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Are you ready for suspended animation of human beings? Because scientists experimenting on mice have successfully been able to freeze slices of their brains, freeze them for a week, then bring them back to life.
According to the study, published on the pre-print server bioRxiv, the scientists arrested brain tissue in time by vitrification and then reactivated it with neuronal and synaptic function preserved by freezing the slices of mouse brains at -150°C.
Study co-author Alexander German of the University of Erlangen-Nuremberg in Germany believes this achievement puts us a step closer to being able to people in suspended animation for things like long space flights. German says one of the big keys to their success is being able to replace the water in cells with cryoprotectants.
“For conventional biologists, it’s often hard to believe that it is possible to replace the majority of water molecules in the tissue with different polar solvents,” German told New Scientist.
They first experimented with different combinations of cryoprotectants and varying methods for applying them to minimise adverse effects – for instance, cryoprotectants can be toxic at the high concentrations required and they can cause cells to swell or shrink.
The researchers then used their optimized technique to cool slices of the hippocampi of mouse brains to -196°C with liquid nitrogen, before storing them in a freezer at -150°C for up to a week. After reviving them, the team did a battery of tests, including measuring electrical activity. All the results were similar to those seen in non-cryopreserved brain slices.
German believes that since there was no damage to the synapses that connect nerve cells to one another, it should mean that memories in the brain can be preserved.
“At the moment, it is not possible, but I think there are existing techniques that can be combined to achieve this, and there is room for careful optimism,” said German. He added, “I personally do believe that it is possible to cryopreserve a whole human and that this could have beneficial applications if done responsibly.”
In 2019, doctors at the University of Maryland Medical Center were able to successfully place humans in suspended animation for the first time by using something called emergency preservation and resuscitation (EPR), which involves rapidly cooling a person to around 10 to 15°C by replacing all of their blood with ice-cold saline.
However, another group of scientists at the Wyss Institute for Biologically Inspired Engineering at Harvard University, with assistance from the Defense Advanced Research Projects Agency (DARPA) Biostasis Program, are also working on how to place people in suspended animation.
They believe that putting people in suspended animation can potentially be done using a drug called donepezil, which has already been approved by the FDA to treat Alzheimer’s Disease. They believe the drug might be able to eliminate the need to aggressively cool a person’s body.