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

Area of Science:

• Reproductive Biology
• Genomics
• Equine Science

Background:

• Maternal recognition of pregnancy (MRP) mechanisms in mares remain unclear despite previous studies.
• Understanding cell-specific endometrial gene expression is vital for elucidating MRP.

Purpose of the Study:

• To perform cell type-specific endometrial gene expression analysis in mares during early pregnancy.
• To identify genes and pathways involved in MRP and conceptus-uterine interactions.

Main Methods:

• Utilized laser capture microdissection to isolate luminal epithelium (LE), glandular epithelium, and stroma from endometrial biopsies.
• Employed RNA sequencing (RNA-Seq) to analyze gene expression differences between pregnant and cyclic states at Day 12.
• Compared results with whole biopsy RNA-Seq data to pinpoint cell-specific expression changes.

Main Results:

• Greater gene expression differences were observed between endometrial cell types than between pregnant and cyclic states.
• Pregnancy-specific gene expression changes were predominantly localized to the luminal epithelium (LE).
• Identified conceptus-induced changes in genes related to vascular development, immune regulation, growth factors, and prostaglandin synthesis, notably PTGFR, essential for preventing luteolysis.

Conclusions:

• This study provides spatial resolution of endometrial gene expression during initial MRP in mares.
• Conceptus signals induce specific gene expression alterations in distinct endometrial cell types, particularly LE.
• The findings highlight the role of PTGFR in mediating MRP and preventing early pregnancy loss in horses.