Endometrial luminal epithelium transcriptome during early diestrus defines pregnancy outcome in cattle

Prior to implantation, embryonic development occurs in the confinement of the reproductive tract lumen. The endometrial epithelia determines the uterine luminal composition and, consequently, the molecular milieu available to the pre-implantation embryo. This cow RNA-seq study was especially designed to (i) evaluate the impact that progesterone concentration has on the transcriptome of luminal epithelial cells, and (ii) evaluate the impact that endometrial gene expression has on pregnancy outcome. Luminal epithelial cells were collected using a cytology brush three days prior to embryo transfer, so that the molecular evaluation and the pregnancy outcome, measured 30 days after estrus, pertained to the same reproductive cycle. Overall design: Forty three multiparous Angus x Brahman cows were enrolled in two rounds (block = 1 or 2) of estrus synchronization for embryo transfer. Estrus was synchronized with (i) the insertion of an intravaginal P4-releasing device and an i.m. injection of GnRH analogue, (ii) seven days later, the P4 device was removed and the animals were treated i.m. with PGF2alpha analogue and fitted with an estrus detection patch, and (iii) three days after P4 device removal, all cows received a dose of GnRH analogue; this was considered experimental day 0. Only cows detected in estrus were used in this study. On D4, cows were subjected to collection of uterine luminal samples for RNA-sequencing using a cytology brush. Also on D4, a blood sample was collected to measure progesterone concentration. On D7, cows received a single in vitro-produced embryo. Finally, pregnancy (yes = 1; no = 0) was evaluated around D30.