Why can't we breed hybrid animals?

Medical research The Japanese allow human-animal hybrids

Human-animal hybrids - such experiments have so far been subject to strict rules. For example, US researchers allowed human cells to grow in a pig embryo for four weeks before ending the experiment. In Japan such experiments were only allowed up to the 14th day of embryonic development. But thanks to a change in the law, the country now allows the development of such human-animal hybrids until birth.

Hiromitsu Nakauchi, a stem cell researcher at Tokyo University, has received permission to conduct the experiments from the Japanese Ministry of Education and Research, according to a report in Nature. Nakauchi plans to first grow human cells in mouse and rat embryos and then transplant them into replacement animals. Later he wants to let hybrid embryos grow up to 70 days in pigs. The aim of the research is to produce animals with organs from human cells so that these organs can later be transplanted into humans.

How does a human organ grow in a foreign embryo?

Nakauchi and his team proceed as follows: They create an animal embryo that is missing a gene. For example one that is responsible for the production of a pancreas. Then they inject human pluripotent stem cells. Such cells can produce virtually all types of cells. In this case, they are programmed to allow a human organ, a pancreas, to grow in the animal embryo.

According to the report, Nakauchi succeeded in carrying out this experiment with mouse cells in a rat embryo as early as 2017. According to the researchers, the pancreas developed in this way was transplanted into the mouse, was able to control the blood sugar level and cure the mouse of diabetes.