Scientists Create Human Embryo-Like Structures with Stem Cells

prevent research on human embryos more than 14 days after fertilization. But the new technique uses stem cells, which have the potential to transform into any other type of cell, such as a heart, skin or even brain cell, to mimic embryos. And without breaking any rules, the result would allow researchers to better understand later stages of human development, according to Magdalena Żernicka-Goetz, a developmental and stem cell biologist at the University of Cambridge and the California Institute of Technology. She says she’s particularly eager to see these models developed through a phase called gastrulation, which occurs about three weeks into human development.

Żernicka-Goetz led the team behind the advance and presented the work on June 14 at the annual meeting of the International Society for Stem Cell Research in Boston. Scientific American spoke to Żernicka-Goetz about the research, which she says will be published soon in a scientific journal.

[An edited transcript of the interview follows.]

What specifically did this experiment create and how?

We combined stem cells to create embryo models that establish three compartments—to my knowledge, for the very first time—at postimplantation stages. One is the embryo. Two are extraembryonic tissues. One is called trophoblast; it’s the tissue that would normally form placenta. And the second stem cell type forms hypoblastlike tissue, and it’s a tissue that will make a yolk sac.

We not only don’t use sperm or egg but also jump over the first seven days of development that occur before implantation. The structures we assemble look like embryos that have just implanted. The model is developed until the equivalent of day 14 in a human embryo.

With this model, we specifically wanted to understand this peri-implantation stage of development, when there is cross talk between the three types of tissues. What we show with our model for the very first time is: we can actually look at this crosstalk and interactions between the tissues. So that’s very fascinating.

We do not provide any extra factors to the culture media that we use, which we established 10 years ago. And in this media, the three types of stem cells self-organized to form this embryolike structure.

It’s not an embryo—it’s an embryolike structure. Or in other words, we can call it a model of a human embryo. It’s three-dimensional, its architecture is beautiful, and it’s very powerful in understanding the causes for pregnancy loss at the time of implantation. But it’s not a real embryo.

What sort of ethical approval process did you go through for this study?

All studies on human embryos have to be approved, and our lab has this approval to study human embryos until day 14. But for human embryo stem cell models, such as the one which we created, research on this is allowed because they are not real human embryos; they are human embryo models.

Is this the first time that synthetic human embryo models have been created from stem cells?

It’s not the first time. A few years ago people created embryo models from stem cells at earlier stages of development, preimplantation stage. Our model is different because it covers later stages of human embryo development, and it contains the three lineages, the three tissues that are very essential at this time.

What do you hope to learn from these models?

Our motivation for creating these models is to really understand this developmental black box. This is the time when the embryo implants, and we cannot see it, and it’s very difficult to understand how tissue interacts.

Seven years ago we published the first study of human embryo development [outside of the uterus past] the implantation stage, so for the first time, we were able to see a real human embryo developing through implantation and how different tissues in that embryo developed. This gave us the idea that we might be able, instead of using human embryos, to mimic this cell-cell communication with stem cells and study human embryo development in a model rather than in a real embryo.

Why do I do it? I am fascinated by this stage of development that’s very difficult to understand. It’s predicted that 30 percent of pregnancies fail soon after implantation. So this model will allow us to understand the reasons behind that failure. Hopefully, with time, we will be able to save the lives of those embryos.