Early pregnancy loss has major economic implications for horse breeders. Despite many previous studies focusing on the endometrial environment during early pregnancy, there remains no long-term in vitro culture system capable of recapitulating the equine endometrium. To advance knowledge in this space, the present study aimed to characterise the transcriptomes of epithelial glands and stromal cells derived from the equine endometrium.
Endometrial tissue samples were collected from two mares immediately post-mortem and dissociated via enzymatic digestion. Cell populations were purified by selective adhesion of the stromal cells. The epithelial cells were pelleted and frozen at -80⁰C whilst stromal cells were cultured to confluence (Day 5) before freezing. RNA isolation was performed on all samples using the Total RNA Isolation Mini Kit (Agilent), before sequencing using DNB-Seq technology. Sequencing data were analysed at SAHMRI and bioinformatics analysis was completed using Database for Annotation, Visualisation and Integrated Discovery (DAVID).
A total of 12,702 genes were identified in epithelial glands, while 11,482 were identified in the stromal cell population (>2 cpm per sample). 11,084 (84.6%) genes were identified in both populations, 1,618 (12.4%) were unique to the glands and 398 (3%) were unique to the stroma. A total of 910 genes were observed to be differentially expressed (Fold-change >log(2); FDR<0.05), 790 upregulated in the glands and 120 upregulated in the stroma. DAVID analysis revealed epithelial enriched genes were associated with signalling, ATP-binding immunoglobulins and the immune response, while those enriched in the stroma were associated with extracellular exosomes, cytoplasm, metabolic pathways and glycolysis. Furthermore, genes associated with oxytocin, oestrogen and prostaglandin receptors were all observed to be significantly enriched within the epithelial gland population. These findings establish a foundation for the development of novel in vitro models required for the advancement of knowledge surrounding uterine priming and early pregnancy in the mare.