Growing human brains in a dish is opening up unprecedented opportunities for neuroscience research.

Ethical concerns can make the study of the human brain particularly challenging, but a new technique allows scientists to grow model brains in a dish by genetically engineering adult skin cells. In a presentation at the Military Health System Research Symposium, a group of researchers from Ohio State University reported that they were able to use this technique grow such a "brain organoid," similar to the brain of a five-week-old fetus.

"It not only looks like the developing brain, its diverse cell types express nearly all genes like a brain," said Rene Anand of Ohio State University in a statement. "We've struggled for a long time, trying to solve complex brain disease problems that cause tremendous pain and suffering. The power of this brain model bodes very well for human health, because it gives us better and more relevant options to test and develop therapeutics other than rodents."

Through genetic engineering, researchers can turn skin cells harvested from adults into pluripotent stem cells. These are the same type of stem cell found in human embryos that have raised ethical concerns — but scientists can now avoid the issue by making them out of skin cells. This particular type of stem cell is so valuable because pluripotency means that it can develop into any organ.

Indeed, scientists have already used skin cell-derived pluripotent stem cells to grow organoids such as stomachs. But the brain is, of course, a far more complex organ and as a result, creating a brain organoid has been more difficult.

To reach the development level of a pencil eraser-sized, five-week-old human fetus's brain, the scientists must let the organoid grow for 12 weeks. At this stage, the organoids have a spinal cord, different types of neurons, brain signaling circuits, and a retina that would eventually become part of the eye. One major drawback the researchers are still working to eliminate is that the organoids lack blood vessels.

Anand and his colleagues have already used this technique to create brain organoids that model Alzheimer's and Parkinson's diseases. They hope that these new tools will allow scientists to overcome some of the roadblocks that are slowing brain-related disease research today.

"In central nervous system diseases, this will enable studies of either underlying genetic susceptibility or purely environmental influences, or a combination," Anand said in a statement. "Genomic science infers there are up to 600 genes that give rise to autism, but we are stuck there. Mathematical correlations and statistical methods are insufficient to in themselves identify causation. You need an experimental system — you need a human brain."

Photo: NICHD | Flickr

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