Failures in the first weeks of human development are associated with low fertility rates and newborn abnormalities. However, studying that period of our life is difficult for ethical and technical reasons. 

Over the last few years, embryonic stem cells have been used to create ‘human embryo models’, presumed copies of embryos that can be used for research. These models have raised ethical sensitivities for their alleged resemblance to natural embryos. However, according to experts, the potential benefits of their study are primordial, since, they can recapitulate developmental events such as tissue patterning and morphogenesis that cannot otherwise be studied.

Even so, experts agree that these models are only useful if they can effectively recapitulate these events. “Currently, claims are made for structures that do not mimic the embryo and that can mislead researchers and the public. The reason for this is the limited knowledge we have of those early stages and the lack of appropriate criteria for this new field.”, says the UPF developmental biologist, Alfonso Martínez Arias.  

For this reason, fourteen experts in stem cell and developmental biology from around the world have joined efforts to set off criteria for standardizing experimental and reporting standards for the creation, characterization, and benchmarking of stem cell-derived human embryo models. This effort is led by Alfonso Martinez Arias, ICREA research professor at the Medicine and Life Sciences Department (MELIS) at UPF, has been published today in Nature Cell Biology as a comment paper. 

 “We have been working on this for over a year, looking for features that will allow us to agree on and call these models, actual ‘embryo’ models. At the moment the field allows for high impact publications of structures that have nothing to do with embryos or that, when they do, happen at such low frequencies that are miracles more than useful tools. That is why our aim is to make clear what should be called an embryo model so that it can be used in reproductive biology, IVF and human embryology.”, says the leader of the paper.

At the moment the field allows for high impact publications of structures that have nothing to do with embryos or that, when they do, happen at such low frequencies that are miracles more than useful tools.

Besides, to ensure universal understanding of the vocabulary used to define the models, the experts have also agreed on the definitions of several concepts related to the subject. In this way, they ensure the correct dialogue between researchers, guaranteeing that the stage of the modelled tissues is determined, as well as the understanding of the field by the media and society.

“If our suggestions for these standards are adopted they should go a long way to curb and misunderstandings that are damaging for the possibilities of this new but important field and assist funding agencies and regulatory authorities in their evaluation of the field”, concludes the developmental biologist. 

Reference article: 

Martínez Arias, A; Rivron, N; Moris, N; Tam, P; Alev C; Fu, J; Hadjantonakis, A-K; Hanna J.H; Minchiotti, G; Pourquie, O; Sheng, G; Solnica Krezel, L; Veenvliet, J.V; Warmflash, A; Criteria for the standarization of stem-cell-based embryo models. Nature Cell Biolgy. September 2024. DOI: 10.1038/s41556-024-01492-x