LPS-Stressed Bovine Endometrial Cells upon Morulae in a Transwell Model of Embryo-Maternal Talk

During the preimplantation period, the nutrition of the embryo is dependent on luminal secretions of the uterus, which can be modified by the health status of the animal. The aim of this study was to mimic the paracrine communication between healthy or LPS-stressed epithelial endometrial cells (EECs) and embryos using aa transwell plate. The rate of in vitro embryo production, size, and concentration of extracellular vesicles (EVs), and level of secretion of Galectin-9 (Gal-9) and leukaemia inhibitory factor (LIF) were detected. Embryos were produced with an established protocol of oocyte in vitro maturation (IVM), in vitro fertilization (IVF), and in vitro embryo culture (IVC). On day 55 of IVC, one hour before the transfer of morulae in the basolateral compartment of the transwell, EECs were treated with 10 ng/mL of LPS, and IVC was continued until the eleventh day. Extracellular vesicles (EVs) were obtained from IVC medium by ultracentrifugation. Levels of Gal-9 and LIF were evaluated by ELISA. On day 7, the results did not show statistically different blastocyst rates between EECs+Embryo and EECs+LPS+Embryo (34.94 ± 1.95% and 33.06 ± 3.08%, respectively). On day 11, the rate of hatched blastocysts was 23.03 ± 3.18% in EECs+Embryo, while in EECs+LPS+Embryo, no hatching was observed. Nanosight revealed higher values in EV size and concentration in EECs+LPS+Embryo medium compared to EECs+Embryo (p < 0.05). In LPS-treated samples, there was a significant decrease in Gal-9 levels and a significant increase in LIF secretions compared with non-non-LPS-treated samples (p < 0.05). These results highlight how bidirectional secretions between EECs and embryos, crucial for embryo development, can be affected by endometritis.