Two independent scientific teams have created cultures of human cells that develop as embryos in the laboratory. Embryoids, as they are called, acquire the different types of cells from which a fetus could develop, but they do not have the cells needed to form the placenta, so they could not lead to a pregnancy.
The aim of the two projects is to study the initial stages of human embryonic development, say the authors of the research, who yesterday presented the results in Nature. It depends on what happens in these stages that the pregnancy is viable and, if it is, the health of the person for life.
However, the study of the critical period of development has so far been limited by restrictions on research with human embryos. It is "the black box of human embryonic development", Magdalena Zernicka-Goetz, from the University of Cambridge (United Kingdom), who has led one of the investigations, declared at a press conference yesterday.
"We would like to study the events that occur up to around day 14 [of embryonic development]. It could help us better understand important biomedical issues, such as pregnancy interruptions or developmental disorders," says Berna Sozen, from Yale University in New Haven (USA), who led the other research, by email.
60% of pregnancies are interrupted in the first 14 days after fertilization, before the woman knows she is pregnant, according to data provided by Zenicka-Goetz. Of the others, one in four is interrupted involuntarily. The researcher hopes that the line of research will help reduce the number of unwanted abortions.
The creation of embryoids opens an ethical and legal debate about how to regulate them, since they are not exactly the same as embryos, but could lead to viable pregnancies in the future. "A consistent regulatory framework is urgently needed," says Darius Widera, a stem cell specialist at the University of Reading, speaking to the UK's Science Media Centre.
Yale University research has been done using human pluripotent stem cells, which have the potential to become any type of cell in the body. They have been cultivated in a medium suitable for them to become embryonic cells.
According to the results presented in Nature, in 72 hours they had acquired a spheroid shape like that of a human embryo. They had differentiated cells of the epiblast (from which the fetus is formed) and those of the hypoblast (from which the yolk sac that provides nutrients and oxygen to the embryo is formed). But they lacked the trophoblast cells (from which the placenta develops).
The researchers allowed the embryoids to develop until the stage when the body begins to take shape, which in a human embryo takes place 14 days after fertilization.
Research led by the University of Cambridge has developed human embryo models also from stem cells, but uses a different method. Also in this case, the embryoids formed three-dimensional structures and were allowed to grow to the equivalent of 14 days of development.
They differentiated the tissues from which the fetus is formed, as well as those that give rise to the structures that surround the fetus. But, as in the other research, they were missing the cells with which the placenta is formed.
At least two other research teams, one in Israel and another in China, have developed similar human embryo models, The New York Times has reported. The teams from the universities of Cambridge and Yale are the first to publish the results in a scientific journal. "Our system offers a reproducible, manageable and scalable experimental platform for understanding the basic cellular and molecular mechanisms that underpin human development," the Yale team concludes in Nature.
In the same vein, Bailey Weatherbee, first author of the Cambridge research, highlighted yesterday at the press conference that "the objective is to create a research platform" to study a crucial period of the development of the human body.
