Researchers have finally received the green light to start making animal-human hybrids.
Scientists in Tokyo have received permission from the Japanese government to grow hybrid embryos for the full term.
The controversial experiment will be used to grow human organs in living animals for transplantation, potentially creating an unlimited supply.
But there are concerns that scientists cannot determine how much of the animal becomes human, and fear that their brains may develop like that of humans.
The team's progress is a world leader in this field, with most other countries banning this type of work or refusing to give scientists the money to do it.
Researchers in Japan and California say they can someday grow human organs by adding human stem cells to mammalian embryos, which would then use the cells to make organs made from human tissue in the womb
Professor Hiromitsu Nakauchi, who leads the research, has been testing his theory in laboratories for years, waiting for the green light to try it in real life.
He believes he can grow a human pancreas by putting stem cells in another mammal, such as a pig, and using it to cure diabetes in a human patient.
The process works by implanting human stem cells – basically empty cells that can change into anything – into an animal embryo.
The animal must already be genetically modified to ensure that it lacks the cells that it would normally use to make the organ that scientists want to make.
Human cells will then be used by the animal's body to form that organ normally, but the organ will consist entirely of human tissue – in theory.
The embryo must then be implanted into the uterus of a living animal and the baby should be grown as normal at the normal age to be later killed and the human organ taken and given to a donor.
Professor Nakauchi told the Asian news website in June the Asahi Shimbun: & # 39; Human organs are not created immediately.
& # 39; But if this method is realized, it will save the lives of many people. We want to continue carefully with our study. & # 39;
Professor Hiromitsu Nakauchi, working at the University of Tokyo and Stanford University, said learning how to grow human organs in animals can save people's lives
WHAT PROGRESS IS MADE WITH HUMAN-ANIMAL ORGAN TRANSPLANTS?
In some operations, animal body parts are already used to treat human patients.
The heart valves of pigs and cows can be used in heart surgery to replace those of people who have been damaged by illness or injury.
Scientists have been researching the idea of implanting animal organs into people to cure diseases for years – people often die on waiting lists for transplants.
In December last year, researchers from the German Heart Center Berlin transplanted an entire pig's heart into a baboon and the monkey survived 195 days.
The team called it a & # 39; landmark & # 39; experiment and said it could pave the way for people receiving animal organs because baboons are close family members.
Experts from the National Institute for Physiological Sciences in Aichi, Japan, have succeeded in growing mouse kidneys in rats, which was praised as a new breakthrough.
They did this using the same gene editing and stem cell technique that the Tokyo researchers want to use for pancreatic creation.
The US Food and Drug Administration said that transplantation of animal organs and tissues – known as xenotransplantation – could one day help treat conditions for which & # 39; human materials are usually not available & # 39 ;.
But even the technical ability to do something and the desire to use it may not be enough to put something into practice.
The FDA warns on its website: & # 39; Although the potential benefits are considerable, the use of xenotransplantation raises concerns about the possible infection of recipients with both approved and unrecognized infectious agents and the possible subsequent transfer to their close contacts and to the general human population. & # 39;
Cross-species, previously unknown infections can be spread from animals to humans through risky procedures, the FDA said.
The experiment has been tried before, but an embryo of human and animal cells has never been born – they had to be terminated by law within two weeks.
The Japanese government specifically forbade an embryo to grow to its full maturity until its policy change this month, allowing them to stay alive longer than 14 days.
The UK, Germany and France do not allow human stem cells to be put into animal embryos.
And there are no laws that explicitly prevent this from being done in Canada or the US, but the governments of both countries have stopped financing field work – effectively blocking research.
Professor Nakauchi said he will not attempt to produce living creatures immediately, initially try to grow rat and mouse embryos for 15 days, and then ask for two months for further permission to allow pig embryos to grow. to grow.
Dr. Tetsuya Ishii, from Hokkaido University in Sapporo, Japan, acknowledged that people are worried about the experiments.
He told the scientific journal Nature: & # 39; It is good to be careful step-by-step, which will make it possible to have a dialogue with the public that feels anxious and worried. & # 39;
There are concerns that the researchers cannot determine how the bodies of animals use human cells, nor how much of the being & # 39; human & # 39; is becoming.
Professor Nakauchi's team said they would stop the experiment if one of the animals' brains became more than 30 percent human.
It is conceivable that if a large number of human cells were used to form the brain, the animal & # 39; humanized & # 39; and could become unusually intelligent.
In earlier work by Professor Nakauchi and Stanford University, however, a sheep embryo that they created had no human organs and very few human cells – about one in 10,000 cells were human – so they don't believe this will be a problem.
& # 39; We try to ensure that human cells only contribute to the generation of certain organs, & # 39; said Professor Nakauchi in the Out There magazine of Stanford Medicine.
& # 39; With our new targeted organ generation, we don't have to worry about human cells integrating where we don't want them, so there should be far fewer ethical concerns. & # 39;
Professor Nakauchi hopes that developing working pancreas that are suitable for transplantation can one day become a cure for diabetes, affecting millions of people worldwide.
He has already tried the method successfully with rodents.
Research published in 2017 showed that his team in Tokyo with Stanford University had been working on implanting working pancreas that were bred in rats in diabetic mice.
The mice only needed a few days of treatment to prevent their bodies from rejecting the organs before the pancreas started to produce insulin normally.
And animal transplants to humans, known as xenotransplantation, are already being used in medicine.
The valves of the hearts of pigs or cows can be used to replace those of people undergoing heart disease surgery.
And patients who may need organ transplants are people with lung disease such as cystic fibrosis, kidney or liver failure or people with severe heart failure.
But a spokesperson for People for the Ethical Treatment of Animals (PETA), Dr. Julia Baines The sun in June: & # 39; Interfering with the genes of intelligent, sensitive animals in a quest to create organ factories for people is out of contact and a waste of lives, time and money. & # 39;
She added: & # 39; History teaches us that transplanting organs from one species to another has been a total failure.
& # 39; Instead, we should encourage more people to register as organ donors and invest in advanced non-animal science to minimize the need for organ transplants in the first place. & # 39;
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