The team managed to create a mouse-chimera that is four percent human. That makes it the highest incidence of human cells ever recorded in an animal.
Unless we desire to become part cyborg with 3D printed organs, this research is good news for anyone who is waiting or will wait for organ transplants, as it brings us one step closer to knowing how to build human organs.
Their findings were published in Science Advances on May 13.
Chimeras and science advances
The team injected developing mouse embryos with human stem cells, and only after two weeks the researchers observed that one mouse showed four percent human cells in its system— a big step forward given human and animal cells don't usually merge smoothly.
This breakthrough is a huge advancement towards genetically modified embryos in the future.
As per the researchers, "It has not been possible to generate naïve [human stem cells] that substantially contribute to mouse embryos." Their work "may enable applications such as human organ generation in animals," as is stated in their study.
After injecting the mice embryos with young human stem cells, the team found evidence of human cells in the liver, eyes, brain, heart, blood, and bone marrow. And after examining the embryos' DNA, it was discovered that the human cells in these mice counted between 0.1% to 4% of the developing tissues.
That said, these mice-human chimeras would not be able to reproduce any human cells, as the team also observed that none of the mice's germline tissue contained any human cells.
While chimeras are still a relatively early process to create and use in science, as well as quite a controversial one for many, it still holds promising opportunities. If one day animal cells and human cells are able to fuse in high proportions, scientists could someday grow entire human organs in vivo. For those on the long organ donor waitlist, this would be a welcome step.
Until further research is carried out, though, it's best to take this news with a pinch of salt at the moment.