Mice receive millions of human brain cells
Scientists at Stanford University have created mice whose brains contain millions of functioning human neurons, developing a new model for studying neurological disorders and potential treatments, reports a Qazinform News Agency correspondent.
In a study published in Nature, researchers genetically engineered mice to lack most of the cerebral cortex and hippocampus before implanting human cortical organoids grown from stem cells.
The team removed approximately 14 million mouse neurons and introduced around four million human neurons. The transplanted tissue expanded, developed blood vessels and connected with the animals’ nervous systems, eventually occupying most of the available cortical space.
“For the past two decades, there’s been a quest to try to build models of the human brain outside of the human body,” said senior author Sergiu Pașca, professor of psychiatry and behavioral sciences at Stanford University.
“This is not going to replace all the models we had before, but it’s going to provide us access to other aspects of human brain function that would be very difficult to study otherwise,” he added.
The altered mice retained broadly normal movement, while the human neurons displayed organized electrical activity. Animals receiving the cells also showed improvements in some memory and social-interaction tasks compared with mice lacking the cortex.
When deprived of oxygen, the transplanted human tissue developed injuries resembling those observed in human newborns. Researchers said this could help study cerebral palsy, intellectual disability and certain forms of epilepsy.
The grafts also contained cells resembling von Economo neurons, which are associated with social behavior and are affected early in some forms of frontotemporal dementia.
However, the experiment has raised ethical questions. The researchers ended it when the human cells reached approximately six months of development.
“They’re trying to stop the study before the markers of consciousness, or the fact of consciousness, might emerge,” said Duke University professor Nita Farahany, who served on an external ethics board advising the project.
She called for caution, particularly if similar experiments are conducted in larger, longer-living animals.
Earlier, Qazinform News Agency reported that younger generations may be aging faster biologically than previous generations, potentially contributing to the rising incidence of cancer among adults under 55 years old.
