Intestinal organoids hold great promise as a valuable tool for studying and treating intestinal diseases. The currently available sources of human intestinal organoids, tissue fragments or pluripotent stem cells, involve invasive procedures or complex differentiation protocols, respectively. Here, we show that a set of four transcription factors, Hnf4α, Foxa3, Gata6, and Cdx2, can directly reprogram mouse fibroblasts to acquire the identity of fetal intestine-derived progenitor cells (FIPCs). These induced FIPCs (iFIPCs) form spherical organoids that develop into adult-type budding organoids containing cells with intestinal stem cell properties. The resulting stem cells produce all intestinal epithelial cell lineages and undergo self-renewing cell divisions. After transplantation, the induced spherical and budding organoids can reconstitute colonic and intestinal epithelia, respectively. The same combination of four defined transcription factors can also induce human iFIPCs. This alternative approach for producing intestinal organoids may well facilitate application for disease analysis and therapy development.

In liver development, hepatoblasts that act as hepatic stem/progenitor cells proliferate and differentiate into both hepatocytes and cholangiocytes to form liver tissues. Although numerous factors contribute to this event, little is known about the roles of microRNAs in hepatoblast proliferation and differentiation. In this study, we focused on the lineage-28 (Lin28) family proteins, which are required for microRNA regulation in pluripotent stem cells and cancer cells, and investigated their roles as regulatory factors for the properties of hepatoblasts. Conclusion: Lin28b was specifically expressed in hepatoblasts, and its suppression induced growth arrest and cholangiocyte differentiation of hepatoblasts; mechanistically, Lin28b positively regulates the expression of Lin28b itself and cell cycle-related proteins in hepatoblasts by suppressing the maturation of target microRNAs, lethal-7b and miR-125a/b, enabling maintenance of the stem cell properties of hepatoblasts, such as their capabilities for proliferation and bi-lineage differentiation, during liver development. (HEPATOLOGY 2016;64:245-260) M icroRNAs (miRNAs), which are composed of 20-25 nucleotides of RNA, bind to partial complementary sequences in the 3 0 -untranslated region (UTR) of their target transcripts, recruit RNA-induced silencing complex to inhibit the translation of these transcripts, and are involved in the regulation of many aspects of cellular function. (1)(2)(3)(4)(5)(6) Regarding the involvement of miRNAs in liver development, miR-122 is highly expressed in the liver after embryonic day (E) 11.5 and contributes to the progression of liver development by suppressing Cut-like homeobox 1 (also known as CCAAT displacement protein), which acts as a transcriptional repressor against terminal differentiation of hepatocytes. (7) It was also reported that miR-23b interferes with the differentiation of cholangiocytes through suppression of the transforming growth factor-b signaling pathway by targeting Smad3/4/5 in the liver of E16.5-E17.5 mouse embryos. (8) Moreover, miR-346 and miR-500 are highly expressed in the developing liver, and their expression gradually decreases in accordance with the progression of liver development. (9) Conversely, miR-30 is specifically expressed in cholangiocytes between E18.5 and neonatal stages and contributes to bile duct formation by targeting trinucleotide repeat containing 6a, which is a subunit of the RNA-induced silencing

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Recent advances have enabled the direct induction of human tissue-specific stem and progenitor cells from differentiated somatic cells. However, it is not known whether human hepatic progenitor cells (hHepPCs) can be generated from other cell types by direct lineage reprogramming with defined transcription factors. Here, we show that a set of three transcription factors, FOXA3, HNF1A, and HNF6, can induce human umbilical vein endothelial cells to directly acquire the properties of hHepPCs. These induced hHepPCs (hiHepPCs) propagate in long-term monolayer culture and differentiate into functional hepatocytes and cholangiocytes by forming cell aggregates and cystic epithelial spheroids, respectively, under three-dimensional culture conditions. After transplantation, hiHepPC-derived hepatocytes and cholangiocytes reconstitute damaged liver tissues and support hepatic function. The defined transcription factors also induce hiHepPCs from endothelial cells circulating in adult human peripheral blood. These expandable and bipotential hiHepPCs may be useful in the study and treatment of human liver diseases.