On 15 November last year, an article was published in the prestigious journal Science, which assessed the development of monkey embryos after their implantation in the uterus.

Since mammalian embryos develop after implantation in the uterus, direct observation of their development and subsequent evolution is virtually impossible. In order to do so, it would be necessary to develop a technology that could maintain the viability and growth of these embryos “ex vivo” in a well-controlled culture medium. This is what has been achieved with primate embryos and published in two articles in Science (see HERE and HERE) (culturing cynomolgus monkey embryos), which has expanded the knowledge of post-implantation embryonic development in animals.

There is no doubt that these experiments are of obvious biomedical and also bioethical importance, since as is generally agreed—and the authors stress—the use of human embryos to investigate early post-implantation phases presents serious bioethical drawbacks.


“Major reservations regarding the transfer of the experiments described therein to humans”


Nonetheless, even though these experiments were conducted using monkeys, mammals close to man, likewise, according to the authors, there are major reservations regarding the transfer of the experiments described therein to humans.

Experiments with preimplantation cynomolgus embryos have previously been carried out, but this is the first time that they have been done in the post-implantation period.

Ethical principles that should govern animal experimentation

In short, the possibility of observing and evaluating the post-implantation development of non-human primate embryos represents an important step forward in order, by analogy, to gain a better understanding of some phases of human embryonic development. This is of interest, if, as the authors of the article in question stress, it also takes into account the ethical principles that should govern animal experimentation, as has been the case in these experiments.