In a world first, scientists at the University of Wisconsin-Madison have successfully 3D printed human brain tissue that can grow and function like real brain tissue.
“This could be an extremely powerful model to help us understand how brain cells and parts of the brain communicate in humans,” said professor of neuroscience and neurology at the University of Wisconsin-Madison Su-Chun Zhang, senior author of the study, in a thesis. “It could change the way we look at stem cell biology, neuroscience and the pathogenesis of many neurological and psychiatric disorders.”
The breakthrough has the potential to provide a versatile and effective tool for researchers looking to tackle some of the biggest challenges in neuroscience today, such as the hunt for treatments for diseases like Alzheimer’s and Parkinson’s.
3D printing technology has made leaps and bounds in recent years, giving rise to a range of impressive applications. Whether your turtle needs a set of wheels, feels like cooking a delicious two-course meal, or wants to watch a snake-like robot grow towards the light, 3D printing can help.
But despite its many applications, attempts to 3D print brain tissue have had only limited success. The innovation came when the UW-Madison team literally decided to turn the problem on its head.
Instead of stacking layers vertically, as is done in traditional 3D printing, they decided to work horizontally. They grew brain cells from induced pluripotent stem cells and arranged them like a line of pencils in a soft gel they call ‘bio-ink’.
“The tissue still has enough structure to hold together, but it is soft enough for the neurons to grow together and talk to each other,” explains Zhang, which is essential if you want your tissue to grow and can develop. as would happen in a human body.
“Our tissue remains relatively thin and this makes it easy for the neurons to get enough oxygen and sufficient nutrients from the growth media,” said first author Yuanwei Yan.
The neurons can reach through each printed gel layer and form connections within and between them, like a web of intricate connections in the brain. They can send signals, form networks and communicate by releasing neurotransmitters. The team even added another type of cell – astrocytes – to the tissue that the neurons can use to communicate.
“Our laboratory is very special because we can produce almost any type of neurons at any time. Then we can merge them at virtually any time and in any way,” Zhang said.
The authors say this level of precision and control goes beyond what is possible with so-called ‘mini brains’, human brain organoids grown from stem cells. They further tested their 3D printing system by producing tissues from two different brain regions.
Red cortical cells and green striatal cells can be seen in this scan of part of the 3D printed tissue.
Image credit: Waisman Center, University of Wisconsin-Madison
“We printed the cerebral cortex and striatum and what we found was quite striking. Even when we printed different cells from different parts of the brain, they could still talk to each other in a very special and specific way,” explains Zhang.
The team hopes their technique will be accessible to many other labs because it doesn’t require a lot of fancy equipment, but they are also working on refinements for more specialized applications.
“In the past, we have often looked at one thing at a time, which means we often miss some crucial components,” says Zhang. “Our brain works in networks. We want to print brain tissue in this way because cells do not work on their own. They are talking to each other. This is how our brains work and it all needs to be studied this way to truly understand it.
The study has been published in the journal Cell Stem Cell.