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.