Effects of periovulatory gonadotrophin treatment on luteal function and endometrial expression of selected genes in cyclic pony mares.

This research mainly focuses on examining the impact of periovulatory gonadotrophin treatment on luteal function and endometrial gene expression in mares, with consideration to the age factor. The study concluded that neither the treatment nor the age affected the endometrial gene expression in the mares’ luteal phase.

Study Design

• The experimental study involved Shetland mares, aged between 4-25 years, undergoing different treatments during five consecutive cycles based on a cross-over design. This means that each mare received all treatments, but in a varied sequence to minimize the “order of treatment” bias.
• The treatments consisted of preovulatory or post-ovulatory injections of either eCG or hCG hormones. A control group received no treatment. Preovulatory injections were given before ovulation while post-ovulatory injections were given upon detection of ovulation.

Data Collection

• Progestin concentration, essential for endometrial function and embryonic development, was assessed using an ELISA test from the ovulation day until Day 10.
• Endometrial cells were collected on Day 10 through a minimally invasive transvaginal cytobrush technique.
• The mRNA expression of key enzymes and hormones, such as COX-2, prostaglandins, progesterone receptor (PR), estradiol receptor (E2R), acyl-CoA-dehydrogenase (ACAD), uteroglobin (UGB), uteroferrin and uterocalin, was analyzed using RT-qPCR, an advanced detection method for gene expression.
• Immunohistological staining was performed on obtained endometrial tissue biopsies to visually assess the tissue for COX-2, PR and UGB.

Findings

• While the day of the cycle had an effect on the P4 concentration, the treatments didn’t impact it.
• Neither treatment nor age affected the mRNA expression of the analyzed genes, suggesting that the regulation of these genes was not influenced by either factor in the context of the study.
• There were also no noticeable effects on the staining of endometrial tissue due to treatment.
• However, age did influence the percentage of PR-positive stromal cells and COX-2 positive stained ciliated cells.

Conclusion

• Periovulatory gonadotrophin treatment and age didn’t demonstrate any significant effect on endometrial gene expression in the luteal phase of pony mares.
• The absence of treatment effects on luteal function and expression of PRs in the endometrium was linked to physiological differences between horses and ponies.