Ovarian steroid regulation of endometrial phospholipase A2 isoforms in horses.

This research article examined the impact of the hormones progesterone (P4) and oestradiol (E2) on the expression of specific genes (PLA2G4A, PLA2G2A, and PLA2G6) in horse endometrial cells, finding that a reduction in progesterone led to an increase in the expression of two of the genes studied, independent of oestradiol levels.

Research Methodology

• The researchers conducted their study using ovariectomized (i.e., having the ovaries surgically removed) mares (i.e., female adult horses).
• They used real-time PCR (Polymerase Chain Reaction) – a sophisticated technique to amplify and quantify targeted DNA molecules – to explore the influence of progesterone (P4) and oestradiol (E2) on the regulation of endometrial (i.e., relating to the lining of the uterus) phospholipase A2 (PLA2) isoforms. PLA2 constitutes a family of enzymes that are responsible for the release of fatty acids from the second carbon group of glycerol in phospholipids.
• The mares underwent a treatment regime involving 6 days of pre-treatment with E2, followed by 14 days of supplementation with P4.

Results and Findings

• The study found that the gene expression of PLA2G4A increased (p < 0.05) on Day 14 as compared to Day 8. Contrastingly, levels of PLA2G2A remained essentially unchanged.
• On Day 16, when P4 concentrations had declined, the gene expression of PLA2G4A and PLA2G2A showed a significant increase. However, no noticeable difference was observed in PLA2G6 gene expression across different days.
• Treatment with oestradiol did not elevate the expression of PLA2 isoforms when compared to the control treatment (vehicle).

Correlation and Conclusion

• The expression of PLA2G4A and PLA2G2A was found to be positively correlated with each other and negatively correlated with P4 concentrations. This implies when one gene expression increased, the other did too and as progesterone concentrations dropped, the gene expressions also increased.
• The study concluded that a decline in progesterone levels led to an increase in the expression of the PLA2G4A and PLA2G2A genes. This pattern was not influenced by the presence of oestradiol.
• The researchers also hypothesized that the regulation of PLA2G4A and PLA2G2A (not PLA2G6) gene expressions might play a role in controlling the synthesis of prostaglandin F2 alpha – a hormone-like compound that plays a role in inflammation, and luteolysis- the degradation of the corpus luteum (a structure in the ovary that produces progesterone during early pregnancy).