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Current Opinion in Genetics &... Oct 2022Synthetic embryology aims to develop embryo-like structures from stem cells to provide new insight into early stages of mammalian development. Recent advances in... (Review)
Review
Synthetic embryology aims to develop embryo-like structures from stem cells to provide new insight into early stages of mammalian development. Recent advances in synthetic embryology have highlighted the remarkable capacity of stem cells to self-organize under certain biochemical or biophysical stimulations, generating structures that recapitulate the fate and form of early mouse/human embryos, in which symmetry breaking, pattern formation, or proper morphogenesis can be observed spontaneously. Here we review recent progress on the design principles for different types of embryoids and discuss the impact of different biochemical and biophysical factors on the process of stem-cell self-organization. We also offer our thoughts about the principal future challenges.
Topics: Animals; Embryo, Mammalian; Embryonic Development; Humans; Mammals; Mice; Morphogenesis; Stem Cells
PubMed: 35988317
DOI: 10.1016/j.gde.2022.101970 -
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 -
Nature Nov 2020Current understandings of cell specification in early mammalian pre-implantation development are based mainly on mouse studies. The first lineage differentiation event... (Comparative Study)
Comparative Study
Current understandings of cell specification in early mammalian pre-implantation development are based mainly on mouse studies. The first lineage differentiation event occurs at the morula stage, with outer cells initiating a trophectoderm (TE) placental progenitor program. The inner cell mass arises from inner cells during subsequent developmental stages and comprises precursor cells of the embryo proper and yolk sac. Recent gene-expression analyses suggest that the mechanisms that regulate early lineage specification in the mouse may differ in other mammals, including human and cow. Here we show the evolutionary conservation of a molecular cascade that initiates TE segregation in human, cow and mouse embryos. At the morula stage, outer cells acquire an apical-basal cell polarity, with expression of atypical protein kinase C (aPKC) at the contact-free domain, nuclear expression of Hippo signalling pathway effectors and restricted expression of TE-associated factors such as GATA3, which suggests initiation of a TE program. Furthermore, we demonstrate that inhibition of aPKC by small-molecule pharmacological modulation or Trim-Away protein depletion impairs TE initiation at the morula stage. Our comparative embryology analysis provides insights into early lineage specification and suggests that a similar mechanism initiates a TE program in human, cow and mouse embryos.
Topics: Adaptor Proteins, Signal Transducing; Animals; Biological Evolution; Blastocyst Inner Cell Mass; Cattle; Cell Lineage; Cell Polarity; Ectoderm; Embryo, Mammalian; Female; GATA3 Transcription Factor; Gene Expression Regulation, Developmental; Hippo Signaling Pathway; Humans; Mice; Morula; Placenta; Pregnancy; Protein Kinase C; Protein Serine-Threonine Kinases; SOXB1 Transcription Factors; Signal Transduction; Transcription Factors; Transcription, Genetic; Trophoblasts; YAP-Signaling Proteins; Yolk Sac
PubMed: 32968278
DOI: 10.1038/s41586-020-2759-x -
Cell Nov 2013Cellular senescence disables proliferation in damaged cells, and it is relevant for cancer and aging. Here, we show that senescence occurs during mammalian embryonic...
Cellular senescence disables proliferation in damaged cells, and it is relevant for cancer and aging. Here, we show that senescence occurs during mammalian embryonic development at multiple locations, including the mesonephros and the endolymphatic sac of the inner ear, which we have analyzed in detail. Mechanistically, senescence in both structures is strictly dependent on p21, but independent of DNA damage, p53, or other cell-cycle inhibitors, and it is regulated by the TGF-β/SMAD and PI3K/FOXO pathways. Developmentally programmed senescence is followed by macrophage infiltration, clearance of senescent cells, and tissue remodeling. Loss of senescence due to the absence of p21 is partially compensated by apoptosis but still results in detectable developmental abnormalities. Importantly, the mesonephros and endolymphatic sac of human embryos also show evidence of senescence. We conclude that the role of developmentally programmed senescence is to promote tissue remodeling and propose that this is the evolutionary origin of damage-induced senescence.
Topics: Animals; Cellular Senescence; Cyclin-Dependent Kinase Inhibitor p21; Embryo, Mammalian; Embryonic Development; Endolymphatic Sac; Female; Humans; Kidney; Male; Mesonephros; Mice; Phosphatidylinositol 3-Kinases; Signal Transduction; Smad Proteins; Transforming Growth Factor beta
PubMed: 24238962
DOI: 10.1016/j.cell.2013.10.019 -
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 -
Nature Aug 2013Mammalian pre-implantation development is a complex process involving dramatic changes in the transcriptional architecture. We report here a comprehensive analysis of...
Mammalian pre-implantation development is a complex process involving dramatic changes in the transcriptional architecture. We report here a comprehensive analysis of transcriptome dynamics from oocyte to morula in both human and mouse embryos, using single-cell RNA sequencing. Based on single-nucleotide variants in human blastomere messenger RNAs and paternal-specific single-nucleotide polymorphisms, we identify novel stage-specific monoallelic expression patterns for a significant portion of polymorphic gene transcripts (25 to 53%). By weighted gene co-expression network analysis, we find that each developmental stage can be delineated concisely by a small number of functional modules of co-expressed genes. This result indicates a sequential order of transcriptional changes in pathways of cell cycle, gene regulation, translation and metabolism, acting in a step-wise fashion from cleavage to morula. Cross-species comparisons with mouse pre-implantation embryos reveal that the majority of human stage-specific modules (7 out of 9) are notably preserved, but developmental specificity and timing differ between human and mouse. Furthermore, we identify conserved key members (or hub genes) of the human and mouse networks. These genes represent novel candidates that are likely to be key in driving mammalian pre-implantation development. Together, the results provide a valuable resource to dissect gene regulatory mechanisms underlying progressive development of early mammalian embryos.
Topics: Alleles; Animals; Blastocyst; Cell Cycle; Embryo, Mammalian; Embryonic Development; Gene Expression Profiling; Gene Expression Regulation, Developmental; Humans; Mice; Morula; Oocytes; Sequence Analysis, RNA; Single-Cell Analysis
PubMed: 23892778
DOI: 10.1038/nature12364 -
International Journal of Molecular... Jan 2021For obvious reasons, such as, e.g., ethical concerns or sample accessibility, model systems are of highest importance to study the underlying molecular mechanisms of... (Review)
Review
For obvious reasons, such as, e.g., ethical concerns or sample accessibility, model systems are of highest importance to study the underlying molecular mechanisms of human maladies with the aim to develop innovative and effective therapeutic strategies. Since many years, animal models and highly proliferative transformed cell lines are successfully used for disease modelling, drug discovery, target validation, and preclinical testing. Still, species-specific differences regarding genetics and physiology and the limited suitability of immortalized cell lines to draw conclusions on normal human cells or specific cell types, are undeniable shortcomings. The progress in human pluripotent stem cell research now allows the growth of a virtually limitless supply of normal and DNA-edited human cells, which can be differentiated into various specific cell types. However, cells in the human body never fulfill their functions in mono-lineage isolation and diseases always develop in complex multicellular ecosystems. The recent advances in stem cell-based 3D organoid technologies allow a more accurate in vitro recapitulation of human pathologies. Embryoids are a specific type of such multicellular structures that do not only mimic a single organ or tissue, but the entire human conceptus or at least relevant components of it. Here we briefly describe the currently existing in vitro human embryo models and discuss their putative future relevance for disease modelling and drug discovery.
Topics: Animals; Cell Culture Techniques; Cell Differentiation; Cells, Cultured; Drug Discovery; Embryo, Mammalian; Embryonic Development; Human Embryonic Stem Cells; Humans; Models, Animal; Organoids; Pluripotent Stem Cells
PubMed: 33440617
DOI: 10.3390/ijms22020637 -
Developmental Biology May 2024Understanding the processes and mechanisms underlying early human embryo development has become an increasingly active and important area of research. It has potential... (Review)
Review
Understanding the processes and mechanisms underlying early human embryo development has become an increasingly active and important area of research. It has potential for insights into important clinical issues such as early pregnancy loss, origins of congenital anomalies and developmental origins of adult disease, as well as fundamental insights into human biology. Improved culture systems for preimplantation embryos, combined with the new tools of single cell genomics and live imaging, are providing new insights into the similarities and differences between human and mouse development. However, access to human embryo material is still restricted and extended culture of early embryos has regulatory and ethical concerns. Stem cell-derived models of different phases of human development can potentially overcome these limitations and provide a scalable source of material to explore the early postimplantation stages of human development. To date, such models are clearly incomplete replicas of normal development but future technological improvements can be envisaged. The ethical and regulatory environment for such studies remains to be fully resolved.
Topics: Humans; Pregnancy; Adult; Female; Animals; Mice; Embryonic Development; Embryo, Mammalian; Blastocyst; Stem Cells
PubMed: 38325560
DOI: 10.1016/j.ydbio.2024.02.001 -
Nature Feb 2024Recently, several studies using cultures of human embryos together with single-cell RNA-seq analyses have revealed differences between humans and mice, necessitating the...
Recently, several studies using cultures of human embryos together with single-cell RNA-seq analyses have revealed differences between humans and mice, necessitating the study of human embryos. Despite the importance of human embryology, ethical and legal restrictions have limited post-implantation-stage studies. Thus, recent efforts have focused on developing in vitro self-organizing models using human stem cells. Here, we report genetic and non-genetic approaches to generate authentic hypoblast cells (naive hPSC-derived hypoblast-like cells (nHyCs))-known to give rise to one of the two extraembryonic tissues essential for embryonic development-from naive human pluripotent stem cells (hPSCs). Our nHyCs spontaneously assemble with naive hPSCs to form a three-dimensional bilaminar structure (bilaminoids) with a pro-amniotic-like cavity. In the presence of additional naive hPSC-derived analogues of the second extraembryonic tissue, the trophectoderm, the efficiency of bilaminoid formation increases from 20% to 40%, and the epiblast within the bilaminoids continues to develop in response to trophectoderm-secreted IL-6. Furthermore, we show that bilaminoids robustly recapitulate the patterning of the anterior-posterior axis and the formation of cells reflecting the pregastrula stage, the emergence of which can be shaped by genetically manipulating the DKK1/OTX2 hypoblast-like domain. We have therefore successfully modelled and identified the mechanisms by which the two extraembryonic tissues efficiently guide the stage-specific growth and progression of the epiblast as it establishes the post-implantation landmarks of human embryogenesis.
Topics: Humans; Cell Differentiation; Embryo Implantation; Embryo, Mammalian; Embryonic Development; Germ Layers; Pluripotent Stem Cells; Interleukin-6; Gastrula; Amnion; Ectoderm; Intercellular Signaling Peptides and Proteins; Otx Transcription Factors
PubMed: 38052228
DOI: 10.1038/s41586-023-06871-2 -
Cell Stem Cell Jan 2022Studying human embryo development is technically and ethically challenging. An improved protocol to generate human embryo-like structures (blastoids) from human...
Studying human embryo development is technically and ethically challenging. An improved protocol to generate human embryo-like structures (blastoids) from human pluripotent stem cells (PSCs) (Kagawa et al., 2021) offers innovative opportunities to dissect the mechanisms of human embryogenesis.
Topics: Embryo, Mammalian; Embryonic Development; Humans; Pluripotent Stem Cells
PubMed: 34995497
DOI: 10.1016/j.stem.2021.12.006