The creation of this type of embryos opens many doors for the investigation of the first stages of human development and congenital diseases.

Mouse embryos from human cells.

Two teams of scientists have created in the laboratory “Similar structures” to early embryos based on human cells, models that will make it possible to expand knowledge about the early stages of development, the appearance of congenital problems at the beginning of life or new therapies to treat infertility.

Both works, presented this Wednesday in the magazine Nature, open now new possibilities in the field of embryologyas researchers have so far faced significant challenges.

Recently, the authors recalled in a virtual meeting with the media, structures similar to the embryos of these animals have been generated from mouse cells. in the blastocyst phase -which occurs about five days after fertilization- and which have been called “blastoids”.

Blasts, they explain, are spherical structures formed by an outer layer of cells that surrounds a liquid cavity, in which it is located a mass of embryonic cells.

These mouse “blastoids” have allowed experts to replicate various aspects of their early development, but have limitations to deepen the knowledge about the beginning of human life.

Although human blasts obtained after in vitro fertilization have provided researchers with valuable information to date, their availability and use are also very limited, they remember.

To overcome these obstacles, the team led by the Argentine researcher José Polo, from Monash University (Australia), has generated, for the first time, “blastoids” similar to blastocysts with human cells, which thus avoid the use of natural embryos to carry out this type of study.

Specific, reprogrammed fibroblasts, the main type of connective tissue cell, to produce three-dimensional models of human blastocytes, which they have called “iBlastoids” (“induced blastoids”).

They later found that “iBlastoids” mimic the general architecture of blasts and are capable of give rise to pluripotent and trophoblastic stem cells, a group of cells that provides nutrients to the embryo and develops as an important part of the placenta.

Although they also managed to mimic various aspects of the early stages of implantation, the authors note that the “iBlastoids” should not be considered as a “human blast equivalent”.

Crop strategy

The second study, led by Jun Wu, from the University of Texas Southwestern (USA), presents the development of a three-dimensional farming strategy that allows the generation of blast-like structures from pluripotent stem cells, which they have called “human blastoids”.

These “sets of cells,” Wu exposes, resemble human blasts in their morphology, size, number of cells and in the composition of different cell lines.

Likewise, “human blastoids” are capable of generating embryonic and extra-embryonic stem cells, while they can organize themselves into structures with characteristics typical of peri-implant human embryos.

Like José Polo, Jun Wu emphasizes that these “human blastoids” neither are they “equivalent” to the original human, since, for example, they cannot give life to a viable embryo.

The two models described in Nature, they celebrate, they get to reproduce “Key aspects” of early development, but they present a number of differences with respect to human embryos and, consequently, they should not be considered as such.

However, two independent experts, Yi Zheng and Jianping Fu, comment in an accompanying review article that, as protocols are optimized, these blastoids will come to more accurately mimic human blasts, which raise bioethical questions.

“Consequently,” they write, “the continuous development of models of human embryos, including human blastoids, demands that they be opened public debates about the scientific importance of these investigations, as well as on the social and ethical questions that they raise ”.

Polo points out that there is still a long way to go to reach that point and that, for the moment, they are “excited” about the “great number of applications” that these two study models already offer to better understand “the functions that many genes have in the first development phases ”.

“In addition, we are sure that it will lead us to understand, for example, infertility problems and how to solve them. Or how, since we can create hundreds of them (blastoids), they can affect toxins and viruses at those early stages ”, he concludes.