In fact the embryo of an animal is a living environment capable of producing the necessary signals for differentiation: in animals (in pigs for example) one has a “natural” environment that is a lot closer to the human than an incubator in a lab, with a 3D cellular culture impregnated with growth promoters.

However, a problem arises: this type of development leads to the creation of chimeras, in other words a mixing of genetic material between the cells transferred for incubation and the cells of the incubating host – a mixing of the human and the animal. We thus rediscover in the most cutting-edge forms of technology, the monstrous chimera of Greek mythology. Here we have an ill omen: a monstrous animal could be created through this type of manipulation, producing creatures half-way between different species.
It is easy to understand why intense discussions about ethics, currently underway in the NIH (National Institute of Health) and elsewhere, result from this, as the review Science has recently reported.1 Evidently, imagining that human brain cells, sperm cells or ovocytes can be developed in a pig or goat can leave one feeling perplexed and anxious, while the thought that a pancreas or a kidney developed in an animal seems less disturbing.

Some argue that the good of humans or that of animals has to be taken into account, while others evoke the “sanctity” of the human, or again the risk of bi-products, with animals potentially carrying an altered and humanised germ line, which would make them capable of transmitting these characteristics.

How can such possibilities, which up ’till now have only existed in mythology, be thought? What is the “sanctity” of the human, when it is a question of organs. Would an organ created in vitro be considered to be more acceptable? Today, while previously reserved for the realms of human imagination, all these unheard of questions are real and open…

1 Gretchen Vogel, “NIH Debates Human-Animal Chimeras”, Science, October 2015