Reacción a "Reactions: macaque embryo-like structures developed and implanted in utero from stem cells"

Human pluripotent embryonic stem cells (hESCs) were first isolated from blastocysts in 1998 by J. Thompson's team. However, this breakthrough came 17 years after the same cells had been independently isolated from mouse blastocysts (mESC) by Martin Evans and Gail Martin. The biology of the pioneering mESC cells took the lead and has developed much further than that of hESCs.  

With mESC cells, it is possible to regenerate an entire mouse by reintroducing them into another blastocyst or by aggregating them with preimplantation embryos from earlier stages. This has been used to generate the thousands of mutant mice that exist today, many of them animal models of human disease. mESCs can also be used to derive any other cell type in vitro, in the laboratory. And there have even been reports of the spontaneous, albeit very inefficient, emergence of synthetic mouse embryos in the laboratory by mixing these mESCs with other types of stem cells. 

All this amazing versatility and malleability shown by mESCs cannot be replicated with hESCs, for a variety of scientific, legal and ethical reasons. For example, it is forbidden in most countries, such as Spain, to culture human embryos beyond 14 days.

For all these reasons, the researchers in this study, now published in the journal Cell Stem Cell, have opted to transfer the new culture and aggregation techniques developed in mouse mESC cells to cyESC, which are pluripotent embryonic stem cells from macaque (Cynomolgus), a non-human primate, evolutionarily related to us, as an intermediate approach to the experiment with hESC, which is currently unfeasible. And, indeed, they managed to obtain a macaque blastoid (similar but not identical to the blastocyst) from cyESC and, using these blastoids, they managed to differentiate different cell types in the laboratory, they managed to obtain embryos with the three germ layers and, after implanting them in the uterus of female macaques, they obtained evidence of gestation.  

The study does not report the birth of any macaque babies so far. This is an experiment that cannot be performed in humans, due to the technical, legal and ethical limitations associated with it, but studies like this one, carried out in macaques, are gradually bringing us closer to such a possibility. The birth of non-human primates derived entirely from embryonic pluripotent stem cells grown in the laboratory (the next work that the authors of this study will no doubt attempt to carry out), without the need to go through fertilisation of an egg by a spermatozoon, as has been possible for years in mice, is getting closer and closer.

It remains to be seen how many of these advances will be tested on human embryonic pluripotent stem cells. And perhaps it would also be legitimate to ask whether we should undertake such experiments, how we should regulate them and for what purposes we should allow them to be undertaken.