Expression of cytosolic phospholipase A2 in equine endometrium during the oestrous cycle and early pregnancy.

The study investigated the levels and role of the enzyme cytosolic phospholipase A2 (cPLA2) in the uterus lining of mares during different stages of their oestrous cycle and early pregnancy. It discovered that the enzyme’s expression is linked to the concentration of progesterone and plays a significant role in luteolysis—the breakdown of the corpus luteum in the ovary.

Research Methodology

• The researchers made use of real-time RT-PCR and immunohistochemistry. These are advanced molecular biology techniques used to measure gene expression and protein levels in tissue samples respectively.
• They collected endometrial biopsy and blood samples from mares at various stages of the their oestrous cycle—days 8, 11, 15, and 18, and from pregnant mares on day 15.
• Progesterone concentrations were also monitored to understand its relationship with cPLA2 levels. Progesterone, typically having high concentration during pregnancy, could provide relevant insights into observed cPLA2 levels and actions.

Key Findings

• cPLA2 was primarily found in the luminal epithelium of the uterus, the layer that covers the internal surface of the organ.
• The enzyme’s expression showed a negative correlation with progesterone levels, suggesting that higher progesterone concentrations might suppress cPLA2 activity.
• The enzyme’s expression varied significantly based on the mare’s oestrous stage. Levels were highest during oestrus—when females are most fertile, then they fell to lowest on day 8. Following this, a trend of rising cPLA2 levels was observed as luteal phase progressed.
• In pregnant mares, cPLA2 expression was similar to non-pregnant mares on day 15 with high progesterone concentrations. But it was lower than in non-pregnant mares with low progesterone.

Conclusion and Implications

• The study concludes that cPLA2, which influences PGF2α secretion, is highly active in the endometrium around the time of luteolysis. PGF2α is a hormone-like compound involved in several important physiological functions including contraction and relaxation of smooth muscle tissues.
• Progesterone may act as an inhibitor of cPLA2 expression. Hence, altering progesterone levels may impact the action of cPLA2 and potentially affect fertility and early pregnancy stages.
• The study does not suggest a direct role of cPLA2 in the maternal recognition of pregnancy. Instead, during pregnancy, cPLA2 expression levels could be sufficient to start the cascade for PGF2α secretion, which could influence womb conditions and potentially affect pregnancy outcomes.