San Diego (AP) - At miniature brains in the lab, researchers have measured electrical activity that resembles brainwaves of premature babies.
The mini-brains are about one million times smaller than a human brain, but show rhythmic network activities from the age of about four months. Researchers led by Alysson Muotri of the University of California at San Diego, California, see such organoids as models that can be used, for example, to study abnormal brain abnormalities or the effects of drugs. The study was published in the journal "Cell Stem Cell".
"The level of neural activity we see is unprecedented in the laboratory," Muotri is quoted in a note from the journal. He and his colleagues have come one step closer to a model that can create the early stages of a sophisticated nerve cell network. Networks arise when nerve cells build connections with each other.
The researchers bred many of the three-dimensional organoids from special stem cells and allowed them to grow in the laboratory for ten months. The environmental conditions shaped them as they are necessary for the development of the cerebral cortex of a human brain.
Using genetic markers, the scientists investigated which cells can be found in different stages in the organoid. After one month, the cell complexes consisted of 70 percent precursor cells. After three and six months specialized cells of the brain were found, like glial cells and nerve cells. The researchers also discovered nerve cells with so-called GABA receptors, which had not previously been generated in the laboratory.
The approximately pea-sized mini brains grew on a plate with numerous electrodes. Thus, the team around Muotri could repeatedly determine the electrical activity of the developing neural network. These measurements compared them to measurements of brain activity recorded by other researchers of premature infants. They trained an artificial intelligence system with the preemie data and the program was able to approximately determine the developmental stage of the organoids.
Muotri and colleagues are aware that their research also raises social and ethical issues. They emphasize that the organoids differ in many ways from the human brain. "The organoid is still a very rudimentary model - we have no other brain parts and structures," says Muotri. For example, there was a lack of blood vessels, even the division into two halves of the brain do not exist. Above all, he emphasizes the opportunities: "I can help people with neurological diseases by giving them better treatments and a better quality of life." Muotri is also involved in a company that uses brain organoids to treat certain neurological disorders Wants to promote illnesses.
Oliver Brüstle from the University Hospital Bonn also sees great opportunities in research on brain organoids. He certifies the group around Muotri a good, serious work, which was made technically sound. However, he bothered by the interpretation that the neuronal activities are similar to those of humans: "With such a statement one should be very careful." For example, inhibitory neurons in organoids are difficult to realize because they are formed elsewhere in the brain and then walk into the cerebral cortex.
Jürgen Knoblich from the Institute of Molecular Biotechnology in Vienna (Austria) also considers the comparison with the brain activities of premature infants to be inappropriate: "This interpretation goes too far and can raise false hopes." In the scientific community, there are also doubts that with the flat electrode plate actually activities of the entire organoid were measured. However, the organoid is a very good research model, much better than the previously used mouse model.
Study (after expiration of the blocking period)
Comment in Nature after presentation of the project at conferences