In a groundbreaking study, researchers have discovered a remarkable method to artificially induce hibernation using ultrasonic pulse technology. This innovative breakthrough holds the potential to enable future astronauts to hibernate during extended space missions. The study, conducted at Washington University in St. Louis, successfully induced a state of torpor in rats, which do not naturally hibernate.
Torpor is a sleep-like state observed in certain mammals and birds, characterized by significantly reduced body temperature and metabolism. It allows organisms to conserve energy and endure harsh environmental conditions, such as extreme cold or limited food availability.
The research team utilized non-invasive ultrasound to stimulate a specific area of the brain called the hypothalamus preoptic, responsible for regulating body temperature and metabolism. When this region was stimulated in mice, their body temperature dropped by nearly 3 degrees Celsius for an hour. Moreover, the mice’s energy metabolism transitioned from utilizing both carbohydrates and fat to relying solely on fat—a key aspect of achieving torpor. During this state, their heart rates also decreased by an impressive 47 percent.
The ultrasound-induced hypothermia and hypometabolism (UIH) technique employed increased acoustic pressure and duration to achieve lower body temperature and slower metabolism. To ensure precise control, the researchers developed an automatic closed-loop feedback controller. This controller maintained the desired body temperature below 34 degrees Celsius, a critical threshold for inducing natural torpor in mice. The feedback-controlled UIH successfully maintained the mouse body temperature at 32.95 degrees Celsius for approximately 24 hours and allowed for a smooth return to normal temperature once the ultrasound stimulation ceased.
Although the exact mechanisms by which ultrasound induces hypothermia and hypometabolism in the brain are not fully understood, the research team discovered increased neuronal activity in response to each ultrasound pulse in the hypothalamus preoptic area. Additionally, through genetic sequencing, they identified the activation of the “TRPM2 ion channel” in these neurons, providing valuable insights into the process.
The researchers replicated their experiments with rats, achieving similar results with a slightly lesser drop in body temperature (1 to 2 degrees Celsius). This development paves the way for potentially attaining the same state in humans, making it a significant milestone, particularly for future medical and space travel applications.
Published in the journal Nature Metabolism, these findings open up new possibilities for inducing a torpor-like hypothermic and hypometabolic state non-invasively, precisely, and safely. By utilizing remote transcranial ultrasound stimulation at the hypothalamus preoptic area, the researchers achieved a long-lasting torpor-like state in mice, surpassing 24 hours. The process involved closed-loop feedback control of ultrasound stimulation with automated body temperature detection.
The study further reveals that UIH is triggered by the activation of POA neurons, involving the dorsomedial hypothalamus as a downstream brain region and subsequent inhibition of thermogenic brown adipose tissue. The researchers conducted single-nucleus RNA-sequencing of POA neurons, identifying TRPM2 as an ultrasound-sensitive ion channel. Suppression of this channel through knockdown experiments effectively reduced the induction of UIH. The team also demonstrated the feasibility of UIH in non-torpid animals, such as rats, expanding the potential applications of this groundbreaking technology.
With these significant findings, the possibility of inducing hibernation-like states in humans for medical purposes and prolonged space travel becomes increasingly tangible. As we unravel the mysteries of torpor induction, this research sets the stage for further advancements and opens a pathway to a future where humans can harness the power of hibernation to overcome the challenges of extended space exploration.
By Impact Lab