothermic machine liver perfusion, and to discuss potential protective mechanisms.

RECENT FINDINGS

Human application of hypothermic machine liver perfusion is still very limited. Currently, three transplant centers apply this novel treatment in donation after cardiac death (DCD) or donation after brain death (DBD) liver grafts. In all cases, endischemic perfusion was performed after initial cold storage for organ transport. Perfusion conditions differ slightly in terms of oxygenation (pO2 15-60 kPa), perfusion route (dual vs. portal), perfusion time (2-4 h), and perfusate.

SUMMARY

The current data support the hypothesis that applying endischemic hypothermic machine liver perfusion protects extended criteria DBD and DCD livers from initial reperfusion injury, with better graft function and less biliary complications. Hypothermic machine perfusion may therefore offer revitalization of liver grafts before implantation by a simple and practical perfusion technique with a high impact on enlarging the donor pool. Multicentric phase III randomized control trials in DBD and DCD liver transplantation have been initiated to further test this strategy, which may establish machine liver perfusion in the clinical setting.

Hypothermic oxygenated machine perfusion (HOPE) for orthotopic liver transplantation of human liver allografts from extended criteria donors (ECD) in donation after brain death (DBD): a prospective multicentre randomised controlled trial (HOPE ECD-DBD)

INTRODUCTION

Orthotopic liver transplantation (OLT) has emerged as the mainstay of treatment for end-stage liver disease. In an attempt to improve the availability of donor allografts and reduce waiting list mortality, graft acceptance criteria were extended increasingly over the decades. The use of extended criteria donor (ECD) allografts is associated with a higher incidence of primary graft non-function and/or delayed graft function. As such, several strategies have been developed aiming at reconditioning poor quality ECD liver allografts. Hypothermic oxygenated machine perfusion (HOPE) has been successfully tested in preclinical experiments and in few clinical series of donation after cardiac death OLT.

METHODS AND ANALYSIS

HOPE ECD-DBD is an investigator-initiated, open-label, phase-II, prospective multicentre randomised controlled trial on the effects of HOPE on ECD allografts in donation after brain death (DBD) OLT. Human whole organ liver grafts will be submitted to 1-2 hours of HOPE (n=23) via the portal vein before implantation and are going to be compared with a control group (n=23) of patients transplanted after conventional cold storage. Primary (peak and Δ peak alanine aminotransferase within 7 days) and secondary (aspartate aminotransferase, bilirubin and international normalised ratio, postoperative complications, early allograft dysfunction, duration of hospital and intensive care unit stay, 1-year patient and graft survival) endpoints will be analysed within a 12-month follow-up. Extent of ischaemia-reperfusion (I/R) injury will be assessed using liver tissue, perfusate, bile and serum samples taken during the perioperative phase of OLT.

ETHICS AND DISSEMINATION

The study was approved by the institutional review board of the RWTH Aachen University, Aachen, Germany (EK 049/17). The current paper represent the pre-results phase. First results are expected in 2018.

TRIAL REGISTRATION NUMBER

NCT03124641.

Hypothermic oxygenated perfusion (HOPE) for fatty liver grafts in rats and humans

BACKGROUND & AIMS

Pretreatment of marginal organs by perfusion is a promising opportunity to make more organs available for transplantation. Protection of human donation after cardiac death (DCD) livers by a novel machine perfusion technique, hypothermic oxygenated perfusion (HOPE), was recently established. Herein, we tested whether HOPE is also useful for fatty liver grafts, using a rodent transplant model.

METHODS

Rats were fed over three weeks with a special methionine-choline-deficient diet (MCDD) to induce severe hepatic macrosteatosis (≥60%). Afterwards, livers were transplanted with either minimal or 12h cold storage. Additional liver grafts were treated after 12h cold storage with 1h HOPE before transplantation. Graft injury after orthotopic liver transplantation (OLT) was assessed in terms of oxidative stress, damage-associated molecular patterns release, toll-like receptor-4 activation, cytokine release, endothelial activation, and the development of necrosis and fibrosis.

RESULTS

Implantation of cold stored macrosteatotic liver grafts induced massive reperfusion injury after OLT, compared to controls (non-fatty livers). HOPE treatment after cold storage failed to change the degree of steatosis itself, but markedly decreased reperfusion injury after OLT, as detected by less oxidative stress, less nuclear injury, less Kupffer- and endothelial cell activation, as well as less fibrosis within one week after OLT. Protective effects were lost in the absence of oxygen in the HOPE perfusate.

CONCLUSION

HOPE after cold storage of fatty livers prevents significant reperfusion injury and improves graft function, comparable to the effects of HOPE in DCD livers and DCD kidneys. HOPE treatment is easy and may become a universal concept to further expand the donor pool.

LAY SUMMARY

An increasing number of donor livers contain fat. It is important to harness marginal livers, which may contain fat, as the stock of donor livers is limited. Hypothermic oxygenated perfusion (HOPE) prevents reperfusion injury and improves liver graft function. HOPE offers a simple and low-cost option for treating liver grafts in transplant centers, even after cold storage, instead of transporting machines to the place of procurement. HOPE could be used globally to expand the donor pool.

An Oxygenated and Transportable Machine Perfusion System Fully Rescues Liver Grafts Exposed to Lethal Ischemic Damage in a Pig Model of DCD Liver Transplantation

BACKGROUND

Control of warm ischemia (WI) lesions that occur with donation after circulatory death (DCD) would significantly increase the donor pool for liver transplantation. We aimed to determine whether a novel, oxygenated and hypothermic machine perfusion device (HMP Airdrive system) improves the quality of livers derived from DCDs using a large animal model.

METHODS

Cardiac arrest was induced in female large white pigs by intravenous injection of potassium chloride. After 60 minutes of WI, livers were flushed in situ with histidine-tryptophan-ketoglutarate and subsequently preserved either by simple cold storage (WI-SCS group) or HMP (WI-HMP group) using Belzer-MPS solution. Liver grafts procured from heart-beating donors and preserved by SCS served as controls. After 4 hours of preservation, all livers were transplanted.

RESULTS

All recipients in WI-SCS group died within 6 hours after transplantation. In contrast, the HMP device fully protected the liver against lethal ischemia/reperfusion injury, allowing 100% survival rate. A postreperfusion syndrome was observed in all animals of the WI-SCS group but none of the control or WI-HMP groups. After reperfusion, HMP-preserved livers functioned better and showed less hepatocellular and endothelial cell injury, in agreement with better-preserved liver histology relative to WI-SCS group. In addition to improved energy metabolism, this protective effect was associated with an attenuation of inflammatory response, oxidative load, endoplasmic reticulum stress, mitochondrial damage, and apoptosis.

CONCLUSIONS

This study demonstrates for the first time the efficacy of the HMP Airdrive system to protect liver grafts from lethal ischemic damage before transplantation in a clinically relevant DCD model.

Opportunities for Therapeutic Intervention During Machine Perfusion

PURPOSE OF REVIEW

There is a vast discrepancy between the number of patients waiting for organ transplantation and the available donor organs. Ex vivo machine perfusion (MP) has emerged in an effort to expand the donor pool, by improving organ preservation, providing diagnostic information, and more recently, acting as a platform for organ improvement. This article reviews the current status of MP with a focus on its role in organ preconditioning and therapeutic interventions prior to transplantation.

RECENT FINDINGS

MP has allowed longer organ preservation compared to conventional static cold storage and allowed the use of organs that might otherwise have been discarded. Moreover, experimental studies have investigated the role of MP in reducing ischemia reperfusion injury of lungs, kidneys and livers by applying mesenchymal stem cells (MSCs), anti-inflammatory agents, cytotopic anticoagulants, and defatting cocktails.

SUMMARY

MP has opened a new era in the field of organ transplantation and tissue medication.

Short, Cool, and Well Oxygenated - HOPE for Kidney Transplantation in a Rodent Model

OBJECTIVES

The aim of this study was to investigate novel and easily applicable preservation perfusion techniques in kidney grafts obtained from donors after circulatory death (DCD).

BACKGROUND

A novel perfusion approach, hypothermic oxygenated perfusion (HOPE), used for DCD liver grafts, is based on cold perfusion for 1 hour by an oxygenated solution before implantation. Here, we aimed to test HOPE in a rodent model of kidney grafts associated with substantial warm ischemia.

METHODS

Rat kidneys were exposed to 30 minutes in situ warm ischemia, without application of heparin. Kidneys were removed and cold stored for 4 and 18 hours, mimicking DCD organ procurement and conventional preservation. In additional experiments, kidneys were normothermically perfused with oxygenated blood for 1 hour after cold storage. In a third group, kidneys were perfused by HOPE for 1 hour after cold storage. In each group, orthotopic kidney transplantation was performed after recipient nephrectomy.

RESULTS

HOPE-treated DCD kidneys showed dramatically better function after transplantation, than cold-stored grafts in terms of nuclear injury, macrophage activation, endothelium activation, tubulus damage, and graft function. A short period of warm oxygenated perfusion before implantation improved graft quality as compared with cold storage, but was significantly less effective in all endpoints compared with HOPE. The effect of HOPE was dependent on perfusate oxygenation in the cold.

CONCLUSIONS

HOPE of DCD kidneys was superior to other clinically used preservation approaches, consistent to earlier results in livers. On the basis of this, we assume a strong and generalized effect on solid organ viability by HOPE before transplantation. These results justify a clinical trial.

Dual hypothermic oxygenated machine perfusion in liver transplants donated after circulatory death

Background

Experimental studies have suggested that end‐ischaemic dual hypothermic oxygenated machine perfusion (DHOPE) may restore hepatocellular energy status and reduce reperfusion injury in donation after circulatory death (DCD) liver grafts. The aim of this prospective case–control study was to assess the safety and feasibility of DHOPE in DCD liver transplantation.

Methods

In consecutive DCD liver transplantations, liver grafts were treated with end‐ischaemic DHOPE. Outcome was compared with that in a control group of DCD liver transplantations without DHOPE, matched for donor age, donor warm ischaemia time, and recipient Model for End‐stage Liver Disease (MELD) score. All patients were followed for 1 year.

Results

Ten transplantations involving liver grafts treated with DHOPE were compared with 20 control procedures. There were no technical problems. All 6‐month and 1‐year graft and patient survival rates were 100 per cent in the DHOPE group. Six‐month graft survival and 1‐year graft and patient survival rates in the control group were 80, 67 and 85 per cent respectively. During DHOPE, median (i.q.r.) hepatic adenosine 5′‐triphosphate (ATP) content increased 11‐fold, from 6 (3–10) to 66 (42–87) µmol per g protein (P = 0·005). All DHOPE‐preserved livers showed excellent early function. At 1 week after transplantation peak serum alanine aminotransferase (ALT) and bilirubin levels were twofold lower in the DHOPE group than in the control group (ALT: median 966 versus 1858 units/l respectively, P = 0·006; bilirubin: median 1·0 (i.q.r. 0·7–1·4) versus 2·6 (0·9–5·1) mg/dl, P = 0·044). None of the ten DHOPE‐preserved livers required retransplantation for non‐anastomotic biliary stricture, compared with five of 20 in the control group (P = 0·140).

Conclusion

This clinical study of end‐ischaemic DHOPE in DCD liver transplantation suggests that the technique restores hepatic ATP, reduces reperfusion injury, and is safe and feasible. RCTs with larger numbers of patients are warranted to assess the efficacy in reducing post‐transplant biliary complications.

Increases donor pool

Biliary complications after liver transplantation; recent developments in etiology, diagnosis and endoscopic treatment

Biliary complications are considered to be the Achilles' heel of liver transplantation. The most common complications are leaks and bile duct strictures. Strictures can arise at the level of the anastomosis (anastomotic strictures; AS) or at other locations in the biliary tree (non-anastomotic strictures; NAS). Endoscopic treatment via endoscopic retrograde cholangiopancreatography (ERCP) is considered to be the preferred therapy for these complications. This review will focus on the diagnostic modalities, new insights in etiology of biliary complications and outcomes after different endoscopic therapies, in both deceased donor transplantation and living-donor liver transplantations. Advances in recent therapies, such as the use of self-expendable metal stents (SEMS) and endoscopic therapy for patients with a bilio-digestive anastomosis will be discussed.

Hypo- and normothermic perfusion of the liver: Which way to go?

The demand of donor livers for transplantation exceeds the supply. In an attempt to maximize the number of potentially usable donor livers, several centers are exploring the role of machine perfusion. This review provides an update on machine perfusion strategies and basic concepts, based on current clinical issues, and discuss challenges, including currently used biomarkers for assessing the quality and viability of perfused organs. The potential benefits of machine perfusion on immunogenicity and the consequences on post-operative immunosuppression management are discussed.

Practical Recommendations for Long-term Management of Modifiable Risks in Kidney and Liver Transplant Recipients: A Guidance Report and Clinical Checklist by the Consensus on Managing Modifiable Risk in Transplantation (COMMIT) Group

Short-term patient and graft outcomes continue to improve after kidney and liver transplantation, with 1-year survival rates over 80%; however, improving longer-term outcomes remains a challenge. Improving the function of grafts and health of recipients would not only enhance quality and length of life, but would also reduce the need for retransplantation, and thus increase the number of organs available for transplant. The clinical transplant community needs to identify and manage those patient modifiable factors, to decrease the risk of graft failure, and improve longer-term outcomes.COMMIT was formed in 2015 and is composed of 20 leading kidney and liver transplant specialists from 9 countries across Europe. The group's remit is to provide expert guidance for the long-term management of kidney and liver transplant patients, with the aim of improving outcomes by minimizing modifiable risks associated with poor graft and patient survival posttransplant.The objective of this supplement is to provide specific, practical recommendations, through the discussion of current evidence and best practice, for the management of modifiable risks in those kidney and liver transplant patients who have survived the first postoperative year. In addition, the provision of a checklist increases the clinical utility and accessibility of these recommendations, by offering a systematic and efficient way to implement screening and monitoring of modifiable risks in the clinical setting.

Can immunosuppression be stopped after liver transplantation?

Liver transplantation has improved dramatically over the past three decades, mainly as a result of advances in surgical techniques and management of post-transplant complications. The focus has now turned towards rescuing additional organs in the face of scarce organ supply, or prevention of long-term toxicity associated with immunosuppression. The liver appears to be privileged in terms of immune tolerance, with a low incidence of antibody-mediated rejection, which is in sharp contrast to other solid organ transplants, such as kidney, lung, and heart transplants. However, tolerogenic processes remain poorly understood, and strategies for complete drug withdrawal should be selected carefully to avoid graft rejection. In this Review, we summarise the current understanding of liver-specific immune responses and provide an outlook on future approaches.

Liver graft preconditioning, preservation and reconditioning

Liver transplantation is the successful treatment of end-stage liver disease; however, the ischaemia-reperfusion injury still jeopardizes early and long-term post-transplant outcomes. In fact, ischaemia-reperfusion is associated with increased morbidity and graft dysfunction, especially when suboptimal donors are utilized. Strategies to reduce the severity of ischaemia-reperfusion can be applied at different steps of the transplantation process: organ procurement, preservation phase or before revascularization. During the donor procedure, preconditioning consists of pre-treating the graft prior to a sustained ischaemia either by a transient period of ischaemia-reperfusion or administration of anti-ischaemic medication, although a multi-pharmacological approach seems more promising. Different preservation solutions were developed to maintain graft viability during static cold storage, achieving substantial results in terms of liver function and survival in good quality organs but not in suboptimal ones. Indeed, preservation solutions do not prevent dysfunction of poor quality organs and are burdened with inadequate preservation of the biliary epithelium. Advantages derived from either hypo- or normothermic machine perfusion are currently investigated in experimental and clinical settings, suggesting a reconditioning effect possibly improving hepatocyte and biliary preservation and resuscitating graft function prior to transplantation. In this review, we highlight acquired knowledge and recent advances in liver graft preconditioning, preservation and reconditioning.

Graft Reconditioning before Liver Transplantation

BACKGROUND

The high demand for livers for transplantation has led to organs of limited quality being accepted to expand the donor pool. This is associated with inferior outcomes due to more pronounced preservation injury. Accordingly, recent research has aimed to develop preservation modalities for improved preservation as well as strategies for liver viability assessment and liver reconditioning.

METHODS

The PubMed database was searched using the terms 'perfusion', 'liver', 'preservation', and 'reconditioning' in various combinations, and the according literature was reviewed.

RESULTS

Several perfusion techniques have been developed in recent years with the potential for liver reconditioning. Preclinical and first emerging clinical data suggest feasibility, safety, and superiority over the current gold standard of cold storage.

CONCLUSION

This review outlines current advances in the field of liver preservation with an emphasis on liver reconditioning methods.

Donations After Circulatory Death in Liver Transplant

The supply of liver grafts for treatment of end-stage liver disease continues to fall short of ongoing demands. Currently, most liver transplants originate from donations after brain death. Enhanced utilization of the present resources is prudent to address the needs of the population. Donation after circulatory or cardiac death is a mechanism whereby the availability of organs can be expanded. Donations after circulatory death pose unique challenges given their exposure to warm ischemia. Technical principles of donations after circulatory death procurement and pertinent studies investigating patient outcomes, graft outcomes, and complications are highlighted in this review. We also review associated risk factors to suggest potential avenues to achieve improved outcomes and reduced complications. Future considerations and alternative techniques of organ preservation are discussed, which may suggest novel strategies to enhance preservation and donor expansion through the use of marginal donors. Ultimately, without effective measures to bolster organ supply, donations after circulatory death should remain a consideration; however, an understanding of inherent risks and limitations is necessary.

Machine Perfusion of Donor Livers for Transplantation: A Proposal for Standardized Nomenclature and Reporting Guidelines

With increasing demand for donor organs for transplantation, machine perfusion (MP) promises to be a beneficial alternative preservation method for donor livers, particularly those considered to be of suboptimal quality, also known as extended criteria donor livers. Over the last decade, numerous studies researching MP of donor livers have been published and incredible advances have been made in both experimental and clinical research in this area. With numerous research groups working on MP, various techniques are being explored, often applying different nomenclature. The objective of this review is to catalog the differences observed in the nomenclature used in the current literature to denote various MP techniques and the manner in which methodology is reported. From this analysis, we propose a standardization of nomenclature on liver MP to maximize consistency and to enable reliable comparison and meta-analyses of studies. In addition, we propose a standardized set of guidelines for reporting the methodology of future studies on liver MP that will facilitate comparison as well as clinical implementation of liver MP procedures.

Past, Present, and Future of Dynamic Kidney and Liver Preservation and Resuscitation

The increased demand for organs has led to the increased usage of "higher risk" kidney and liver grafts. These grafts from donation after circulatory death or expanded criteria donors are more susceptible to preservation injury and have a higher risk of unfavorable outcomes. Dynamic, instead of static, preservation could allow for organ optimization, offering a platform for viability assessment, active organ repair and resuscitation. Ex situ machine perfusion and in situ regional perfusion in the donor are emerging as potential tools to preserve and resuscitate vulnerable grafts. Preclinical findings have ignited clinical organ preservation research that investigates dynamic preservation, its various modes (continuous, preimplantation) and temperatures (hypo-, sub, or normothermic). This review outlines the current status of dynamic preservation of kidney and liver grafts and describes ongoing research and emerging clinical trials.

Liver Transplantation Using Donation After Brain and Cardiac Death: A Single-Center Experience in China

BACKGROUND

Liver transplantation (LTx) using donation after brain and cardiac death (DBCD) has increased steadily in China. The aims of this study were to evaluate the outcomes of DBCD LTx and to assess its feasibility to expand the donor pool.

METHODS

We retrospectively analyzed the clinical characteristics of DBCD donors and recipients, survival of allografts and recipients, and prognostic factors in DBCD LTx recipients from March 2010 to December 2014 in our institution.

RESULTS

DBCD LTx (n = 102) were performed in our institution during the research period, and the successful donation rate was 26.0%. Mean warm ischemia time and cold ischemia time were 14.39 minutes and 5.29 hours, respectively. The overall and biliary complication rates were 45.1% and 16.7%, respectively. Donor age (P = .043), intra-operative blood loss (P = .048), and operation time (P = .045) were significantly different between the complication and non-complication groups. The 1-, 2-, and 3-year survival rates of patients and grafts were 88.0%, 84.6%, 84.6%, and 85.7%, 78.6%, and 78.6%, respectively. The 1- and 2-year overall survival rates of hepatocellular carcinoma patients were 91.9% and 80.5%, respectively whereas the recurrence-free survival rates were 84.9% and 77.2%, respectively. The patient and graft survival rates were not statistically different between the <55-year and ≥55 year groups, but complication rate was higher in the older group than in the younger group (P = .003).

CONCLUSIONS

The outcome of DBCD LTx is favorable in our institution, with careful donor and recipient selection and careful peri-operative management. DBCD is an optimized solution for organ shortage in today's China.

Potential approaches to improve the outcomes of donation after cardiac death liver grafts

There is a growing discrepancy between the supply and demand of livers for transplantation resulting in high mortality rates on the waiting list. One of the options to decrease the mortality on the waiting list is to optimize organs with inferior quality that otherwise would be discarded. Livers from donation after cardiac death (DCD) donors are frequently discarded because they are exposed to additional warm ischemia time, and this might lead to primary-non-function, delayed graft function, or severe biliary complications. In order to maximize the usage of DCD livers several new preservation approaches have been proposed. Here, we will review 3 innovative organ preservation methods: (1) different ex vivo perfusion techniques; (2) persufflation with oxygen; and (3) addition of thrombolytic therapy. Improvement of the quality of DCD liver grafts could increase the pool of liver graft’s for transplantation, improve the outcomes, and decrease the mortality on the waiting list.