Genetic-Based Approaches to Inherited Metabolic Liver Diseases

In vertebrates, the liver is the central metabolic organ of the body, which carries out an estimated 500 functions that range from general detoxification to protein synthesis, bile production, metabolism of fats, carbohydrates, proteins, bilirubin, vitamin and mineral storage and it even has an immune function. Hepatocytes are considered the professional liver cells, which carry out all of these functions. With such a variety of tasks to perform, it is not surprising that more than 400 rare monogenic disorders of hepatic origin have been described. For many of these, liver transplantation remains the only curative strategy, however, this is limited by organ availability and requires lifelong immune suppression. The fact that liver transplantation is curative led to the assumption that the restoration of the expression of the defective gene would result in the resolution of the disease. Indeed, liver-directed gene therapy trials for hemophilia A and B have demonstrated the potential of gene therapy to provide long-lasting clinical benefit in the treatment of monogenic liver disorders. Thus, liver-directed gene therapy and gene editing strategies have emerged as promising alternatives to transplantation in inherited monogenic liver disorders. Herein, we review the advances and limitations of gene therapy for such disorders, covering therapeutic strategies based on gene addition and gene editing and the exciting clinical results obtained with the use of ribonucleic acid as therapeutic molecules.