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Developmental Cell Jan 2022There has been recent renewed interest in studying human early embryonic development. The advent of improved culture conditions to maintain blastocysts in vitro for an... (Review)
Review
There has been recent renewed interest in studying human early embryonic development. The advent of improved culture conditions to maintain blastocysts in vitro for an extended period and the emerging stem-cell-based models of the blastocyst and peri-implantation embryos have provided new information that is relevant to early human embryogenesis. However, the mechanism of lineage development and embryonic patterning, and the molecular pathways involved in their regulation, are still not well understood. Interest in human embryonic development has been reinvigorated recently given numerous technical advances. In this review, Rossant and Tam discuss new insights into human embryogenesis gathered from successes in culturing human embryos in vitro and stem-cell-based embryo models. Then they outline what questions still need answering.
Topics: Blastocyst; Body Patterning; Cell Lineage; Embryo Culture Techniques; Embryo, Mammalian; Embryonic Development; Embryonic Stem Cells; Gastrulation; Gene Expression Regulation, Developmental; Humans
PubMed: 35077679
DOI: 10.1016/j.devcel.2021.12.022 -
Nature Jan 2022One week after fertilization, human embryos implant into the uterus. This event requires the embryo to form a blastocyst consisting of a sphere encircling a cavity...
One week after fertilization, human embryos implant into the uterus. This event requires the embryo to form a blastocyst consisting of a sphere encircling a cavity lodging the embryo proper. Stem cells can form a blastocyst model that we called a blastoid. Here we show that naive human pluripotent stem cells cultured in PXGL medium and triply inhibited for the Hippo, TGF-β and ERK pathways efficiently (with more than 70% efficiency) form blastoids generating blastocyst-stage analogues of the three founding lineages (more than 97% trophectoderm, epiblast and primitive endoderm) according to the sequence and timing of blastocyst development. Blastoids spontaneously form the first axis, and we observe that the epiblast induces the local maturation of the polar trophectoderm, thereby endowing blastoids with the capacity to directionally attach to hormonally stimulated endometrial cells, as during implantation. Thus, we propose that such a human blastoid is a faithful, scalable and ethical model for investigating human implantation and development.
Topics: Blastocyst; Cell Differentiation; Cell Lineage; Embryo Implantation; Embryonic Development; Female; Humans; Pluripotent Stem Cells
PubMed: 34856602
DOI: 10.1038/s41586-021-04267-8 -
Cell Stem Cell May 2023Understanding the mechanisms of blastocyst formation and implantation is critical for improving farm animal reproduction but is hampered by a limited supply of embryos....
Understanding the mechanisms of blastocyst formation and implantation is critical for improving farm animal reproduction but is hampered by a limited supply of embryos. Here, we developed an efficient method to generate bovine blastocyst-like structures (termed blastoids) via assembling bovine trophoblast stem cells and expanded potential stem cells. Bovine blastoids resemble blastocysts in morphology, cell composition, single-cell transcriptomes, in vitro growth, and the ability to elicit maternal recognition of pregnancy following transfer to recipient cows. Bovine blastoids represent an accessible in vitro model for studying embryogenesis and improving reproductive efficiency in livestock species.
Topics: Pregnancy; Female; Cattle; Animals; Blastocyst; Trophoblasts; Embryo Implantation; Embryonic Development; Stem Cells; Cell Culture Techniques
PubMed: 37146582
DOI: 10.1016/j.stem.2023.04.003 -
Cellular and Molecular Life Sciences :... Jun 2022Human pregnancy depends on the proper development of the embryo prior to implantation and the implantation of the embryo into the uterine wall. During the... (Review)
Review
Human pregnancy depends on the proper development of the embryo prior to implantation and the implantation of the embryo into the uterine wall. During the pre-implantation phase, formation of the morula is followed by internalization of blastomeres that differentiate into the pluripotent inner cell mass lineage, while the cells on the surface undergo polarization and differentiate into the trophectoderm of the blastocyst. The trophectoderm mediates apposition and adhesion of the blastocyst to the uterine epithelium. These processes lead to a stable contact between embryonic and maternal tissues, resulting in the formation of a new organ, the placenta. During implantation, the trophectoderm cells start to differentiate and form the basis for multiple specialized trophoblast subpopulations, all of which fulfilling specific key functions in placentation. They either differentiate into polar cells serving typical epithelial functions, or into apolar invasive cells that adapt the uterine wall to progressing pregnancy. The composition of these trophoblast subpopulations is crucial for human placenta development and alterations are suggested to result in placenta-associated pregnancy pathologies. This review article focuses on what is known about very early processes in human reproduction and emphasizes on morphological and functional aspects of early trophoblast differentiation and subpopulations.
Topics: Blastocyst; Cell Differentiation; Embryo Implantation; Female; Humans; Placenta; Placentation; Pregnancy; Trophoblasts
PubMed: 35661923
DOI: 10.1007/s00018-022-04377-0 -
International Journal of Molecular... Mar 2020Somatic cell nuclear transfer (SCNT) has been an area of interest in the field of stem cell research and regenerative medicine for the past 20 years. The main biological... (Review)
Review
Somatic cell nuclear transfer (SCNT) has been an area of interest in the field of stem cell research and regenerative medicine for the past 20 years. The main biological goal of SCNT is to reverse the differentiated state of a somatic cell, for the purpose of creating blastocysts from which embryonic stem cells (ESCs) can be derived for therapeutic cloning, or for the purpose of reproductive cloning. However, the consensus is that the low efficiency in creating normal viable offspring in animals by SCNT (1-5%) and the high number of abnormalities seen in these cloned animals is due to epigenetic reprogramming failure. In this review we provide an overview of the current literature on SCNT, focusing on protocol development, which includes early SCNT protocol deficiencies and optimizations along with donor cell type and cell cycle synchrony; epigenetic reprogramming in SCNT; current protocol optimizations such as nuclear reprogramming strategies that can be applied to improve epigenetic reprogramming by SCNT; applications of SCNT; the ethical and legal implications of SCNT in humans; and specific lessons learned for establishing an optimized SCNT protocol using a mouse model.
Topics: Animals; Blastocyst; Cell Differentiation; Cellular Reprogramming; Cloning, Organism; Embryo, Mammalian; Embryonic Development; Embryonic Stem Cells; Epigenomics; Eye Enucleation; Humans; Nuclear Transfer Techniques; Oocytes
PubMed: 32230814
DOI: 10.3390/ijms21072314 -
Fertility and Sterility May 2021To study how the attributes of mosaicism identified during preimplantation genetic testing for aneuploidy relate to clinical outcomes, in order to formulate a ranking...
OBJECTIVE
To study how the attributes of mosaicism identified during preimplantation genetic testing for aneuploidy relate to clinical outcomes, in order to formulate a ranking system of mosaic embryos for intrauterine transfer.
DESIGN
Compiled analysis.
SETTING
Multi-center.
PATIENT(S)
A total of 5,561 euploid blastocysts and 1,000 mosaic blastocysts used in clinical transfers in patients undergoing fertility treatment.
INTERVENTION(S)
None.
MAIN OUTCOME MEASURE(S)
Implantation (gestational sac), ongoing pregnancy, birth, and spontaneous abortion (miscarriage before 20 weeks of gestation).
RESULT(S)
The euploid group had significantly more favorable rates of implantation and ongoing pregnancy/birth (OP/B) compared with the combined mosaic group or the mosaic group affecting only whole chromosomes (implantation: 57.2% vs. 46.5% vs. 41.8%; OP/B: 52.3% vs. 37.0% vs. 31.3%), as well as lower likelihood of spontaneous abortion (8.6% vs. 20.4% vs. 25%). Whole-chromosome mosaic embryos with level (percent aneuploid cells) <50% had significantly more favorable outcomes than the ≥50% group (implantation: 44.5% vs. 30.4%; OP/B: 36.1% vs. 19.3%). Mosaic type (nature of the aneuploidy implicated in mosaicism) affected outcomes, with a significant correlation between number of affected chromosomes and unfavorable outcomes. This ranged from mosaicism involving segmental abnormalities to complex aneuploidies affecting three or more chromosomes (implantation: 51.6% vs. 30.4%; OP/B: 43.1% vs. 20.8%). Combining mosaic level, type, and embryo morphology revealed the order of subcategories regarding likelihood of positive outcome.
CONCLUSION(S)
This compiled analysis revealed traits of mosaicism identified with preimplantation genetic testing for aneuploidy that affected outcomes in a statistically significant manner, enabling the formulation of an evidence-based prioritization scheme for mosaic embryos in the clinic.
Topics: Adult; Aneuploidy; Blastocyst; Data Interpretation, Statistical; Embryo Implantation; Embryo Transfer; Embryonic Development; Female; Fertilization in Vitro; Genetic Testing; Humans; Infant, Newborn; Infertility; Karyotyping; Male; Mosaicism; Pregnancy; Pregnancy Outcome; Pregnancy Rate; Preimplantation Diagnosis; Prognosis; Treatment Outcome
PubMed: 33685629
DOI: 10.1016/j.fertnstert.2020.11.041 -
Cell Oct 2019A single mouse blastomere from an embryo until the 8-cell stage can generate an entire blastocyst. Whether laboratory-cultured cells retain a similar generative capacity...
A single mouse blastomere from an embryo until the 8-cell stage can generate an entire blastocyst. Whether laboratory-cultured cells retain a similar generative capacity remains unknown. Starting from a single stem cell type, extended pluripotent stem (EPS) cells, we established a 3D differentiation system that enabled the generation of blastocyst-like structures (EPS-blastoids) through lineage segregation and self-organization. EPS-blastoids resembled blastocysts in morphology and cell-lineage allocation and recapitulated key morphogenetic events during preimplantation and early postimplantation development in vitro. Upon transfer, some EPS-blastoids underwent implantation, induced decidualization, and generated live, albeit disorganized, tissues in utero. Single-cell and bulk RNA-sequencing analysis revealed that EPS-blastoids contained all three blastocyst cell lineages and shared transcriptional similarity with natural blastocysts. We also provide proof of concept that EPS-blastoids can be generated from adult cells via cellular reprogramming. EPS-blastoids provide a unique platform for studying early embryogenesis and pave the way to creating viable synthetic embryos by using cultured cells.
Topics: Animals; Blastocyst; Cell Differentiation; Cell Line; Cell Lineage; Cells, Cultured; Cellular Reprogramming Techniques; Embryo Implantation; Female; Humans; Induced Pluripotent Stem Cells; Male; Mice; Mice, Inbred C57BL; Mice, Inbred ICR; Mouse Embryonic Stem Cells; Research Embryo Creation; Transcriptome
PubMed: 31626770
DOI: 10.1016/j.cell.2019.09.029 -
Cell Apr 2021Interspecies chimera formation with human pluripotent stem cells (hPSCs) represents a necessary alternative to evaluate hPSC pluripotency in vivo and might constitute a...
Interspecies chimera formation with human pluripotent stem cells (hPSCs) represents a necessary alternative to evaluate hPSC pluripotency in vivo and might constitute a promising strategy for various regenerative medicine applications, including the generation of organs and tissues for transplantation. Studies using mouse and pig embryos suggest that hPSCs do not robustly contribute to chimera formation in species evolutionarily distant to humans. We studied the chimeric competency of human extended pluripotent stem cells (hEPSCs) in cynomolgus monkey (Macaca fascicularis) embryos cultured ex vivo. We demonstrate that hEPSCs survived, proliferated, and generated several peri- and early post-implantation cell lineages inside monkey embryos. We also uncovered signaling events underlying interspecific crosstalk that may help shape the unique developmental trajectories of human and monkey cells within chimeric embryos. These results may help to better understand early human development and primate evolution and develop strategies to improve human chimerism in evolutionarily distant species.
Topics: Animals; Blastocyst; Cell Differentiation; Cell Lineage; Cells, Cultured; Chimerism; Embryo, Mammalian; Female; Humans; Macaca fascicularis; Pluripotent Stem Cells; RNA-Seq; Single-Cell Analysis; Transcriptome
PubMed: 33861963
DOI: 10.1016/j.cell.2021.03.020 -
The EMBO Journal Sep 2023Embryo implantation into the uterus marks a key transition in mammalian development. In mice, implantation is mediated by the trophoblast and is accompanied by a...
Embryo implantation into the uterus marks a key transition in mammalian development. In mice, implantation is mediated by the trophoblast and is accompanied by a morphological transition from the blastocyst to the egg cylinder. However, the roles of trophoblast-uterine interactions in embryo morphogenesis during implantation are poorly understood due to inaccessibility in utero and the remaining challenges to recapitulate it ex vivo from the blastocyst. Here, we engineer a uterus-like microenvironment to recapitulate peri-implantation development of the whole mouse embryo ex vivo and reveal essential roles of the physical embryo-uterine interaction. We demonstrate that adhesion between the trophoblast and the uterine matrix is required for in utero-like transition of the blastocyst to the egg cylinder. Modeling the implanting embryo as a wetting droplet links embryo shape dynamics to the underlying changes in trophoblast adhesion and suggests that the adhesion-mediated tension release facilitates egg cylinder formation. Light-sheet live imaging and the experimental control of the engineered uterine geometry and trophoblast velocity uncovers the coordination between trophoblast motility and embryo growth, where the trophoblast delineates space for embryo morphogenesis.
Topics: Female; Mice; Animals; Embryo Implantation; Blastocyst; Trophoblasts; Uterus; Embryonic Development; Mammals
PubMed: 37522872
DOI: 10.15252/embj.2022113280 -
International Journal of Molecular... Jul 2020Nobiletin is a polymethoxylated flavonoid isolated from citrus fruits with wide biological effects, including inhibition of reactive oxygen species (ROS) production and...
Nobiletin is a polymethoxylated flavonoid isolated from citrus fruits with wide biological effects, including inhibition of reactive oxygen species (ROS) production and cell cycle regulation, important factors for oocyte in vitro maturation (IVM). Therefore, the objective of the present study was to evaluate the antioxidant activity of nobiletin during IVM on matured bovine oocyte quality (nuclear and cytoplasmic maturation; oocyte mitochondrial activity; intracellular ROS and glutathione (GSH) levels) and their developmental competence, steroidogenesis of granulosa cells after maturation, as well as quantitative changes of gene expression in matured oocytes, their cumulus cells, and resulting blastocysts. Bovine cumulus-oocyte complexes were in vitro matured in TCM-199 +10% fetal calf serum (FCS) and 10 ng/mL epidermal growth factor (EGF) (Control) supplemented with 10, 25, 50, or 100 μM of nobiletin (Nob10, Nob25, Nob50, and Nob100, respectively) or 0.1% dimethyl sulfoxide (CDMSO: vehicle for nobiletin dilution). A significantly higher percentage of matured oocytes in metaphase II was observed in Nob25 and Nob50 compared to other groups. Similarly, cleavage rate and cumulative blastocyst yield on Days 7 and 8 were significantly higher for Nob25 and Nob50 groups. Oocytes matured with 25 and 50 μM nobiletin showed a higher rate of migration of cortical granules and mitochondrial activity and a reduction in the ROS and GSH content in comparison with all other groups. This was linked to a modulation in the expression of genes related to metabolism (), communication (), apoptosis (), maturation ( and ), and oxidative stress ( and ). In conclusion, nobiletin offers a novel alternative for counteracting the effects of the increase in the production of ROS during IVM, improves oocyte nuclear and cytoplasmic maturation, and subsequent embryo development and quality in cattle.
Topics: Animals; Antioxidants; Blastocyst; Cattle; Cumulus Cells; Embryonic Development; Female; Flavones; In Vitro Oocyte Maturation Techniques; Oocytes
PubMed: 32727154
DOI: 10.3390/ijms21155340