Scientists have created models of human embryos by programming stem cells. The models give a glimpse into a key stage of development that can reveal new insights into genetic disorders and preventing failure in early pregnancy.
The second week of human development is a make-or-break stage – this is when the embryo implants into the uterus. Birth defects and genetic diseases can begin to take hold, and unfortunately, many pregnancies are lost at this stage. But this key time remains largely unstudied by scientists and doctors, as the embryo is still too tiny to observe in live patients. Donations from patients undergoing IVF are available for study, but are in limited supply and subject to strict ethical regulations.
Now, scientists at Cambridge and Caltech have developed new 3D models of human embryos, grown from stem cells, that mimic development between days nine and 14 in a way that can be easily studied in the lab. This window was previously only able to be studied in animal cells.
“Our human embryo-like model, created entirely from human stem cells, gives us access to the developing structure at a stage that is normally hidden from us due to the implantation of the tiny embryo into the mother’s womb,” said Professor Magdalena Zernicka-Goetz, lead author of the study. “This exciting development allows us to manipulate genes to understand their developmental roles in a model system. This will let us test the function of specific factors, which is difficult to do in the natural embryo.”
The models contain most of the cells needed to make a human embryo, including precursors to germ cells that will eventually form their own sperm or eggs. They also contain cells that support the embryo, including those that go on to form the placenta, yolk sac and amniotic sac.
For ethical reasons, however, the models are made to be missing brain and beating heart cells, so they cannot develop beyond the 14-day mark. This is to comply with the current legal limit for culturing human embryos in the lab.
This milestone is the culmination of a decade’s worth of work by Zernicka-Goetz and her team, gradually improving mouse embryo models. Other researchers, including a team from the Weizmann Institute of Science in Israel, have also pushed mouse embryo models to the point of beating heart cells.
The growing body of work from multiple teams in this area could help improve viability rates for couples looking to conceive, better treatments for genetic diseases, and lab-grown organs for transplant.
The new research was published in the journal Nature.
Sources: Cambridge University, Caltech