Murine pluripotent stem cells that escape differentiation inside teratomas maintain pluripotency

Switching the polarity of mouse enteroids affects the epithelial interplay with prenylated phenolics from licorice (Glycyrrhiza) roots

The utility of 3D-small intestinal organoid (enteroid) models for evaluating effects of e.g. food (related) compounds is limited due to the apical epithelium facing the interior. To overcome this limitation, we developed a novel 3D-apical-out enteroid model for mice, which allows apical exposure. Using this model, we evaluated the effects on the enteroids' intestinal epithelium (including cytotoxicity, cell viability, and biotransformation) after exposure to glabridin, a prenylated secondary metabolite with antimicrobial properties from licorice roots (Glycyrrhiza glabra). Apical-out enteroids were five times less sensitive to glabridin exposure compared to conventional apical-in enteroids, with obtained cytotoxicities of 1.5 mM and 0.31 mM, respectively. Apical-out enteroids showed a luminal/apical layer of fucose rich mucus, which may contribute to the protection against potential cytotoxicity of glabridin. Furthermore, in apical-in enteroids IC50 values for cytotoxicity were determined for licochalcone A, glycycoumarin, and glabridin, the species-specific prenylated phenolics from the commonly used G. inflata, G. uralensis, and G. glabra, respectively. Both enteroid models differed in their functional phase II biotransformation capacity, where glabridin was transformed to glucuronide- and sulfate-conjugates. Lastly, our results indicate that the prenylated phenolics do not show cytotoxicity in mouse enteroids at previously reported minimum inhibitory concentrations (MICs) against a diverse set of Gram positive bacteria. Altogether, we show that apical-out enteroids provide a better mimic of the gastrointestinal tract compared to conventional enteroids and are consequently a superior model to study effects of food (related) compounds. This work revealed that prenylated phenolics with promising antibacterial activity show no harmful effects in the GI-tract at their MICs and therefore may offer a new perspective to control unwanted microbial growth.

Culture conditions of mouse ESCs impact the tumor appearance in vivo

Various culture conditions by small molecules have been explored to extend pluripotency of stem cells, but their impacts on cell fate in vivo remain elusive. We systematically compared the effects of various culture conditions on the pluripotency and cell fate in vivo of mouse embryonic stem cells (ESCs) by tetraploid embryo complementation assay. Conventional ESC cultures in serum/LIF-based condition produced complete ESC mice and also the survival to adulthood at the highest rates of all other chemical-based cultures. Moreover, long-term examination of the survived ESC mice demonstrated that conventional ESC cultures did not lead to visible abnormality for up to 1.5-2 years, whereas the prolonged chemical-based cultures developed retroperitoneal atypical teratomas or leiomyomas. The chemical-based cultures exhibited transcriptomes and epigenomes that typically differed from those of conventional ESC cultures. Our results warrant further refinement of culture conditions in promoting the pluripotency and safety of ESCs in future applications.

Cancer cells as a new source of induced pluripotent stem cells

Over the last 2 decades, induced pluripotent stem cells (iPSCs) have had various potential applications in various medical research areas, from personalized medicine to disease treatment. Different cellular resources are accessible for iPSC generation, such as keratinocytes, skin fibroblasts, and blood or urine cells. However, all these sources are somatic cells, and we must make several changes in a somatic cell's transcriptome and chromatin state to become a pluripotent cell. It has recently been revealed that cancer cells can be a new source of iPSCs production. Cancer cells show similarities with iPSCs in self-renewal capacity, reprogramming potency, and signaling pathways. Although genetic abnormalities and potential tumor formation in cancer cells pose a severe risk, reprogrammed cancer-induced pluripotent stem cells (cancer-iPSCs) indicate that pluripotency can transiently overcome the cancer phenotype. This review discusses whether cancer cells can be a preferable source to generate iPSCs.

Direct in vivo application of induced pluripotent stem cells is feasible and can be safe

Increasing evidence suggests the consensus that direct in vivo application of induced pluripotent stem cells (iPSCs) is infeasible may not be true. Methods: Teratoma formation and fate were examined in 53 normal and disease conditions involving brain, lung, liver, kidney, islet, skin, hind limb, and arteries. Results: Using classic teratoma generation assays, which require iPSCs to be congregated and confined, all mouse, human, and individualized autologous monkey iPSCs tested formed teratoma, while iPSC-derived cells did not. Intravenously or topically-disseminated iPSCs did not form teratomas with doses up to 2.5×10⁸ iPSCs/kg and observation times up to 18 months, regardless of host tissue type; autologous, syngeneic, or immune-deficient host animals; presence or absence of disease; disease type; iPSC induction method; commercial or self-induced iPSCs; mouse, human, or monkey iPSCs; frequency of delivery; and sex. Matrigel-confined, but not PBS-suspended, syngeneic iPSCs delivered into the peritoneal cavity or renal capsule formed teratomas. Intravenously administered iPSCs were therapeutic with a dose as low as 5×10⁶/kg and some iPSCs differentiated into somatic cells in injured organs. Disseminated iPSCs trafficked into injured tissue and survived significantly longer in injured than uninjured organs. In disease-free animals, no intravenously administered cell differentiated into an unwanted long-lasting cell or survived as a quiescent stem cell. In coculture, the stem cell medium and dominant cell-type status were critical for iPSCs to form cell masses. Conclusion: Teratoma can be easily and completely avoided by disseminating the cells. Direct in vivo iPSC application is feasible and can be safe.