Reproductive biology: How embryos foretell their developmental potential

Human embryos may produce signals that forewarn of their developmental potential prior to implantation, a study in Scientific Reports this week suggests. The research identifies two distinct mechanisms that have an important role in embryo selection during the implantation stage that make the process adaptable to each individual embryo.

Human embryos often harbour complex chromosomal errors that impede normal development. Some affected embryos fail to implant, but many do manage to embed in the cells that are forming the uterine lining before being rejected by mechanisms that have remained poorly understood.

Jan Brosens, Nick Macklon and colleagues used experiments in cultured human material and in living mice to study the processes that underlie failure during embryo implantation. They show that developmentally competent human embryos, like mouse embryos, produce trypsin signals to actively enhance the uterine environment for implantation and further development. Conversely, developmentally impaired embryos seem to elicit a stress response in the cells of the uterine lining. The research adds to our understanding of the processes that govern embryo selection at implantation.