Anabiosis: technology of deep freezing of people

2024 Author: Seth Attwood | [email protected]. Last modified: 2023-12-16 15:55

Last week, a group of experts gathered in New Orleans to study the possibility of immersing humans in "synthetic" hibernation, or artificial hibernation. Scientists are learning from nature by trying to understand the factors that lead to hibernation and reawakening in animals.

No movie about interstellar travel is complete without deep sleep. "Prometheus", "Passengers", everywhere we see how the main characters awaken in hibernation cabins, restart their fragile physiology from a long state of immobile fossil - often with the eruption of gastric fluids, that is, simply vomiting. This brutal process seems to make sense. After all, humans do not naturally hibernate. But a small group of scientists are trying to overcome nature and put humans into artificial hibernation. If successful, they can delay aging, cure life-threatening diseases, and take us to Mars and beyond.

Last week, a group of experts gathered in New Orleans to study the possibility of immersing humans in "synthetic" hibernation, or artificial hibernation. Scientists are learning from nature by trying to understand the factors that lead to hibernation and reawakening in animals.

The mystery of hibernation

What could be better for overcoming long stretches of life in conditions of threatening cold and lack of food than plunging into deep unconsciousness? Most of the animal world goes into hibernation: bears, squirrels, hedgehogs. Even our primate cousins, the fat-tailed lemur, plummet their metabolic rate when food supplies dwindle.

How about us? While we unfortunately do not hibernate, some "miracles" suggest that metabolic deep freezing can help preserve our damaged bodies for the future.

In 1999, radiologist Anna Bagenholm fell through the ice while skiing in Norway. By the time she was rescued, she had been under the ice for over 80 minutes. By all accounts, clinically she was dead - no breath, no pulse. Her body temperature dropped to an unprecedented 13.7 degrees Celsius.

However, when the doctors gradually heated her blood, her body slowly healed. The next day, the heart was restarted. Twelve days later, she opened her eyes. She eventually made a full recovery.

Bagenholm's case is just one clue that humans have the ability to recover from severely depressed metabolic states. For years, doctors have used therapeutic hypothermia, lowering body temperature by several degrees over several days to help patients cope with brain injury or delayed epilepsy.

Rapid cooling helps preserve tissues that have been cut off from the blood supply, so they require less oxygen to function. In China, experiments have kept people frozen for up to two weeks.

The promise of therapeutic hypothermia is so big that in 2014 NASA partnered with Atlanta-based SpaceWorks and provided pre-funding for a space travel hibernator for a mission to Mars.

Although a flight into space only lasts a few months, putting astronauts in an inactive state can severely reduce the amount of food needed and the size of the habitat. Falling asleep can also prevent serious side effects from low gravity, such as changes in cerebrospinal fluid flow, which can negatively affect vision. Direct muscle stimulation, courtesy of the hibernation cradle, can prevent muscle loss in zero-gravity conditions, and a deep state of unconsciousness can potentially minimize psychological problems such as boredom and loneliness.

The project has entered the second stage of funding, but many questions remain for it. One of them is associated with the fact that prolonged hypothermia has a terrible effect on health: blood clots, bleeding, infection, liver failure may appear. On a spacecraft without sophisticated medical devices, these complications can be fatal.

Another problem is that we do not fully understand what happens to the animal when it goes into hibernation. This is what the New Orleans conference was trying to solve.

Biological inspiration

Dr. Hannah Carey from the University of Wisconsin believes that the possibility of immersion in hibernation should be sought not in medicine, but in nature.

Carey studies the hibernation habits of the land squirrel, a small omnivorous rodent that roams the North American prairies. From late September to May, the ground squirrel hibernates in underground burrows, surviving severe winters.

One of Carey's curious observations is that low metabolic rates don't last all winter. Periodically sleeping animals come out of their torpor for half a day, increasing their body temperature to a normal level. However, animals still do not eat or drink during these periods.

Neuroscientists have been trying to put together a comprehensive list of the benefits of sleep for a long time. For example, research shows that sleep helps the brain clear toxic waste from the lymphatic system and allows the brain's synapses to “reboot”. If hibernation in itself leads to a state of sleep deprivation, can periodic sleep help with this?

We don't know yet. But Carey believes that the results of animal studies show that in the search for human hibernation, studying the biology of natural hibernators will yield more results than applying medical practices based on hypothermia, that is, hypothermia.

Artificial immersion in sleep

While Carey and Vyazovsky are exploring how hibernation helps animals stay healthy, Dr. Matteo Serri of the University of Bologna in Italy took a slightly different path: how to artificially induce numbness in animals that do not hibernate?

The answer may lie in a small group of neurons in the raphe pallidus brain region. Since metabolism slows down dramatically during hibernation, hormonal and brain mechanisms are likely to trigger this process.

Back in 2013, his team of scientists was one of the first to put rats into hibernation. Usually these animals do not sleep in winter. They were injected with a chemical into raphe pallidus to inhibit neuronal activity. These neurons are usually involved in "thermoregulatory protection from cold," Serry says, which means they trigger biological responses that counteract the decrease in body temperature.

The rats were then placed in a dark, cold room and fed a diet high in fat, which is known to reduce metabolic rate.

Turning off the protective neurons for six hours led to a sharp drop in temperature in the rats' brains. Their heart rates and blood pressure also slowed and fell. Eventually, the pattern of brain waves began to resemble the pattern of the waves of animals in a state of natural hibernation.

The most interesting thing was that when the scientists stopped the "treatment", the rats recovered - the very next day they showed no signs of abnormal behavior.

Previous attempts to induce torpor in animals that do not hibernate have failed, but this study showed that inhibition of neurons in raphe pallidus is essential for inducing a torpor-like state.

If these results are confirmed by the example of larger mammals, it will make sense to move on to hibernation in humans. Serri and others are working to further analyze the brain's control over numbness and how to hack it to put the brain into hibernation.

What's next?

The immersion of a person in a state of hibernation, hibernation, suspended animation - call it what you want - is still far from reality. But research results are gradually revealing molecular and neuronal factors that could, in theory, provide us with a deep freeze state.