Similar to the experiment from 2017: At that time, the researchers planted human cells in a pig's embryo and allowed it to grow for four weeks
Last Saturday, scientists reported that they had successfully created a human-animal hybrids for the second time, this time in the form of sheep embryos, which were 0.01 percent human in terms of their total number of cells.
The embryos were terminated after 28 days and brought researchers one step closer to a future where human organs could be transplanted.
INCREASINGLY HUMAN
To create such chimeras, the researchers isolate the stem cells of a living organism. Then they inject some stem cells of one species into the embryo of a different kind - a complicated process that does not always succeed.
The DNA of the embryo must be changed so that a specific organ should not be formed. If successful, the injected cells are the only ones that could close this gap. In this way, researchers could, for example, breed a sheep with a human liver.
Using this method, Scientists have already successfully bred mice pancreas in rats in 2017 and showed that these organs could cure mice with diabetes in a transplantation. Only a day later, scientists from the Salk Institute announced that they could keep pig embryos alive with human cells for 28 days.
Stem cell experts praised the pig study, but pointed out that the number of human cells in pigs - about one per hundred thousand - is too low for successful organ transplants.
At the annual American Association for the Advancement of Science meeting in Austin, Texas, researcher Pablo Ross of the University of California at Davis and his colleagues then announced that they could improve the process: they reduced the number of human cells in sheep embryos to one increased in ten thousand.
"We think that's probably still not enough to make an organ," Ross said at a press conference. According to the Guardian, about one percent of the embryo would need to be human for organ transplantation to work. In order to prevent an immune response, one would also need to take additional measures to remove residues of animal viruses in the DNA of the pig or sheep. Her new work, however, shows a progress towards functioning organs.
ETHICAL CONCERNS
According to Ross, the research would progress faster if it were better funded. Currently the US National Institutes of Health prohibits the public financing of human-animal hybrid research, although in 2016 they already indicated that the ban could be lifted. (So far, early research has been funded by private donors.)
As the work progresses, the controls on the ethical acceptability of the experiments will probably increase. Ross and his colleagues are aware of the controversial nature of their work, but stress that they are careful.
"Currently, the contribution of human cells is very small. It's not like we have a pig with a human face or a human brain, "said Ross's colleague and researcher at Stanford University Hiro Nakauchi during the meeting. He emphasized that researchers are trying to limit cell proliferation to certain areas to ensure that they do not implant themselves in the brain or reproductive organs.
In any case, for Ross, the many-faceted approaches to organ research are grounds for optimism.
"All of these approaches are controversial, and none is perfect, but they give hope to the people who die every day," he said. "We need to explore all sorts of alternatives to provide organs to sick people."