On April 15, 2021, Juan Carlos Izpisua’s research group published an article in Cell (read HERE) describing the generation of human-monkey chimeras.

Chimeras alive in the laboratory

Regardless of the technical aspects and the purpose that — according to the authors — these experiments may have in better understanding human embryonic development and in their use to produce human-animal organs for possible use in clinical transplantation, the work presents unquestionable bioethical difficulties that we think are interesting to analyze (read the full article HERE). Elaborating on what the authors themselves say about these ethical difficulties in the “Discussion” section of their article, they focus primarily on the production of human-animal chimeras, which in itself is ethically highly problematic, but specifying further, also on the degree of colonization by human cells that may occur in the organs produced, especially if such colonization reaches the brain and reproductive gametes. In relation to the brain, a few weeks ago, the US National Academies of Sciences, Engineering and Medicine appeared to confirm this possibility ( read HERE), although the authors also say that the chimeras produced, since they only live for 20 days, still have no nerve tissue, so the brain cannot be colonized with human cells. However, we would add that, in order for these chimeras to be clinically useful, they would have to be allowed to develop into adult animals so that their organs could be removed from them; in this case, their brain would have developed and could be colonized with a certain number of human cells.

Nonetheless, from an ethical perspective, this study has one positive aspect, and that is that it does not use human embryos.

Therefore, from a bioethical point of view, in our opinion, the principle of prudence should be considered before proceeding with this type of research.