Transcriptome analysis shows ambiguous phenotypes of murine primitive endoderm-related stem cell lines

A pendulum of induction between the epiblast and extra-embryonic endoderm supports post-implantation progression

Embryogenesis is supported by dynamic loops of cellular interactions. Here, we create a partial mouse embryo model to elucidate the principles of epiblast (Epi) and extra-embryonic endoderm co-development (XEn). We trigger naive mouse embryonic stem cells to form a blastocyst-stage niche of Epi-like cells and XEn-like cells (3D, hydrogel free and serum free). Once established, these two lineages autonomously progress in minimal medium to form an inner pro-amniotic-like cavity surrounded by polarized Epi-like cells covered with visceral endoderm (VE)-like cells. The progression occurs through reciprocal inductions by which the Epi supports the primitive endoderm (PrE) to produce a basal lamina that subsequently regulates Epi polarization and/or cavitation, which, in return, channels the transcriptomic progression to VE. This VE then contributes to Epi bifurcation into anterior- and posterior-like states. Similarly, boosting the formation of PrE-like cells within blastoids supports developmental progression. We argue that self-organization can arise from lineage bifurcation followed by a pendulum of induction that propagates over time.

Chemical-based primary human hepatocyte monolayer culture for the study of drug metabolism and hepatotoxicity: Comparison with the spheroid model

Traditionally cultured monolayers of primary human hepatocytes (PHHs) deteriorate within days and thereby become unsuitable for drug-related studies. PHH spheroids (3D PHHs) maintain liver functions for weeks, but are considerably more demanding. Recently, a chemical-based approach (5C PHHs) succeeded in long-term culture of hepatocyte monolayers, but it remains unclear whether the drug-related functions are preserved. To clarify this, we compared the 5C and 3D PHHs in terms of gene expression analysis, proteomic analysis, functionality (basal and induced activities of representative CYP450 enzymes and urea and albumin secretions), survival in culture, and sensitivity to representative drugs. In all comparisons, which spanned culture durations of up to 4 weeks, the 5C PHHs performed at least as well as the 3D PHHs. Hence, the novel 5C PHH monolayer format combines the convenience of the traditional monolayer format with the functionality and maintainability of the spheroid format. Our results suggest that 5C PHH monolayers can be used more conveniently and efficiently for high-throughput drug screening, preclinical drug safety evaluations, and mechanistic studies.

Comparative analysis of the mitochondrial morphology, energy metabolism, and gene expression signatures in three types of blastocyst-derived stem cells

Pre-implantation mouse blastocyst-derived stem cells, namely embryonic stem cells (ESCs), trophoblast stem cells (TSCs), and extraembryonic endoderm (XEN) cells, have their own characteristics and lineage specificity. So far, several studies have attempted to identify these three stem cell types based on genetic markers, morphologies, and factors involved in maintaining cell self-renewal. In this study, we focused on characterizing the three stem cell types derived from mouse blastocysts by observing cellular organelles, especially the mitochondria, and analyzing how mitochondrial dynamics relates to the energy metabolism in each cell type. Our study revealed that XEN cells have distinct mitochondrial morphology and energy metabolism compared with that in ESCs and TSCs. In addition, by analyzing the energy metabolism (oxygen consumption and extracellular acidification rates), we demonstrated that differences in the mitochondria affect the cellular metabolism in the stem cells. RNA sequencing analysis showed that although ESCs are developmentally closer to XEN cells in origin, their gene expression pattern is relatively closer to that of TSCs. Notably, mitochondria-, mitochondrial metabolism-, transport/secretory action-associated genes were differentially expressed in XEN cells compared with that in ESCs and TSCs, and this feature corresponds with the morphology of the cells.