Embryo-maternal communication mediated by extracellular vesicles in the early stages of embryonic development is modified by in vitro conditions

Extracellular vesicles (EVs) have become important in embryo-maternal communication during early development. The aim of this study was to evaluate the effect of an in vitro system on early bidirectional embryo-maternal communication mediated by EVs. For this purpose, two experiments were performed: one to evaluate the effect of embryonic EVs on maternal cells and the second to determine the effect of maternal EVs on early embryonic development. For the first in vitro (IVP) and in vivo (IVV) experiments, bovine blastocysts were selected and individually cultured for 48 h to collect embryonic EVs secreted during days 7-9 of embryonic development. Embryonic EVs were added to the medium of in vitro-cultured bovine endometrial cells to evaluate their effect on the expression pattern of genes associated with endometrial function and response to interferon tau (IFNT). Nonclassical interferon-stimulated genes (ISGs) were only induced by in vitro-derived embryos. In the second experiment, EVs released by endometrial cells cultured in vitro (EVC) and collected from uterine fluid (EV-UF) of cows in the early luteal phase were added to the culture medium of bovine embryos produced in vitro during days 5-9 of development. The effect of maternal in vitro or in vivo-derived EVs differs in the quality of bovine embryos produced in vitro during the pre-implantation period. The expression of IFNT in bovine embryos is increased by the effect of EV-UF treatment. Additionally, EV-UF treatment induces a sustained increase in diameter during embryonic development and a tendency towards a greater number of expanded and hatched blastocysts. However, some genes related to embryo quality are induced by EVC treatment.