Oxygen in the preimplantation development of mammals: concentration in the oviduct/uterus, in vitro cultivation

This review present two aspects regarding the oxygen regime in the development of the pre-implantation embryo: measurement of oxygen concentration in the genital tract (oviduct/uterus) of females of various mammalian species, taking into account the estrous cycle of the animal; development and optimization of the conditions for the development of the embryo in vitro, taking into account the concentration of oxygen in the culture medium. It has been shown that for the twelve mammalian species presented in the review, the value of oxygen concentration in the oviduct/uterus (regardless of the phase of the estrous cycle) is, as a rule, significantly lower than the oxygen concentration under normoxic conditions (~20% oxygen). The phenomenon of functioning under hypoxic conditions indicates the uniqueness of the pre-implantation mammalian embryo, given the evolutionary tendency of more highly organized life forms to life under normoxic conditions (~20% oxygen). The experimentally established fact of the development of an intact pre-implantation embryo under hypoxic conditions is consistent with the overwhelming majority of studies regarding the comparative analysis of the cultivation of pre-implantation embryos in vitro under various oxygen regimes.