How can we optimize the outcome of liver grafts from pediatric donors?

Utility of neonatal donors in pediatric liver transplantation: A single-center experience

BACKGROUND

The lack of age- and size-matched organs result in higher waiting list mortality in pediatric recipients than adults. Organs from deceased newborns and infants are a valuable source to increase donor pool in pediatric liver transplantation. However, the feasibility and safety of using neonatal donors have not been well evaluated.

METHODS

From 2014 to 2016, 48 deceased donor pediatric liver transplantations with donor age younger than 1 year old in our center were enrolled in this study. The recipients were divided into three groups based on the donor age (<1 month, 1 month ≤ to <3 months, and 3 months ≤ to <1 year). Recipient's characteristics, perioperative data, and postoperative complications were compared.

RESULTS

Two-year patient survival rates were 87.5%, 94.4%, and 95.5%, and 2-year graft survival rates were 75%, 94.4%, and 95.5%, respectively, without significant difference. The liver grafts from donors younger than 3 months were more advantageous in terms of acute rejection and virus infection, while the young grafts were related to slight higher incidence of hepatic artery thrombosis and SFSS. Those complications could be effectively prevented or treated by our perioperative care strategies. In addition, eight recipients who received neonatal livers achieved comparable outcomes with recipients with older livers.

CONCLUSION

Our data revealed that the application of liver grafts from donors younger than 1 year old could achieve excellent outcome. In particular, neonatal donors could be safely used in well-selected patients.

Pharmacological Induction of a Progenitor State for the Efficient Expansion of Primary Human Hepatocytes

The liver is an organ with strong regenerative capacity, yet primary hepatocytes have a low amplification potential in vitro, a major limitation for the cell-based therapy of liver disorders and for ex vivo biological screens. Induced pluripotent stem cells (iPSCs) may help to circumvent this obstacle but often harbor genetic and epigenetic abnormalities, limiting their potential. Here, we describe the pharmacological induction of proliferative human hepatic progenitor cells (HPCs) through a cocktail of growth factors and small molecules mimicking the signaling events involved in liver regeneration. Human HPCs from healthy donors and pediatric patients proliferated vigorously while maintaining their genomic stability and could be redifferentiated in vitro into metabolically competent cells that supported the replication of hepatitis B and delta viruses. Redifferentiation efficiency was boosted by three-dimensional culture. Finally, transcriptome analysis showed that HPCs were more closely related to mature hepatocytes than iPSC-derived hepatocyte-like cells were. Conclusion: HPC induction holds promise for a variety of applications such as ex vivo disease modeling, personalized drug testing or metabolic studies, and development of a bioartificial liver.

Using pediatric liver grafts (≤ 6 yr) for adult recipients: A considerable option?

In LT, the common policy is to allocate pediatric liver grafts to pediatric recipients. Pediatric organs are also offered to adults if there is no pediatric recipient. However, they are rarely accepted for adult recipients. So far, there is no information available reporting outcome of LT in adult recipients using pediatric livers from donors ≤ 6 yr. In this study, we included nine adult recipients (seven females and two males) who received grafts from children ≤ 6 yr from January 2008 to December 2013. We evaluated the graft quality, the GBWR and analyzed the recipients' perioperative course. Laboratory samples and graft perfusion were analyzed. Nine adults with a median age of 49 yr (range: 25-65) and a median weight of 60 kg (range: 48-64) underwent LT with a pediatric donor graft. Median donor age was five yr (range: 3-6). Median GBWR was 1.02 (range: 0.86-1.45). After a median follow-up of 3.9 yr (range: 11 months-6.6 yr), patient survival was 100%; graft survival was 89%. One patient needed re-transplantation on the second postoperative day due to PNF. Eight recipients were discharged from the ICU after 2-9 days with a regular graft function. Doppler scans revealed regular flow patterns at any time. Only if denied for pediatric recipients, the use of pediatric livers from donors ≤ 6 yr for adult recipients is a considerable option.

Liver transplantation in children using organs from young paediatric donors

Nowadays, most paediatric liver transplant recipients receive a split or other technical variant graft from adult deceased or live donors, because of a lack of available age- and size matched paediatric donors. Few data are available, especially for liver grafts obtained from very young children (<6 years). We analysed all paediatric liver transplantations between 1989 and 2009. Recipients were divided into five groups (1-5) depending on donor age (<1, ≥1 to <6, ≥6 to <16, ≥16 to <45, ≥45 years). Overall, 413 paediatric liver transplantations from deceased donors were performed; 1- and 5-year graft survival rates were 75%, 80%, 78%, 81%, 74% and 75%, 64%, 70%, 67%, 46%, and 1- and 5-year patient survival rates were 88%, 91%, 90%, 89%, 78% and 88%, 84%, 84%, 83%, 63% for groups 1-5, respectively, without significant difference. Eight children received organs from donors younger than 1 year and 45 children received organs from donors between 1 and 6 years of age. Overall, vascular complications occurred in 13.2% of patients receiving organs from donors younger than 6 years. Analysis of our data revealed that the usage of liver grafts from donors younger than 6 years is a safe procedure. The outcome was comparable with grafts from older donors with excellent graft and patient survival, even for donors younger than 1 year.

Current status of liver transplantation in children

There are two critical issues on opposite ends of the timeline for patients who are eligible for liver transplantation. On the one hand, the crisis in the cadaveric organ supply makes surviving to transplant ever more risky. On the other hand, patients who receive successful transplants face the consequences of long-term immunosuppression and its potentially life-threatening complications. The donor shortage is forcing difficult decisions that affect all patients who await liver transplantation. It is important to scrutinize carefully the results of all policies that govern allocation and the ethics of the solutions we advocate to ensure that no patient subgroup is being at a disadvantage. Current immunosuppression practices are being challenged by an increasing understanding of the immunologic events triggered by the allograft and the goal to free patients from consequences of a lifetime of immunosuppression. Clinicians can expect, and perhaps require, that new immunosuppressive protocols will address how the planned intervention might be expected to advance the understanding of tolerance mechanisms. As knowledge increases, clinicians can anticipate innovative new immunosuppressive proposals. Calcineurin and steroid-free induction, the use of donor-derived bone marrow infusion, recipient pretreatment, costimulatory blockade, and new antibody induction approaches are all being proposed--often in combination--for clinical trials. Researchers face additional challenges in defining endpoints if the goal is not just the short-term reduction in rejection but the minimization, and eventual discontinuation, of immunosuppressive drugs while maintaining excellent long-term graft function. How much "failure" will be accepted and how will it be defined? How will clinicians interpret liver biopsies if they begin to accept that some lymphocytic infiltrates may be beneficial mediators of the ongoing immune activation necessary for the maintenance of tolerance? How will they adjust immunosuppression practices to the dynamic processes in the immune response that maintain tolerance? Remarkable short-term successes in providing transplants for thousands of children with liver failure have brought these challenges into sharp focus. Clinicians must seek to move the life-giving science of transplantation toward a new goal: providing long lifetimes of excellent graft function with minimal toxicity from immunosuppressive drugs and the hope of freedom from immunosuppression altogether. Pediatric liver recipients, whose grafts have inherent tolerogenic potential and for whom we can anticipate decades of life after transplant, may prove to be an ideal study population to further these goals.

Intrahepatic cholestasis after liver transplantation

Cholestasis is a common sequela of liver transplantation. Although the majority of cases remain subclinical, severe cholestasis may be associated with irreversible liver damage, requiring retransplantation. Therefore, it is essential that clinicians be able to identify and treat the syndromes associated with cholestasis. In this review, we consider causes of intrahepatic cholestasis. These may be categorized by time of occurrence, namely, within 6 months of liver transplantation (early) and thereafter (late), although there may be an overlap in their causes. The causes of intrahepatic cholestasis include ischemia/reperfusion injury, bacterial infection, acute cellular rejection, cytomegalovirus infection, small-for-size graft, drugs for hepatotoxicity, intrahepatic biliary strictures, chronic rejection, hepatic artery thrombosis, ABO blood group incompatibility, and recurrent disease. The mechanisms of cholestasis in each category and the clinical presentation, diagnosis, treatment, and outcome are discussed in detail.