Matrix metalloproteinase-2 and -9 secretion by the equine ovary during follicular growth and prior to ovulation.

This research article explores the role and regulation of enzymes matrix metalloproteinase-2 and matrix metalloproteinase-9 in the follicular development and ovulation processes in equine ovaries.

Overview of Research Objectives and Methodology

• The researchers conducted this study with the aim to understand the regulation and the role of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) during follicular growth and ovulation in horse ovaries. These two enzymes are known to be crucial for tissue remodelling, a process that is hormonally controlled and happens intensively in the equine ovary during follicular development and changes in the shape of the follicle that lead to ovulation
• The researchers used a technique called gelatin substrate zymography to measure the quantity of these two enzymes in the fluid of large anovulatory follicles, during the spring transition period, early dominant follicles, and oestrus follicles 3 days before ovulation. The quantities are also measured after post-hCG treatment, an event that usually precedes ovulation by around 4 hours.
• Five different regions of the ovary were also maintained in explant culture for a day in order to monitor any changes in the secretion levels of these two enzymes by the stromal tissues in the ovary.

Major Findings

• The study found that the most abundant enzyme in the follicle fluid was MMP-2, however, the secretion or the activation did not change in relation with ovulation.
• Even though MMP-9 was found in lower quantities, there were no changes prior to ovulation, but it was found to decrease significantly post the administration of hCG.
• When the secretion of the enzymes in the different regions of the ovary was observed over a day, there were no significant changes in the secretion of either MMP-2 or MMP-9.
• They also noticed that levels of follicular progesterone and oestradiol increased significantly over the same period, but oestradiol showed a tendency to decrease following hCG administration.

Conclusion

• The results of the study suggest that neither MMP-2 nor MMP-9 are acute regulators for changes in the shape of the follicle immediately prior to ovulation, despite them being key enzymes involved in ovarian tissue remodelling during follicular growth and ovulation. This indicates that the regulation of follicle shape, crucial for ovulation, may involve other enzymatic or non-enzymatic factors.