Abstract

Embryo models are aggregates of pluripotent stem cells that exhibit aspects of embryonic development. Investigators use embryo models to study mammalian development and prevent adverse outcomes in pregnancy. However, researchers have called for debate on ethical guidelines for the use of embryo models. In addition, the International Society for Stem Cell Research has announced that it will update its research guidelines to more fully address embryo models. If embryo models are equivalent to human embryos, then they deserve the respect afforded to all humans. The definition of the organismic potential of an embryo model should not require complete mature development or the presence of all of the typical organism’s parts. There are explanatory gaps in the ISSCR’s published recommended guidelines. The research needed to determine the nature of the human embryo model places the model in danger; thus, principled caution is needed in moving forward.