Science just learned to buy more time for life — by putting it on hold

A study reviving frozen mouse brain tissue offers hope for medicine and space travel.

A sliced portion of mouse brain. PNAS

A recent experiment in which scientists in Germany restored activity in frozen mammalian brain tissue has renewed hopes that medicine may one day be capable of placing critically ill patients into a state of suspended animation until treatment becomes possible.

The findings are also encouraging for those dreaming of interstellar travel, where astronauts might spend years in a hibernation-like state inside special cryogenic chambers, saving both time and resources.

If astronauts could slow down their metabolism or enter hibernation, missions to places like Alpha Centauri would not require carrying enormous amounts of food, water, and supplies.

But no one may be following such experiments more closely than the wealthy enthusiasts who have already paid to have their bodies cryopreserved after death, hoping that future technology will one day resurrect them.

https://medium.com/reflections-and-realities/can-humans-outlive-the-stars-f63d63dd9765

The new study, however, published in the Proceedings of the National Academy of Sciences, offers little support for that ambition.

While the experiments are still limited to rodent tissue, they offer a glimpse at how living neural tissue can survive extreme freezing.

So, what is the story about?

A tiny piece of frozen brain tissue is challenging one of biology’s long-standing assumptions: that complex mammalian cells cannot survive extreme freezing.

Researchers from a number of scientific institutions within or affiliated to the Friedrich-Alexander University in Erlangen-Nürnberg have restored activity in slices of adult mouse brains after storing them at -196 degrees Celsius, the temperature of liquid nitrogen. The experiment sounds like science fiction and has sparked discussions about human hibernation, emergency medicine and long-duration spaceflight.

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But there is an important caveat.

Despite some headlines suggesting that scientists “revived frozen mouse brains,” the study’s strongest findings involved only thin slices of brain tissue, specifically from the hippocampus, a region involved in learning and memory. The researchers also experimented with whole mouse brains and observed some signs of recovery, but those results were preliminary and far less convincing.

It was established that adult mouse hippocampal tissue can indeed recover after rewarming: the neurons and synapses responsible for learning and memory remained functional. Meaning that they did more than simply survived — they returned to work.

To those preparing to drum a victory march — this is still premature. No dead mouse was brought back to life, nor was an entire frozen brain restored to normal function.

Only a slice of brain.

Even so, the findings suggest that living tissue may tolerate conditions once thought impossible. And this is important.

If scientists could one day place humans into a low-metabolism or torpor-like state, long missions to distant stars such as Alpha Centauri would become far more practical. Spacecraft would require dramatically smaller supplies of food, water and oxygen.

https://medium.com/@sensmedia.srl/all-living-organisms-emit-light-that-fades-after-death-03d63bfbb481

The study, published in the Proceedings of the National Academy of Sciences, examined whether adult mammalian brain tissue could recover after a process known as vitrification — a form of ultra-rapid freezing that prevents the formation of destructive ice crystals.

Freezing brains without breaking them

Vitrification is already used in fertility clinics to preserve human eggs and embryos. Applying the same principle to complex tissues and organs, however, is a far greater challenge.

The process followed by the researchers involved several carefully controlled steps:

1. Brain tissue was removed from healthy, living mice.
2. The tissue was exposed to cryoprotective chemicals that prevent ice formation.
3. It was rapidly cooled to minus 196 degrees Celsius.
4. It was later rewarmed in a controlled manner.
5. Scientists then tested whether the cells remained alive and functional.

A cryogenic chamber being prepared to host a tissue. PNAS

The crucial point is that the tissue was alive when it was frozen. The cells had not yet suffered the oxygen deprivation and chemical breakdown associated with death.

The researchers also experimented with whole mouse brains. Some recovery signs were observed, but they cautioned that these findings remain preliminary.

Moving from mouse tissue to humans remains an even more enormous challenge. Larger organs require entirely new cooling and rewarming methods, and scientists still need long-term studies in bigger animals.

What hibernating animals can teach us

To understand how humans might survive low-metabolism states, researchers are looking to animals that naturally hibernate.

Species such as ground squirrels can repeatedly cool down and rewarm themselves without suffering lasting tissue damage. Their blood circulation slows dramatically and oxygen becomes scarce, yet their cells survive.

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There are also fat-tailed dwarf lemurs — the only known primates capable of true hibernation. Studying these animals is difficult because they are vulnerable in the wild, but they demonstrate that primates may possess biological mechanisms that allow metabolism to slow safely for extended periods.

They fall into what is called deep hibernation.

Brown bear and American black bear spend months in a hibernation-like state, during which heart rate drops dramatically (from around 40–70 beats per minute to as low as 8–10) and metabolism decreases by about 50–75%. They do not eat, drink or urinate for months, losing surprisingly little muscle and bone mass.

However, unlike ground squirrels, bears do not cool their bodies very much. Their body temperature falls only a few degrees, from about 37°C to around 30–34°C, meaning they are shallow hibernators.

Could humans ever hibernate?

Whole-body vitrification remains a distant prospect. But the new findings suggest that milder torpor-like states, in which biological activity is temporarily suppressed, may eventually become possible.

A company called Hiber, which is owned by the study’s leading author Alexander German, is already experimenting with cryopreserving human brain tissue as a “biological archive” and is investigating whether organs such as the heart could eventually be preserved for transplantation.

https://medium.com/reflections-and-realities/hats-off-scientists-just-increased-the-survival-rate-from-pancreatic-cancer-26450ae1cce7

Developing human hibernation technology would require decades of research and substantial funding, the team noted. If it can be done safely, it could transform long-duration space travel and critical care medicine.

Still, there’s reason to celebrate. Even though scientists remain far from freezing astronauts for interstellar journeys, the experiments demonstrate that living tissue can tolerate conditions once considered fatal.

And yes, the cryochambers might help indeed — but not the dead.

Cryogenic science, what is it about?

The study is also likely to excite supporters of cryonics, who hope future technology will resurrect people preserved in liquid nitrogen after death.

But the procedures used in cryonics are fundamentally different from those used in this experiment.

First and foremost, cryonics can only begin after a person has been declared legally dead.

At that point, the heart has stopped and blood no longer carries oxygen to the brain. Within minutes, brain cells begin to run out of energy, their membranes start failing, toxic chemicals accumulate and irreversible damage begins.

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Only then does the cryonics procedure start.

Typically, the process involves four steps:

1. A person is declared legally dead.
2. The body is cooled and blood circulation is artificially maintained for a short period.
3. Blood is replaced with cryoprotective chemicals designed to reduce ice formation.
4. The body — or in some cases only the head — is cooled to minus 196 degrees Celsius and stored in liquid nitrogen.

Unlike the German experiment, the goal is not to preserve a living system in suspended animation. It is to preserve the structure of a body that has already suffered varying degrees of biological deterioration.

This distinction is critical.

The mouse brain tissue in the study was frozen before catastrophic cellular damage occurred and later demonstrated signs of recovery. Cryonics begins after the processes associated with death are already underway.

Freezing may halt further deterioration, but there is currently no known technology capable of reversing the damage that occurred between death and preservation, rebuilding destroyed cells or restoring the complex patterns of neural activity that underpin memory, personality and consciousness.

The new study suggests that one day medicine may learn to pause life temporarily and restart it later. It does not suggest that science is any closer to resurrecting the dead.

So, billionaires betting on cryogenic tubes may have a point — but they are wrong about resurrection.

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