This isn't the first time that brain-like tissue has been created in the lab, but previous efforts have always ended up with a rather ineffectual two-dimensional layer that would die within days. The problem seemed to be the two-dimentional collagen plate that was being used as scaffolding to coax the tissue into a particular shape - once the tissue tried to expand beyond a simple flat layer, everything fell apart.
But now researchers from the Tissue Engineering Resource Center at Tufts University in the US have come up with a new type of scaffolding, shaped like a doughnut and made from a spongy silk protein and a softer, collagen-based gel. The silk protein structure provides a place for the neurons to attach themselves, and the collagen gel encourages the nerve fibres to grow through the scaffold and make contact with the neurons.
It took just a few days for the neurons, which were grown from rats, to form functional networks with the nerve fibres. For the first time, the researchers were even able to create a distinct region of 'white matter' made from bundles of nerve fibres in the centre of the doughnut, and a surrounding area of 'grey matter’, made from neuron cell bodies - just like a living brain has. Because brain injuries and diseases affect these areas in different ways, it was crucial for the researchers to separate them in their brain models.
So far, the team has been using their brain-like tissue to test the effects of traumatic injuries on the brain, including concussions and bomb blasts. Previously, researchers have been forced to perform these tests using actual brains in the bodies of deceased humans or animals, which obviously isn't ideal. The tests the team performs on the brain models are very simple - a weight is dropped onto the tissue from varying heights, and the team records changes in the neurons' electrical and chemical activity. What they found reflected the results of similar tests performed on lab animals.
“With the system we have, you can essentially track the tissue response to traumatic brain injury in real time. Most importantly, you can also start to track repair and what happens over longer periods of time,” said lead researcher and professor of bioengineering David Kaplan in a press release. "The fact that we can maintain this tissue for months in the lab means we can start to look at neurological diseases in ways that you can't otherwise because you need long timeframes to study some of the key brain diseases."
The researchers have published their findings in the Proceedings of the National Academy of Sciences.
"This work is an exceptional feat," said Rosemarie Hunziker, program director of tissue engineering at the US National Institute of Biomedical Imaging and Bioengineering. "It combines a deep understand of brain physiology with a large and growing suite of bioengineering tools to create an environment that is both necessary and sufficient to mimic brain function.