Porcine oviductal extracellular vesicles facilitate early embryonic development via relief of endoplasmic reticulum stress

The key to successful in vitro embryo production (IVEP) is to mimic the natural in vivo oviductal microenvironment. Although the chemically defined media in extensive use for the in vitro culture of mammalian embryos is based on the composition of oviductal fluid, the IVEP systems in current use must still bypass the oviduct to produce embryos in vitro. Extracellular vesicles (EVs) in the oviduct are versatile intercellular delivery vehicles for maternal-embryo communication, and a lack of them can be associated with failed early embryonic development under in vitro culture conditions. Herein, we isolated EVs from porcine oviduct fluid and confirmed that oviductal EV supplementation improves the embryonic development of parthenogenetically activated (PA) embryos in terms of blastocyst formation rates and total cell numbers. Our experiments also revealed that a beneficial effect of oviductal EVs on PA embryos was achievable, at least in part, by relieving endoplasmic reticulum stress. These results suggest that the maternal-embryo communication mediated by oviductal EVs benefits early embryonic development. Given the contribution of oviductal EVs to early embryonic development, these findings offer novel insights for the optimization of current IVEP systems.