Synthetic human embryos let researchers study early development while sidestepping ethical and logistical hurdles

• This has made it difficult for scientists to understand early human development.
• By offering new tools to explore the enigmatic earliest stages of human development, synthetic embryology can help researchers overcome the challenges of using real human embryos.
• With these new models, researchers can also better understand conditions that affect human reproduction and development as well as maternal-fetal health, potentially leading to new therapies.

Making human embryos from stem cells

• This triggers the egg to rapidly divide into embryonic cells that soon form an inner cell mass that eventually develops into the fetus and a outer layer of cells that will give rise to the placenta.
• Synthetic embryology artificially recreates these developmental stages using human pluripotent stem cells derived from human embryos or induced from adult human cells.
• Like early embryonic cells, these cells have the ability to develop into any type of cell in the human body.

• Researchers created the first human embryo model from embryonic stem cells in 2014.
• This pioneering model, also called a gastruloid, captured key aspects of early human development and showed that scientists can drive pluripotent stem cells to form patterned layers echoing the three germ layers and the outer layers of the embryo.

Advancements in human embryo models

• Over the years, various models have been able to replicate different facets of human embryogenesis, such as amniotic sac development, germ layer formation and body plan organization.
• However, none of these models fully captures the entire process of a single cell type developing into the complete structure of a whole embryo.
• Blastoids form in a similar way to human embryos, starting from just a few cells that proliferate and organize themselves.
• Recently, researchers have successfully created more complex models in the lab that mimic what happens after embryos attach to the womb.

Choosing the right models

• This goal underscores the importance of carefully choosing the model best suited to the specific research objectives at hand.
• Creating embryo models from a patient’s own cells could also allow researchers to study the genetics of development and aid in personalizing treatments.
• The International Society for Stem Cell Research strictly prohibits transferring these embryo models into the uterus of a human or an animal.
• Although these models mimic certain features of early developmental stages, they cannot and will not develop into the equivalent of a human baby after birth.

Min (Mia) Yang receives funding from University of Washington