The key stage in the development of the human embryo is the second week, when it implants into the uterus. It is at this stage that birth defects and genetic diseases can begin to appear, which often lead to pregnancy loss. However, the study of this period has so far been limited because the embryo is too small to be observed in living patients.
Now scientists from Cambridge and the California Institute of Technology have created new 3D models of human embryos grown from stem cells. These models simulate development between day nine and 14 and allow scientists to study them in the laboratory. Previously, such a window could only be studied on animals.
Professor Magdalena Zernicka-Getz, lead author of the study, notes: “Our human embryo-like model, created entirely from human stem cells, gives us access to the developing structure at a stage that is usually hidden from us due to the implantation of the tiny embryo into the mother’s uterus. This exciting development allows us to manipulate genes to understand their role in the development of the model system.”
The models contain most of the cells needed to create a human embryo, including germ cell precursors and the cells that form the placenta, yolk sac and amniotic sac. However, for ethical reasons, the models lack a brain and beating heart cells, limiting their development to the 14-day mark.
This breakthrough is the result of decades of work by Zernicka-Getz and her team to improve mouse embryo models. Other researchers, including a team from the Weizmann Institute of Science in Israel, have also succeeded in creating mouse embryo models in which heart cells begin to beat.
These new stem cell embryo models offer new perspectives in the study of early development and allow scientists to better understand genetic disorders and prevent early pregnancy failure. In addition, research in this area can help improve the viability of couples wishing to conceive, as well as develop new treatments for genetic diseases and growing organs for transplantation.