Therapeutic Approaches and Tools for Metabolic Liver Disorders

Abstract

Patients with inborn errors of metabolism (IEMs) constitute a significant portion of the population despite individual IEMs being classified as rare diseases. However, generally these patients have only very poor therapeutic alternatives (1-3). For metabolic liver disorders these encompass substrate reduction, emergency care and in severe cases, organ transplantation. Therefore, development of new therapeutic approaches is urgently needed but limited by availability of preclinical tools.Clinical translation of AAV-mediated gene therapy requires preclinical development across different experimental models, often confounded by variable transduction efficiency (1-3). Here, we describe a human liver chimeric transgene-free Il2rg−/−/Rag2−/−/Fah−/−/Aavr−/− (TIRFA) mouse model overcoming this translational roadblock, by combining liver humanization with AAV receptor (AAVR) ablation, rendering murine cells impermissive to AAV transduction. Using human liver chimeric TIRFA mice, we demonstrate increased transduction of clinically used AAV serotypes in primary human hepatocytes compared to humanized mice with wild-type AAVR. Further, we demonstrate AAV transduction in human teratoma-derived primary cells and liver cancer tissue, displaying the versatility of the humanized TIRFA mouse. From a mechanistic perspective, our results support the notion that AAVR functions as both an entry receptor and an intracellular receptor essential for transduction. The TIRFA mouse should allow prediction of AAV gene transfer efficiency and the study of AAV vector biology in a preclinical human setting.