A description of 34 human ova within the first 17 days of development

Hertig, Arthur T.; Rock, John; Adams, Eleanor C.

doi:10.1002/aja.1000980306

Cited by 603 publications

(245 citation statements)

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“…(There is some confusion over this: in three publications 38, 91, 97 , 21 embryos are described as normal and 13 as abnormal. It appears that the three alternatively described embryos (C-8299; C-8000; C-8290) were originally defined as abnormal based on their position or depth of implantation 38 .) Table 4 provides information about the 34 embryos found in these 107 women.…”

Section: What the Data Saymentioning

confidence: 99%

Early embryo mortality in natural human reproduction: What the data say

Jarvis

2016

F1000Res

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It is generally accepted that natural human embryo mortality during pregnancy is high – losses of 70% and higher from fertilisation to birth are frequently claimed. The first external sign of pregnancy occurs two weeks after fertilisation with a missed menstrual period. Establishing the fate of embryos before this is challenging, and hampered by a lack of data on the efficiency of fertilisation under natural conditions. Four distinct sources are cited to justify quantitative claims regarding embryo loss: (i) a hypothesis published by Roberts & Lowe in The Lancet is widely cited but has no quantitative value; (ii) life table analyses give consistent assessments of clinical pregnancy loss, but cannot illuminate losses at earlier stages of development; (iii) studies that measure human chorionic gonadotrophin (hCG) reveal losses in the second week of development and beyond, but not before; and (iv) the classic studies of Hertig and Rock offer the only direct insight into the fate of human embryos from fertilisation under natural conditions. Re-examination of Hertig’s data demonstrates that his estimates for fertilisation rate and early embryo loss are highly imprecise and casts doubt on the validity of his numerical analysis. A recent re-analysis of hCG study data suggests that approximately 40-60% of embryos may be lost between fertilisation and birth, although this will vary substantially between individual women. In conclusion, it is clear that some published estimates of natural embryo mortality are exaggerated. Although available data do not provide a precise estimate, natural human embryo mortality is lower than is often claimed.

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Section: What the Data Saymentioning

confidence: 99%

Early embryo mortality in natural human reproduction: What the data say

Jarvis

2016

F1000Res

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“…Unfortunately, this period of early pregnancy is poorly studied because of the lack of available human tissue. Most of what is known has come from older literature (68)(69)(70), archived samples (71), and from analogies drawn from histological studies on nonhuman primates (71)(72)(73). As the primate embryo implants, a penetrating mass of invasive STB forms in the implantation zone and soon surrounds the conceptus.…”

Section: Release Of Infection-competent Virus By Esc and Esc-derived mentioning

confidence: 99%

Vulnerability of primitive human placental trophoblast to Zika virus

Sheridan

Yunusov

Balaraman

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

157

155

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Infection of pregnant women by Asian lineage strains of Zika virus (ZIKV) has been linked to brain abnormalities in their infants, yet it is uncertain when during pregnancy the human conceptus is most vulnerable to the virus. We have examined two models to study susceptibility of human placental trophoblast to ZIKV: cytotrophoblast and syncytiotrophoblast derived from placental villi at term and colonies of trophoblast differentiated from embryonic stem cells (ESC). The latter appear to be analogous to the primitive placenta formed during implantation. The cells from term placentas, which resist infection, do not express genes encoding most attachment factors implicated in ZIKV entry but do express many genes associated with antiviral defense. By contrast, the ESC-derived trophoblasts possess a wide range of attachment factors for ZIKV entry and lack components of a robust antiviral response system. These cells, particularly areas of syncytiotrophoblast within the colonies, quickly become infected, produce infectious virus and undergo lysis within 48 h after exposure to low titers (multiplicity of infection > 0.07) of an African lineage strain (MR766 Uganda: ZIKVU) considered to be benign with regards to effects on fetal development. Unexpectedly, lytic effects required significantly higher titers of the presumed more virulent FSS13025 Cambodia (ZIKVC). Our data suggest that the developing fetus might be most vulnerable to ZIKV early in the first trimester before a protective zone of mature villous trophoblast has been established. Additionally, MR766 is highly trophic toward primitive trophoblast, which may put the early conceptus of an infected mother at high risk for destruction.

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“…The first coincides with early implantation when a multinucleated syncytium forms, presumably by cell fusion events, ahead of proliferating, mononucleated, cytotrophoblast (CTB) cells originating from polar trophectoderm (3,4). This invasive syncytium emerges either during or soon after the trophoblast passes through the breached uterine epithelium and into the decidualized stromal layer beneath and appears to be responsible for hollowing out regions within the stroma to form lacunae (5), which become filled with fluid and cells from maternal blood and uterine glands and presumably provide a source of nutrients for the conceptus (3,6). By about 12 d of gestation, soon after the blastocyst has sunk below the endometrial surface, strands of cytotrophoblast begin to form and penetrate through the primitive syncytium to form primary chorionic villi, which are subsequently invaded by extraembryonic mesoderm to form secondary and tertiary villi (villous trees) (2)(3)(4).…”

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confidence: 99%

Comparison of syncytiotrophoblast generated from human embryonic stem cells and from term placentas

Yabe

Alexenko

Amita

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

149

148

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Human embryonic stem cells (ESCs) readily commit to the trophoblast lineage after exposure to bone morphogenetic protein-4 (BMP-4) and two small compounds, an activin A signaling inhibitor and a FGF2 signaling inhibitor (BMP4/A83-01/PD173074; BAP treatment). During differentiation, areas emerge within the colonies with the biochemical and morphological features of syncytiotrophoblast (STB). Relatively pure fractions of mononucleated cytotrophoblast (CTB) and larger syncytial sheets displaying the expected markers of STB can be obtained by differential filtration of dispersed colonies through nylon strainers. RNA-seq analysis of these fractions has allowed them to be compared with cytotrophoblasts isolated from term placentas before and after such cells had formed syncytia. Although it is clear from extensive gene marker analysis that both ESC-and placenta-derived syncytial cells are trophoblast, each with the potential to transport a wide range of solutes and synthesize placental hormones, their transcriptome profiles are sufficiently dissimilar to suggest that the two cell types have distinct pedigrees and represent functionally different kinds of STB. We propose that the STB generated from human ESCs represents the primitive syncytium encountered in early pregnancy soon after the human trophoblast invades into the uterine wall.is encountered during at least two stages of human placental development (1-3). The first coincides with early implantation when a multinucleated syncytium forms, presumably by cell fusion events, ahead of proliferating, mononucleated, cytotrophoblast (CTB) cells originating from polar trophectoderm (3,4). This invasive syncytium emerges either during or soon after the trophoblast passes through the breached uterine epithelium and into the decidualized stromal layer beneath and appears to be responsible for hollowing out regions within the stroma to form lacunae (5), which become filled with fluid and cells from maternal blood and uterine glands and presumably provide a source of nutrients for the conceptus (3, 6). By about 12 d of gestation, soon after the blastocyst has sunk below the endometrial surface, strands of cytotrophoblast begin to form and penetrate through the primitive syncytium to form primary chorionic villi, which are subsequently invaded by extraembryonic mesoderm to form secondary and tertiary villi (villous trees) (2-4). The cytotrophoblast cells associated with the villi continue to divide and provide a progenitor cell population for the villous STB, which is the cell layer that covers the outer surface of the villi and forms the definitive interface involved in exchange of gases, nutrients, and excretory materials between the fetal placenta and maternal blood. Villous STB is also the major site for production of placental hormones. Cytotrophoblast cells at the tips of the anchoring villi proliferate and colonize the endometrium, thus expanding the placental bed and simultaneously remodeling maternal spiral arteries. The extent to which extravillous trophoblast becom...

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A description of 34 human ova within the first 17 days of development

Cited by 603 publications

References 5 publications

Early embryo mortality in natural human reproduction: What the data say

Early embryo mortality in natural human reproduction: What the data say

Vulnerability of primitive human placental trophoblast to Zika virus

Comparison of syncytiotrophoblast generated from human embryonic stem cells and from term placentas

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