Reviving a frozen brain sounds like something out of a sci-fi novel, but a new study gives clues to how scientists might one day do that.
Researchers in Germany managed to freeze mouse-brain tissue in a way that preserved its circuits and functionality after thawing. Their method could be helpful for testing drugs, examining neurodegenerative diseases, or, someday, preserving entire organs or bodies.
“As a proof of principle, it genuinely shifts the boundary of what seems biologically possible,” according to Kirill Volynski, a neuroscience professor at the Queen Square Institute of Neurology at University College London who wasn’t involved in the research.
Preserving organisms by storing them at very low temperatures has long been a scientific dream. But mammalian tissues, including ours, don’t handle being frozen well. Our bodies are full of water that crystallizes when frozen. Those ice crystals can damage delicate brain and nerve tissue.
Some tissues, like embryos, can be preserved with the help of chemicals that prevent ice crystals, but the chemicals can be toxic in large quantities. And it has been almost impossible to deep freeze parts of the brain in a way that allows them to work properly after thawing.
Until now, that is, according to Alexander German, a neurologist at the University of Erlangen-Nuremberg in Germany who was lead author of a study describing the work this month in the journal Proceedings of the National Academy of Sciences.
“Scientifically, this moves the needle from just preserving the structure of brain tissue to preserving its function,” he said.
The group came up with a method that used liquid nitrogen to rapidly cool mouse brain tissue to minus 196 degrees Celsius, then kept it in a minus-150-degree-Celsius freezer, he said. Prior to cooling, they treated the tissue with cryopreservation chemicals.
The researchers looked at brain slices from the hippocampus, a structure important for learning and memory. Up to seven days later, when the brain tissue was thawed, the neurons inside not only survived but also remained functional and able to exchange electrical signals again.
The secret, German said, was finding a recipe of cryopreservation chemicals in optimal concentrations, as well as the right temperatures and exposure times, to vitrify the tissue—trapping the water molecules inside in a glasslike state that prevented ice crystals from forming.
Still, German acknowledges that successfully applying this method to intact human organs or whole bodies remains far off.
“Scalability remains the major limitation,” said Shigeki Watanabe, a neuroscientist at Johns Hopkins University who wasn’t involved in the research. “Going from thin slices to an entire brain requires tremendous effort.”
Write to Aylin Woodward at aylin.woodward@wsj.com