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

Prostaglandin E2 (PGE2) and prostaglandin F2α (PGF2α) are involved in equine embryo mobility throughout the uterus on Days 11-15 (ovulation = Day 0). On a day (Day 12) of maximal embryo mobility in pregnant mares (n = 13) and before luteolysis in nonbred mares (n = 10), gene expressions were compared between the uterine horns that did and did not contain the mobile embryo and between pregnant and nonbred mares. A cytobrush was used to collect an endometrial sample from the middle of each uterine horn. In nonbred mares, there was no difference for any of the considered gene expressions between the uterine horn ipsilateral and contralateral to the CL or for side (left vs right). For endometrial estrogen receptors, ESR1 was lower (P < 0.03) and ESR2 was greater (P < 0.04) for pregnant than nonbred mares. The mRNA abundance for PGE2 synthase (PTGES) was greater (P < 0.05) in the horn with (1.40 ± 0.10) than without (0.89 ± 0.10) the embryo and was greater (P < 0.05) in the horn with the embryo than in the combined horns of nonbred mares (1.06 ± 0.10). The hypothesis that the embryo locally upregulates PGE2 and PGF2α synthesis in the endometrium adjacent to the embryo in the pregnant group but not in the uterine horns of the nonbred group, was partially supported; only PGE2 synthase (PTGES) was locally upregulated in the endometrium adjacent to the mobile embryo.