A liver-humanized mouse model of carbamoyl phosphate synthetase 1-deficiency.

Raghuraman C Srinivasan,Christina Hammarstedt,Johannes Häberle,Ahmad Karadagi,Stephen C Strom,Mihaela Zabulica,Véronique Rüfenacht,Beat Thöny,Kristina Kannisto,Roberto Gramignoli,Gabriella Allegri,Tingting Wu,Ralph Fingerhut,Jean‐Marc Nuoffer,Ewa Ellis

doi:10.1002/jimd.12067

Abstract

A liver-humanized mouse model for CPS1-deficiency was generated by the high-level repopulation of the mouse liver with CPS1-deficient human hepatocytes. When compared with mice that are highly repopulated with CPS1-proficient human hepatocytes, mice that are repopulated with CPS1-deficient human hepatocytes exhibited characteristic symptoms of human CPS1 deficiency including an 80% reduction in CPS1 metabolic activity, delayed clearance of an ammonium chloride infusion, elevated glutamine and glutamate levels, and impaired metabolism of [15 N]ammonium chloride into urea, with no other obvious phenotypic differences. Because most metabolic liver diseases result from mutations that alter critical pathways in hepatocytes, a model that incorporates actual disease-affected, mutant human hepatocytes is useful for the investigation of the molecular, biochemical, and phenotypic differences induced by that mutation. The model is also expected to be useful for investigations of modified RNA, gene, and cellular and small molecule therapies for CPS1-deficiency. Liver-humanized models for this and other monogenic liver diseases afford the ability to assess the therapy on actual disease-affected human hepatocytes, in vivo, for long periods of time and will provide data that are highly relevant for investigations of the safety and efficacy of gene-editing technologies directed to human hepatocytes and the translation of gene-editing technology to the clinic.

Highlights

Excess nitrogen in the form of ammonia is accumulated during the breakdown of proteins and amino acids
Perhaps one of the most noteworthy examples was Fialuridine, which showed little to no toxicity and great potential for the treatment of HBV infection in preclinical animal studies, but when the drug was provided to human patients, it caused severe liver failure.[24]
Studies with liver-humanized mice were initiated in efforts to make the extrapolation of preclinical studies more likely to translate to the clinic.[18,34,37]

Summary

| INTRODUCTION

Current murine models available for each UCD have shown both advantages and disadvantages.[7,8,27,28,29] A CPS1 knockout mouse was generated, and while it recapitulates aspects of the human disease phenotype, including severe hyperammonemia, all affected mice died within 36 hours of birth, making it difficult to study or treat the disease or even to maintain the animal model.[28] The original CPS1 gene knockout mouse model may no longer exist.[7] A more recent study reported the conditional disruption of the CPS1 gene in mice that survived only for 4 weeks and provided a phenotype with hyperammonemia but without orotic aciduria .19. NTBC is withdrawn, toxic tyrosine metabolites accumulate and severely injure the Fah-deficient mouse hepatocytes creating a strong liver regeneration stimulus. Chimeric mice were generated by the transplantation of human hepatocytes from normal donors as well as from a patient with CPS1-D, and the resulting phenotypes were investigated

| MATERIALS AND METHODS

| RESULTS

| DISCUSSION

Findings

CONFLICT OF INTEREST