A large variety of animals can go into hibernation. Their metabolism, heart rate, and breathing slow to the bare minimum, which allows them to withstand harsh environmental conditions such as cold winters or droughts. Bears are most famous for this, but now researchers have discovered how to induce a similar state in mice.
The discovery is reported in two studies published in Nature (here and here). The teams discovered a neural circuit in the hypothalamus of mice that control torpor, a hibernation-like state akin to suspended animation seen in movies. By stimulating these neurons, researchers were able to induce torpor in mice for days.
Scientists are not only curious about how such a state can happen but they are excited about its potential applications in the future. An induced torpor state in humans could be used in medicine to protect brains during a stroke, help treat metabolic diseases, or even put someone into a similar suspended state during space travel.
"The imagination runs wild when we think about the potential of hibernation-like states in humans. Could we really extend lifespan? Is this the way to send people to Mars?" co-lead author Dr Sinisa Hrvatin, from Harvard Medical School (HMS), said in a statement. "To answer these questions, we must first study the fundamental biology of torpor and hibernation in animals. We and others are doing this – it is not science fiction."
Mice do not normally hibernate but if the external temperature is low enough and they lack food, they can enter this torpor state.
"In warm-blooded animals, body temperature is tightly regulated," co-author Senmiao Sun explained. "A drop of a couple of degrees in humans, for example, leads to hypothermia and can be fatal. However, torpor circumvents this regulation and allows body temperatures to fall dramatically. Studying torpor in mice helps us understand how this fascinating feature of warm-blooded animals might be manipulated through neural processes."
The researchers investigated which areas of the brains were activated during such a state. Then they activated these areas in well-fed mice to see if they could induce torpor, which indeed proved to be the case.
"It's far too soon to say whether we could induce this type of state in a human, but it is a goal that could be worthwhile," Professor Michael Greenberg, also at HMS, said. "It could potentially lead to an understanding of suspended animation, metabolic control and possibly extended lifespan. Suspended animation in particular is a common theme in science fiction, and perhaps our ability to traverse the stars will someday depend on it."
The team will continue to study this process to better understand the long-term effects as well as the role of other neural circuits in all of this.
