Effects of in vitro production on the transcriptomic profile of the embryonic disc and extra-embryonic membranes of day 15 elongated bovine embryo.

In vitro-produced (IVP) embryos continue to surpass in vivo-produced (IVV) embryos worldwide. However, there is increased concern about the current drawbacks of IVP embryos, such as a higher pregnancy loss in the early stages of development often associated with impairment in conceptus elongation, which begins from ~day 13 of gestation. The embryonic disc (ED) and the embryonic membranes (EEM) differentiate during this period, and their transcriptomes might be impacted by the in vitro procedures, impairing conceptus development. This study aimed to identify changes in the ED and EEM transcriptome of day 15 IVP conceptuses compared to those conceived in vivo For IVP embryos, oocytes aspirated from slaughterhouse ovaries were matured, fertilized, and cultivated in serum-free medium until transfer at day 7. IVV embryos (n=8) were generated after ovarian super-stimulation and artificial insemination. Eight days after in vitro embryo transfer or 15 days after AI on superovulated cows, the embryos were non-surgically flushed out of the uterine horns using an 18 FR Foley catheter (Minitube) and BoviFlush (Minitube) solution. The recovered day 15 embryos were washed twice with BoviFlush (Minitube) and held in BoviHold medium (Minitube). The embryos were gently checked for the presence of ED and washed twice with 0.1% PVA and PBS medium. Embryos without ED were discarded. The selected embryos were cut into three pieces. The ED and 2 pieces of surrounding EEM were snap-frozen in liquid nitrogen. The final sample size used in the bioinformatic analyses was, for the EEM n=6 and n=8 for IVP and IVV embryos, respectively, while for the ED was n=7 and n=9 for IVP and IVV embryos, respectively.