Humanimales: Japan supports the development of human organs in other species

IPS are able to produce any type of cell according to the part of the body in which they are implanted and in this way as a basis for the creation of a particular organ. It's only the first step in a long way that could lead to the manufacturing inside animals of human organs to be transplanted, scientists predict.

Until last March, Japanese law required the destruction of embryos into which human cells had been introduced after two weeks., and forbidden to these embryos to be implanted in the uterus of animals for their development. But the regulation has changed and these works for the development of "humanimals", led by the geneticist of Stanford University Hiromitsu Nakauchi, are the first to obtain permission from the Japanese authorities.

"It took more than 10 years but in the present we can start the experiment", Professor Nakauchi celebrated in statements to the AFP.

The investigation will consist of develop animal embryos (mice, rats or pigs) to those who miss a certain organ, for example, a pancreas. Then, human iPS cells will be implanted to multiply and thus form the missing pancreas. Later, the embryos will be introduced into the uterus of an animal, where they will develop theoretically to generate a fully functioning human pancreas.

At present, some preliminary work with these "humanimals" has shown promising results, such as the creation of a mouse pancreas in rats. These reimplanted organs in rodents functioned normally, regulating glucose levels in diabetic mice.

However, other tests with other types of organs have been unsuccessful. For Professor Nakauchi, although the new regulations allow for progress, the end of the road is still far.

"Although we have tested on rodents, it is not so easy to cross the genetic distance between a human being and a pig," he said, saying that the first human organs would arrive in a year or two.

The process of implantation of human cells into animal embryos poses complex ethical problems. One of them is not knowing for sure which organs the human stem cells will produce in the animal.

Ethics experts are concerned that these types of procedures leave the nature of the animal used for experimentation in limbo.

Meanwhile, scientific experts point out that qualifying this process of creating "man-animal hybrids" is false. "In a human-animal hybrid, each cell's DNA would be half-human and half-animal, "said Dr. William Lensch, a strategy consultant at Harvard Medical School.

In the case of experiments in progress, he added, the cells will be mixed, but they will be entirely animal or entirely human, he said.

Professor Nakauchi stated that his team would be extremely cautious and that In the first phase, embryos will not be worn until the end of gestation.

"We have two phases of control throughout the embryonic development of chimeras," he added. "In each of them, we will check for the presence or absence of human cells in the brain and once we have checked, we will move on to the next step.