In the fairy tale, Sleeping Beauty sleeps for 100 years, time is stagnant and old-fashioned; in a sci-fi movie, astronauts lie quietly in dormant pods, through vast space, during a long interstellar journey. Although these are fantasy scenarios, the idea of pressing the “life pause button” may not be as far from reality, according to a new set of findings by scientists. Two recent research papers published online in the leading academic journal Nature, two teams from Harvard Medical School in the United States and Tsukuba University in Japan, found a special group of nerve cells in the brains of mice that play a key role in body temperature control.
Artificialactivation of these nerve cells can trigger mice into a hibernating state, resulting in significantly lower body temperature and energy consumption. Moreover, after the animal recovered from this state, there were no tissue organs and behavioral abnormalities. The researchers hope that based on this finding, “artificial hibernation” can be achieved in humans.
According to a review published in Nature, the two studies have refreshed our understanding of body temperature regulation.
In nature, animals such as frogs, snakes, and bears can survive hibernation (seasonal sleep) through harsh winters, food shortages or other extreme conditions. Unlike everyday sleep, hibernation involves physical changes throughout the body, with a slower heartbeat, weaker breathing, less oxygen consumption, and a significant drop in body temperature.
Why do some animals hibernate, and some animals do not hibernate? The problem not only curiouss five or six-year-olds, but also inspires many scientists to explore it.
One reason for the difficulty of hibernating research, the researchers note, is that commonly used experimental animal mice and rats do not hibernate. However, the team, led by Professor Michael Greenberg of Harvard Medical School, noted that mice entered a short-lived state of insensitivity when food was scarce and cold around them. At ambient temperatures as low as 22 degrees C, the core body temperature of mice hungry for 24 hours decreased, and metabolic rates and physical activity decreased significantly, compared with those who ate enough to maintain normal body temperature.
Using biomarkers of neuronal activity, the team looked in the brains of mice for neurons that were activated when they entered a numbing state.
Find and confirm neurons that are activated in a numbing state
In the process, they focused their search on the hypothalamus, the brain region responsible for body temperature regulation, hunger, thirst, hormone secretion, and so on. In hundreds of different regions of the hypothalamus, the researchers identified which regions of neurons caused numbness in mice when activated.
After a painstaking search, they eventually identified a group of neurons in a specific area of the hypothalamus (the inner and outer side front area). Stimulating the neurons alone allowed the mice to rapidly lower their body temperature and significantly reduce their activity, and inhibited the activity of these neurons, which prevented hungry mice from getting numb. The researchers then identified the groups of neurons that expressed iconic proteins, such as neurotransmitters, using single-cellRNA sequencing.
In another research paper, scientists at the University of Tsukuba in Japan used different methods to find the same “neural switch” in similar areas of the hypothalamus. They named the nerve cells Q neurons.
Genetically modified, the researchers were able to activate Q neurons in the brains of mice with chemical or light-specific activation. They were surprised to find that the mice’s core body temperature dropped by nearly 10 degrees and showed the animal’s hibernating state for 48 hours: incontinturity, lower heart rate, reduced oxygen consumption, and so on. “When the surroundings drop significantly, their function remains normal and their body temperature becomes lower, staying around 22 degrees Celsius. Professor Sakurai, who was the head of the study, said.
After the brief activation of the Q neuron, the core body temperature of the mice was reduced from 37 degrees C to 24 degrees C.
“What’s even more surprising is that in rats that neither hibernate nor daily numbness,” the activation of Q neurons also triggers a state of hibernation similar to that in mice. “Although we don’t yet know the exact answer, humans may also have Q neurons that can trigger similar states, ” said lead author Takahashi. “
Next, can humans “sleep at one click”? “It’s too early to say whether we can induce the same state in people, but it’s a goal worth exploring. Professor Greenberg said.
Our journey is the sea of stars (Photo: Pixabay)
When it comes to the future application of “artificial hibernation,” both teams have developed ideas such as replacing anesthesia in clinical surgery; slowing down metabolism after a stroke or trauma to avoid further brain damage; extending lifespan; and even turning fantasy into reality to help humans travel to Mars and space.
“Imagination gets wilder when we imagine that humans can also have a state of hibernation. One of the study’s authors, Dr. Sinisa Hrvatin of Harvard Medical School, said.