Human Brain Cells Functioned Perfectly in Mouse Brain [Reading Science]

Published 14 Oct.2022 09:02(KST)

Mouse brain implanted with brain organoids made from human stem cells. Photo by Stanford University, USA

[Asia Economy Reporter Kim Bong-su] It has been confirmed that human brain cells function even when transplanted into a rat's brain. This is seen as opening the path for treating human brain disorders using rats.

According to the international journal Nature on the 14th, a research team at Stanford University in the United States succeeded on the 12th in an experiment where brain cells created using human stem cells were transplanted into the brains of rats and made to function, and published a paper in the journal. The team transplanted human brain organoids into the rat's somatosensory cortex, the area that receives signals from whiskers or other sensory tissues and transmits them to other regions for interpretation.

Human brain cells grow much more slowly than rat brain cells. Because of this, the research team had to wait six months to confirm whether the two cells had fused. Finally, they confirmed that the two cells had perfectly merged and were exchanging signals. Serge Pascal, a professor of neurobiology at Stanford University, explained, "It was like inserting one more transistor into a circuit," adding, "The transplanted rats did not show symptoms such as seizures or memory loss, and no significant behavioral changes were observed."

The research team devised a special experiment to verify whether the optical fibers of the human brain organoid's nerve cells were properly connected and functioning with the rat brain cells. They trained the rats to lick water from a faucet only when a light was on. The team conducted the same training on rats with transplanted human brain cells and observed that they licked water only when the light was on. According to the team, this indicates that signals captured by the rat's sensory cells were normally transmitted through the transplanted human brain cells, leading to decision-making.

The team also conducted experiments transplanting human brain organoids made from stem cells taken from three patients with Timothy syndrome, a type of autism, into rats. While these brain organoids grew normally during laboratory culture, after transplantation into the rat brains, unlike other normal organoids, they did not grow significantly and neural connections were not formed.

Nature evaluated, "The fact that brain nerve cells created from human stem cells exchanged information with the nerve cells of living rodents could lead to a path for testing treatments for human brain disorders (using rats) in the future."