American researchers have identified a process capable of lowering the
body temperature, like mammals capable of hibernating. Applied to humans, this method could save lives in emergency situations, such as heart attacks or strokes.
Will humans one day be able to lower their body temperature, as bears and marmots do during hibernation, to get through delicate periods like surgery or long periods like space travel?
The question is not science fiction since the discoveries of researchers bring us a little closer every day to this physiological option.
The latest one is to be credited to the team of Dr Domenico Tupone from Oregon Health & Science University, who in their study, published in Current Biology deciphers how the brain regulates body temperature – a process he calls “thermoregulatory inversion” or IT.
As Dr. Tupone, lead author of the study and research assistant professor of neurological surgery at the OHSU School of Medicine, explains, the discovery has potentially interesting clinical applications: “The idea is to reduce the body temperature at a lower level so that tissues like the brain or heart do not need as much oxygen, allowing them to survive ischemia longer [manque d’oxygène dans les tissus] and improve functional outcomes from stroke or heart attack.”
This temperature control system is directly inspired by the process of hibernation, or torpor, that we observe in certain hibernating mammals such as bears or Arctic ground squirrels. In their case, the body’s usual reactions to cold exposure are reversed, so that exposure to cold results in a reduction in heat production and a drop in body temperature – a process controlled by the system. normal thermoregulation of the brain, which keeps body temperature stable.
A “torpor switch”
The researchers discovered that by blocking a certain area of the brain, called the ventromedial periventricular zone (VMPeA), they could trigger this state of thermoregulatory inversion in rats – animals which, like humans, do not naturally hibernate. .
During the state of “thermoregulatory inversion,” exposure to cold environments prevents the body from producing heat, a process known as thermogenesis, while exposure to hot environments increases heat production .
Their research reveals that VMPeA acts like a “torpor switch”: When active, the body responds normally to changes in temperature. However, when activity in this part of the brain is reduced, the body goes into IT, which decreases heat production, even in the cold. This discovery could make it possible to control hypothermia in humans.
Therapeutic hypothermia
“If we had a mechanism that allowed us to turn humans into hibernating animals, we could achieve and control therapeutic hypothermia much better,” says Dr. Tupone.
Initially, the latter option could prove useful in human medicine, for example during surgical operations or to manage brain injuries. In these particular situations, lowering body temperature and slowing metabolism would reduce tissue damage and improve recovery.
In the longer term, this state of hypothermia could allow the body to cross time and space without alteration, like the hypersleep chambers in which space travelers rest, in a state of hibernation in science fiction series (see box).
A man hibernating within 10 years?
There are many fiction films and series, like films Prometheus, Alien or 2001, Space Odysseywhere the crew of an interstellar ship arrives at their destination after a journey of x years spent in a “sleeping chamber”. In reality, many space agencies around the world are working on the possibility of plunging bodies into a deep state of dormancy for long periods of time. The advantages are endless: avoiding boredom and reducing the costs of the mission, in terms of food, drink and oxygen. Furthermore, the bodies of hibernating astronauts could degrade much less than those of people awake in microgravity. L’European Space Agency (ESA)) is no exception to the rule and, as part of the preparation for a trip to the planet Mars, has initiated the MicRA (Mission Concept and Requirements Assessment) research program which aims to study “the controlled use of torpor , the state of hibernation with reduced metabolism, as a tool for human spaceflight.” Based on their analyses, the researchers developed “a comprehensive scenario encompassing the most recent knowledge on hibernation, in order to consider appropriate animal models to design hibernation scenarios for humans, as well as systems survival, security aspects and consumables necessary to enable hibernation as part of a long-term mission on Mars” they explained in Neuroscience & Biobehavioral Reviews in 2021. Depending on available funds, the first tests of “human torpor” could even take place as early as the mid-2030s, said Jennifer Ngo-Anhco-author of the article and research coordinator for human and robotic exploration at ESA at Space.com in March 2023.
This research was financially supported by the National Institute of Neurological Disorders and Stroke.
