Progestin treatment does not affect expression of cytokines, steroid receptors, oxytocin receptor, and cyclooxygenase 2 in fetal membranes and endometrium from pony mares at parturition.

The research article investigates whether the synthetic progestin altrenogest, commonly used to maintain pregnancy, has an impact on the regulation of various elements involved in the horse birthing process, including cytokines, steroid receptors, the oxytocin receptor, and cyclooxygenase 2. It concluded that altrenogest doesn’t significantly affect gene expressions in the amnion, allantochorion, and endometrium, but does slightly influence inflammatory cells and estrogen receptor expression.

Study Overview and Purpose

• The primary objective of this study was to explore whether altrenogest – a synthetic form of progestin often used to keep mares pregnant – affects the expression of inflammatory cytokines, steroid receptors, oxytocin receptor, and cyclooxygenase 2 in the fetal membranes and endometrium of pony mares during birth.
• These elements are significant as they play crucial roles during labor and parturition process. The inflammatory cytokines interleukin (IL)-6 and -8, for example, get involved in the inflammation process during parturition which bears resemblances with the physiological onset of parturition.

Method and Sample Groups

• The researchers used a sample group of pony mares, some of which were treated with altrenogest from day 280 of gestation until birth, while others were left untreated as controls.
• Tissue samples were collected from the amnion, allantochorion, and endometrium of the mares at the time of foaling. These samples were then analysed for mRNA expression of IL-6 and -8, cyclooxygenase 2 (COX2), estrogen receptor α, progesterone receptor, and oxytocin receptor.

Findings

• The research found a higher mRNA expression of IL-6 and IL-8 in the amnion and endometrium compared to the allantochorion. COX2 was found to be highly expressed in allantochorion, while steroid receptors and oxytocin receptor were predominantly found in endometrium.
• Interestingly, no significant differences in mRNA expressions were found between the altrenogest-treated mares and untreated ones. Thus, indicating that altrenogest treatment does not significantly affect the mRNA expression of these key elements which play a role in parturition.
• However, mares treated with altrenogest showed a rise in endometrial polymorphonuclear leukocytes. Additionally, staining for estrogen receptors was higher in the amnion of altrenogest-treated mares.

Conclusion

• The study concluded that though altrenogest has no significant impact on the gene expression in the amnion, allantochorion, and endometrium of pony mares, it does have minor localized effects on inflammatory cells and estrogen receptor expression.
• Additionally, the research highlighted the importance of the fetal membranes’ role in the horse labor process due to the high expression of COX2 in the allantochorion.
• This could pave way for further research into the role of fetal membranes and potential influence of hormones in horse parturition.