Host conditioning and rejection monitoring in hepatocyte transplantation in humans.

BACKGROUND & AIMS: Hepatocyte transplantation partially corrects genetic disorders and has been associated anecdotally with reversal of acute liver failure. Monitoring for graft function and rejection has been difficult, and has contributed to limited graft survival. Here we aimed to use preparative liver-directed radiation therapy, and continuous monitoring for possible rejection in an attempt to overcome these limitations. METHODS: Preparative hepatic irradiation was examined in non-human primates as a strategy to improve engraftment of donor hepatocytes, and was then applied in human subjects. T cell immune monitoring was also examined in human subjects to assess adequacy of immunosuppression. RESULTS: Porcine hepatocyte transplants engrafted and expanded to comprise up to 15% of irradiated segments in immunosuppressed monkeys preconditioned with 10Gy liver-directed irradiation. Two patients with urea cycle deficiencies had early graft loss following hepatocyte transplantation; retrospective immune monitoring suggested the need for additional immunosuppression. Preparative radiation, anti-lymphocyte induction, and frequent immune monitoring were instituted for hepatocyte transplantation in a 27year old female with classical phenylketonuria. Post-transplant liver biopsies demonstrated multiple small clusters of transplanted cells, multiple mitoses, and Ki67+ hepatocytes. Mean peripheral blood phenylalanine (PHE) level fell from pre-transplant levels of 1343±48µM (normal 30-119µM) to 854±25µM (treatment goal ≤360µM) after transplant (36% decrease; p<0.0001), despite transplantation of only half the target number of donor hepatocytes. PHE levels remained below 900µM during supervised follow-up, but graft loss occurred after follow-up became inconsistent. CONCLUSIONS: Radiation preconditioning and serial rejection risk assessment may produce better engraftment and long-term survival of transplanted hepatocytes. Hepatocyte xenografts engraft for a period of months in non-human primates and may provide effective therapy for patients with acute liver failure. LAY SUMMARY: Hepatocyte transplantation can potentially be used to treat genetic liver disorders but its application in clinical practice has been impeded by inefficient hepatocyte engraftment and the inability to monitor rejection of transplanted liver cells. In this study, we first show in non-human primates that pretreatment of the host liver with radiation improves the engraftment of transplanted liver cells. We then used this knowledge in a series of clinical hepatocyte transplants in patients with genetic liver disorders to show that radiation pretreatment and rejection risk monitoring are safe and, if optimized, could improve engraftment and long-term survival of transplanted hepatocytes in patients.

Byler disease: early natural history.

OBJECTIVES: Byler disease, originally described in Amish kindred, results from mutations in ATPase Class I Type 8b Member 1 (ATP8b1). Specific clinical reports of Amish Byler disease were last published 40 years ago. These investigations were directed at the present detailed clinical understanding of the early course of hepatic manifestations of Byler disease. METHODS: This study analyzed routine clinical practice and outcomes of children with Byler disease (defined by homozygous c.923G>T mutation in ATP8b1), who initially presented to Children's Hospital of Pittsburgh of UPMC between January 2007 and October 2014. Data were analyzed to the earlier of 24 months of age or partial external biliary diversion. RESULTS: Six children presented between 1 and 135 days of life: 2 presented with newborn direct hyperbilirubinemia, 2 had complications of coagulopathy, 1 had failure to thrive and rickets, and 1 sibling was identified by newborn genetic testing. Intensive fat-soluble vitamin supplementation was required to prevent insufficiencies in vitamins D, E, and K. Hyperbilirubinemia was variable both over time and between children. Serum bile acid levels were elevated, whereas γ-glutamyltranspeptidase levels were low normal. Scratching behavior (pruritus) was intractable in 4 of 6 children with onset between 6 and 12 months of age. Features of portal hypertension were not observed. Partial external biliary diversion was used during the second year of life in 4 children. CONCLUSIONS: Detailed analysis of Byler disease revealed varied disease presentation and course. Nutritional issues and pruritus dominated the clinical picture in the first 2 years of life.

Parent perspectives on decisions to participate in a phase I hepatocyte transplant trial.

We examined factors that affect decision-making for families presented with a phase I clinical trial of hepatocyte transplant as a potential alternative to liver transplant for their children among two groups: (i) families who were actually offered enrollment in the hepatocyte trial and; (ii) families whose children had liver transplants before the trial was available. We conducted semi-structured interviews about actual and hypothetical decision-making regarding trial participation and used grounded theory analysis to identify common themes. The most common motivator for participation was decline in the child's health. The most common deterrent was lack of data from prior hepatocyte transplants, particularly when compared with data available about liver transplant. Interviewees' point of comparison for evaluating relative benefits and risks of hepatocyte transplant oscillated between the alternative of doing nothing while waiting for a liver (the relevant alternative) vs. the alternative of getting a liver. These results suggest that families' reluctance to participate may result from misconceptions about severity of the child's disease, underestimating risks of liver transplant, or confusion about the role of hepatocyte transplant in the treatment pathway. Clarification of available treatment alternatives and associated risks as part of informed consent may improve the quality of decision-making regarding trial enrollment.

Design and rationale of a clinical trial to increase cardiomyocyte division in infants with tetralogy of Fallot.

BACKGROUND: Patients with Tetralogy of Fallot with pulmonary stenosis (ToF/PS), the most common form of cyanotic congenital heart disease (CHD), develop adverse right ventricular (RV) remodeling, leading to late heart failure and arrhythmia. We recently demonstrated that overactive ß-adrenergic receptor signaling inhibits cardiomyocyte division in ToF/PS infants, providing a conceptual basis for the hypothesis that treatment with the ß-adrenergic receptor blocker, propranolol, early in life would increase cardiomyocyte division. No data are available in ToF/PS infants on the efficacy of propranolol as a possible novel therapeutic option to increase cardiomyocyte division and potentially reduce adverse RV remodeling. METHODS: Using a randomized, double-blind, placebo-controlled trial, we will evaluate the effect of propranolol administration on reactivating cardiomyocyte proliferation to prevent adverse RV remodeling in 40 infants with ToF/PS. Propranolol administration (1 mg/kg po QID) will begin at 1 month of age and last until surgical repair. The primary endpoint is cardiomyocyte division, quantified after 15N-thymidine administration with Multi-isotope Imaging Mass Spectrometry (MIMS) analysis of resected myocardial specimens. The secondary endpoints are changes in RV myocardial and cardiomyocyte hypertrophy. CONCLUSION: This trial will be the first study in humans to assess whether cardiomyocyte proliferation can be pharmacologically increased. If successful, the results could introduce a paradigm shift in the management of patients with ToF/PS from a purely surgical approach, to synergistic medical and surgical management. It will provide the basis for future multi-center randomized controlled trials of propranolol administration in infants with ToF/PS and other types of CHD with RV hypertension. CLINICAL TRIAL REGISTRATION: The trial protocol was registered at clinicaltrials.gov (NCT04713657).