AsianScientist (May 6, 2019) – Scientists in Japan have devised a method to create nerve tissue that mimics the architecture of the brain. Their findings are published in the journal iScience.
Intelligence depends on contacts between multiple regions of the brain. For example, the cortex is divided into areas of neurons with distinct roles, such as creating or processing speech, movement, vision and so on. These cortical areas communicate through cerebral tracts, formed by bundles of thin and long extensions of nerve cells, otherwise known as fascicles.
Using a microdevice consisting of two wells connected by a channel, researchers led by Professor Yoshiho Ikeuchi at the University of Tokyo, Japan, were able to mimic connected brain regions in cell culture. They first derived neurons from human induced pluripotent stem cells (iPSCs) and grew them into spheroids at two ends of their microdevice. Over time, the spheroids began to extend connections, or axons, toward each other along the channel of the microdevice.
“After 25 days, both tendrils of axons reached all the way down the channel, and the two cortical spheroids were connected,” said Ikeuchi. “We know this was a functional electrical connection, because if one spheroid was electrically stimulated, the other would respond after a short delay. This resembles the situation in a real brain, where distant regions communicate during cognition.”
When one end of the microdevice was empty, axons still emerged from the neurons at the other end, but significantly less efficiently. Placing an object such as a glass bead at the empty end did nothing to improve fascicle growth.
“The spheroids promoting each other to grow fascicles is very interesting,” said study first author Dr. Takaaki Kirihara of the University of Tokyo. “It implies that opposing axons mutually guide each other, connecting two groups of neurons. This could help explain how reciprocal connections are formed between distant regions of the brain, sometimes even between different hemispheres.”
The researchers also found that the gene L1CAM was necessary for the formation of fascicles between the two spheroids. Going forward, the group intends to transcend the current setup by building a culture device that expands as the cortical spheroids grow—similar to how the skull gets bigger throughout childhood.
The article can be found at: Kirihara et al. (2019) A Human IPS Cell-derived Tissue Model of a Cerebral Tract Connecting Two Cortical Regions.
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Source: University of Tokyo.
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