In Vivo Selection of Transplanted Hepatocytes by Pharmacological Inhibition of Fumarylacetoacetate Hydrolase in Wild-type Mice

Genetic fumarylacetoacetate hydrolase (Fah) deficiency is unique in that healthy gene-corrected hepatocytes have a strong growth advantage and can repopulate the diseased liver. Unfortunately, similar positive selection of gene-corrected cells is absent in most inborn errors of liver metabolism and it is difficult to reach the cell replacement index required for therapeutic benefit. Therefore, methods to transiently create a growth advantage for genetically modified hepatocytes in any genetic background would be advantageous. To mimic the selective pressure of Fah deficiency in normal animals, an efficient in vivo small molecule inhibitor of FAH, 4-[(2-carboxyethyl)-hydroxyphosphinyl]-3-oxobutyrate (CEHPOBA) was developed. Microarray analysis demonstrated that pharmacological inhibition of FAH produced highly similar gene expression changes to genetic deficiency. As proof of principle, hepatocytes lacking homogentisic acid dioxygenase (Hgd) and hence resistant to FAH inhibition were transplanted into sex-mismatched wild-type recipients. Time course analyses of 4-6 weeks of CEHPOBA administration after transplantation showed a linear relationship between treatment length and replacement index. Compared to controls, recipients treated with the FAH-inhibitor had 20-100-fold increases in liver repopulation. We conclude that pharmacological inhibition of FAH is a promising approach to in vivo selection of hepatocytes.