Quantitative histological analysis of equine embryos at exactly 156 and 168 h after ovulation.
Abstract: Equine embryos were collected at exactly 156 +/- 0.5 (n=8) and 168 +/- 0.5 h (n=11) after ovulation. The embryos were fixed in glutaraldehyde, sectioned serially and observed using light microscopy. In the 156 h group, all embryos were early blastocysts except for one, which was a morula. The morula and one early blastocyst had no capsule. The capsules of the other embryos were thin. The mean +/- SD total number of cells was 275 +/- 105 (range 117-417). The mean +/- SD proportions of mitotic and pycnotic cells were 2.5 +/- 1.2 and 1.1 +/- 1.8%, respectively, and there were no differences between each inner cell mass (ICM) and trophoblast. The mean +/- SD proportion of ICM cells was 36.5 +/- 5.2%. In the 168 h group, there were early, mid- and expanded blastocysts, all of which had a capsule. The mean +/- SD total number of cells was 1093 +/- 666 (range 272-2217). The mean +/- SD proportions of mitotic and pycnotic cells were 3.5 +/- 1.4% and 0.1 +/- 0.03%, respectively, and there were no differences between each ICM and trophoblast. The mean +/- SD proportion of ICM cells was 21.1 +/- 9.7%. In the 168 h group, there was a significant correlation (P < 0.01) between the total number of cells and the diameters and proportions of ICM cells. The 168 h embryos were composed of significantly (P < 0.01) more cells (approximately four times) than were the 156 h embryos but had lower proportions of ICM cells. These results indicate that in equine embryos there is: (i) an individual (perhaps seasonal) variability in the rate of development; (ii) a doubling in the number of cells every 6 h between 156 h and 168 h after ovulation; and (iii) a decrease in the proportion of ICM cells between the early and expanded blastocyst stages of development.
Publication Date: 2000-01-01 PubMed ID: 20681167
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This research aimed to capture an in-depth, quantitative cellular profile of horse (equine) embryos at specific hours post-ovulation. The results uncover variable rates of development in embryos, a sharp rise in cell numbers between 156 and 168 hours post-ovulation, and a decrease in the proportion of key cells during certain stages of development.
Objective and Methodology
- The study aimed to undertake a quantitative histological analysis of equine embryos taken precisely at 156 and 168 hours post-ovulation.
- A total of 8 embryos belonging to the 156-hour category and 11 embryos of the 168-hour category were carefully retrieved. The embryos were then preserved in a glutaraldehyde solution and serially sectioned for viewing under a light microscope.
Findings in the 156 Hours Group
- All embryos at 156 hours post-ovulation were classified as early blastocysts, apart from one that was a morula. Two of these early blastocysts lacked a capsule.
- The embryos at this stage had an average of 275 cells apiece. Mitotic cells, representing cell division, accounted for an average of 2.5% of all the cells; pycnotic cells, representing cellular death or injury, accounted for an average of 1.1%.
- The proportion of Inner Cell Mass (ICM) cells was approximately 36.5%. ICM cells are critical because they will become the fetus.
Findings in the 168 Hours Group
- The 168-hour category had a variety of early, middle, and expanded blastocysts, each exhibiting a noticeable capsule.
- These embryos had a significantly higher average cell count – 1093 compared to the 275 in the 156-hour group. They also had slightly higher proportions of mitotic cells (3.5%), but lower proportions of pycnotic cells (0.1%).
- ICM cells represented a smaller percentage – about 21.1% of the total, in contrast with the 156-hour group.
- The research identified a significant correlation in the 168-hour group between the total number of cells in each embryo and the proportions and diameters of ICM cells.
Significant Outcomes
- This research provided intriguing insights into the cellular development timing of equine embryos.
- There was a rapid acceleration in the number of cells between 156 and 168 hours post-ovulation, representing a doubling every 6 hours.
- These results also exposed a decline in the proportion of ICM cells as progression from the early to the expanded blastocyst stages occurred.
- Lastly, the findings underscore the presence of individual (possibly seasonal) variations in the developmental rate of equine embryos.
Cite This Article
APA
Colchen S, Battut I, Fiéni F, Tainturier D, Siliart B, Bruyas JF.
(2000).
Quantitative histological analysis of equine embryos at exactly 156 and 168 h after ovulation.
J Reprod Fertil Suppl(56), 527-537.
Publication
Researcher Affiliations
- Pathologie de la Reproduction, Ecole Nationale Vétérinaire de Nantes, BP 40706, 44307 Nantes Cedex 03, France.
MeSH Terms
- Animals
- Blastocyst / cytology
- Embryo, Mammalian / cytology
- Female
- Horses / embryology
- Horses / physiology
- Microscopy
- Ovulation / physiology
- Progesterone / blood
- Time Factors
Citations
This article has been cited 3 times.- 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.
- Gastal GDA, Scarlet D, Melchert M, Ertl R, Aurich C. Epigenetic Changes in Equine Embryos after Short-Term Storage at Different Temperatures. Animals (Basel) 2021 May 6;11(5).
- Aurich C, Budik S. Early pregnancy in the horse revisited - does exception prove the rule?. J Anim Sci Biotechnol 2015;6:50.
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