Expression of receptors for ovarian steroids and prostaglandin E2 in the endometrium and myometrium of mares during estrus, diestrus and early pregnancy.

The research project investigates the expression patterns of certain receptor types, specifically estrogen receptors alpha and beta, progesterone receptor, and prostaglandin receptors in horse tissue during different stages of the female reproductive cycle. The study revealed a variable regulation of estrogen and progesterone receptors during the cycle and early pregnancy and demonstrated an abundant presence of EP2 protein in the early pregnancy stage.

Objective

The study aimed to understand the behavior of specific receptors in mares during different stages of their reproductive cycle—estrus, diestrus and early pregnancy.

Methodology

• The team collected tissue samples from the horses during different stages: estrus, diestrus and early pregnancy.
• They conducted qPCR analysis to quantify the transcripts for each of the receptors they were studying—ER-α (ESR1), ER-β (ESR2), PR (PGR), EP2 (PTGER2) and EP4 (PTGER4).
• To localize these receptors, the team resorted to immunohistochemistry.
• The transcript differences in endometrium and myometrium tissues were calculated using the ΔΔCT method.

Findings

• The expression for ESR1 tended to be higher during estrus than diestrus and pregnancy in both endometrium and myometrium.
• Expression for PR was significantly higher in the endometrium during estrus and diestrus than during pregnancy. In the myometrium, the expression was higher during estrus than pregnancy.
• No significant differences were noted in the expression of ESR2, PTGER2 and PTGER4 mRNA across the reproductive stages.
• Immunolabeling indicated a more intense presence of ER-α in the endometrium during estrus as compared to diestrus and pregnancy. PR during pregnancy appeared to show more intense labeling in the stroma and less intense in glands and epithelium compared to estrus and diestrus.
• EP2 showed more intense immunoreactivity during early pregnancy in both endometrium and myometrium while weak immunolabeling for EP4 was noted across all reproductive stages.

Conclusion

The research successfully uncovered differential regulation of estrogen receptor and PR in the myometrium and endometrium during the reproductive cycle and early pregnancy stages in mares. Furthermore, abundant expression of EP2 protein during early pregnancy was noted in the endometrium and myometrium. These findings may contribute to a better understanding of reproductive biology of mares which can be leveraged to ensure their health and productivity.