Equine endometrial gene expression changes during and after maternal recognition of pregnancy.

The study investigates how horse endometrial gene expression changes during and after the maternal recognition of pregnancy. The researchers aim to identify key genes involved in this process, which, if not correctly recognized by the uterus by day 14 post ovulation, may lead to a failure in maintaining pregnancy.

Objective and Methodology

• The primary objective of this research was to assess and compare gene expression in the endometrium of pregnant and nonpregnant mares during and after the maternal recognition of pregnancy in a bid to identify genes that could be involved in this process.
• The study involved twelve regularly cycling mares following a crossover design. They were randomly assigned to a specific collection day for sample collection.
• Endometrial samples were collected from both pregnant and non-pregnant (non-mated) mares on cycle days 12, 14, 16, and 18 post ovulation. The choice of these days was likely based on the established knowledge that successful maternal recognition should occur by day 14 post ovulation in horses to maintain pregnancy.
• Researchers then conducted a comprehensive microarray analysis to compare the endometrial gene expression in pregnant and non-pregnant mares.

Major Findings

• The microarray analysis did not reveal any significant differences in endometrial gene expression for pregnant and non-pregnant mares at day 12 post ovulation.
• However, ten genes were identified to have consistently enhanced or reduced expression levels in the endometrium from pregnant versus nonpregnant mares on days 14, 16, and 18 post ovulation.
• The researchers undertook further analysis of these ten genes’ expression levels using real-time PCR. The patterns of gene expression changes on days 14, 16, and 18 were found to be consistent with the microarray analysis. On the other hand, 4 out of the 10 genes were identified as differentially expressed on day 12.
• Further analysis conducted with western blot and immunohistochemical tests on two proteins (SPLA2 and DKK1) identified because of their reproductive significance did not yield any significant differences between samples from pregnant and non-pregnant mares.

Conclusion and Implications

• This study provides the first description of gene expression and cellular localization in the endometrium at the time of maternal recognition of pregnancy for these genes.
• The findings indicate that the horse uterus does not prepare to support a pregnancy until day 14 post ovulation.
• The identified genes and their functions might be crucial in comprehending the process of maternal recognition of pregnancy in horses. This knowledge could be vital for understanding and addressing reproductive issues in horses and possibly other mammals.