Frozen human brain tissue can now be revived
Using a new approach, scientists have successfully frozen and thawed brain organoids and brain tissue cubes from a person with epilepsy, which could lead to better research into neurological diseases.
New technology has allowed scientists to freeze human tissue brainso that they regain normal function after thawing, potentially opening the way to better ways to study neurological diseases.
Brain tissue typically does not survive freezing and thawing, making medical research difficult. To overcome this, Zhicheng Shao of Fudan University in Shanghai, China, and colleagues used human embryonic stem cells to grow self-organizing brain samples, known as organoids, for three weeks—long enough to develop neurons and neural stem cells that can become different kinds of functional brain cells.
The researchers then placed these organoids, which averaged 4 millimeters across, in various chemicals, such as sugars and antifreeze, which they suspected might help keep the brain cells alive while frozen and allow them to grow after thawing.
After storing these organoids in liquid nitrogen for at least 24 hours, the team thawed them and monitored them for cell death or growth of neurites – the “branches” of nerve cells – over the next two weeks.
Based on the cell death and growth rates associated with each substance, the researchers selected the best substances by trying different combinations during freeze-thaw tests on a new set of organoids.
The combination that led to the least cell death and the most growth was a mixture of chemicals called methylcellulose, ethylene glycol, DMSO, and Y27632 – which the scientists dubbed MEDY. They believe MEDY interferes with a metabolic pathway that otherwise programs cell death.
Shao and his colleagues tested MEDY in a series of experiments with brain organoids ranging in age from 28 to more than 100 days. The team placed the organoids in MEDY before freezing them — typically for 48 hours — and thawing them. The researchers then monitored their growth in the lab for 150 days after thawing.
They found that the appearance, growth, and function of the thawed organoids were very similar to those of the same age that had never been frozen, even among those that had been frozen at MEDY for 18 months. The team also observed similar results for organoids representing different areas of the brain.
Finally, the researchers took 3-millimeter cubes of brain tissue from a 9-month-old girl with epilepsy and placed them in MEDY, then froze and thawed them. The tissue retained its structure before freezing and remained active in lab culture for at least two weeks after thawing.
According to Roman Bauer from the University of Surrey in the UK, the ability to freeze human brain tissue could lead to better studies of brain development in the laboratory for medical research.
Joao Pedro Magalhaes from the University of Birmingham in the UK says he is impressed that the team’s method successfully prevented cell death and preserved function. “We know that brain cells are very fragile and sensitive to stress,” he says.
With much more research and larger tissue samples, this work could one day lead to freezing entire brains, Magalhaes says. “If we think decades or centuries ahead, we can imagine patients in the terminal stages of a disease or astronauts being cryopreserved for travel to other star systems,” he says. MEDY could be “one small step” toward that goal, Magalhaes says.
Cell Reporting Methods DOI: 10.1016/j.crmeth.2024.100777
