Generation of human hepatocytes from extended pluripotent stem cells

Human pluripotent stem cells have great potential for application in regenerative medicine, as they permit the generation of different lineages of functional cell types via directed differentiation. 1 However, application of conventional human pluripotent stem cells is limited due to several factors, including heterogeneity in pluripotency, differentiation bias, relatively slow proliferation, and poor single-cell survival. 2 To overcome these problems, extensive efforts have been made in recent years, including optimizing the culture conditions of conventional human pluripotent stem cells 3 and deriving new human pluripotent cell types such as naive human pluripotent cell lines. 1 Recently, our group established a new type of pluripotent stem cells designated as extended pluripotent stem (EPS) cells, 4 which have both embryonic and extraembryonic developmental potential. Compared to known pluripotent stem cell types, these cells have superior differentiation potential, as demonstrated by single-cell chimeric assays in vivo. Furthermore, EPS cells can be long-term expanded through single-cell passaging with a high proliferation rate. These unique features of EPS cells make them valuable in biomedical applications, such as gene targeting and animal model generation. 5 , 6 In particular, it is promising to apply human EPS cells in directed differentiation but has not yet been explored. In this study, we sought to use human EPS cells in directed differentiation by generating human hepatocytes from these cells. Our group has made great efforts in establishing directed differentiation protocols for generation of human functional hepatocytes from conventional human pluripotent stem cells. 7 , 8 , 9 In this work, we demonstrated that human EPS cells could be efficiently differentiated into functional hepatocytes (EPS-Heps) through adding a pretreatment step before hepatic differentiation. Importantly, compared to hepatocytes derived from conventional human pluripotent stem cells, EPS-Heps transcriptionally more resemble primary human hepatocytes.