An aggregation of human embryonic and trophoblast stem cells reveals the role of trophectoderm on epiblast differentiation.

The interactions between extra-embryonic tissues and embryonic tissues are crucial to ensure proper early embryo development. However, the understanding of the crosstalk between the embryonic tissues and extra-embryonic tissues is lacking, mainly due to ethical restrictions, difficulties in obtaining natural human embryos, and lack of appropriate in vitro models. Here by aggregating human embryonic stem cells (hESCs) with human trophoblast stem cells (hTSCs), we revealed the hESCs robustly self-organized into a unique asymmetric structure which the primitive streak (PS) like cells exclusively distributed at the distal end to the TS-compartment, and morphologically flattened cells, presumed to be the extra-embryonic mesoderm cells (EXMC) like cells, were induced at the proximal end to hTSCs. Our study revealed two potential roles of extra-embryonic trophectoderm in regulating the proper PS formation during gastrulation and EXMCs induction from the human epiblast.

Neurulation of the cynomolgus monkey embryo achieved from 3D blastocyst culture.

Neural tube (NT) defects arise from abnormal neurulation and result in the most common birth defects worldwide. Yet, mechanisms of primate neurulation remain largely unknown due to prohibitions on human embryo research and limitations of available model systems. Here, we establish a three-dimensional (3D) prolonged in vitro culture (pIVC) system supporting cynomolgus monkey embryo development from 7 to 25 days post-fertilization. Through single-cell multi-omics analyses, we demonstrate that pIVC embryos form three germ layers, including primordial germ cells, and establish proper DNA methylation and chromatin accessibility through advanced gastrulation stages. In addition, pIVC embryo immunofluorescence confirms neural crest formation, NT closure, and neural progenitor regionalization. Finally, we demonstrate that the transcriptional profiles and morphogenetics of pIVC embryos resemble key features of similarly staged in vivo cynomolgus and human embryos. This work therefore describes a system to study non-human primate embryogenesis through advanced gastrulation and early neurulation.

Identifying a dynamic transcriptomic landscape of the cynomolgus macaque placenta during pregnancy at single-cell resolution.

Supporting healthy pregnancy outcomes requires a comprehensive understanding of the cellular hierarchy and underlying molecular mechanisms in the primate placenta during gestation. Here, we present a single-cell transcriptome-wide view of the cynomolgus macaque placenta throughout gestation. Bioinformatics analyses and multiple validation experiments suggested that placental trophoblast cells exhibited stage-specific differences across gestation. Interactions between trophoblast cells and decidual cells also showed gestational stage-dependent differences. The trajectories of the villous core cells indicated that placental mesenchymal cells were derived from extraembryonic mesoderm (ExE.Meso) 1, whereas placental Hofbauer cells, erythrocytes, and endothelial cells were derived from ExE.Meso2. Comparative analyses of human and macaque placentas uncovered conserved features of placentation across species, and the discrepancies of extravillous trophoblast cells (EVTs) between human and macaque correlated to their differences in invasion patterns and maternal-fetal interactions. Our study provides a groundwork for elucidating the cellular basis of primate placentation.

Primate gastrulation and early organogenesis at single-cell resolution.

Our understanding of human early development is severely hampered by limited access to embryonic tissues. Due to their close evolutionary relationship with humans, nonhuman primates are often used as surrogates to understand human development but currently suffer from a lack of in vivo datasets, especially from gastrulation to early organogenesis during which the major embryonic cell types are dynamically specified. To fill this gap, we collected six Carnegie stage 8-11 cynomolgus monkey (Macaca fascicularis) embryos and performed in-depth transcriptomic analyses of 56,636 single cells. Our analyses show transcriptomic features of major perigastrulation cell types, which help shed light on morphogenetic events including primitive streak development, somitogenesis, gut tube formation, neural tube patterning and neural crest differentiation in primates. In addition, comparative analyses with mouse embryos and human embryoids uncovered conserved and divergent features of perigastrulation development across species-for example, species-specific dependency on Hippo signalling during presomitic mesoderm differentiation-and provide an initial assessment of relevant stem cell models of human early organogenesis. This comprehensive single-cell transcriptome atlas not only fills the knowledge gap in the nonhuman primate research field but also serves as an invaluable resource for understanding human embryogenesis and developmental disorders.