For the first time ever, researchers have successfully grown a fully-functioning embryo in the laboratory using two different kinds of stem cells. As important step towards creating artificial life, the breakthrough could enhance our understanding of how life actually begins. The process, according to the scientists, involved growing stem cells in a gel-filled Petri dish, which eventually differentiated to form the rudimentary versions of several essential internal organs. Speaking about the study, the team’s leader Magdalena Zernicka-Goetz said:
It has anatomically correct regions that develop in the right place and at the right time. This was the most amazing thing for us.
In the past, researchers have attempted to create a lab-grown embryo using only one type of stem cells: embryonic stem cells (or ESCs) that are responsible for producing a free-moving cellular mass called blastocyst following the fertilization of the egg. As explained by the team, this particular approach is viable because it requires two additional kinds of stem cells, namely the extra-embryonic trophoblast stem cells (TSCs) and the primitive endoderm stem cells, to generate a functional embryo.
The job of these extra stem cells, the scientists point out, is to help the ESCs build the placenta and the yolk sac, which are in turn there to hold the developing organs in place as well as ensure proper supply of nourishment and nutrition to the tissues. For the research, the team relied on genetically-altered mouse ESCs and TSCs. To assist the embryo’s growth, they created a special 3D gel that acted as a scaffold for the stem cells to develop around. A researcher at the University of Cambridge, Zernicka-Goetz added:
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. Without this partnership, the correct development of shape and form and the timely activity of key biological mechanisms don’t take place properly.
At around the 4.5-day mark, the scientists found a number of functional embryos in the Petri dish that looked remarkably similar to real ones. Seven days after the start of the experiment, the artificial embryo seemed to have developed further, showing signs of a placenta and the beginnings of the mouse itself. What is truly amazing about the breakthrough is that it marks the first time that researchers have been able to create life from scratch without the use of egg or even sperm cells. The team went on to say:
They are very similar to natural mouse embryos. We put the two types of stem cells together – which has never been done before – to allow them to speak to each other. We saw that the cells could self-organize themselves without our help.
The current approach enabled the embryo to reach around one-third of the growth process of an actual mouse pregnancy. Beyond this, the team explains, the embryo would have needed help from primitive endoderm stem cells to be able to build the yolk sac, which is what delivers the nutrients and blood cells while the placenta is still under development.
More than being able to create life in the laboratory, the objective of the research was to shed some light on what happens at the early stages of embryonic formation. The findings, recently published in the Science journal, could also help uncover the reason why two out of three cases of human pregnancy end in miscarriage within the first trimester. The team is currently focused on conducting a similar experiment using human stem cells. Zernicka-Goetz stated:
We think that it will be possible to mimic a lot of the developmental events occurring before 14 days using human embryonic and extra-embryonic stem cells using a similar approach to our technique using mouse stem cells. We are very optimistic that this will allow us to study key events of this critical stage of human development without actually having to work on embryos. Knowing how development normally occurs will allow us to understand why it so often goes wrong.
Source: University of Cambridge