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The capacity of 3D organoids to mimic physiological tissue organization and functionality has provided an invaluable tool to model development and disease in vitro. However, conventional organoid cultures primarily represent the homeostasis of self-organizing stem cells and their derivatives. Here, we established a novel intestinal organoid culture system composed of 8 components, mainly including VPA, EPZ6438, LDN193189, and R-Spondin 1 conditioned medium, which mimics the gut epithelium regeneration that produces hyperplastic crypts following injury; therefore, these organoids were designated hyperplastic intestinal organoids (Hyper-organoids). Single-cell RNA sequencing identified different regenerative stem cell populations in our Hyper-organoids that shared molecular features with in vivo injury-responsive Lgr5+ stem cells or Clu+ revival stem cells. Further analysis revealed that VPA and EPZ6438 were indispensable for epigenome reprogramming and regeneration in Hyper-organoids, which functioned through epigenetically regulating YAP signaling. Furthermore, VPA and EPZ6438 synergistically promoted regenerative response in gut upon damage in vivo. In summary, our results demonstrated a new in vitro organoid model to study epithelial regeneration, highlighting the importance of epigenetic reprogramming that pioneers tissue repair.

It is challenging to derive totipotent stem cells in vitro that functionally and molecularly resemble cells from totipotent embryos. Here, we report that a chemical cocktail enables the derivation of totipotent-like stem cells, designated as totipotent potential stem (TPS) cells, from 2-cell mouse embryos and extended pluripotent stem cells, and that these TPS cells can be stably maintained long term in vitro. TPS cells shared features with 2-cell mouse embryos in terms of totipotency markers, transcriptome, chromatin accessibility and DNA methylation patterns. In vivo chimera formation assays show that these cells have embryonic and extraembryonic developmental potentials at the single-cell level. Moreover, TPS cells can be induced into blastocyst-like structures resembling preimplantation mouse blastocysts. Mechanistically, inhibition of HDAC1/2 and DOT1L activity and activation of RARγ signaling are important for inducing and maintaining totipotent features of TPS cells. Our study opens up a new path toward fully capturing totipotent stem cells in vitro.

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Extended pluripotent stem (EPS) cells have shown great applicative potentials in generating synthetic embryos, directed differentiation and disease modeling. However, the lack of a xeno-free culture condition has significantly limited their applications. Here, we report a chemically defined and xeno-free culture system for culturing and deriving human EPS cells in vitro. Xeno-free human EPS cells can be long-term and genetically stably maintained in vitro, as well as preserve their embryonic and extraembryonic developmental potentials. Furthermore, the xeno-free culturing system also permits efficient derivation of human EPS cells from human fibroblast through reprogramming. Our study could have broad utility in future applications of human EPS cells in biomedicine.

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Human extended pluripotent stem (EPS) cells have shown great applicative potentials in basic and translational research. One prerequisite for the wide applications of EPS cells is the development of a xeno-free culture system for maintain these cells in vitro. Here we report a protocol for culturing and generating human EPS cells using a chemically defined and xeno-free culture system.