Loss of polar trophoblast during differentiation of the blastocyst of the horse.
Abstract: Twelve blastocysts, collected 7-12 days after ovulation (Day 0), were examined by light and electron microscopy to investigate the nature of the relationship of the polar trophoblast (Rauber's layer) to the inner cell mass. On Day 7, the polar trophoblast was intact and formed a flattened layer overlying the epiblast cells of the inner cell mass. As blastocysts enlarged to greater than 1 mm in diameter, small discontinuities appeared in the polar trophoblast, where epiblast cells intruded onto the surface. At this time, trophoblast cells adhered closely to adjacent and underlying epiblast cells, forming an irregular layer of cells capping the epiblast. With continued increase in blastocyst size, polar trophoblast cells became isolated but maintained their characteristic apical endocytic structures. By Days 10-12, the scattered trophoblast cells showed evidence of deterioration, and vacuoles containing cell debris were common within the epiblast. It is suggested that polar trophoblast cells become scattered, rather than withdrawing as a unit, because they become more adherent to subjacent epiblast cells than to adjacent trophoblast cells. It is further suggested that most of the isolated cells are eventually phagocytosed by epiblast cells.
Publication Date: 1988-05-01 PubMed ID: 3397953DOI: 10.1530/jrf.0.0830447Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
- Research Support
- U.S. Gov't
- P.H.S.
Summary
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This research investigates the relationship between the polar trophoblast (Rauber’s layer) and the inner cell mass in twelve horse blastocysts, observing how the trophoblast disappears during the blastocysts’ expansion with possible processes being individual cell scattering and eventual absorption by surrounding cells.
Study Methodology
- The researchers collected twelve blastocysts from horses between 7-12 days after ovulation (Day 0) for observation under light and electron microscopy.
- These blastocysts were analyzed to study the relationship between the polar trophoblast (Rauber’s layer) and the inner cell mass throughout their expansion process.
Findings
- On Day 7, the polar trophoblast was observed to be intact, forming a flattened layer overlying the epiblast cells of the inner cell mass.
- The researchers noticed that as the blastocysts expanded beyond 1mm in diameter, small discontinuities appeared in the polar trophoblast. These discontinuities were due to the intrusion of epiblast cells onto the surface.
- During this time, the trophoblast cells adhered closely to the underlying epiblast cells and those adjacent to them, forming an irregular layer of cells capping the epiblast.
- As the blastocyst size increased, polar trophoblast cells became scattered, even though they maintained their apical endocytic structures. Trophoblast cells became more attached to the subjacent epiblast cells rather than to the adjacent trophoblast cells.
- By Days 10-12, researchers found scattered trophoblast cells showing signs of deterioration, and vacuoles filled with cell debris were common within the epiblast.
Conclusion
- The researchers suggested that the polar trophoblast cells scatter instead of withdrawing as a unit because they become more adherent to subjacent epiblast cells than to adjacent trophoblast cells.
- Furthermore, it is proposed that the majority of these scattered cells are eventually engulfed and broken down (phagocytosed) by the surrounding epiblast cells. This process might play a critical role in the disappearance of the polar trophoblast during the expansion of a blastocyst.
Cite This Article
APA
Enders AC, Lantz KC, Liu IK, Schlafke S.
(1988).
Loss of polar trophoblast during differentiation of the blastocyst of the horse.
J Reprod Fertil, 83(1), 447-460.
https://doi.org/10.1530/jrf.0.0830447 Publication
Researcher Affiliations
- Department of Human Anatomy, School of Medicine, University of California, Davis 95616.
MeSH Terms
- Animals
- Blastocyst / physiology
- Blastocyst / ultrastructure
- Female
- Horses / physiology
- Microscopy, Electron
- Pregnancy
- Pregnancy, Animal / physiology
- Trophoblasts / physiology
- Trophoblasts / ultrastructure
Grant Funding
- HD 10342 / NICHD NIH HHS
Citations
This article has been cited 4 times.- Pfeffer PL. Alternative mammalian strategies leading towards gastrulation: losing polar trophoblast (Rauber's layer) or gaining an epiblast cavity. Philos Trans R Soc Lond B Biol Sci 2022 Dec 5;377(1865):20210254.
- Derisoud E, Jouneau L, Dubois C, Archilla C, Jaszczyszyn Y, Legendre R, Daniel N, Peynot N, Dahirel M, Auclair-Ronzaud J, Wimel L, Duranthon V, Chavatte-Palmer P. Maternal age affects equine day 8 embryo gene expression both in trophoblast and inner cell mass. BMC Genomics 2022 Jun 15;23(1):443.
- Pérez-Gómez A, González-Brusi L, Bermejo-Álvarez P, Ramos-Ibeas P. Lineage Differentiation Markers as a Proxy for Embryo Viability in Farm Ungulates. Front Vet Sci 2021;8:680539.
- van Leeuwen J, Rawson P, Berg DK, Wells DN, Pfeffer PL. On the enigmatic disappearance of Rauber's layer. Proc Natl Acad Sci U S A 2020 Jul 14;117(28):16409-16417.
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