The developmental potency of mouse embryonic stem (ES) cells, which is the ability to contribute to a whole embryo, is known to deteriorate during long-term cell culture. Previously, we have shown that ES cells oscillate between Zscan4⁻ and Zscan4⁺ states, and the transient activation of Zscan4 is required for the maintenance of telomeres and genome stability of ES cells. Here we show that increasing the frequency of Zscan4 activation in mouse ES cells restores and maintains their developmental potency in long-term cell culture. Injection of a single ES cell with such increased potency into a tetraploid blastocyst gives rise to an entire embryo with a higher success rate. These results not only provide a means to rejuvenate ES cells by manipulating Zscan4 expression, but also indicate the active roles of Zscan4 in the long-term maintenance of ES cell potency.

The antral compartment in the ovary consists of two populations of oocytes that differ by their ability to resume meiosis and to develop to the blastocyst stage. For reasons still not entirely clear, antral oocytes termed surrounded nucleolus (SN; 70% of the population of antral oocytes) develop to the blastocyst stage, whereas those called not-surrounded nucleolus (NSN) arrest at two cells. We profiled transcriptomic, proteomic, and morphological characteristics of antral oocytes and observed that NSN oocyte arrest is associated with lack of cytoplasmic lattices coincident with reduced expression of MATER and ribosomal proteins. Cytoplasmic lattices have been shown to store maternally derived mRNA and ribosomes in mammalian oocytes and embryos, and MATER has been shown to be required for cytoplasmic lattice formation. Thus, we isolated antral oocytes from a Mater^tm/tm mouse and we observed that 84% of oocytes are of the NSN type. Our results provide the first molecular evidence to account for inability of NSN-derived embryos to progress beyond the two-cell stage; these results may be relevant to naturally occurring preimplantation embryo demise in mammals.

Introduction: Crohn’s disease (CD) is a disabling chronic enteropathy sustained by a harmful T-cell response toward antigens of the gut microbiota in genetically susceptible subjects. Growing evidence highlights the safety and possible efficacy of mesenchymal stem cells (MSCs) as a new therapeutic tool for this condition. Therefore, we aimed to investigate the effects of bone marrow-derived MSCs on pathogenic T cells with a view to clinical application.Methods: T-cell lines from both inflamed and non-inflamed colonic mucosal specimens of CD patients and from healthy mucosa of control subjects were grown with the antigen muramyl-dipeptide in the absence or presence of donors’ MSCs. The MSC effects were evaluated in terms of T-cell viability, apoptotic rate, proliferative response, immunophenotype, and cytokine profile. The role of the indoleamine 2,3-dioxygenase (IDO) was established by adding a specific inhibitor, the 1-methyl-DL-tryptophan, and by using MSCs transfected with the small interfering RNA (siRNA) targeting IDO. The relevance of cell-cell contact was evaluated by applying transwell membranes.Results: A significant reduction in both cell viability and proliferative response to muramyl-dipeptide, with simultaneous increase in the apoptotic rate, was found in T cells from both inflamed and non-inflamed CD mucosa when co-cultured with MSCs and was reverted by inhibiting IDO activity and expression. A reduction of the activated CD4⁺CD25⁺subset and increase of the CD3⁺CD69⁺population were also observed when T-cell lines from CD mucosa were co-cultured with MSCs. In parallel, an inhibitory effect was evident on the expression of the pro-inflammatory cytokines tumor necrosis factor-α, interferon-γ, interleukin-17A and -21, whereas that of the transforming growth factor-β and interleukin-6 were increased, and production of the tolerogenic molecule soluble HLA-G was high. These latter effects were almost completely eliminated by blocking the IDO, whose activity was upregulated in MSCs co-cultured with CD T cells. The use of a semipermeable membrane partially inhibited the MSC immunosuppressive effects. Finally, hardly any effects of MSCs were observed when T cells obtained from control subjects were used.Conclusion: MSCs exert potent immunomodulant effects on antigen-specific T cells in CD through a complex paracrine and cell-cell contact-mediated action, which may be exploited for widespread therapeutic use.