Conceptus attachment in the Ewe: an ultrastructural study

Guillomot, Michel; Fléchon, J.‐E.; Wintenberger-Torrès, Suzanne

doi:10.1016/s0143-4004(81)80021-5

Cited by 152 publications

(135 citation statements)

References 20 publications

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“…Based on a comparative implantation scheme proposed by Guillomot and colleagues (Guillomot et al 1981, 1993, Guillomot 1995, the phases of implantation include: 1. shedding of the zona pellucida; 2. precontact and blastocyst orientation; 3. apposition; 4. adhesion; 5. endometrial invasion. In contrast to rodents and humans, true endometrial invasion does not occur in ruminants.…”

Section: Anatomic and Cellular Aspects Of Conceptus Implantation In Smentioning

confidence: 99%

“…A close association of the apical membranes of both cell types is observed, although the conceptus can still be recovered intact from the uterus by lavage. In most species, the onset of apposition is accompanied by a reduction of the apical microvilli covering the trophectoderm, a reduction which occurs between days 13 and 15 on the sheep conceptus (Guillomot et al 1981(Guillomot et al , 1993. In rodents, the endometrial epithelium undergoes the same modification, allowing a closer association with the trophoblast (Enders & Schlafke 1969); however, loss of apical microvilli on the uterine LE does not appear to occur in sheep (Guillomot et al 1981.…”

Section: Apposition (Phase 3)mentioning

confidence: 99%

“…The permeability of uterine capillaries increases for pontamine blue at the same time (Boshier 1970). The apposition of the blastocyst is ensured by interdigitation of cytoplasmic projections of the trophectoderm cells and uterine epithelial microvilli (Guillomot et al 1981(Guillomot et al , 1993. In sheep, apposition occurs first in the vicinity of the inner cell mass, that is, the embryo, and spreads toward the extremity of the elongated conceptus.…”

Section: Apposition (Phase 3)mentioning

confidence: 99%

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Implantation mechanisms: insights from the sheep

Spencer

Johnson²,

Bazer³

et al. 2004

Reproduction

283

232

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Implantation in all mammals involves shedding of the zona pellucida, followed by orientation, apposition, attachment and adhesion of the blastocyst to the endometrium. Endometrial invasion does not occur in domestic ruminants; thus, definitive implantation is achieved by adhesion of the mononuclear trophoblast cells to the endometrial lumenal epithelium (LE) and formation of syncytia by the fusion of trophoblast binucleate cells with the LE. This review highlights new information on mechanisms regulating the implantation cascade in sheep. The embryo enters the uterus on day 4 at the morula stage of development and then develops into a blastocyst by day 6. The blastocyst sheds the zona pellucida (day 8), elongates to a filamentous form (days 11-16), and adheres to the endometrial LE (day 16). Between days 14 and 16, the binucleate cells begin to differentiate in the trophoblast and subsequently migrate and fuse with the endometrial LE to form syncytia. Continuous exposure of the endometrium to progesterone in early pregnancy downregulates the progesterone receptors in the epithelia, a process which is associated with loss of the cell-surface mucin MUC1 and induction of several secreted adhesion proteins. Recurrent early pregnancy loss in the uterine gland knockout ewe model indicates that secretions of the endometrial epithelia have a physiologic role in blastocyst elongation and implantation. A number of endometrial proteins have been identified as potential regulators of blastocyst development and implantation in sheep, including glycosylated cell adhesion molecule 1 (GlyCAM-1), galectin-15, integrins and osteopontin. The epithelial derived secreted adhesion proteins (GlyCAM-1, galectin-15 and osteopontin) are expressed in a dynamic temporal and spatial manner and regulated by progesterone and/or interferon tau, which is the pregnancy recognition signal produced by the trophoblast during blastocyst elongation. The noninvasive and protracted nature of implantation in domestic animals provides valuable opportunities to investigate fundamental processes of implantation that are shared among all mammals. Understanding of the cellular and molecular signals that regulate uterine receptivity and implantation can be used to diagnose and identify causes of recurrent pregnancy loss and to improve pregnancy outcome in domestic animals and humans.

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Section: Anatomic and Cellular Aspects Of Conceptus Implantation In Smentioning

confidence: 99%

Section: Apposition (Phase 3)mentioning

confidence: 99%

Section: Apposition (Phase 3)mentioning

confidence: 99%

See 1 more Smart Citation

Implantation mechanisms: insights from the sheep

Spencer

Johnson²,

Bazer³

et al. 2004

Reproduction

283

232

View full text Add to dashboard Cite

show abstract

“…The ovoid conceptus is about 2 mm in length on Day 13 and then reaches a length of about 60 mm by Day 16; however there is significant variation in conceptus length at this time. Elongated conceptuses can be readily recovered by standard uterine flushing techniques up to Day 19, after which time the fully elongated conceptus begins implantation with firm apposition and attachment of the trophectoderm to endometrial luminal epithelium (LE) (Guillomot et al, 1981). The objective of this manuscript is to briefly review maternal-embryo/conceptus interaction around the time of pregnancy establishment in cattle.…”

Section: Introductionmentioning

confidence: 99%

Maternal-embryo interaction leading up to the initiation of implantation of pregnancy in cattle

Lonergan¹,

Forde²

2014

Animal

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Early embryo development following fertilization occurs in the oviduct. However, despite being the site of fertilization in cattle, it is possible to by-pass the oviduct by producing embryos in vitro and/or by transferring blastocysts recovered from one female into the uterus of another. While there is substantial evidence for the oviduct having an influence on the quality of the developing embryo, manifested in altered morphology, gene expression and cryotolerance, evidence for a two-way dialogue is weak. In contrast, successful growth and development of the post-hatching blastocyst and pregnancy establishment are a result of the two-way interaction between a competent embryo and a receptive uterine environment. Progesterone (P4) plays a key role in reproductive events associated with establishment and maintenance of pregnancy through its action on the uterine endometrium. Elevated concentrations of circulating P4 in the immediate post-conception period have been associated with an advancement of conceptus elongation, an increase in interferon-tau production and, in some studies, higher pregnancy rates in cattle. This review summarizes current knowledge on the communication between the developing embryo and the maternal reproductive tract.

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“…Conceptus attachment in the ewe has been studied using scanning and transmission electron microscopy. Three stages could be determined: i) from day 14 on precontact was established and the conceptus appeared to be immobilized in the uterine lumen, ii) on day 15 apposition occurred and iii) between days 16 and 18 adhesion began (Guillomot et al, 1981). Several adhesion molecules have been implicated in the process of embryonic implantation, such as Muc-1, integrins, and selectins.…”

Section: Blastocyst Implantation and The Adhesion Cascadementioning

confidence: 99%

2 Identification of Genes Induced by the Conceptus in the Bovine Endometrium During the Pre-Implantation Period

Klein¹,

Bauersachs²,

Ulbrich³

et al. 2006

Reprod. Fertil. Dev.

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Early embryonic development, implantation, and maintenance of a pregnancy are critically dependent on an intact embryo-maternal communication. So far, only few signals involved in this dialogue have been identified. In ruminants, interferon tau (IFN�) plays a key role in the process of maternal recognition of pregnancy by exhibiting antiluteolytic activity. Even though many experimental findings indicate a pivotal role of IFN� in the context of embryo-maternal communication in ruminants, a number of other systems may be involved. To identify genes induced in the bovine endometrium by the signaling of the embryo, a combination of subtracted cDNA libraries and cDNA array hybridization was applied. Monozygotic twin pairs (n = 5) were used as the biological model. Pregnancy was created in one twin by transferring two in vitro-produced embryos on Day 7 of the estrous cycle; the other twin received a sham embryo transfer. Pregnant and nonpregnant twins were slaughtered at Day 18; endometrial tissue samples were recovered and processed for transcriptome analysis as described (Bauersachs et al. 2005 J. Mol. Endocrinol. 34, 889-908). Screening of 4608 clones of two subtracted libraries revealed 90 different up-regulated genes and mRNAs, of which almost 50% are known to be stimulated by type I interferons. Among these interferon-stimulated genes, the ISG15 system is assumed to be of particular interest, and several components were studied in more detail using in situ hybridization. The pattern of mRNA expression suggests that modification of endometrial proteins through ISG15ylation plays a fundamental role during the pre-implantation period. A classification of the identified genes based on Gene Ontologies revealed the prevalence of genes involved in regulation of gene expression, cell communication, cell growth, cell differentiation, cell proliferation, and cell adhesion, and also the prevalence of genes with immune-related functions. These results underline the intense response of the endometrium to the presence of a conceptus, culminating in the preparation of the maternal environment for embryonic implantation. Further, for eleven selected genes the expression in the endometrium was quantified by the use of real-time RT-PCR. Overall, the results of quantitative RT-PCR and array hybridization correlated very well. To our knowledge this study provides the first holistic gene expression analysis of the bovine endometrium during the pre-implantation period. The results underline the importance of IFN� as an embryo-derived pregnancy recognition signal and depict the molecular mechanisms at the mRNA level underlying the intense embryo-maternal dialog taking place at Day 18 of gestation.

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Conceptus attachment in the Ewe: an ultrastructural study

Cited by 152 publications

References 20 publications

Implantation mechanisms: insights from the sheep

Implantation mechanisms: insights from the sheep

Maternal-embryo interaction leading up to the initiation of implantation of pregnancy in cattle

2 Identification of Genes Induced by the Conceptus in the Bovine Endometrium During the Pre-Implantation Period

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