Single-cell atlas of the pregnant equine endometrium before and after implantation.
Abstract: Embryo implantation in the mare occurs just over one month after fertilization, coinciding with the production of chorionic gonadotropin. The factors that regulate this late implantation in the mare, and whether they are unique to horses or shared with more invasive embryo implantation in other species, remain poorly understood. This study aimed to determine and compare the transcriptome and subpopulations of endometrial cells before and after embryo implantation in the horse. Single-cell RNA sequencing was used to characterize the transcriptome of nearly 97,000 endometrial cells collected from biopsies of the endometrium at the beginning (day 33 of gestation) and after embryo implantation (day 42 of gestation) in mares. Sixteen immune and 24 non-immune cell clusters were identified, representing known major cell populations as well as novel subpopulations of horse immune cells such as resident innate lymphoid cells and mucosal-associated invariant T cells. Contrary to current knowledge, endometrial natural killer (eNK) cells were the most abundant endometrial leukocyte population during implantation in horses. Moreover, eNK cells not only expressed genes that may interact with fetal MHC I, such as LY49F, but also exert immunoregulatory functions independent of MHC I expression, such as CD96/TIGIT. Analogous to other species studied, upregulation of CXCR4 was found in several subpopulations of immune cells. Our results suggest that despite distinctive and later placentation compared with humans, horses share some key similarities in the mechanisms of embryo implantation.
© The Author(s) 2025. Published by Oxford University Press on behalf of Society for the Study of Reproduction. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
Publication Date: 2025-01-05 PubMed ID: 39756438DOI: 10.1093/biolre/ioaf004Google Scholar: Lookup
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Summary
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This research article conveys an exploration into the transcriptome and subpopulations of endometrial cells in pregnant horses, with a specific focus on the period before and after embryo implantation. Single-cell RNA sequencing was utilized to study nearly 97,000 endometrial cells and highlight similarities and differences in the processes of horse versus human embryo implantation.
Objective of Study
- The aim of this research was to determine and compare the transcriptome and subpopulations of endometrial cells before and after embryo implantation in mares. Researchers wanted to investigate the regulation factors of late implantation in horses, and if horse implantation shares similarities with other species.
Methodology
- The researchers utilized single-cell RNA sequencing to study the endometrial cellular composition.
- Nearly 97,000 endometrial cells were collected from horse endometrium biopsies on day 33 (before implantation) and day 42 (after implantation) of gestation.
Findings
- The research identified 16 immune and 24 non-immune cell clusters. These clusters incorporated known major cell populations and potentially new subpopulations of horse immune cells such as resident innate lymphoid cells and mucosal-associated invariant T cells.
- Contrary to current knowledge, the study found endometrial natural killer (eNK) cells to be the most prevalent leukocyte population present during horse embryo implantation.
- The eNK cells expressed genes which may interact with fetal MHC I, such as LY49F, and also exerted immunoregulatory functions independent of MHC I expression, such as CD96/TIGIT.
- Similar to other species studied, an upregulation of CXCR4 was found in several immune cell subpopulations.
Conclusions
- The study concluded that despite differences in placentation timings as compared to humans, horses share some key similarities with humans concerning embryo implantation mechanisms.
- This knowledge can potentially aid in understanding the biology behind species-specific variations in the pregnancy process.
Cite This Article
APA
Jaworska J, Tobolski D, Salem SE, Kahler A, Wocławek-Potocka I, Mestre AM.
(2025).
Single-cell atlas of the pregnant equine endometrium before and after implantation.
Biol Reprod, ioaf004.
https://doi.org/10.1093/biolre/ioaf004 Publication
Researcher Affiliations
- Department of Gamete and Embryo Biology, IAR&FR, PAS, Olsztyn, Poland.
- Department of Large Animal Diseases and Clinic, University of Life Sciences, Warsaw, Poland.
- Department of Biomedical Sciences, Baker Institute for Animal Health, Cornell University, Ithaca, NY 14853.
- Department of Comparative Biomedical Sciences, Royal Veterinary College, Hatfield, Hertfordshire, UK.
- Department of Gamete and Embryo Biology, IAR&FR, PAS, Olsztyn, Poland.
- Department of Biomedical Sciences, Baker Institute for Animal Health, Cornell University, Ithaca, NY 14853.
- Department of Comparative Biomedical Sciences, Royal Veterinary College, Hatfield, Hertfordshire, UK.
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