Depending on your point of view, the creation of an embryo that is partly human and partly ape is an excellent opportunity for medical experts to create organs and tissues for human transplantation; or, the starting point of a horror movie.
Either way, that premise is now a reality.
According to a new study published in the scientific journal “Cell”, a team of scientists led by Dr. Juan Carlos Izpisua Belmonte of the Salk Institute for Biological Studies in California created the first embryo that both human cells and those of contains a non-human primate – in this case that of long-tailed macaques. This type of creation is known as a ‘chimera’, or an organism that contains genetic material from two or more individuals.
The team at Izpisua Belmonte injected 25 human cells, known as induced pluripotent stem cells (or iPS cells in general, and hiPS cells when they came from humans) into the embryos of long-tailed monkeys. Human cells were able to grow within 132 of the embryos and the scientists were able to study the results for up to 19 days. Many sources report it as the first half-human half-monkey embryo, although The Guardian claims that the same team actually developed one in 2019. Salon has issued Izpisua Belmonte to explain the story and will update the story as or when he responds.
This chimera experiment was not the product of mad scientists testing ethical limits: it had real scientific purpose and value. Indeed, with more research and a little luck, scientists were able to use the knowledge of these experiments to grow human organs in other animals.
“This knowledge will enable us to go back now and try to redesign these pathways that are successful in enabling appropriate development of human cells in these other animals,” Izpisua Belmonte told NPR.
The embryo in question is not the first chimera created by scientists: for example, Izpisua Belmonte and the Salk Institute were slightly effective in creating human pig chimeras in 2017, the same year that researchers in Portugal created a chimera virus (in their case, a mouse virus with a human viral gene). There are also chimeras that occur naturally, such as twins that absorb the DNA of their sibling. American singer Taylor Muhl says that a large part of the skin on her upper body is darker because it comes from the genetic material of her twins.
The potential benefit of creating human-monkey chimeras is important. It is often difficult for doctors to have enough organs to give transplants to patients who desperately need them, and creating successful chimeras can allow scientists to produce organs rather than relying on donors. As Izpisua Belmonte told NPR: “This is one of the biggest problems in medicine – organ transplantation. The demand for it is much higher than the supply.”
Julian Koplin, a research fellow at the Biomedical Ethics Research Group, Murdoch Children’s Research Institute and Melbourne Law School at the University of Melbourne, pointed out in an email to Salon that the biggest concern about chimeras is when it leads to live beings. This was only in the early embryonic stage, but if scientists can eventually develop chimeric animals for human pigs for organ transplants, things could become ethically questionable.
“Most people think that people have much greater moral status than (say) a pig,” Koplin explained. “However, a human-pig chimera will stand out in these categories; it is not entirely a pig nor a human. How should we treat this being then?”
Indeed, the chimeric embryo experiment has already entered ethical gray areas. As Koplin noted, “in many jurisdictions, research on human embryos is subject to the ’14-day rule ‘(which limits research to the first 14 days of embryo development.) These chimeric embryos were cultured until some 19 days after Fertilization should have stopped at 14 days? Probably not because only a small part of their cells were human.But how many human cells are too many? At what stage should a chimeric embryo be treated like a human embryo word? ‘
Dr. Daniel Garry, a professor at the University of Minnesota who has written extensively on the science and ethics of chimeras, outlined the issues with Salon by email. He noted that ethical concerns regarding the technology include fears that human cells contribute to organs such as the brain that are outside the target, although he added that he and his colleagues “recently showed that this contribution does not occur.” Similarly, he was afraid of the possibility that a human embryo would accidentally develop into a large animal.
In addition, Garry said that with ethical research in general, ethical issues abound about humans contributing cells to such research. In the case of the monkey-human chimera embryo experiment, people who contributed cells that had been reprogrammed were aware of it and gave their consent to make it happen.
Garry added that there are also questions about “whether some organs may be appropriate but others are not – for example, raising a pancreas or heart is OK, but for some it may not be OK to have a monkey or a pig with human skin or human hair. ”He also noted that ethical arguments usually arise when there is a“ paradigm-shifting discovery ”of people who are‘ lusting for scientific progress ’.
At the same time, Garry said there are a number of strong ethical arguments in favor of chimeras. He pointed out that there are many terminal chronic diseases that do not have curative therapies and whose patients will benefit from the biotechnology created by chimera research. It can lower healthcare costs, increase the supply of transplant organs and reduce or eliminate the need for drugs to prevent an adverse reaction to the immune system.
Koplin said such chimera studies could advance medical science.
“As I understand it, the purpose of this study was to help improve techniques for creating human-animal chimeras,” Koplin explained. ‘Chimeric animals can be used to model diseases or to generate transplantable human organs. This progress can save lives, which is an important moral reason to pursue it. ‘
Henry T. Greely, a professor at the Center for Law and the Biosciences at Stanford University, who wrote on the ethical questions regarding chimeras in ‘Cell’, told Salon that it is difficult to define what constitutes a chimera tel.
“Every time a person gets an organ transplant, the result is an intra-species chimera: an organism consisting of cells from two members of the same species,” Greely noted. “Another example is the way some pregnant women end up carrying cells from their fetus. When one gets a pig heart valve, it becomes a chimera between species. If a mouse gets human cells, for example to test how committed to a developmental pathway (whether they are “pluripotent”), it is a chimera. ‘He also noted that scientists can place human brain tissue in a rat’s brain to study the human cells in a way that is not ethical in other people, as they will eventually have to kill the subject and study their brain chips. .
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What makes the new ape-human chimeras unique, Greely explained, is that they are produced by injecting human cells into an embryo, or just before an embryo can normally develop outside the body without being implanted in a uterus. to become.
“This means that the human cells and the monkey cells are so early in their development that the human cells can end up in any body tissue,” Greely said. This type of chimeras is not difficult to create within the same species, but it is more difficult to do the more two types differ. Of course, the researchers’ ultimate goal is to develop technology that enables them to create large quantities of human organs for transplantation.
“They tried the monkeys to see if the human cells would do better in this closer species (answer: yes) and if it could help them to make human cells thrive in pig or sheep embryos (answer: completely too quick to tell), “Greely pointed out.