ABC of the future: prolonged coculture of human embryos with endometrium in a nutrient medium in vitro

BACKGROUND: The development of new systems for the cultivation of embryos of model objects and the creation of embryonic models based on stem cells allow for describing the events of early embryogenesis in more detail. However, these models have a number of limitations, endorsing only indirect extrapolation of the knowledge gained to events occurring in vivo. Despite certain limitations, including those related to some differences between embryos developing in vivo and in vitro, implantation conditions in vivo and in vitro, and limited time for culturing human embryos, the study of post-implantation development has great prospects. AIM: The aim of this study was to evaluate the viability and potential for the development of human embryos from the blastocyst stage during their prolonged coculture with the endometrium in culture media designed to support the growth to the blastocyst stage. MATERIALS AND METHODS: Embryos obtained through assisted reproductive technology were cultured from the blastocyst stage to day 19st of development in culture media designed to support the growth to the blastocyst stage, in the presence of the endometrium. On day 19st, embryos and endometrial fragments were assessed under an inverted microscope using Hoffman modulation contrast. RESULTS: During visual assessment under an inverted microscope on day 19st of development and days 13–14st of coculture with the endometrium, viable developing embryos without signs of degradation were recorded, both freely located in a mass of undifferentiated cells and in direct contact with the endometrium. CONCLUSIONS: The data obtained indicate the ability of the embryo to further develop in the presence of the endometrium from the blastocyst stage to day 19st in in culture media that supports the growth to the blastocyst stage. This may serve as an experimental model for both evaluating endometrial receptivity in vitro and studying intercellular communication during implantation.