GSE112236
Cell type-specific endometrial transcriptome changes in comparison of equine endometrium samples collected on Day 12 of pregnancy and Day 12 of the estrous cycle
The results of endometrial gene expression studies during the time of conceptus migration (Days 8 to 16) did not provide final conclusions on possible mechanisms of maternal recognition of pregnancy (MRP) in the mare. This finding called for the analysis of cell type-specific gene expression in the endometrium in response to the equine embryo, which could be the key for improved understanding of gene expression regulation in context of MRP. In a pilot study, we used laser capture microdissection (LCM) to collect samples of the luminal epithelium (LE), glandular epithelium (GE), and stroma from endometrial biopsies taken from five mares on Day 12 of pregnancy and Day 12 of the estrous cycle, respectively. RNA was isolated from the LCM samples in order to perform RNA sequencing. Data analysis showed that gene expression differences were greater between cell types than between pregnant and cyclic state. Differential gene expression between pregnant and cyclic state was mainly found in the LE but also in GE and stroma. The comparison with a previous RNA-Seq data set for whole biopsy samples derived from Day 12 of pregnancy revealed the specific origin of the observed gene expression differences. Furthermore, we found that a number of genes are specifically differentially expressed (DE) in only one cell type. Some genes not DE when looking at the whole biopsy were DE in one cell type and showed similar levels in the other cell types in comparison of pregnancy and cyclic stage. Overall, this study revealed new and important spatial information about endometrial gene expression during the phase of initial recognition of pregnancy in the mare. The results indicated induction of angiogenesis and blood vessel development by the presence of the conceptus, a specific spatial regulation of the immune system, spatial regulation of growth factors controlling cell differentiation and endometrial remodeling, and regulation of genes involved in production of prostaglandin (PG) precursors, PG transport, and PG receptors, specifically PTGFR in context of prevention of luteolysis. Furthermore, these results support our hypothesis of the existence of a specific response in different endometrial cell types in the mare and call for further studies. Overall design: Messenger RNA profiles of laser capture microdissection samples (luminal epithelium, glandular epithelium, stroma) from equine endometrial biopsies collected on Day 12 of pregnancy and Day 12 of estrous cycle, respectively, from in total 6 healthy mares were generated by RNA-sequencing using Illumina HiSeq 2500