Evaluation of genes involved in prostaglandin action in equine endometrium during estrous cycle and early pregnancy.

The study focuses on investigating the expression of genes related to the production and function of prostaglandins (PTGs) in the endometrium of mares during their estrous cycle and the early phase of pregnancy. It notes changes in PTGS1, PTGS2, PTGFS, PTGES, PTGFR, PTGER2, PTGER4, SLCO2A1, and HPGD expression levels during different stages of the estrous cycle and pregnancy.

Research Methods and Experimental Procedures

• The researchers extracted endometrial tissues from mares during various stages of their reproductive cycle and early pregnancy.
• Stages of the reproductive cycle were confirmed by measuring daily plasma progesterone concentrations and ultrasound examinations.
• The mRNA expressions of the different genes were quantified using real-time reverse transcription PCR (RT-PCR).
• To find meaningful results, a statistical model was applied to the normalized data.

Findings of the Research

• PTGS1 mRNA expression was low during the estrous cycle and early pregnancy, but increased on the 18th and 22nd days of pregnancy.
• PTGS2 expression increased during early luteolysis (decline in the corpus luteum after ovulation) but was reduced during pregnancy on the 15th, 18th, and 22nd days of the reproductive cycle.
• Expression of PTGFS (responsible for prostaglandin synthesis) was high during both cyclic and pregnancy stages compared to the day of ovulation.
• Expresssion of PTGFR (prostaglandin receptor) was temporarily increased during late diestrus and early luteolysis stages, but was reduced during early pregnancy.
• Both PTGES and PTGER2 expressions increased during late diestrus, early luteolysis, and early pregnancy, but were decreased after luteolysis during the cycle period as they remained high on the 18th and 22nd days of the pregnancy.
• PTGER4 expression levels remained constant throughout the entire cycle and during early pregnancy.
• Levels of HPGD and SLCO2A1 significantly increased only on the 22nd day of pregnancy.

Conclusion and Interpretation

• PTGS2 expression increases during luteolysis suggesting an increased capability for the equine endometrium to produce PTGs at this time.
• Early pregnancy reduces PTGS2 expression but maintains high levels of PTGES along with PTGER2, suggesting that PGE₂ luteotrophic action may be required early in equine pregnancy.
• PTGS1 is not associated with luteolysis, but is upregulated later during early pregnancy indicating that it may be the main PTGS enzyme present during this time.
• The increase in HPGD and SLCO2A1 levels on day 22 suggests a tight control of PTG function by pregnancy.