4.8 Article

Host conditioning and rejection monitoring in hepatocyte transplantation in humans

Journal

JOURNAL OF HEPATOLOGY
Volume 66, Issue 5, Pages 987-1000

Publisher

ELSEVIER SCIENCE BV
DOI: 10.1016/j.jhep.2016.12.017

Keywords

Hepatocyte transplantation; Liver-based metabolic disease; Liver-directed radiation therapy; Phenylketonuria; Rejection risk monitoring; Hepatocyte xenotransplantation

Funding

  1. DoD [W81XWH-11-1-0803]
  2. NIH [R01 AI49472, R01 AI122369, HL52297, R01 DK064670, R33 CA121051, R01 DK092469, R01 DK099257]
  3. Children's Hospital of Pittsburgh Foundation
  4. Children's Hospital of Pittsburgh of UPMC
  5. Department of Surgery and McGowan Institute for Regenerative Medicine, University of Pittsburgh School of Medicine

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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 10 Gy 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 27 year 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 +/- 48 mu M (normal 30-119 mu M) to 854 +/- 25 mu M (treatment goal <= 360 mu M) after transplant (36% decrease; p < 0.0001), despite transplantation of only half the target number of donor hepatocytes. PHE levels remained below 900 lM 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. (C) 2016 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

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