To what extent are stem cell-based embryonic models embryos?

Malfunctions in the first weeks of human development are associated with low fertility rates and abnormalities in newborns. However, studying this period of our life is difficult for ethical and technical reasons. In recent years, embryonic stem cells have been used to create “human embryo models” – supposed copies of embryos that can be used for research. These models have raised ethical concerns because of their apparent similarity to natural embryos.

However, according to experts, the potential benefits of studying such models are paramount, as they can recapitulate developmental events such as tissue patterning and morphogenesis that cannot be studied otherwise.

However, experts agree that these models are only useful if they can effectively recapitulate these events. “Currently, claims are made about structures that do not mimic the embryo and that can mislead researchers and the public. The reason is the limited knowledge we have of these early stages and the lack of adequate criteria to evaluate this new field,” says developmental biologist Alfonso Martínez Arias of Pompeu Fabra University (UPF) in Barcelona.

For this reason, fourteen stem cell and developmental biology experts from around the world have joined forces to establish a set of criteria to standardise experimental and information standards for the creation, characterisation and comparative evaluation of human embryo models derived from stem cells. This effort has been led by Alfonso Martínez Arias, ICREA research professor at the Department of Medicine and Life Sciences (MELIS) ​​at UPF.

A gastruloid developed at the SEL (Stembryo Engineering Lab) of the UPF. (Photo: UPF)

“We have been working on this for over a year, looking for characteristics that allow us to agree and call these models truly ‘embryonic’ models. At the moment, the field allows for high-impact publications on structures that have nothing to do with embryos or that, when they do, occur at such low frequencies that they are miracles rather than useful tools. Therefore, our goal is to clarify what should be called an embryonic model so that it can be used in reproductive biology, IVF and human embryology,” says the ICREA researcher responsible for the work.

In addition, to ensure universal understanding of the vocabulary used to define the models, experts have also agreed on the definitions of several concepts related to the topic. In this way, they ensure proper dialogue between researchers, guaranteeing the determination of the stage of the modelled tissues, as well as the understanding of the field by the media and society.

“If our suggestions for these guidelines are adopted, they should go a long way toward curbing misunderstandings that are detrimental to the potential of this new but important field and assist funding agencies and regulatory authorities in their assessment of the field,” the developmental biologist concludes.

The document prepared by these scientists is entitled “Criteria for the standardization of stem-cell-based embryo models”. It has been published in the academic journal Nature Cell Biology. (Source: UPF)