Coculture of Preimplantation Embryos With Outgrowth Embryos Improves Embryonic Developmental Competence in Mice

Mammalian embryonic development is an intricate succession of physiological and morphological events. Many studies have focused on optimizing in vitro culture systems for improvement in embryonic development. In this study, we established a novel coculture method with outgrowth embryos and investigated how this coculture system improves the preimplantation and peri-implantation embryonic development both in vitro and in utero. We found that outgrowth embryos secrete vesicles, as observed by time-lapse monitoring and scanning electron microscopy. Coculture with outgrowth embryos also significantly increased the percentages of morula, blastocyst, hatching, and outgrowth (P < .01). The total number of cells and inner cell mass were increased, and apoptotic index was decreased (P < .05) by upregulating Survivin and Lif messenger RNA expression levels (P < .05) in the coculture compared to the control group. Furthermore, implantation rates in utero after embryo transfer were significantly higher for cocultured embryos than those for the control group (P < .05). We conclude that embryotrophic factors secreted from outgrowth embryos could improve the developmental competence of in vitro cultured mouse preimplantation embryos. Findings of specific embryotrophic factors from outgrowth embryos might be valuable for advancing reproductive technologies in the future.