Non-Anastomotic Biliary Strictures After Liver Tran Non-anastomotic biliary strictures (NAS) are a...

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Transcript of Non-Anastomotic Biliary Strictures After Liver Tran Non-anastomotic biliary strictures (NAS) are a...

  • Non-Anastomotic Biliary Strictures After Liver Transplantation:

    Injury, Regeneration and Preservation of the Biliary Tree

    Final report for the M3 Research Clerkship of: Pepijn D. Weeder S1823264 Under supervision of: Prof. Dr. R.J. Porte, Chirurg Afdeling Hepatobiliaire Chirurgie & Levertransplantatie Universitair Medisch Centrum Groningen/ Rijksuniversiteit Groningen

    Prof. Korkut Uygun, PhD Center of Engineering in Medicine Harvard Medical School/ Massachusetts General Hospital Boston, MA, USA

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    Summary: Non-anastomotic biliary strictures (NAS) are a feared complication causing significant morbity and mortality in liver transplant recipients. The etiology of NAS is not fully understood, although ischemia is believed to be a major risk factor for biliary injury. In this study, injury of the peribiliary vascular plexus and deep peribiliary glands (dPBGs) in donor bile ducts at the end of cold storage were strongly associated with donor risk factors. Injury of the dPBGs is an independent risk factor for the development of NAS after transplantation. A method for the quantification of biliopancreatic progenitor cells in the PBGs was developed and a proof-of-concept was achieved in a pilot study. Secondly, a putative mouse model to study the role of biliopancreatic progenitor cells in biliary regeneration after injury was presented. Finally, a new bile duct model for the comparison of different static preservation solutions was designed. This model was applied to assess the effect of oxygen (carrier) enrichment of University of Wisconsin preservation solution. However, because of high variability and relatively low power, the results were inconclusive. Overall, the work presented in this thesis may contribute to a better understanding of injury, regeneration and preservation of the biliary tree in the liver transplant patient. Samenvatting: Het ontstaan van niet-anastomotische galwegstricturen (NAS) is een gevreesde complicatie bij levertransplantatiepatiënten die aanzienlijke morbiditeit en mortaliteit veroorzaakt. Het exacte onstaansmechanisme van NAS is niet bekend, maar ischemie wordt beschouwd als een belangrijke risicofactor voor galwegschade. Dit onderzoek toont aan dat schade aan de peribiliare vasculaire plexus en de diepe peribiliary klieren (dPBGs) in de extrahepatische donorgalweg aan het einde van de koude bewaartijd sterk is geassocieerd met al bekende risicofactoren. Schade aan de dPBGs is een onafhankelijke risicofactor voor het ontwikkelen van NAS na transplantatie. Verder wordt een methode beschreven voor de kwantificatie van biliopancreatische voorloper cellen in de PBGs, die succesvol werd getest in een pilot studie. Ten tweede wordt in deze scriptie een protocol voorgesteld voor de ontwikkeling van een nieuw muismodel waarmee de rol van biliopancreatische voorlopercellen in het herstel van de galweg na ischemische schade zou kunnen worden bestudeerd. Tot slot is er een nieuw galwegmodel ontwikkeld dat kan worden gebruikt om het effect van verschillende preservatievloeistoffen te vergelijken. Dit model is toegepast om het effect van oxygenatie van University of Wisconsin oplossing te onderzoeken. Helaas heeft dit door hoge variabiliteit en een kleine groepsgrootte nog geen eenduidig resultaat opgeleverd. In het algemeen kan dit verslag mogelijk een bijdrage leveren aan een beter begrip van schade, herstel en bescherming van de galwegen in de context van levertransplantatie.

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    Contents

    1. Preface..............................................................................................................

    2. Chapter 1: Is the number of bipotent biliary progenitor cells associated with

    the development of non-anastomotic biliary strictures after liver

    transplantation?................................................................................................

    i. Introduction

    ii. Materials and methods……………………………………….

    iii. Results……………………………..........................................

    iv. Discussion and Conclusion......................................................

    3. Chapter 2: Brief proposal of a novel mouse model for non-anastomotic

    biliary strictures. .............................................................................................

    4. Chapter 3: Does oxygenation during static cold storage enhance bile duct

    preservation in liver transplantation?...............................................................

    i. Introduction..............................................................................

    ii. Materials and methods.............................................................

    iii. Results .....................................................................................

    iv. Discussion and Conclusion......................................................

    5. Conclusion.......................................................................................................

    6. References........................................................................................................

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    Preface Orthotopic liver transplantation is currently the only available life-saving treatment for patients with end-stage liver disease. Unfortunately, the number of organs available for transplantation greatly surpasses the supply, prompting strict selection criteria for transplant candidates and long waiting lists for those patients that reach candidate status. As a result of this shortage about 15% of patients die while on the waiting list.1 More notably, according to studies of death certificates, about 60,000 patients die of liver disease annually in the United States2; Many of whom could (theoretically) have been treated with a liver transplant, causing gross underestimation of the magnitude of the problem when only waitlist mortality is considered. In fact, only about 1.5% of liver disease mortality concerns waitlisted patients.3 Because of the grave shortage of livers available for transplantation, the transplant community is continuously pushing to increase the availability of organs. Also, improved treatments for liver diseases are pursued aiming to decrease the demand for transplantation. As a part of this effort, the limits of the criteria used for donor selection have been progressively expanded, allowing more marginal grafts to be used. Donors that fall outside of standard criteria, termed ‘extended criteria donors (ECDs), have gained ground significantly worldwide in the past decades. For example, in the United Kingdom 42% of transplanted liver now come from donation after cardiac death (DCD) donors.4 The most important other criteria that are being extended include donor age, prolonged cold ischemia time, ABO incompatibility, steatosis and infection.5,6 It has been estimated that the use of ECDs can increase the organ pool by 10% to 20%.7,8 At first, the use of ECDs came at the cost of increased primary non-function, delayed graft function and decreased survival, but with meticulous donor selection the initial rise of these problems has been successfully reversed to a level comparable to grafts from donation after brain death10-13 However, a serious remaining problem is the rise of biliary complications in recipients of ECD grafts.14-17 The incidence of non-anastomotic biliary strictures (NAS) varies between 4 and 15% after transplantation of livers donated after brain death (DBD) but can be as high as 30% after transplantation of DCD grafts.18 Developing NAS critically impacts patients’ long-term survival, rate of retransplantation, quality of life and the cost of care.9,19 Patients that develop NAS typically present between one to twelve months after liver

    Figure 1. Examples of the radiological findings associated with NAS. Left: “ERCP showing a long nonanastomotic stricture extending proximally from the site of the anastomosis.”(adopted from Sharma et al. 20089). Right: ERCP showing the hallmark sign of ‘Beads on a string’ resulting from alternating stenosis and dilatation (adopted from Buis et al. 2007 24).

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    transplantation. Their symptoms are characterized by cholestasis, often accompanied by cholangitis and abdominal pain.20 The diagnosis is made by ultrasound examination followed by endoscopic retrograde cholangiopancreatography (ERCP) or percutaneous transhepatic cholangiography (PTC).9 Examples of the radiological findings associated with NAS can be found in figure 1. Strictures are progressive in 60% of cases, ultimately leading to cirrhosis.21 The work reported in this thesis is centered on the problem of NAS. It focuses on the etiology of NAS (chapter 1) and proposes a novel animal model to study the role of progenitor cells in this process (chapter 2). Finally, an experiment was conducted to investigate whether oxygenation has a protective effect on the bile duct during cold storage (chapter 3). The research efforts presented here were made between November 1, 2013 and March 21, 2014 in the context of my research clerkship, which is an integral part of the Master’s of Medicine program that I attend at the University of Groningen. The work took place at the Center of Engineering in Medicine at H