Scientists have grown miniature human brains in test tubes, creating a “tool” that will allow them watch how the organs develop in the womb and, they hope, increase their understanding of neurological and mental problems.
Just a few millimeters across, the “cerebral organoids” are built up of layers of brain cells with defined regions that resemble those seen in immature embryonic brains.
The scientists say the organoids will be useful for biologists who want to analyze how conditions such as schizophrenia or autism occur in the brain; though these are usually diagnosed in older people, some of the underlying defects occur during the brain’s early development.
The organoids are expected also to be useful in the development and testing of drugs. At present this is done using laboratory animals or isolated human cells; the new organoids could allow pharmacologists to test drugs in more human-like settings.
Scientists have previously made models of other human organs in the lab, including eyes, pituitary glands and livers.
In the latest work, researchers at the Institute of Molecular Biotechnology, in Vienna, Austria, started with stem cells encouraged to grow into brain cells in a nourishing gel-like matrix, which recreated conditions similar to those inside the human womb.
After several months the cells had formed spheres measuring about 3mm to 4mm in diameter.
“The cerebral organoids display discrete regions that resemble different areas of the early developing human brain. These include the dorsal cortex identity — the dorsal cortex is the largest part of the human brain — they also include regions representing the ventral forebrain and even the immature retina,” said Madeline Lancaster, who was first author of the paper published in Nature magazine on Wednesday.
Juergen Knoblich, who was part of the team that created the organoids, said that tests on the brain cells in the structures showed that they were functional.
“Previous models were pieces of small tissue that aggregated to a decent size but there was no success so far in generating something that would resemble the cortex in a particular stage of development,” he said.
At the moment the structures did not grow larger than a few millimeters in the culture dishes because nutrients and oxygen could not reach into the center of the organoids as they grew. To grow much bigger the organoids would need to be equipped with a blood supply of some kind that could feed their centers.
However, he said the organoids were unlikely to reach the complexity required to model cognition or any other higher brain function.