The use of non-model organisms in medical research is an expanding field that has already had a significant impact on human health. Information gained from studying the unique characteristics of mammals is used to develop new therapeutic agents. The remarkable ability of mammals to hibernate provides unique physiological and metabolic benefits that are being actively explored for potential applications in human health on Earth. These benefits also promise to reduce many of the physical and mental health risks associated with space travel.
An essential feature of hibernation is an energy-sparing state called torpor, which involves an active and often profound reduction in metabolic rate relative to baseline homeostasis. Additional potential benefits include maintaining muscle and bone stability despite prolonged immobilization and protection from radiation injury. Despite this remarkable potential, the space infrastructure needed to study torpor in laboratory rodents does not currently exist, and hibernation in microgravity has never been studied. This is a major gap in the understanding of hibernation and its potential applications for human spaceflight.
The STASH facility will also have animal chambers of a size that will accommodate a variety of hibernating and non-hibernating animal species, increasing its applicability to a variety of studies on the ISS by enabling real-time physiological measurements. The STASH facility is being developed in collaboration with BioServe Space Technologies for integration into the Space Automated Biological Laboratory (SABL). This will enable practical applications of this research and improve our understanding of both hibernation and the physiology of mammals in space.
The short-term goals of the STASH project are new research into the basic science of hibernation in microgravity, laying the foundation for its potential benefits to human health. These include determining whether hibernation provides the expected protection against loss of normal bone and muscle function. The mid-term goals of the project are to develop translational applications of hibernation research. These include the use of STASH both to test bioactive molecules that mimic transcriptional signatures of hibernation and to evaluate synthetic torpor induction methods for their ability to provide similar protection.
As a long-term goal during a manned mission to Mars, synthetic human torpor could act as an appropriate countermeasure that would change everything in space exploration, mitigating or eliminating all the hazards included in NASA’s RIDGE acronym for the hazards of space travel: cosmic radiation, isolation, and conclusion, distance from Earth, gravitational fields and hostile/closed environments.
Torpor is a state of short-term torpor, accompanied by a slowing of the pulse, breathing and a decrease in body temperature, the transition to which and awakening occur quite quickly. If you carefully pick up the animals, they may not wake up. Many terms related to states of slow metabolism – suspended animation, torpor, hibernation, hibernation, torpor, diapause, stupor – can be divided into two large categories: suspended animation and hypobiosis.
The word “anabiosis” means “return to life”, and this is the most severe metabolic slowdown that a living organism is capable of. The best species to survive unfavorable conditions that are lethal to other organisms are bacterial spores and protozoan cysts, as well as tardigrades, famous for their amazing vitality. In a state of suspended animation, these tiny organisms are able to withstand extreme cooling down to -217 degrees Celsius, boiling for several hours, irradiation, and even exposure to outer space.
For more complex organisms, such a “complete stop” of metabolism is impossible, but in nature there are many variations of its slowdown. One of them, torpor, occurs in poikilothermic (cold-blooded, not maintaining a constant body temperature) animals – reptiles, amphibians, fish, insects. During winter torpor, their body temperature can drop below zero. Animals preparing to freeze to the bone accumulate cryoprotective substances in their cells, such as glycerol or sucrose, to protect them from damage by ice crystals.
A special type of torpor, described in great detail for insects – diapause – can occur at any stage of organism development (ontogenesis), while development stops and is postponed until better times. These and other forms of reduced functional activity, such as hibernation or hypothermia, are collectively termed hypobiosis. It can be either natural – in the form of an adaptive mechanism that allows the body to adapt to changing environmental conditions – or artificial.
Homeothermic – warm-blooded – animals hibernate to wait out unfavorable conditions. Winter hibernation (hibernation) helps to wait out the cold and lack of food, and summer hibernation (estivation) helps to wait out the heat and drought. By hibernating, homeothermic animals actually lose the ability to maintain body temperature for a while, which is why they are also called heterothermic because sometimes they are warm-blooded and sometimes not.
During hibernation, breathing, heartbeat and nervous activity slow down, and body temperature decreases. Some rodents, insectivores, bats, bears and even birds hibernate. It was thought that primates did not hibernate until it was discovered in 2004 that the fat-tailed lemur (Cheirogaleus medius) spends seven months of the year hibernating, hidden in a hollow, to survive the hot season in Madagascar.