Hepatocytes from wild-type or heterozygous donors are equally effective in achieving successful therapeutic liver repopulation in murine phenylketonuria (PKU)

Kelly Hamman, Shelley R. Winn, Cary Harding

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

Successful restoration of phenylalanine (Phe) clearance following liver-directed gene therapy in murine phenylketonuria (PKU) is likely dependent upon both the number of cells successfully transduced and the amount of phenylalanine hydroxylase (PAH) activity expressed per cell. At low levels of transduction, Phe clearance could be limited by the low absolute number of PAH-expressing cells rather than the total amount of PAH activity produced in the liver. We have evaluated the interrelationship between the number of PAH positive cells, the amount of PAH activity produced and Phe clearance through experiments with hepatocyte-mediated therapeutic liver repopulation in the Pah enu2 mouse, a model of PKU. We compared the therapeutic efficacy of transplantation with either wild-type hepatocytes or hepatocytes from heterozygous Pah enu2/+ donors into PAH deficient, hyperphenylalaninemic Pah enu2/Pah enu2 mice. The recipient mice were also homozygous for fumarylacetoacetate hydrolase (FAH) deficiency. In this model system, FAH positive donor hepatocytes enjoy a selective growth advantage in the FAH-deficient recipient. If Phe clearance is governed predominantly by the total PAH activity, then more heterozygous cells, which express lower PAH activity than wild-type cells, should be required to correct Phe clearance. If the absolute donor cell number is more important, then wild-type hepatocytes should have no advantage over heterozygous cells. We successfully carried out therapeutic liver repopulation with heterozygous donor cells in fifteen mice and an additional thirteen transplants with wild-type cells. Blood Phe was successfully reduced in both transplant groups, and the relationship between the final blood Phe level and the extent of liver repopulation with donor cells did not differ between the two donor groups. Regardless of the type of donor cell, liver repopulation of approximately 3-10% was sufficient to at least partially reduce blood phenylalanine, and blood Phe levels were completely corrected in mice that had attained greater than approximately 10% liver repopulation. We conclude from our study that the absolute number of PAH-expressing cells likely governs Phe clearance at least at the levels of repopulation reported here and that the amount of PAH activity per donor cell is a less critical variable. The implication for liver-directed gene therapy of PKU is that only partial correction of cellular PAH deficiency may yet improve Phe clearance as long as a sufficient number of hepatocytes is successfully transduced.

Original languageEnglish (US)
Pages (from-to)235-240
Number of pages6
JournalMolecular Genetics and Metabolism
Volume104
Issue number3
DOIs
StatePublished - Nov 2011

Fingerprint

Phenylalanine Hydroxylase
Phenylketonurias
Phenylalanine
Liver
Hepatocytes
Blood
Therapeutics
Gene therapy
Transplants
Genetic Therapy
Cell Count
Restoration

Keywords

  • Hepatocyte transplantation
  • Mouse model
  • Phenylalanine
  • Phenylalanine hydroxylase deficiency
  • Phenylketonuria
  • Therapeutic liver repopulation

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Genetics
  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

Cite this

@article{96bd1c32a57742b482e0713ffd983b3e,
title = "Hepatocytes from wild-type or heterozygous donors are equally effective in achieving successful therapeutic liver repopulation in murine phenylketonuria (PKU)",
abstract = "Successful restoration of phenylalanine (Phe) clearance following liver-directed gene therapy in murine phenylketonuria (PKU) is likely dependent upon both the number of cells successfully transduced and the amount of phenylalanine hydroxylase (PAH) activity expressed per cell. At low levels of transduction, Phe clearance could be limited by the low absolute number of PAH-expressing cells rather than the total amount of PAH activity produced in the liver. We have evaluated the interrelationship between the number of PAH positive cells, the amount of PAH activity produced and Phe clearance through experiments with hepatocyte-mediated therapeutic liver repopulation in the Pah enu2 mouse, a model of PKU. We compared the therapeutic efficacy of transplantation with either wild-type hepatocytes or hepatocytes from heterozygous Pah enu2/+ donors into PAH deficient, hyperphenylalaninemic Pah enu2/Pah enu2 mice. The recipient mice were also homozygous for fumarylacetoacetate hydrolase (FAH) deficiency. In this model system, FAH positive donor hepatocytes enjoy a selective growth advantage in the FAH-deficient recipient. If Phe clearance is governed predominantly by the total PAH activity, then more heterozygous cells, which express lower PAH activity than wild-type cells, should be required to correct Phe clearance. If the absolute donor cell number is more important, then wild-type hepatocytes should have no advantage over heterozygous cells. We successfully carried out therapeutic liver repopulation with heterozygous donor cells in fifteen mice and an additional thirteen transplants with wild-type cells. Blood Phe was successfully reduced in both transplant groups, and the relationship between the final blood Phe level and the extent of liver repopulation with donor cells did not differ between the two donor groups. Regardless of the type of donor cell, liver repopulation of approximately 3-10{\%} was sufficient to at least partially reduce blood phenylalanine, and blood Phe levels were completely corrected in mice that had attained greater than approximately 10{\%} liver repopulation. We conclude from our study that the absolute number of PAH-expressing cells likely governs Phe clearance at least at the levels of repopulation reported here and that the amount of PAH activity per donor cell is a less critical variable. The implication for liver-directed gene therapy of PKU is that only partial correction of cellular PAH deficiency may yet improve Phe clearance as long as a sufficient number of hepatocytes is successfully transduced.",
keywords = "Hepatocyte transplantation, Mouse model, Phenylalanine, Phenylalanine hydroxylase deficiency, Phenylketonuria, Therapeutic liver repopulation",
author = "Kelly Hamman and Winn, {Shelley R.} and Cary Harding",
year = "2011",
month = "11",
doi = "10.1016/j.ymgme.2011.07.027",
language = "English (US)",
volume = "104",
pages = "235--240",
journal = "Molecular Genetics and Metabolism",
issn = "1096-7192",
publisher = "Academic Press Inc.",
number = "3",

}

TY - JOUR

T1 - Hepatocytes from wild-type or heterozygous donors are equally effective in achieving successful therapeutic liver repopulation in murine phenylketonuria (PKU)

AU - Hamman, Kelly

AU - Winn, Shelley R.

AU - Harding, Cary

PY - 2011/11

Y1 - 2011/11

N2 - Successful restoration of phenylalanine (Phe) clearance following liver-directed gene therapy in murine phenylketonuria (PKU) is likely dependent upon both the number of cells successfully transduced and the amount of phenylalanine hydroxylase (PAH) activity expressed per cell. At low levels of transduction, Phe clearance could be limited by the low absolute number of PAH-expressing cells rather than the total amount of PAH activity produced in the liver. We have evaluated the interrelationship between the number of PAH positive cells, the amount of PAH activity produced and Phe clearance through experiments with hepatocyte-mediated therapeutic liver repopulation in the Pah enu2 mouse, a model of PKU. We compared the therapeutic efficacy of transplantation with either wild-type hepatocytes or hepatocytes from heterozygous Pah enu2/+ donors into PAH deficient, hyperphenylalaninemic Pah enu2/Pah enu2 mice. The recipient mice were also homozygous for fumarylacetoacetate hydrolase (FAH) deficiency. In this model system, FAH positive donor hepatocytes enjoy a selective growth advantage in the FAH-deficient recipient. If Phe clearance is governed predominantly by the total PAH activity, then more heterozygous cells, which express lower PAH activity than wild-type cells, should be required to correct Phe clearance. If the absolute donor cell number is more important, then wild-type hepatocytes should have no advantage over heterozygous cells. We successfully carried out therapeutic liver repopulation with heterozygous donor cells in fifteen mice and an additional thirteen transplants with wild-type cells. Blood Phe was successfully reduced in both transplant groups, and the relationship between the final blood Phe level and the extent of liver repopulation with donor cells did not differ between the two donor groups. Regardless of the type of donor cell, liver repopulation of approximately 3-10% was sufficient to at least partially reduce blood phenylalanine, and blood Phe levels were completely corrected in mice that had attained greater than approximately 10% liver repopulation. We conclude from our study that the absolute number of PAH-expressing cells likely governs Phe clearance at least at the levels of repopulation reported here and that the amount of PAH activity per donor cell is a less critical variable. The implication for liver-directed gene therapy of PKU is that only partial correction of cellular PAH deficiency may yet improve Phe clearance as long as a sufficient number of hepatocytes is successfully transduced.

AB - Successful restoration of phenylalanine (Phe) clearance following liver-directed gene therapy in murine phenylketonuria (PKU) is likely dependent upon both the number of cells successfully transduced and the amount of phenylalanine hydroxylase (PAH) activity expressed per cell. At low levels of transduction, Phe clearance could be limited by the low absolute number of PAH-expressing cells rather than the total amount of PAH activity produced in the liver. We have evaluated the interrelationship between the number of PAH positive cells, the amount of PAH activity produced and Phe clearance through experiments with hepatocyte-mediated therapeutic liver repopulation in the Pah enu2 mouse, a model of PKU. We compared the therapeutic efficacy of transplantation with either wild-type hepatocytes or hepatocytes from heterozygous Pah enu2/+ donors into PAH deficient, hyperphenylalaninemic Pah enu2/Pah enu2 mice. The recipient mice were also homozygous for fumarylacetoacetate hydrolase (FAH) deficiency. In this model system, FAH positive donor hepatocytes enjoy a selective growth advantage in the FAH-deficient recipient. If Phe clearance is governed predominantly by the total PAH activity, then more heterozygous cells, which express lower PAH activity than wild-type cells, should be required to correct Phe clearance. If the absolute donor cell number is more important, then wild-type hepatocytes should have no advantage over heterozygous cells. We successfully carried out therapeutic liver repopulation with heterozygous donor cells in fifteen mice and an additional thirteen transplants with wild-type cells. Blood Phe was successfully reduced in both transplant groups, and the relationship between the final blood Phe level and the extent of liver repopulation with donor cells did not differ between the two donor groups. Regardless of the type of donor cell, liver repopulation of approximately 3-10% was sufficient to at least partially reduce blood phenylalanine, and blood Phe levels were completely corrected in mice that had attained greater than approximately 10% liver repopulation. We conclude from our study that the absolute number of PAH-expressing cells likely governs Phe clearance at least at the levels of repopulation reported here and that the amount of PAH activity per donor cell is a less critical variable. The implication for liver-directed gene therapy of PKU is that only partial correction of cellular PAH deficiency may yet improve Phe clearance as long as a sufficient number of hepatocytes is successfully transduced.

KW - Hepatocyte transplantation

KW - Mouse model

KW - Phenylalanine

KW - Phenylalanine hydroxylase deficiency

KW - Phenylketonuria

KW - Therapeutic liver repopulation

UR - http://www.scopus.com/inward/record.url?scp=82455179463&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=82455179463&partnerID=8YFLogxK

U2 - 10.1016/j.ymgme.2011.07.027

DO - 10.1016/j.ymgme.2011.07.027

M3 - Article

VL - 104

SP - 235

EP - 240

JO - Molecular Genetics and Metabolism

JF - Molecular Genetics and Metabolism

SN - 1096-7192

IS - 3

ER -