Sanna op den Dries

Criteria for Viability Assessment of Discarded Human Donor Livers during Ex Vivo Normothermic Machine Perfusion

Although normothermic machine perfusion of donor livers may allow assessment of graft viability prior to transplantation, there are currently no data on what would be a good parameter of graft viability. To determine whether bile production is a suitable biomarker that can be used to discriminate viable from non-viable livers we have studied functional performance as well as biochemical and histological evidence of hepatobiliary injury during ex vivo normothermic machine perfusion of human donor livers. After a median duration of cold storage of 6.5 h, twelve extended criteria human donor livers that were declined for transplantation were ex vivo perfused for 6 h at 37°C with an oxygenated solution based on red blood cells and plasma, using pressure controlled pulsatile perfusion of the hepatic artery and continuous portal perfusion. During perfusion, two patterns of bile flow were identified: (1) steadily increasing bile production, resulting in a cumulative output of ≥30 g after 6 h (high bile output group), and (2) a cumulative bile production <20 g in 6 h (low bile output group). Concentrations of transaminases and potassium in the perfusion fluid were significantly higher in the low bile output group, compared to the high bile output group. Biliary concentrations of bilirubin and bicarbonate were respectively 4 times and 2 times higher in the high bile output group. Livers in the low bile output group displayed more signs of hepatic necrosis and venous congestion, compared to the high bile output group. In conclusion, bile production could be an easily assessable biomarker of hepatic viability during ex vivo machine perfusion of human donor livers. It could potentially be used to identify extended criteria livers that are suitable for transplantation. These ex vivo findings need to be confirmed in a transplant experiment or a clinical trial.

Hypothermic oxygenated machine perfusion prevents arteriolonecrosis of the peribiliary plexus in pig livers donated after circulatory death.

Background Livers derived from donation after circulatory death (DCD) are increasingly accepted for transplantation. However, DCD livers suffer additional donor warm ischemia, leading to biliary injury and more biliary complications after transplantation. It is unknown whether oxygenated machine perfusion results in better preservation of biliary epithelium and the peribiliary vasculature. We compared oxygenated hypothermic machine perfusion (HMP) with static cold storage (SCS) in a porcine DCD model. Methods After 30 min of cardiac arrest, livers were perfused in situ with HTK solution (4°C) and preserved for 4 h by either SCS (n = 9) or oxygenated HMP (10°C; n = 9), using pressure-controlled arterial and portal venous perfusion. To simulate transplantation, livers were reperfused ex vivo at 37°C with oxygenated autologous blood. Bile duct injury and function were determined by biochemical and molecular markers, and a systematic histological scoring system. Results After reperfusion, arterial flow was higher in the HMP group, compared to SCS (251±28 vs 166±28 mL/min, respectively, after 1 hour of reperfusion; p = 0.003). Release of hepatocellular enzymes was significantly higher in the SCS group. Markers of biliary epithelial injury (biliary LDH, gamma-GT) and function (biliary pH and bicarbonate, and biliary transporter expression) were similar in the two groups. However, histology of bile ducts revealed significantly less arteriolonecrosis of the peribiliary vascular plexus in HMP preserved livers (>50% arteriolonecrosis was observed in 7 bile ducts of the SCS preserved livers versus only 1 bile duct of the HMP preserved livers; p = 0.024). Conclusions Oxygenated HMP prevents arteriolonecrosis of the peribiliary vascular plexus of the bile ducts of DCD pig livers and results in higher arterial flow after reperfusion. Together this may contribute to better perfusion of the bile ducts, providing a potential advantage in the post-ischemic recovery of bile ducts.

Protection of Bile Ducts in Liver Transplantation: Looking Beyond Ischemia

Biliary complications, especially nonanastomotic biliary strictures (NAS), are a major cause of morbidity after orthotopic liver transplantation. Of all donor and recipient characteristics known to increase the risk of developing NAS, the role of prolonged ischemia times is most extensively described in the literature. However, there is increasing evidence that several other, non-ischemia-related factors play a critical role in the pathogenesis of NAS as well. The clinical presentation of NAS may vary considerably among liver transplant recipients, including large variations in time of occurrence, and in location and severity of the strictures. Additional underlying causes such as bile salt toxicity and immune-mediated injury are believed to explain the wide spectrum of biliary strictures after orthotopic liver transplantation. Current and emerging insight in the pathogenesis of NAS and potential targets to reduce biliary injury and preserve bile ducts are discussed in this overview.

Injury to peribiliary glands and vascular plexus before liver transplantation predicts formation of non-anastomotic biliary strictures.

BACKGROUND & AIMS The peribiliary glands of large bile ducts have been identified as a niche of progenitor cells that contribute to regeneration of biliary epithelium after injury. We aimed to determine whether injury to the peribiliary glands of donor livers is a risk factor for development of non-anastomotic biliary strictures (NAS) after liver transplantation. METHODS In 128 liver transplant procedures, biopsies were taken from the donor bile duct and injury was assessed using an established histological grading system. Histological severity of injury was subsequently compared in liver grafts that later developed biliary structures vs. uncomplicated liver grafts. RESULTS Luminal biliary epithelial loss >50% was observed in 91.8% of the grafts before transplantation, yet NAS occurred in only 16.4%. Periluminal peribiliary glands were more severely injured than deep peribiliary glands located near the fibromuscular layer (>50% loss in 56.9% vs. 17.5%, respectively; p<0.001). Injury of deep peribiliary glands was more prevalent and more severe in livers that later developed NAS, compared to grafts without NAS (>50% loss in 50.0% vs. 9.8%, respectively; p=0.004). In parallel, injury of the peribiliary vascular plexus was more severe in livers that developed NAS, compared to grafts without NAS (>50% vascular changes in 57.1% vs. 20.3%; p=0.006). CONCLUSION Injury of peribiliary glands and vascular plexus before transplantation is strongly associated with the occurrence of biliary strictures after transplantation. This suggests that insufficient regeneration due to loss of peribiliary glands or impaired blood supply may explain the development of biliary strictures.

Regeneration of human extrahepatic biliary epithelium : the peribiliary glands as progenitor cell compartment

Although regeneration of intrahepatic bile ducts has been extensively studied and intrahepatic progenitor cells have been identified, few studies have focussed on the extrahepatic bile duct (EHBD). We hypothesized that local progenitor cells are present within the EHBD of humans. Human EHBD specimens (n = 17) were included in this study.

The origin of biliary strictures after liver transplantation: Is it the amount of epithelial injury or insufficient regeneration that counts?

Biliary complications continue to be a major problem after orthotopic liver transplantation (OLT). The incidence of biliary complications varies between 10% and 40% in different series and this type of complications is associated with frequent hospital admissions and high morbidity and mortality rates [1–3]. Among the variety of biliary complications that can occur after OLT, bile duct strictures are of the most concern. Bile duct strictures can be classified as anastomotic strictures (AS) or non-anastomotic strictures (NAS). Solitary strictures at the biliary anastomosis have been reported in 9%–12% of the patients [4–6], and NAS have been reported in 1%–20% of patients receiving a liver from donation after brain death and in up to 30% of patients receiving a liver from donation after cardiac death (DCD) [4,7,8]. NAS may occur in the extrahepatic donor bile duct as well as the intrahepatic bile ducts, but they are usually limited to the larger bile ducts. NAS may be accompanied by intraductal biliary sludge and cast formation. For many years researchers have been trying to understand the underlying mechanisms of AS and NAS. Current evidence suggests that AS are mainly related to the surgical technique and local ischemia of the distal bile duct stump, leading to fibrotic scarring of the anastomosis [1,6]. The etiology of NAS is thought to be multifactorial and three relevant types of biliary injury have been identified as a potential cause of NAS: ischemia/reperfusion related injury; immune-mediated injury; and cytotoxic injury caused by hydrophobic bile salts [1,9]. Current understanding of the occurrence of these types of biliary injury is that they originate mainly after transplantation of the liver. Depending on the severity of bile duct injury, the healing process may lead to scar formation and subsequent stricturing of the affected bile duct segments. Thus far, it remains unclear as to which extent bile ducts of donor livers are injured already before transplantation. In this issue of the Journal of Hepatology, Brunner et al. describe a clinical cohort study including 79 liver transplant procedures in

Matrix metalloproteinase 2 genotype is associated with nonanastomotic biliary strictures after orthotopic liver transplantation.

Background: Nonanastomotic biliary strictures (NAS) are a serious complication after orthotopic liver transplantation (OLT). Matrix metalloproteinases (MMPs) are involved in connective tissue remodelling in chronic liver disease and complications after OLT.

Normothermic machine perfusion reduces bile duct injury and improves biliary epithelial function in rat donor livers.

Bile duct injury may occur during liver procurement and transplantation, especially in livers from donation after circulatory death (DCD) donors. Normothermic machine perfusion (NMP) has been shown to reduce hepatic injury compared to static cold storage (SCS). However, it is unknown whether NMP provides better preservation of bile ducts. The aim of this study was to determine the impact of NMP on bile duct preservation in both DCD and non‐DCD livers. DCD and non‐DCD livers obtained from Lewis rats were preserved for 3 hours using either SCS or NMP, followed by 2 hours ex vivo reperfusion. Biomarkers of bile duct injury (gamma‐glutamyltransferase and lactate dehydrogenase in bile) were lower in NMP‐preserved livers compared to SCS‐preserved livers. Biliary bicarbonate concentration, reflecting biliary epithelial function, was 2‐fold higher in NMP‐preserved livers (P < 0.01). In parallel with this, the pH of the bile was significantly higher in NMP‐preserved livers (7.63 ± 0.02 and 7.74 ± 0.05 for non‐DCD and DCD livers, respectively) compared with SCS‐preserved livers (7.46 ± 0.02 and 7.49 ± 0.04 for non‐DCD and DCD livers, respectively). Scanning and transmission electron microscopy of donor extrahepatic bile ducts demonstrated significantly decreased injury of the biliary epithelium of NMP‐preserved donor livers (including the loss of lateral interdigitations and mitochondrial injury). Differences between NMP and SCS were most prominent in DCD livers. Compared to conventional SCS, NMP provides superior preservation of bile duct epithelial cell function and morphology, especially in DCD donor livers. By reducing biliary injury, NMP could have an important impact on the utilization of DCD livers and outcome after transplantation. Liver Transplantation 22 994–1005 2016 AASLD

Shared decision making in transplantation: How patients see their role in the decision process of accepting a donor liver

At the time of the organ offer for transplantation, donor‐related risks such as disease transmission and graft failure are weighed against the patients risk of remaining on the waiting list. The patients commonly inactive role in decision making and the timing and extent of donor‐specific risk information have been discussed in the medical literature. This is the first study revealing the opinions of liver patients on these issues. Forty patients listed for liver transplantation and 179 liver transplant patients participated in an anonymous questionnaire‐based survey. The majority of the patients wanted to be informed about donor‐related risks (59.8%‐74.8%). The preferred timing for being informed about donor‐related risks was the time of the organ offer for 53.3% of the patients. Among these patients, 79.8% wished to be involved in making the decision to accept or not accept a liver for transplantation, 10.6% wished to make the final decision alone, and only 9.6% did not want to be involved in the decision‐making process. Implementing this knowledge through the standardization of the content, the manner of transfer, and the amount of information that we provide to our patients will improve opportunities for shared decision making at different time points during the transplant allocation process. This will enable us to provide the same opportunities and care to every patient on the waiting list. Liver Transpl 20:1072‐1080, 2014.

Opinions of Dutch Liver Transplant Recipients on Anonymity of Organ Donation and Direct Contact With the Donors Family

Background In the Netherlands, anonymity of organ donation, which is currently protected by legislation, has come under discussion. In the Dutch society, a tendency to allow direct contact between transplant recipients and their donor’s family is noticeable. As little is known about the opinion of Dutch liver transplant recipients on anonymity of organ donation and direct contact with the donor’s family, this study examines their opinions. Methods A cross-sectional study was conducted in 244 liver transplant recipients. Their opinions were examined in relation to demographic, transplant-related and emotional variables. Data were collected by questionnaire. Transplant-related variables were retrieved from the hospital’s liver transplant database. Results Fifty-three percent of the respondents (n = 177) agreed with anonymity of organ donation, mainly out of respect for the donor. Living situation, age, and level of positive affect influenced this opinion. The majority of the respondents (65%) indicated that they would like to receive some information about their donor, like age, sex, and health status. Only 19% of the respondents favored direct contact with the donor’s family, mainly to express their gratitude personally. Respondents transplanted for alcoholic cirrhosis were less in favor of direct contact. Respondents with feelings of guilt doubted more about direct contact. Conclusion There is no need to change the current legislation on anonymity of organ donation. However, most liver transplant recipients would like to receive some general information about their donor. Therefore, clear guidelines on the sharing of donor data with recipients need to be established.