- The stem cells are capable of producing any type of cell according to the part of the body in which they are implanted
- Japan previously required researchers to destroy in 14 days embryos into which human cells had been introduced
- It involves developing animal embryos (mice, rats or pigs) that lack a particular organ, such as the pancreas, for example.
Japanese scientists will begin to try to make human organs in animals after receiving permission from the government for the first time in Japan’s history to conduct such studies. This controversial area of research consists of implanting human stem cells called “iPS” in modified animal embryos. The stem cells are capable of producing any type of cell according to the part of the body in which they are implanted and can thus form the basis for the creation of a particular organ.
The work conducted by Hiromitsu Nakauchi, a Stanford University geneticist , is the first of its kind to get government approval after Japan changed its rules on the implantation of human cells. Japan previously required researchers to destroy in 14 days embryos into which human cells had been introduced, and prohibited such embryos from being implanted in the wombs of developing animals. These restrictions were dropped in March, allowing researchers to request individual approvals for their projects.
Just the beginning
“It took almost ten years, but now we can start the experiment,” Nakauchi told the media. It involves developing animal embryos (mice, rats or pigs) that lack a particular organ, such as the pancreas, for example. Human iPS cells destined to multiply to form the missing pancreas will be implanted.
The embryos will then be introduced into the womb of an animal, where, in theory, they will develop until eventually generating a functioning human pancreas. Preliminary research has shown promising signs, such as the creation of mouse pancreas in rats. These reimplanted organs in mice functioned well and regulated the glucose level in diabetic mice. Other tests proved more complicated.
For Nakauchi, authorized research will help to understand the obstacles in this area. He warns, however, that it is still far from the goal. “Although we have obtained proof of concept studies using rodents, it is not easy to cross the genetic distance between humans and pigs,” he said. “The study is just beginning, don’t expect us to manage human organs in a year or two.”
The implantation of animal embryos with human cells creates what is called a “chimera“: an entity composed of animal and human cells.
There will be no ‘hybrids’
This process raises complex ethical questions, particularly the fear that it is not entirely possible to know for certain which organs human iPS cells will produce in the animal. Rules vary from country to country. The United States, for example, has no federal restrictions on chimera breeding, while other countries prohibit them from being left alive for more than two weeks.
Ethicists are concerned that chimeras in the human brain, or equipped with human reproductive cells, raise serious questions about the true nature of the animal being tested. Experts point out, however, that qualifying this breeding process as “human-animal hybrids” is wrong. There is a big difference between “hybrids and chimeras,” says William Lensch, a strategy advisor at Harvard Medical School. “In a human-animal hybrid, half of each cell’s DNA would be human and half animal, unlike a human-animal chimera, which contains a mixture of fully animal and fully human cells,” he said. “It’s important to use the right term,” he insists.