In science fiction, space crews often get rid of the tedium and inconvenience of long-distance space travel by entering a state of suspended animation. Now that goal may have come a step closer after scientists have shown that hibernation can be artificially induced in rodents using ultrasonic pulses.
The progress is considered significant because the method has been effective in rats, animals that do not naturally hibernate. This raises the possibility that humans may also retain a rudimentary hibernation circuit in the brain that can be artificially reactivated.
“If it turns out to be possible for humans, we could imagine astronauts wearing a helmet-like device designed to target the hypothalamus region to induce a state of hypothermia and hypometabolism,” he said. Hong Chenassistant professor at Washington University in St. Louis, who supervised the work.
The team is the first to identify a specific group of neurons in a deep region of the brain called the hypothalamic preoptic area, which has been found to be involved in regulating body temperature and metabolism during hibernation. They showed that in mice, these neurons can be artificially activated using ultrasound delivered noninvasively through a helmet.
When stimulated, the mice experienced a drop in body temperature of about 3°C for about one hour. The mice’s metabolism also shifted from using both carbohydrates and fat for energy to using only fat, a key feature of torpor, and their heart rate dropped by about 47%, all at room temperature.
The scientists also developed an automatic feedback loop system that delivered an ultrasonic pulse to keep mice in an induced torpor if they showed signs of warming up. This allowed the mice to be kept at 33°C in a hibernation-like state for 24 hours. . . When the ultrasound system was turned off, they woke up again.
Experiments described in the journal Nature Metabolism, showed that the same device worked in rats, whose body temperature dropped by 1 degree when exposed to the same area of the brain. Chen said the result was “surprising and exciting” and the team planned to test the technique on larger animals.
In humans, inducing a torpor-like state has potential medical applications, with some speculating that slowing the metabolism could buy critical time to treat life-threatening conditions such as heart attack and stroke. “By expanding the window for medical intervention, this method offers promising prospects for improving patients’ chances of survival,” Chen said. “Furthermore, the non-invasive nature of the technique opens up the possibility of developing wearable ultrasound devices such as helmets for easy access in emergency situations.”
Stockholm University professor Martin Jaastroch, who was not involved in the study, called the work a breakthrough. “Everything they see repeats what you see in nature,” he said.
“They can also do it on rats, which is very interesting,” he added, saying that “the chances are pretty high” that the same technique would theoretically work on humans. “Perhaps we have some residual abilities left there. Until this article, no one even thought about how you can safely experiment with this.