The mechanism of action of coculture on embryo development in the mouse model: direct embryo-to-cell contact and the removal of deleterious components

Objective: To elucidate the mechanism for the mode of action of coculture by the use of a coculture system for mouse one-cell embryos with human oviductal epithelial cells. Design: Prospective, controlled in vitro experimental study. Setting: Academic research laboratory. Animal(s): Female ICR strain mice aged between 6 and 8 weeks. Intervention(s): Flushed one-cell embryos were cultured in human tubal fluid medium alone (control), in coculture system with human oviductal cells, in five kinds of conditioned media, and in a contactless coculture system using a cell-culture insert. Main Outcome Measure(s): The percentage of the embryos developed to hatching blastocyst stage and the level of superoxide anion in the supernatant from each culture condition. Result(s): The rates of embryo development to the hatching blastocyst stage were significantly higher in the coculture group (43%) than in the control group (none) ( P