Cell type-specific endometrial transcriptome changes during initial recognition of pregnancy in the mare.

The research discusses the changes in gene expression in different cell types found in the endometrium of pregnant mares, specifically focusing on the early phase where the mother’s biology initially recognizes the pregnancy. It uses the technique of laser capture microdissection for sample collection and RNA sequencing for analysis.

Methodology and Findings

• The researchers used laser capture microdissection to collect samples of different cell types — luminal epithelium (LE), glandular epithelium and stroma — from the endometrium of mares both 12 days into their pregnancy and in the 12th day of their oestrous cycle.
• The RNA sequencing (RNA-Seq) technique was used for mapping and quantifying RNA molecules within these samples. This method revealed more expression differences between the types of cells than between pregnant and non-pregnant states, and most differences between pregnant and non-pregnant states were found specifically in the LE.
• A comparison with previously obtained RNA-Seq data from whole biopsy samples allowed the researchers to track the specific origins of gene expression differences. They found genes that were differentially expressed (DE), meaning they showed different levels of expression, in one type of cell that weren’t noticeable in the biopsy samples.

Significance and Implications

• This study uncovers spatial information about endometrial gene expression changes during the initial phase of pregnancy recognition in mares. Specific gene expression changes were induced by the embryo (the developing baby horse).
• These changes pertain to genes involved in several significant biological processes such as blood vessel development, spatial regulation of the immune system, and growth factors. They also touched upon the regulation of synthesis and transport of prostaglandin receptors, particularly prostaglandin F receptor (PTGFR), which plays a role in preventing luteolysis — the degradation of the corpus luteum, a temporary endocrine structure required for pregnancy maintenance.
• The findings help in understanding the complex mechanisms involved in the initial recognition and support of pregnancy in mares and may prove valuable in veterinary medicine and reproductive biology research.