Temporal relationship between proliferating and apoptotic hormone-producing and endothelial cells in the equine corpus luteum.

This research examines the time and sequence of cell death events in horse ovary cells. It finds that hormone-releasing and endothelial cell death occurs simultaneously and is part of the process of ovary regression but endothelial cell death does not cause regression.

Research objective

• The objective of this study was to investigate the temporal relationship between endothelial cell death, vascular regression and the death of hormone-producing cells in the mare, specifically during the luteal phase.

Methodology

• The study was conducted on corpora lutea, the temporary endocrine structure in female ovaries, at different stages: early, middle and late luteal phase, and after treatment with cloprostenol in the mid-luteal phase.
• Cloprostenol, a powerful synthetic prostaglandin F2α, was used to induce early luteolysis, the degeneration of the corpus luteum.
• The research utilized specific markers which enabled tracking of changes in cell proliferation and cell death (apoptosis). Phosphorylated histone-3 was used to mark proliferating cells, and activated caspase-3 was used for identifying apoptotic cells.

Findings

• Results showed that phosphorylated histone-3, indicating cell proliferation, was most abundant during the early luteal phase and was mainly present in endothelial cells. The activity of histone-3 significantly increased in hormone-producing cells 36 hours after cloprostenol treatment.
• Activated caspase-3, indicating cell death, reached its peak on the 14th day, and its presence was recorded 36 hours after administration of cloprostenol during the mid-luteal phase.
• Cell death was found to occur simultaneously in the endothelial and hormone-producing cells.
• Some of the hormone-producing cells enter the early stages of cell division around the time of luteolysis, while the majority of the cells are undergoing cell death.

Conclusion

• The authors conclude that natural and induced functional and structural regression of the corpus luteum in horses can be partially attributed to concurrent apoptosis of endothelial and hormone-producing cells. However, they found no evidence suggesting that endothelial cell death triggers the luteolysis process.