Effect of extracellular vesicles derived from oviductal and uterine fluid on the development of porcine preimplantation embryos

To improve the efficiency of in-vitro-produced (IVP) porcine embryos, we focused on the events that usually occur during in-vivo embryonic transit from the oviduct to the uterus. Extracellular vesicles (EVs) are released by different mammalian cells and are imperative for intercellular communication and reflect the cell's physiological state. Based on these characteristics, EVs were isolated from oviductal and uterine fluid to imitate the in vivo environment and improve the efficiency of IVP embryos. Parthenogenesis (PA) and somatic cell nuclear transfer (SCNT) embryos were divided into four groups based on treatment methods designed to mimic the in vivo migration pathways of porcine embryos. (Group 1) control group; (Group 2) a group treated with EVs from oviduct-derived fluid for 0-3 days (Ov-EVs), (Group 3) a group treated with EVs from uterus-derived fluid for 3-7 days (Ut-EVs); (Group 4) and a group treated with both (Ov, Ut-EVs). The EVs were characterized using various techniques, and their uptake into oocytes was confirmed using PKH67. The results demonstrated an increase in mitochondrial activity of PA embryos in Groups 2 and 4 at the 4-cell stage. Furthermore, compared with Group 1, the total number of cells in PA blastocysts was higher in the Group 2, 3 and 4, and the number of apoptotic cells was significantly lower. In SCNT experiments, the blastocyst development rate was increased in the EV-treated groups compared to the Group 1. Therefore, Ov-EVs and Ut-EVs can improve the embryonic development rate of IVP embryos, increase cell numbers and mitochondrial activity, and reduce apoptosis, thereby improving embryonic quality. Thus, integrating EV-based support into IVP embryos may advance swine reproductive technology and improve its practical applications.