Scientists Create First Functional Brain Tissue Using 3D Printing

Instead of Vertical Printing, Prefer Horizontal

The tissue can grow and function just like typical brain tissue, but it does not come from a human. The method of producing artificial brain tissue was described by a team of scientists in a current issue of the journal Cell Stem Cell. Previous attempts to print functional brain tissue using laboratory 3D printers were only partially successful. The authors of the cited study based their methods on these previous attempts but introduced innovations.

Neurons grown from pluripotent stem cells were placed in a softer gel-like bioink than was used previously. Instead of the traditional 3D printing approach, which involves layering vertical layers one on top of the other, the researchers opted for horizontal printing. “In this way, the tissue still gains an optimal structure to hold together, but it is flexible enough to allow neurons to grow into each other and start connecting,” explains team member Professor Su-Chun Zhang. When talking about the structure of the printed tissue, he likens it to pencils lined up side by side on a tabletop and notes that this arrangement keeps the tissue relatively thin. This thinness allows neurons to get enough oxygen and nutrients from the medium in which they grow. The cells connect through the medium both within printed layers and across them, leading to networks comparable to those in the human brain.

Printed Tissue Offers Multiple Uses

The team is convinced that the results of their work speak for themselves – neurons in the produced tissue can indeed communicate. They transmit signals, interact through neurotransmitters, and can form proper networks with supporting cells added to the printed tissue. For instance, they created brain cortex and striatum. Even though cells from different parts of the brain were printed, they could communicate in a very specialized and specific way.

Professor Zhang adds that his lab holds a unique capability of producing any type of neurons on demand, which can then be assembled into functional tissue. Since the team can print virtually any brain tissue, it is possible to focus on how neurons communicate under certain conditions using it. According to him, the tissue can also be used to study signal transmission between cells in Down syndrome or capture interactions between healthy tissue and tissue affected by Alzheimer's disease. Furthermore, it can assess new potential drugs or simply observe how the brain grows. “In the past, we always focused on one selected thing when studying the brain. This often meant that we missed some critical components. Our brain operates based on networks. That's why we want to print its tissue in this way, because cells in the brain do not operate alone, they communicate with each other. That's how the brain works and it must be studied to be understood,” he clarifies.

The new printing technique should be available to many laboratories. It does not require special equipment for printing biological materials or cultivation methods to maintain healthy tissue. It can be deep-studied using microscopes, standard imaging techniques, and electrodes common in this field of research.

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Sources:
1. Yan Y., Li X., Gao Y. et al. 3D bioprinting of human neural tissues with functional connectivity. Cell Stem Cell 2024; 31 (2): 260–274.e7, doi: 10.1016/j.stem.2023.12.009.
2. Researchers 3D-print functional human brain tissue. Science News, 2024 Feb 01. Available at: https://sciencedaily.com/releases/2024/02/240201212823.htm