For the first time, scientists have detected human-like electrical activity in tiny brains developed in vitro from stem cells, opening the door to research into complex neurological diseases.
Scientists think that brains are unaware because they look like premature babies, but can not prove it, which in itself raises new ethical questions.
It's been a decade since researchers learned how to exploit adult stem cells to develop organoids, that is, cell structures that model an organ they want to study.
But never have these brain organoids developed an active neural network.
"If you had asked me five years ago if I thought it would be possible for a brain organoid to develop a sophisticated network capable of generating oscillations, I would have said no," says AFP Alysson Muotri, biologist at the University of California San Diego.
The breakthrough was partly driven by improved stem cell culture and procedure, the researchers describe in their article published Thursday by Cell Press.
Another advance was to give more time for neurons to develop, just like the brains of fetuses in the belly.
"The first stages of human neurodevelopment are inscribed in our genome," says Alysson Muotri.
The first waves were detected in the organoids after two months. The signals were rare and kept the same frequency, just as in the very immature human brains. But while continuing to grow, the waves were produced at different frequencies, and at more regular intervals.
By comparing the development of these organoids with the curves observed in 39 premature babies, the scientists realized that the trajectories were similar.
What could it be used for? Organoids could be developed from stem cells of individuals with neurological problems such as epilepsy and autism. This would better model these syndromes in order to possibly find treatments.
The research also aims to answer fundamental questions. For example, it is not known why the development of organoids no longer evolves from nine or ten months. Perhaps it is due to the lack of blood supply, or simply sensory stimulation, suggests Alysson Muotri.
© 2019 AFP