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Patches of human brain tissue have been transplanted into the brains of working rats, which could pave the way for new treatments for devastating brain injuries.
The groundbreaking study showed that the “human brain organelles” – balls of neurons the size of sesame seeds – were able to integrate into the rat brain, connecting to its blood supply and communicating with the rat neurons.
The team behind the work suggest that doctors may be able to grow bulbs of brain tissue from the patient’s own cells in the laboratory and use them to repair brain injuries caused by stroke or trauma.
“This is very exciting for me as a doctor,” said Isaac Chen, a physician and assistant professor of neurosurgery at the University of Pennsylvania.
This study is the latest in the fast-growing and ethically complex field of brain organs. Scientists have shown that when cultivated in the right conditions, neurons begin to form small brain structures, allowing scientists to investigate developmental conditions such as autism and a wide range of basic neuroscience questions.
The new work is the first demonstration that lab-grown brain tissue can be successfully implanted into an injured site to repair an adult brain, suggesting potential future clinical applications.
Chen and colleagues grew human brain organisms in a dish until they were about 1.5mm in diameter. The tissue balls were then transplanted into the brains of adult rats with injuries to their visual cortex. Within three months, the grafted organs had integrated with their host’s brain, connecting to the blood supply, expanding to the original volume several times over and sending out projections that connect to neurons. the rat, according to the study published in Cell Gas Cell.
“We didn’t expect to see this level of functional integration so soon,” says Chen. “[This] suggests that the transplantation of neural tissue into an adult mammalian brain, particularly one that has been disrupted by some form of injury, is a viable path forward for neural repair.”
The scientists did not assess whether the implants improved how well the rats were able to function, but tests showed that the human neurons fired electrical signals when the rats were exposed to flashing lights. Chen said this supported the idea that organisms could act as “white processing units” that the brain could absorb and use to rebuild itself after injury.
“By rationally introducing these engineered processing units to specific areas of the injured brain, we think the increased computing capacity of those areas would lead to sufficient restoration of brain networks to restore neurological function,” Chen said.
In theory, personalized brain organisms could be created in the lab from a patient’s own cells, although Chen predicted that clinical applications would be at least five to 10 years away. “We are at the beginning of this journey,” he said.
Dr Serena Barral, a lecturer in developmental neuroscience at UCL, who was not involved in the work, described it as an “incredible” demonstration of the sheer adaptability of neurons. “There’s a lot of information in the DNA itself that allows the neurons to work wherever they are – whether they’re in a plastic box in the lab or in the brain,” she said.
She added that in future clinical applications, the extent to which the brain could be repaired would likely depend on the functions that were lost.
“The visual cortex is simpler, but if you think about replacing the areas that are important for speech, mathematical calculations, thinking – that could be a bit more difficult because there are many capacities in the brain that are grown with experience. ,” she said.