Implantation initiation of self-assembled embryo-like structures generated using three types of mouse blastocyst-derived stem cells

Abstract

Spatially ordered embryo-like structures self-assembled from blastocyst-derived stem cells can be generated to mimic embryogenesis in vitro. However, the assembly system and developmental potential of such structures needs to be further studied. Here, we devise a nonadherent-suspension-shaking system to generate self-assembled embryo-like structures (ETX-embryoids) using mouse embryonic, trophoblast and extra-embryonic endoderm stem cells. When cultured together, the three cell types aggregate and sort into lineage-specific compartments. Signaling among these compartments results in molecular and morphogenic events that closely mimic those observed in wild-type embryos. These ETX-embryoids exhibit lumenogenesis, asymmetric patterns of gene expression for markers of mesoderm and primordial germ cell precursors, and formation of anterior visceral endoderm-like tissues. After transplantation into the pseudopregnant mouse uterus, ETX-embryoids efficiently initiate implantation and trigger the formation of decidual tissues. The ability of the three cell types to self-assemble into an embryo-like structure in vitro provides a powerful model system for studying embryogenesis.

Self-organization of stem cells into embryos: A window on early mammalian development

“…This event has been observed after substituting the ECM with the third stem cell type, extraembryonic endoderm (XEN) stem cells (Fig. 1), which provide the natural basement membrane (59,60). As a result the formed structures look remarkably like early post-implantation embryos in morphology, gene expression, and signaling communication.…”

“…2 and 3). compartments that then join, in response to Nodal signaling (58,60). A domain of asymmetric Brachyury expression develops at the boundary between the ESC and TSC compartments.…”

Computational modelling unveils how epiblast remodelling and positioning rely on trophectoderm morphogenesis during mouse implantation

“…1B). Furthermore, a recent study highlighted more clearly the role of the trophectoderm [14]. In this study, ExE-embryoids (ExE: extra-embryonic ectoderm), cultured from EPI and PE stem cells separated by an ECM basement membrane, did not break the symmetry of their initial spherical shape (Fig.…”

“…In contrast, both ETS-and ETX-embryoids (ETX: embryonic, trophoblast and extra-embryonic endoderm) made from all three blastocyst lineages did reproduce the symmetry breaking observed in real embryos. Together, these studies established the necessity of the trophectoderm for the remodelling of the epiblast [13,14].…”

“…Here the presence of the trophecdoderm shows that this tissue might be required for symmetry breaking in the epiblast and cup shape acquisition. C. Embryoid structures featuring epiblast and primitive endoderm stem cells surrounded by an ECM acting as a basement membrane (EXE-embryoids) do not break symmetry in the epiblast, but initiate lumenogenesis [14]. This evidences the requirement of the trophectoderm for the remodelling of the epiblast.…”