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Nature Oct 2023The ability to study human post-implantation development remains limited owing to ethical and technical challenges associated with intrauterine development after...
The ability to study human post-implantation development remains limited owing to ethical and technical challenges associated with intrauterine development after implantation. Embryo-like models with spatially organized morphogenesis and structure of all defining embryonic and extra-embryonic tissues of the post-implantation human conceptus (that is, the embryonic disc, the bilaminar disc, the yolk sac, the chorionic sac and the surrounding trophoblast layer) remain lacking. Mouse naive embryonic stem cells have recently been shown to give rise to embryonic and extra-embryonic stem cells capable of self-assembling into post-gastrulation structured stem-cell-based embryo models with spatially organized morphogenesis (called SEMs). Here we extend those findings to humans using only genetically unmodified human naive embryonic stem cells (cultured in human enhanced naive stem cell medium conditions). Such human fully integrated and complete SEMs recapitulate the organization of nearly all known lineages and compartments of post-implantation human embryos, including the epiblast, the hypoblast, the extra-embryonic mesoderm and the trophoblast layer surrounding the latter compartments. These human complete SEMs demonstrated developmental growth dynamics that resemble key hallmarks of post-implantation stage embryogenesis up to 13-14 days after fertilization (Carnegie stage 6a). These include embryonic disc and bilaminar disc formation, epiblast lumenogenesis, polarized amniogenesis, anterior-posterior symmetry breaking, primordial germ-cell specification, polarized yolk sac with visceral and parietal endoderm formation, extra-embryonic mesoderm expansion that defines a chorionic cavity and a connecting stalk, and a trophoblast-surrounding compartment demonstrating syncytium and lacunae formation. This SEM platform will probably enable the experimental investigation of previously inaccessible windows of human early post implantation up to peri-gastrulation development.
Topics: Humans; Embryo Implantation; Embryo, Mammalian; Embryonic Development; Fertilization; Gastrulation; Germ Layers; Human Embryonic Stem Cells; Trophoblasts; Yolk Sac; Giant Cells
PubMed: 37673118
DOI: 10.1038/s41586-023-06604-5 -
Nature Oct 2023Investigating human development is a substantial scientific challenge due to the technical and ethical limitations of working with embryonic samples. In the face of...
Investigating human development is a substantial scientific challenge due to the technical and ethical limitations of working with embryonic samples. In the face of these difficulties, stem cells have provided an alternative to experimentally model inaccessible stages of human development in vitro. Here we show that human pluripotent stem cells can be triggered to self-organize into three-dimensional structures that recapitulate some key spatiotemporal events of early human post-implantation embryonic development. Our system reproducibly captures spontaneous differentiation and co-development of embryonic epiblast-like and extra-embryonic hypoblast-like lineages, establishes key signalling hubs with secreted modulators and undergoes symmetry breaking-like events. Single-cell transcriptomics confirms differentiation into diverse cell states of the perigastrulating human embryo without establishing placental cell types, including signatures of post-implantation epiblast, amniotic ectoderm, primitive streak, mesoderm, early extra-embryonic endoderm, as well as initial yolk sac induction. Collectively, our system captures key features of human embryonic development spanning from Carnegie stage 4-7, offering a reproducible, tractable and scalable experimental platform to understand the basic cellular and molecular mechanisms that underlie human development, including new opportunities to dissect congenital pathologies with high throughput.
Topics: Female; Humans; Pregnancy; Cell Differentiation; Cell Lineage; Embryo Implantation; Embryonic Development; Germ Layers; Human Embryonic Stem Cells; Placenta; Pluripotent Stem Cells; Primitive Streak; Yolk Sac
PubMed: 37369348
DOI: 10.1038/s41586-023-06354-4 -
Cell Stem Cell Sep 2023Naive human pluripotent stem cells have the remarkable ability to self-organize into blastocyst-like structures ("blastoids") that model lineage segregation in the...
Naive human pluripotent stem cells have the remarkable ability to self-organize into blastocyst-like structures ("blastoids") that model lineage segregation in the pre-implantation embryo. However, the extent to which blastoids can recapitulate the defining features of human post-implantation development remains unexplored. Here, we report that blastoids cultured on thick three-dimensional (3D) extracellular matrices capture hallmarks of early post-implantation development, including epiblast lumenogenesis, rapid expansion and diversification of trophoblast lineages, and robust invasion of extravillous trophoblast cells by day 14. Extended blastoid culture results in the localized activation of primitive streak marker TBXT and the emergence of embryonic germ layers by day 21. We also show that the modulation of WNT signaling alters the balance between epiblast and trophoblast fates in post-implantation blastoids. This work demonstrates that 3D-cultured blastoids offer a continuous and integrated in vitro model system of human embryonic and extraembryonic development from pre-implantation to early gastrulation stages.
Topics: Humans; Gastrulation; Embryo Implantation; Embryo, Mammalian; Blastocyst; Epithelial Cells
PubMed: 37683602
DOI: 10.1016/j.stem.2023.08.005 -
Emerging Topics in Life Sciences Dec 2023The young field of gastruloids brings promise to modeling and understanding early embryonic development. However, being a complex model, gastruloids are prone to...
The young field of gastruloids brings promise to modeling and understanding early embryonic development. However, being a complex model, gastruloids are prone to variability at different levels. In this perspective, we define the different levels of gastruloid variability, and parameters over which it can be measured. We discuss potential sources for variability, and then propose methods to better control and reduce it. We provide an example from definitive endoderm progression in gastruloids, where we harness gastruloid-to-gastruloid variation in early parameters to identify key driving factors for endoderm morphology. We then devise interventions that steer morphological outcome. A better control over the developmental progression of gastruloids will enhance their utility in both basic research and biomedical applications.
Topics: Female; Pregnancy; Humans; Gastrula; Endoderm; Embryonic Development
PubMed: 37815089
DOI: 10.1042/ETLS20230096 -
Cell Research Sep 2023Studies of cultured embryos have provided insights into human peri-implantation development. However, detailed knowledge of peri-implantation lineage development as well...
Studies of cultured embryos have provided insights into human peri-implantation development. However, detailed knowledge of peri-implantation lineage development as well as underlying mechanisms remains obscure. Using 3D-cultured human embryos, herein we report a complete cell atlas of the early post-implantation lineages and decipher cellular composition and gene signatures of the epiblast and hypoblast derivatives. In addition, we develop an embryo-like assembloid (E-assembloid) by assembling naive hESCs and extraembryonic cells. Using human embryos and E-assembloids, we reveal that WNT, BMP and Nodal signaling pathways synergistically, but functionally differently, orchestrate human peri-implantation lineage development. Specially, we dissect mechanisms underlying extraembryonic mesoderm and extraembryonic endoderm specifications. Finally, an improved E-assembloid is developed to recapitulate the epiblast and hypoblast development and tissue architectures in the pre-gastrulation human embryo. Our findings provide insights into human peri-implantation development, and the E-assembloid offers a useful model to disentangle cellular behaviors and signaling interactions that drive human embryogenesis.
Topics: Humans; Germ Layers; Embryo, Mammalian; Embryo Implantation; Endoderm; Mesoderm; Embryonic Development
PubMed: 37460804
DOI: 10.1038/s41422-023-00846-8