Investigating liver tissue dynamics to improve the efficiency and durability of gene therapy for inherited liver metabolic diseases

Transfer to the liver of therapeutic genes may provide a one-time cure for genetic diseases affecting this organ. Transfer of genes encoding coagulation factors to the liver by virus-derived vehicles to treat the coagulation disorder hemophilia is among the most successful applications of gene therapy in humans. However, these vehicles do not actively integrate into the target cell genome, thus they are lost upon cell division in liver growth and for this reason their use in pediatric patients is currently limited. We have developed other virus-derived vehicles that integrate into the target cell DNA and are maintained as cells divide, thus bearing the potential for stable long-term maintenance after a single administration. Maintenance of the therapeutic genetic modification upon liver cells proliferation in post-natal liver growth and turnover in adulthood also requires targeting the cells underlying these processes. Here we aim to dissect the role of liver cells heterogeneity in these processes and identify specific cell subsets supporting them. The efficiency of gene transfer into liver cells depends on the age of administration, thus we will investigate the mechanisms underlying this outcome to exploit them to improve gene therapy. These studies have implications to understand liver tissue dynamics and for the design and development of liver-directed gene therapy strategies. Since gene transfer remains associated with imperfect control of expression of the therapeutic gene and some safety risks related to integration into target cells DNA, we will also explore targeted genetic modification strategies. We will compare the efficacy, safety and durability gene transfer and site-specific gene correction in a mouse model of progressive familial intrahepatic cholestasis, chosen as a first representative of a class of inherited diseases of liver metabolism. This work may lead to development of novel gene therapies for this disease so far neglected by gene therapy and pave the way to application to other inherited liver metabolic diseases.