Scientist Juan Carlos Izpisúa (see ethical assessment of his latest research HERE) and his research team in China have managed for the first time to culture monkey embryos in the laboratory for up to 20 days after fertilization, according to an article published in the journal Science.

Their aim is to be able to study stages of embryonic development that could hitherto only occur in utero, since in earlier procedures, the embryos obtained in the laboratory were transferred to the mother’s womb before that time or were destroyed after 14 days. “Little is known about the molecular and cellular processes that occur during embryonic development,” explained Izpisúa, speaking to Spanish newspaper El País. “Our method allows us to observe key development processes for the first time. This research, even though it has been done with cells from non-human primates, could have direct implications for human health, such as the generation of cells, tissues and organoids”, said the Spanish researcher.

Years ago, culturing a primate embryo for 14 days in the laboratory was a technical challenge, but it was only a matter of time until technology refined it enough to make it possible. However, the 14-day limit has also been legally established in many countries to restrict experimentation with human embryos on the basis of ethical arguments.

Thus, since gastrulation begins from day 15—the time during embryonic development at which cellular reorganization occurs, giving rise to the three germ cell layers—advocates of the 14-day limit argue that the moral status of the embryo grows from then on, because it has greater potential for personhood and is unquestionably an individual, as it can no longer result in twins. Another argument is the “slippery slope”, according to which extending this limit would open the door to ever-increasing permissiveness in terms of the length of time during which research with embryos can be performed. One final argument is that, after gastrulation, the embryo may acquire a level of sensitivity through which it may experience pain and suffering. However, at 28 days, there are no functional neural connections or sensory systems in the embryo, so some authors argue that the 14-day limit should be extended to 28 days or more.

Speaking to El Pais, biologist Elisa Martí said, “We have to tread carefully with ethics, but scientists have to make an effort to convince society that we must go beyond the 14-day limit.” Along the same lines, Javier López-Ríos of the Andalusian Center for Developmental Biology, in Seville (Spain), believes that “the 14-day limit was imposed at the time due to a series of moral and religious issues. Some think that an individual arises at the time of fertilization, but others say that a 14-day embryo is just a collection of cells that neither feels nor suffers.”

In our opinion, defending the 14-day limit may certainly be debatable, but not because an embryo at that stage of development lacks moral status, but because it is difficult, once research on human embryos is allowed, to set a firm limit. Indeed, the process of biological development of the individual begins from the moment of fertilization (see “Biological status of the human embryo”, and as a human being, it is worthy of full dignity (see “Status of person of the human embryo”), which makes the possibility of disposing of it as mere research material ethically unacceptable, either before or beyond 14 days. The research discussed here has been conducted in monkeys, so they would not be subject to the ethical limitations set forth, but the possibility of transferring these experiments to humans is evident. Nonetheless, we reiterate that the greatest ethical difficulty would not be in exceeding the 14-day limit of in vitro development, but that of human embryo experimentation itself.