In Japan they already experiment with growing organs for humans in animals: the obstacle remains the ethics of this activity
Transplanting organs is something that, as humans, we already know how to do relatively well. The problem that doctors usually find is rather with obtaining the organs with which to replace those affected or those that are lacking. Despite the proliferation of organ donation, it remains a shortage in most countries. Hiromitsu Nakauchi in Japan wants to create them for himself with the help of animals.
The use of animals to grow human embryos is a peculiar topic. Each country and area has its own rules in this regard, although the general line is to prohibit or limit them as a precaution. In Japan specifically, until March of this year, it was forbidden to experiment with the growth of animal embryos containing human cells after 14 days of conception. But things are changing, according to Nature, this month the Ministry of Education and Science has changed the regulation to allow the creation of embryos modified with organs that can later be transplanted into substitute animals.
Sheep embryo with human stem cells.
Human organs growing in animals
Hiromitsu Nakauchi is the name to keep in mind in all this, he is a scientist who leads the teams that study the use of human-animal embryos at the University of Tokyo and Stanford University in California. Its mission is to "grow" human-animal organs from scratch in animals so that they can later be transplanted into people who need them. The idea is to create these organs using human stem cells that, in principle, allow the body to tolerate the organ even if it is not completely human.
Achieving this, of course, is not something simple. In the first place, what is done is to modify an animal embryo so that it lacks the specific gene that allows the growth of a certain organ. After this, human pluripotent stem cells are injected into the embryo, so that it can be used to create the organs that its own cells cannot create because they lack the necessary gene for it.
But of course, there is still more, once the organ is developed, it must be transplanted and the body does not reject it. So that the organ is not rejected, it must contain a good proportion of human cells. Previous experiments I achieved a ratio of one human cell per 100,000 of the animal, Hiromitsu Nakauchi's experiments reach a ratio of one human per 10,000 of the animal. Creating 100% compatible organs is still tricky, but these experiments bring us closer together.
In one of the experiments that have already been carried out, it has been possible to create a mouse that was born without the gene that allows the growth of the pancreas. Stem cells have been inserted into this mouse to develop the modified pancreas. Subsequently, in another mouse, its DNA was modified so that it was born with diabetes. The scientists transplanted the pancreas from the initial mouse to the one with diabetes and found that the new pancreas controlled blood sugar levels to cure mouse diabetes. From there to achieve it with humans there is a lot, and above all it requires being able to experiment with it.
Ethical committees as the main obstacle
Apart from the technical difficulties that we have seen so far, the main obstacle that scientists encounter has to do more with the ethics of their activity and the legislation of each country. Many countries allow this research to be done, but by limiting growth to a few weeks or in some cases by not offering funding for such research. The case of Japan and Hiromitsu Nakauchi is especially relevant because it is the first to be approved under the new rules of the Japanese country and by a committee of scientific experts.
There are bioethicists who are concerned about such experiments because of the possibility that human stem cells may be diverted to other parts than the organs that they want to reproduce. On the other hand, a clear function of these investigations is often not seen either, given the limited early results.
As Hiromitsu Nakauchi has warned, he will seek to proceed slowly, with mouse and rat embryos no older than two weeks at the moment. Over time you will plan to grow pig embryos (for the similarity of their organs / tissues to humans) and for longer periods, up to 70 days. Laxer regulations and approval by ethical committees allow for better and longer experience of this type of aspect.