A group of Oxford University researchers including St Anne’s Fellow, Professor Francis Szele, have developed a breakthrough 3D printing method which could one day help repair brain injuries on a tailored basis. The research, which shows that neural cells can be 3D printed, was published in the journal Nature Communications. It has since received global press attention.
Brain injuries, including those caused by trauma, stroke and surgery for brain tumours, typically result in significant damage to the cerebral cortex (the outer layer of the human brain), leading to difficulties in cognition, movement and communication. For example, each year, around 70 million people globally suffer from traumatic brain injury (TBI), with 5 million of these cases being severe or fatal. Currently, there are no effective treatments for severe brain injuries, leading to serious impacts on quality of life.
Tissue regenerative therapies, especially those in which patients are given implants derived from their own stem cells, could be a promising route to treat brain injuries in the future. Up to now, however, there has been no method to ensure that implanted stem cells mimic the architecture of the brain.
In this new study, the University of Oxford researchers fabricated a two-layered brain tissue by 3D printing human neural stem cells. When implanted into mouse brain slices, the cells showed convincing structural and functional integration with the host tissue.
The cortical structure was made from human induced pluripotent stem cells (hiPSCs), which have the potential to produce the cell types found in most human tissues. A key advantage of using hiPSCs for tissue repair is that they can be easily derived from cells harvested from patients themselves, and therefore would not trigger an immune response.
The hiPSCs were differentiated into neural progenitor cells for two different layers of the cerebral cortex, by using specific combinations of growth factors and chemicals. The cells were then suspended in solution to generate two ‘bioinks’, which were then printed to produce a two-layered structure. In culture, the printed tissues maintained their layered cellular architecture for weeks, as indicated by the expression of layer-specific biomarkers.
When the printed tissues were implanted into mouse brain slices, they showed strong integration, as demonstrated by the projection of neural processes and the migration of neurons across the implant-host boundary. The implanted cells also showed signalling activity, which correlated with that of the host cells. This indicates that the human and mouse cells were communicating with each other, demonstrating functional as well as structural integration.
The researchers now intend to further refine the droplet printing technique to create complex multi-layered cerebral cortex tissues that more realistically mimic the human brain’s architecture. Besides their potential for repairing brain injuries, these engineered tissues might be used in drug evaluation, studies of brain development, and to improve our understanding of the basis of cognition.
The new advance builds on the team’s decade-long track record in inventing and patenting 3D printing technologies for synthetic tissues and cultured cells.
Senior author Francis Szele (Department of Physiology, Anatomy and Genetics, University of Oxford) observed: ‘The use of living brain slices creates a powerful platform for interrogating the utility of 3D printing in brain repair. It is a natural bridge between studying 3D printed cortical column development in vitro and their integration into brains in animal models of injury.’
The researchers are part of the Oxford Martin Programme on 3D Printing for Brain Repair which is working to use 3D printing technologies to generate a low-cost medical technology to address the growing global catastrophe of brain damage through trauma and disease.
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