Without sperm or egg, how scientists grew whole model of human embryo

The researchers from Israel used a mix of stem cells and chemicals, a small portion of which was able to spontaneously assemble to form different types of cells that form the foetus, those that provide nutrients to the foetus, cells that lay out the plan for development of the body, and cells that create structures like placenta and umbilical cord to support the foetus.

One of the problems that the team faced, however, was that only 1% of this mixture actually assembled spontaneously, making the process not very efficient.

Why are embryo models and research important?

There is no way for scientists to ethically research the early stages of development of an embryo, as it is difficult to study it after it implants in the uterus. Scientists currently study these initial changes in various lab models or donated embryos.

This research is crucial because the initial days of embryo development is when the majority of miscarriages and birth defects occur. Studying the initial stages, scientists say, may help understand genetic and inherited diseases better.

The understanding of why some embryos develop normally, retain the proper genetic code, and implant properly in the womb while others do not, may also help in improving success rates of in vitro fertilisation.

Debojyoti Chakraborty, principal scientist at the Institute of Genomics and Integrative Biology who works on embryonic stem cell biology, said: “Embryonic research is very important because currently one of the only ways of studying these early processes is through developing alternative models that can be grown in the lab. Although they mimic several aspects of development, they are not surrogates of actual embryos.”

Chakraborty said these embryo-like models can allow scientists to understand the genetic, epigenetic and environmental effects on a developing embryo. “Scientists are slowly mimicking the organisation of cells as seen in real embryos, and thus bringing us closer to understanding how genetic defects lead to certain diseases or how futuristic genetic medicines can be implemented for the treatment of certain conditions.”

Can lab-grown embryos be used to get pregnant?

No. These models are meant to just study the early stages of development of a foetus.

It is generally accepted — and legally supported in most countries — that these embryo models will be destroyed after studying the first 14 days. Attempts to implant are not allowed.

Also, creating a lab-based model that mimics the properties of early embryos is still far from an actual embryo that can implant to the lining of the womb.

Why is there a 14-day limit on embryo research?

The limit was first proposed by a committee in the UK in 1979 after the birth of the first test tube baby Louise Brown demonstrated that embryos could be kept alive in laboratories. The 14-day period is equivalent to when embryos naturally finish implantation. It is also when cells start becoming an “individual”, and breaking off into a twin is not possible.

“The ethical considerations become different when it is a clump of cells and when it becomes an individual, often related to what is referred to as the Primitive Streak,” Chakraborty said. While the models are not human embryos, they come very close to it. Primitive Streak is a linear structure that appears in the embryo that marks its transition from having a radial symmetry (like an egg) to the bilateral symmetry of our bodies (marked by left and right hands and legs).

What have these models shown about the early stages of development?

Models such as the one developed by the team from Israel have helped scientists understand why sometimes errors arise when the DNA is duplicated, why sometimes one of the daughter cells receives too many or too few chromosomes.

Researchers used to assume that the errors occurred when the two daughter cells were separated, but one such model helped researchers understand that it happened much earlier in the process, when DNA duplication is ongoing. When the duplication is not normal, the split is not normal.

These models allow scientists to see what roles various genes play in the development of the foetus.

“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,” biologist Magdalena Zernicka-Goetz said in a release earlier this year after her team published a similar model.