Local embryo-mediated changes in endometrial gene expression during embryo mobility in mares

Area of Science:

• Reproductive Biology
• Equine Science
• Molecular Endocrinology

Background:

• Prostaglandins E2 (PGE2) and F2α (PGF2α) are crucial for equine embryo transport.
• Embryo mobility is maximal between Days 11-15 post-ovulation.

Purpose of the Study:

• To investigate local gene expression changes in the equine uterus related to embryo presence.
• To compare endometrial gene expression between pregnant and non-bred mares on Day 12 of the estrous cycle.

Main Methods:

• Endometrial samples were collected from uterine horns of pregnant (n=13) and non-bred (n=10) mares using a cytobrush.
• Gene expression of estrogen receptors (ESR1, ESR2) and prostaglandin E2 synthase (PTGES) was analyzed.
• Comparisons were made between uterine horns with and without an embryo, and between pregnant and non-bred groups.

Main Results:

• Pregnant mares had lower ESR1 and higher ESR2 mRNA abundance than non-bred mares.
• Prostaglandin E2 synthase (PTGES) mRNA was significantly higher in the uterine horn containing the embryo compared to the horn without the embryo.
• PTGES mRNA was also higher in the pregnant horn than in the combined horns of non-bred mares.

Conclusions:

• The equine embryo appears to locally upregulate prostaglandin E2 synthesis in the adjacent endometrium.
• PTGES is a key gene involved in the localized uterine response to embryo presence in mares.
• These findings contribute to understanding the molecular dialogue between the early embryo and the maternal uterus in horses.