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American Journal of Reproductive... Mar 2016Blastocyst implantation into the uterine endometrium establishes early pregnancy. This event is regulated by blastocyst- and/or endometrium-derived molecular factors... (Review)
Review
Blastocyst implantation into the uterine endometrium establishes early pregnancy. This event is regulated by blastocyst- and/or endometrium-derived molecular factors which include hormones, growth factors, cell adhesion molecules, cytokines and proteases. Their coordinated expression and function are critical for a viable pregnancy. A rate-limiting event that immediately precedes implantation is the hatching of blastocyst. Ironically, blastocyst hatching is tacitly linked to peri-implantation events, although it is a distinct developmental phenomenon. The exact molecular network regulating hatching is still unclear. A number of implantation-associated molecular factors are expressed in the pre-implanting blastocyst. Among others, cytokines, expressed by peri-implantation blastocysts, are thought to be important for hatching, making blastocysts implantation competent. Pro-inflammatory (IL-6, LIF, GM-CSF) and anti-inflammatory (IL-11, CSF-1) cytokines improve hatching rates; they modulate proteases (MMPs, tPAs, cathepsins and ISP1). However, functional involvement of cytokines and their specific mediation of hatching-associated proteases are unclear. There is a need to understand mechanistic roles of cytokines and proteases in blastocyst hatching. This review will assess the available knowledge on blastocyst-derived pro-inflammatory and anti-inflammatory cytokines and their role in potentially regulating blastocyst hatching. They have implications in our understanding of early embryonic loss and infertility in mammals, including humans.
Topics: Animals; Blastocyst; Cytokines; Embryo Implantation; Endometrium; Female; Humans; Pregnancy; Trophoblasts
PubMed: 26706391
DOI: 10.1111/aji.12464 -
Molecular Reproduction and Development Sep 2017Appropriate embryonic and fetal development significantly impact pregnancy success and, therefore, the efficiency of swine production. The pre-implantation period of... (Review)
Review
Appropriate embryonic and fetal development significantly impact pregnancy success and, therefore, the efficiency of swine production. The pre-implantation period of porcine pregnancy is characterized by several developmental hallmarks, which are initiated by the dramatic morphological change that occurs as pig blastocysts elongate from spherical to filamentous blastocysts. Deficiencies in blastocyst elongation contribute to approximately 20% of embryonic loss, and have a direct influence on within-litter birth weight variation. Although factors identified within the uterine environment may play a role in blastocyst elongation, little is known about the exact mechanisms by which porcine (or other species') blastocysts initiate and progress through the elongation process. This is partly due to the difficulty of replicating elongation in vitro, which would allow for its study in a controlled environment and in real-time. We developed a three dimensional (3-D) culture system using alginate hydrogel matrices that can encapsulate pig blastocysts, maintain viability and blastocyst architecture, and facilitate reproducible morphological changes with corresponding expression of steroidogenic enzyme transcripts and estrogen production, consistent with the initiation of elongation in vivo. This review highlights key aspects of the pre-implantation period of porcine pregnancy and the difficulty of studying blastocyst elongation in vivo or by using in vitro systems. This review also provides insights on the utility of 3-D hydrogels to study blastocyst elongation continuously and in real-time as a complementary and confirmatory approach to in vivo analysis.
Topics: Alginates; Animals; Blastocyst; Embryo Culture Techniques; Glucuronic Acid; Hexuronic Acids; Hydrogels; Swine
PubMed: 28407335
DOI: 10.1002/mrd.22814 -
Methods in Molecular Biology (Clifton,... 2020The ability to delete the function of an endogenous gene in the mouse was made possible by the development of embryonic stem (ES) cells, pluripotent cells that retain...
The ability to delete the function of an endogenous gene in the mouse was made possible by the development of embryonic stem (ES) cells, pluripotent cells that retain the ability to develop into all tissues of a developing embryo. The ability to genetically modify these cells followed, allowing targeted mutation of ES cells in vitro and the deletion of specific gene function. However, regardless of the simplicity or complexity of the genetic modification, all ES cells require injection into host embryos to establish pregnancies and result in chimeric mice. Blastocysts are commonly used as the host embryos for this purpose, as it is relatively easy to inject cells into the blastocoel cavity of the developing embryo. This chapter describes the procedure for injection of ES cells into blastocyst stage embryos for the generation of knockout mice.
Topics: Animals; Blastocyst; Chimera; Embryo Transfer; Embryonic Stem Cells; Female; Mice; Mice, Knockout; Microinjections; Pregnancy
PubMed: 31512208
DOI: 10.1007/978-1-4939-9837-1_6 -
Cytogenetic and Genome Research 2011Studies of human cleavage stage embryos, 3 days after fertilization of the oocyte, have revealed remarkably high levels of chromosome abnormality. In addition to meiotic... (Review)
Review
Studies of human cleavage stage embryos, 3 days after fertilization of the oocyte, have revealed remarkably high levels of chromosome abnormality. In addition to meiotic errors derived from the gametes, principally the oocyte, mitotic errors occurring after fertilization are also common, leading to widespread chromosomal mosaicism. The prevalence of chromosome anomalies in embryos may explain the relatively poor fertility and fecundity in humans and the low success rates of assisted reproductive treatments (e.g., IVF). While much is known concerning the incidence of aneuploidy during the first 3 days following fertilization, it is only in the last couple of years that large numbers of embryos at the final stage of preimplantation development, the blastocyst stage, 5 days after fertilization, have been subjected to detailed analysis. Here we discuss the latest data from the comprehensive cytogenetic analysis of blastocysts. These findings indicate that the majority of selection against chromosome abnormalities does not occur until the time of implantation or shortly after, with aneuploidy typically affecting more than 50% of blastocysts. Additionally, clinical results presented suggest that screening of blastocyst stage embryos for chromosome abnormality, with preferential transfer to the uterus of those found to be euploid, may help to improve the success rates of assisted reproductive treatments.
Topics: Aneuploidy; Animals; Blastocyst; Cytogenetic Analysis; Humans; In Situ Hybridization, Fluorescence; Mosaicism
PubMed: 21252488
DOI: 10.1159/000323500 -
Molecular Human Reproduction Oct 1997Cell death is a widespread feature in the blastocysts of many mammals. Isolated cells in both the inner cell mass and the trophectoderm undergo cell death. These dying... (Review)
Review
Cell death is a widespread feature in the blastocysts of many mammals. Isolated cells in both the inner cell mass and the trophectoderm undergo cell death. These dying cells appear morphologically to be undergoing apoptosis. In mouse blastocysts, a wave of cell death is seen in vivo, suggesting that it plays an important role in normal development. However, cell death is increased under suboptimal culture conditions. There is evidence that levels of cell death are regulated by 'survival' factors produced both by the embryo itself and by the maternal reproductive tract. The role of cell death in development is unknown, but could involve the elimination of abnormal cells, or a sublineage of cells with an inappropriate developmental potential. Work in other systems has demonstrated that cell death is regulated by the activity of apoptosis genes. Whether these genes are implicated in blastocyst cell death, and the reasons for apoptosis in the early embryo, remain to be determined.
Topics: Animals; Blastocyst; Cell Death; Humans
PubMed: 9395266
DOI: 10.1093/molehr/3.10.919 -
Journal of Stem Cells 2013Blastocyst activation, a process for the blastocyst to achieve implantation competency is equally important as attainment of uterine receptivity for the success of... (Review)
Review
Blastocyst activation, a process for the blastocyst to achieve implantation competency is equally important as attainment of uterine receptivity for the success of embryo implantation. While a wide range of regulatory molecules have been identified as essential players in conferring uterine receptivity in both laboratory animal models and humans, it remains largely unknown how blastocysts achieve implantation competency. This chapter will highlight our current knowledge about the mechanisms governing the process of blastocyst activation. A better understanding of this periimplantation event is hoped to alleviate female infertility and help to develop novel contraceptives and new strategies for accessing embryo quality in clinical practice.
Topics: Animals; Blastocyst; Embryo Implantation; Embryo Transfer; Humans; Signal Transduction; Tissue Survival
PubMed: 24698984
DOI: No ID Found -
JBRA Assisted Reproduction Jan 2020In this study we investigate the correlation between spontaneous blastocyst collapse and pregnancy outcome.
OBJECTIVE
In this study we investigate the correlation between spontaneous blastocyst collapse and pregnancy outcome.
METHODS
This is a retrospective study performed at Edinburgh Assisted Conception Programme, EFREC, Royal Infirmary of Edinburgh, UK. Embryos were cultured individually in 6.0% CO2, 5.0% O2, 89.0% N2, using single step medium (GTL™ Vitrolife, Göteborg, Sweden) and selected for transfer using standard morphological criteria. Using the EmbryoScope™ time-lapse monitoring (TLM), blastocysts collapse was analyzed by measuring the maximum volume reduction and defined as having collapsed if there was >50% volume reduction. Couples undergoing IVF/ICSI treatment and having an elective single embryo transfer (eSET) at blastocyst stage were included in this study. After the embryo transfer, retrospectively, each blastocyst was allocated to one of two groups (collapsed or not collapsed). 62 blastocysts collapsed once or more during development (17.4%), the remaining 294 showed no collapse (82.6%).
RESULTS
A significantly higher implantation rate (IR) of 61.2% and ongoing pregnancy rate (OPR) of 53.7% was observed when blastocysts which had not collapsed were replaced compared to cycles in which collapsed blastocysts were replaced (IR rate 22.6% and OPR 17.7%).
CONCLUSION
This study demonstrated that human blastocysts which collapse spontaneously during in vitro development are less likely to implant and generate a pregnancy compared with embryos which do not. Although this is a retrospective study, the results establish the utility of collapse episodes as new marker of embryo selection following eSET at blastocyst stage.
Topics: Adult; Blastocyst; Embryo Culture Techniques; Female; Humans; Pregnancy; Pregnancy Outcome; Retrospective Studies; Single Embryo Transfer
PubMed: 31397550
DOI: 10.5935/1518-0557.20190044 -
Reproductive Biomedicine Online Jul 2019How can the kinetics of human blastocyst expansion be used to evaluate an embryo's ploidy identified using preimplantation genetic testing for aneuploidy (PGT-A)? (Observational Study)
Observational Study
RESEARCH QUESTION
How can the kinetics of human blastocyst expansion be used to evaluate an embryo's ploidy identified using preimplantation genetic testing for aneuploidy (PGT-A)?
DESIGN
This was a retrospective observational study of 188 autologous blastocysts from 34 sequential treatment cycles using PGT-A and blastocyst biopsy. Using time-lapse imaging, blastocyst expansion was evaluated using a quantitative standardized expansion assay (qSEA). Trophectoderm cell division was examined in selected, unbiopsied embryos (n = 7) to evaluate the contribution of mitosis to the expansion rate.
RESULTS
The averaged euploid blastocyst expansion rate was significantly (52.8%) faster than in aneuploid blastocysts (P = 0.0041). Scatterplots, representing 'expansion maps', revealed that both populations showed a similarly overlapping distribution of blastocyst formation times at 80-140 h from fertilization. Euploidy and aneuploidy were better distinguished in regions of higher and lower expansion, respectively, in expansion maps. Based upon the expansion slopes, rank-ordering of individual embryos within cohorts resulted in more than 90% euploid embryos in the first two ranks in patients less than 35 years of age. Additional detailed time-lapse image analysis provided evidence that rapid expansion was associated with robust, integrative cellular mitosis in trophectoderm cells.
CONCLUSIONS
The kinetics of human blastocyst expansion are related to an embryo's ploidy. These preliminary observations describe a new quantitative, non-invasive approach to embryo assessment that may be useful to identify single blastocysts for transfer, particularly in younger patient groups. However, this approach may also be useful for euploid embryo selection after PGT-A. The results support the hypothesis that aneuploidy universally impairs general cellular processes, including cell division, in differentiated cells.
Topics: Adult; Aneuploidy; Biomarkers; Blastocyst; Cell Separation; Cells, Cultured; Cleavage Stage, Ovum; Embryo Culture Techniques; Embryo Transfer; Embryo, Mammalian; Female; Genetic Testing; Humans; Ploidies; Pregnancy; Preimplantation Diagnosis; Retrospective Studies; Young Adult
PubMed: 31130402
DOI: 10.1016/j.rbmo.2019.01.010 -
Cellular Signalling Jan 2019Thiamethoxam (TMX) is a neonicotinoid insecticide. It has specific high toxicity to insects. Residues of TMX have been detected in various crops. Early embryo quality is...
Thiamethoxam (TMX) is a neonicotinoid insecticide. It has specific high toxicity to insects. Residues of TMX have been detected in various crops. Early embryo quality is vital for fertility. Excessive production of reactive oxygen species (ROS) can override embryonic antioxidant defenses, producing oxidative stress that triggers apoptosis, necrosis, and/or permanent DNA damage responses in the early embryo. Comparative studies have indicated that TMX hepatotoxicity is significant in mammals in acute tests, but little is known about accumulated chronic toxicity in early embryonic development. Porcine embryos were obtained here by the parthenogenetic activation of meiosis II oocytes and cultured in the PZM-5 medium with or without TMX. These embryos were evaluated by various methods. The expansion and hatching of blastocysts treated with TMX decreased by 21.73% and 16.71%, respectively, as compared with controls. In an analysis of 5-bromo-2-deoxyuridine (BrdU) incorporation, the rate of cell proliferation was 44.33% lower as compared with expanded blastocysts of the control group. ROS and γH2AX levels were higher in the TMX group than in the control group. Real-time reverse-transcription polymerase chain reaction showed that Sod1 expression increased and the expression of Mnsod, Gpx1, Igta5, and Cox2 decreased. A CDK1 kinase assay revealed that maturation-promoting factor (MPF) activity diminished by 31.41% in expanding blastocysts. In conclusion, these results suggest that TMX inhibits blastocyst expansion and hatching by ROS-induced DNA damage checkpoint activation, which inhibits the activation of MPF and cell cycle progression in porcine blastocysts.
Topics: Animals; Blastocyst; Embryonic Development; Female; G2 Phase Cell Cycle Checkpoints; Insecticides; Pregnancy; Reactive Oxygen Species; Swine; Thiamethoxam
PubMed: 30145217
DOI: 10.1016/j.cellsig.2018.08.014 -
Proceedings of the National Academy of... Nov 1993The present investigation studied the influence of the blastocyst's state of activity on the "window" of implantation in the receptive uterus in the mouse. The receptive...
The present investigation studied the influence of the blastocyst's state of activity on the "window" of implantation in the receptive uterus in the mouse. The receptive state of the uterus is defined as the limited time when the uterine milieu is favorable to blastocyst acceptance and implantation. In the mouse, implantation occurs on day 4 (day 1 = vaginal plug). Ovariectomy in the morning of day 4 prior to preimplantation estrogen secretion results in blastocyst dormancy and delayed implantation. These conditions are maintained by continued progesterone (P4) treatment but can be terminated with an injection of estrogen leading to blastocyst activation and subsequent implantation. Blastocyst transfers into intact pseudopregnant mice demonstrated that the window of implantation on day 4 remains open at least through 1800 h for normal day 4 blastocysts but only up to 1400 h for dormant blastocysts. These results suggested that the blastocyst's state of activity influenced the normally operative window of implantation in the receptive uterus. This finding was further confirmed by inducing conditions of delayed implantation in pregnant donors and pseudopregnant recipients. They were ovariectomized on the morning of day 4 and maintained with daily injections of P4 from days 5 to 7. On day 7, dormant blastocysts from P4-treated delayed donors were transferred into the uteri of P4-treated delayed pseudopregnant recipients at 1, 2, 4, or 8 h after an injection of 17 beta-estradiol (E2). Dormant blastocysts transferred into delayed recipients at 1 h after E2 treatment resulted in implantation in most of the animals as compared to complete failure of blastocysts to implant after transfer to P4-treated delayed recipients at 4 or 8 h after E2 treatment. However, implantation did occur in P4-treated delayed recipients at these later hours of E2 treatment when the P4-treated delayed donors also received E2 prior to blastocyst transfer. Furthermore, the majority of day 4 normal blastocysts implanted when transferred into P4-treated delayed recipients even at 16 h after E2 treatment. Interestingly, day 7 dormant blastocysts cultured for 8 or 24 h for in vitro activation failed to implant after transfer to P4-treated delayed pseudopregnant recipients at 4 ir 8 h after E2 treatment, although they did implant after transfer at 1 h after E2 treatment. As expected, normal day 4 blastocysts failed to implant after transfer to P4-treated delayed pseudopregnant recipients. Thus, these results establish that the blastocyst's state of activity alters the timing of implantation (window) in the receptive uterus. Thus, the window for successful implantation could be defined as a limited time span when the activated stage of the blastocyst is superimposed on the receptive state of the uterus. This window remains open for a shorter period for dormant blastocysts than for a normal or dormant blastocysts after E2 activation. Furthermore, dormant blastocysts, which apparently achieved metabolic activation in vitro, failed to attain the same status as blastocysts activated in utero by E2 for implantation into the receptive uterus. A key finding of this investigation is that E2 induces very rapidly, but transiently (1 h), a factor(s) in the P4-primed uterus that activates the dormant blastocysts for implantation in the receptive uterus.
Topics: Animals; Blastocyst; Embryo Implantation; Embryo Transfer; Estradiol; Female; Male; Mice; Mice, Inbred Strains; Pregnancy; Pseudopregnancy; Time Factors; Uterus; Vasectomy
PubMed: 8234270
DOI: 10.1073/pnas.90.21.10159