Long-Term Culture of Genom,9

st h, a ic ka a c tit e, re eThe liver is mainly composed of two epithelial cell types, hepa-tocytes and ductal cells. Hepatocytes synthesize essential Sato et al., 2011) and have shown that patient-derived intestinal organoids recapitulate the pathology of hereditary intestinal diseases (Bigorgne et al., 2014; Dekkers et al., 2013; Wiegerinckserum proteins, control metabolism, and detoxify a wide variety of endogenous and exogenous molecules (Duncan et al., 2014). Here, we pursue the establishment of an organoid culture system for human liver.Despite the enormous replication potential of the hu-man liver, there are currently no culture systems available that sustain hepatocyte replication and/or function in vitro. We have shown previously that sin-gle mouse Lgr5+ liver stem cells can be expanded as epithelial organoids in vitro and can be differentiated into functional hepatocytes in vitro and in vivo. We now describe conditions allowing long-term expan-sion of adult bile duct-derived bipotent progenitor cells from human liver. The expanded cells are highly stable at the chromosome and structural level, while single base changes occur at very low rates. The cells can readily be converted into functional hepatocytes in vitro and upon transplantation in vivo. Organoids from a1-antitrypsin deficiency and Ala-gille syndrome patients mirror the in vivo pathology. Clonal long-term expansion of primary adult liver stem cells opens up experimental avenues for disease modeling, toxicology studies, regenerative medicine, and gene therapy