Brains in a jar: how cryopreservation will change medicine
Science fiction is gradually turning into reality. Researchers from Germany have demonstrated an amazing experiment: after deep freezing, the mouse brain retained the activity of neurons. This discovery not only confirms that complex brain structures can survive extreme conditions, but also brings the prospect of applying similar methods to humans closer. Read more about the results of this experiment and how cryopreservation can change medicine in the Izvestia article.
What is the essence of the discovery?
An experiment by German scientists, described by the prestigious journal Nature, showed that the mouse brain is able to partially maintain functionality after deep cryopreservation — a result that seemed fantastic until recently. With a normal brain freeze, the problem is ice crystals. They destroy cell membranes, making tissue repair almost impossible.
The solution was found in a special fast freezing, in which the liquid inside the cells becomes glassy, without ice formation. The molecules "freeze", preserving the structure of tissues, while key cellular processes remain intact. This method is called vitrification.
The researchers first tested its operation on slices of the hippocampus of mice, an area of the brain responsible for short—term memory and spatial navigation. The tissues were treated with a cryoprotectant solution and instantly cooled to -196 °C, after which they were stored at -150 ° C for several minutes to seven days. After thawing, the sections were analyzed under a microscope and using electrophysiological tests. The brain showed amazing results: the neurons reacted to electrical stimuli almost as in a living brain, the membranes remained intact, and the mitochondria maintained metabolic activity. Even long—term potentiation persisted, a process that involves strengthening connections between neurons and is considered the physical basis for memory.
The next step was to work with the whole mouse brain. It was stored in a vitreous state at -140 °C for eight days. After defrosting, the slices showed the preservation of functional neural circuits of the hippocampus, including pathways responsible for memory formation.
Scientists note that there is already preliminary evidence that the cortex of the human brain will also remain viable after such a freeze, and the possibility of applying the method to other organs, such as the heart, is also being considered.
Why would a person need to freeze?
Medicine remains the main focus of cryopreservation, in particular, the preservation of organs for transplantation. Currently, most donated organs can be stored for only a few hours after extraction, which creates a huge logistical burden: you need to quickly check the organ for viability and infections, find a suitable recipient, prepare him for surgery and deliver the organ — sometimes halfway around the world.
— The creation of organ banks can dramatically change this situation. It will be possible to slowly select a transplant that is optimal in compatibility and infection—tested, prepare the recipient and perform the operation in the safest possible conditions," says Igor Artyukhov, Director of Science at KrioRus Cryonics Company.
In addition to transplantation, cooling technologies are already being used to protect the brain in critical conditions. Therapeutic hypothermia helps preserve nerve cells during injury, stroke, and cardiac arrest.
The results with the mouse brain open up prospects for working with larger organs, but scaling the technology remains a major challenge. Igor Artyukhov notes that these are not so much "barriers" as rather a long way along which the main problems are already known: the formation of ice crystals, possible damage during thawing due to the re-formation of ice, as well as the toxicity of cryoprotectors, which have to be used in high concentrations to prevent the formation of crystals.
— While these issues are gradually being resolved at the level of small tissue samples, the transition to large organs dramatically increases the complexity. This is a path where neither fences nor precipices are visible, and which must be gradually traversed," adds Artyukhov.
At the same time, as biologist Evgeny Mashchenko, senior researcher at the Paleontological Institute of the Russian Academy of Sciences, emphasizes, it is premature to talk about getting closer to understanding how to preserve the cognitive functions of even a relatively simple brain.
— No one knows how the brain stores information. It is difficult to restore any of its functions after it has been defrosted: the structure is too thin," he notes.
What is missing for success?
The results of the German researchers are of great interest to the scientific community, it remains only to understand how significant this experiment is for neurobiology and cryobiology. According to Igor Artyukhov, this is a really important step.
— The result did not come from scratch. There have been several comparable achievements in recent years. It has already been shown that individual neurons are able to restore electrical activity after cryopreservation in liquid nitrogen. However, such experiments were usually conducted on very thin sections of the brain, for example, the hippocampus," the expert notes.
The main difference between the new work is that it demonstrates the restoration of activity in the whole brain.
"Not only the viability of individual cells is important here, but also the safety of neural networks,— Artyukhov explains. — This shows that the very idea of reversible cryopreservation of the brain does not contradict modern biology.
During the experiment, the scientists recorded the structural integrity of the membranes, the activity of mitochondria and the electrical excitability of neurons. The mechanism of learning and memory has also been preserved. All this allows us to consider the work as a fundamental step towards reversible cryopreservation of the brain, although so far there is no talk of restoring consciousness or cognitive functions in full.
Artyukhov draws attention to the context. He notes that the cryopreservation of an entire animal is already a close but separate topic. So, for some small organisms, it has already been solved.
— For example, rotifers and nematodes that had been frozen there for more than 40 thousand years were extracted and warmed from the Kolyma permafrost. For vertebrates, the record is 92 years old — the Siberian anglerfish, also found in Kolyma. As for mammals, reversible conservation with revitalization has not yet been achieved," explains the scientist.
What will happen next?
According to Igor Artyukhov, the movement towards reversible cryopreservation of tissues is slow but inevitable. Each new achievement makes such scenarios less fantastic and more subject to scientific discussion. Although there is a huge difference between the mouse brain and the human brain, the expert emphasizes that it is purely quantitative and will be overcome sooner or later. According to him, the first experiments with large animals can be carried out within a dozen years, at most two.
Artyukhov notes that the promising technology has already been confirmed, including by experimenting with the mouse brain, although not all skeptics will agree with this.
— Until recently, it was argued that it is impossible to reversibly preserve the brain of a mammal, even a mouse. Now we have to admit that they were wrong. Now the main difficulty is not to prove the principle, but to learn how to preserve the brains of animals of ever larger sizes — rats, pigs, and beyond. The question about a person is gradually changing: from "is it possible?" to "when?" and "how?", he says.
The next steps, according to the expert, are quite obvious. First, it is necessary to increase the volume of preserved tissue, while checking the integrity of large neural networks. Secondly, it is necessary to improve the methods of rapid and uniform cooling and thawing in order to avoid cell damage.
The mouse brain experiment opens a window into the future, where preserving the functions of neural networks in a frozen state can become part of medicine, transplantation and, in the long term, the foundation for scientifically based approaches to cryonics.
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