For the first time ever, researchers have created an artificial mouse “embryo” from stem cells in the lab. By combining two types of stem cells on a 3D scaffold, they could watch as the cells organize and communicate with each other during development.
The developmental process begins when an egg cell is fertilized by a sperm, forming what is known as a zygote. After around 24 hours, the zygote, which is still a single cell, makes its first division and starts to form an embryo. At this stage, the embryo is formed of a free-floating ball of stem cells, but they are quickly divided into three separate types as the developing embryo forms a blastocyst.
Those that go on to form the actual body of the developing embryo, known as embryonic stem cells (ESCs), cluster towards one end of the blastocyst, while a second type called extra-embryotic trophoblast stem cells (TSCs) migrate to the other, eventually giving rise to the placenta. The third type are known as primitive endoderm cells, which create a yolk sac that will provide growing organs with the vital nutrients they need.
It is how these three cell types organize themselves and communicate during development that interests scientists, and the team behind the latest study wanted to see if they could achieve it within the lab. They took both ESCs and TSCs and placed them on a 3D scaffold, before testing what would happen. They found that the two types of stem cells were indeed able to grow and organize themselves in a manner that closely matched how it occurs with natural embryos.
“We knew that interactions between the different types of stem cell are important for development, but the striking thing that our new work illustrates is that this is a real partnership – these cells truly guide each other,” explains Professor Magdalena Zernicka-Goetz, who led the research published in Science, in a statement. "Without this partnership, the correct development of shape and form and the timely activity of key biological mechanisms doesn't take place properly.”
The researchers were able to watch the “embryo” grow and develop, but it is unlikely to ever form a viable fetus. For a start, it lacks the third type of stem cell, those that form the yolk sac, but it would also be unable to develop a proper placenta necessary for healthy growth.
One of the main barriers to this field of research is the availability of human embryos. Currently, they have to be donated by IVF clinics, but that means there is frequently a shortage. If researchers could therefore make their own embryos from stem cells, it could help them uncover why miscarriages occur.