Depending on your point of view, creating an embryo that is part human and part monkey is either an excellent opportunity for medical experts to create organs and tissues for human transplantation; or, the starting point of a horror movie.
In any case, this 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 has created the first embryo to contain both human and human cells. non-human primate – in this case, those 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.
Izpisua Belmonte’s team injected 25 human cells known as induced pluripotent stem cells (or iPS cells in general and hiPS cells when they come from humans) into long-tailed macaque monkey embryos. Human cells were able to grow inside 132 embryos, and scientists were able to study the results for up to 19 days. Many sources report this as the first half-human half-monkey embryo, although The Guardian claims that the same team developed one in 2019. Salon contacted Izpisua Belmonte to clarify and update the story if or when she responds.
This chimera experiment was not the product of crazy scientists testing ethical limits: it had a real scientific purpose and value. Indeed, with more research and a little luck, scientists could use the knowledge from these experiments to grow human organs in other animals.
“This knowledge will allow us to go back now and try to redesign these successful pathways to allow for the proper 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 marginally effective in creating human-pig chimeras in 2017, the same year that Portuguese researchers created a chimera virus (in case , a mouse virus with a human viral gene). There are also naturally occurring chimeras, such as twins that absorb some of their brother’s DNA. American singer Taylor Muhl says that a large part of the skin on the trunk is darker, because it comes from the genetic material of her fraternal twin.
The potential advantage of creating human-ape chimeras is significant. It is often difficult for doctors to have enough organs to provide transplants to patients who desperately need them, and creating successful chimeras could allow scientists to make organs rather than depend on donors. As Izpisua Belmonte told NPR, “This is one of the major 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, the Murdoch Children’s Research Institute and the University of Melbourne School of Law at Melbourne, said in an email to Salon that the greater concern about chimeras it is when they lead to living creatures. These were even in the early embryonic stage, but if scientists eventually manage to develop human chimeric pig animals for organ transplants, things could become ethically questionable.
“Most people think that people have a much higher moral status than (say) a pig,” Koplin explained. “However, a human-pig chimera would be in the way of these categories; it is neither fully pig nor fully human. So how should we treat this creature?”
Indeed, the chimeric embryonic experiment has already entered some gray ethical areas. As Koplin noted, “in many jurisdictions, human embryo research 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 reached 19 days. after fertilization. Should the study have stopped at 14 days? Probably not, because only a small part of their cells were human. But how many human cells are there? At what stage should a chimeric embryo be treated as a human embryo? “
Dr. Daniel Garry, a professor at the University of Minnesota who has written extensively on the science and ethics of chimeras, decomposed the issues with the Salon by email. He noted that ethical concerns against this technology include fears about human cells contributing to “non-target” organs, such as the brain, although he added that he and colleagues “have recently shown that this contribution does not take place.” He also feared that a human embryo might accidentally develop into a large animal.
Moreover, Garry said that with chimera research in general, ethical issues abound regarding the people who contribute cells to such research. In the case of the human monkey-chimera embryo experiment, the people who contributed to the cells that were reprogrammed were aware and gave their consent for this to happen.
Garry added that there are also questions about “whether some organs may be adequate but others are not – for example, the generation of a pancreas or a heart is fine, but having a monkey or a pig with skin human hair or human hair may not be OK for some. He also noted that there are usually ethical arguments that arise whenever there is a “paradigm-shifting discovery” from people who are that “discouraging scientific progress.”
At the same time, Garry said there are a number of strong ethical arguments in favor of chimeras. He showed how there are many chronic terminal diseases that do not have curative therapies and whose patients would benefit from the biotechnology created by chimera research. It could reduce healthcare costs, increase the number of transplant organs, and reduce or eliminate the need for medication to prevent an adverse immune response.
Koplin said such chimera studies could advance medical science.
“As I understand it, the purpose of this study was to help improve the techniques for creating human-animal chimeras,” Koplin explained. “Chimeric animals could be used to model disease or to generate transplantable human organs. These advances could save lives – which is an important moral reason to pursue them.”
Henry T. Greely, a professor at the Center for Law and Biosciences at Stanford University who wrote about ethical questions about chimeras in “Cell,” told Salon that defining what matters as a chimera is “difficult.”
“Every time a person receives an organ transplant, the result is an intra-species chimera: an organism made up of cells from two members of the same species,” Greely noted. “Another example is how some pregnant women end up constantly carrying cells from the fetus. When a man receives a pig heart valve, it becomes an inter-species chimera. When a mouse receives human cells, for example to test how to see how employees are on a developmental path (whether or not they are “pluripotent”), this is a chimera. ”He also mentioned that scientists could insert human brain tissue into a rat’s brain. to study human cells in a way that would not be ethical to do in other people, because in the end they have to kill the tested subject and study his brain slices.
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What makes the new ape-human chimeras unique, Greely explained, is that they were made by injecting human cells into the embryo I have in its blastocyst stage or even before an embryo outside the body can develop properly. normal without being implanted in a uterus.
“This means that human cells and monkey cells are so early in their development that human cells could reach any tissue in the body,” Greely said. These types of chimeras are not difficult to create within the same species, but are more difficult to achieve as the two species diverge. Naturally, the ultimate goal of researchers is to develop a technology that allows them to create large amounts of human organs for transplant.
“The monkeys tried to see if human cells would do better in this closer species (answer: yes) and if this could help them learn how to make human cells thrive in pig or sheep embryos ( answer: too early to say) “, Greely pointed out.