Ole Frøbert, a cardiologist, gently placed the blood samples from his latest ‘patient’ in a bag. Taking blood had been much more difficult than he was used to because of the fat, fur and freezing temperatures. Finding a bear’s vein was no easy task.
Frøbert, a doctor normally working at Örebro University Hospital in Sweden, traveled to the region where his bears live to answer the question: How do bears survive the long winter hibernation without dying?
Blood clots, bedsores, bone loss, muscle wasting… Bears and other hibernating animals have a lot on their plate. That’s why doctors and veterinarians around the world are studying the deep sleep habits of hibernating animals. This knowledge could help develop drugs to treat cardiovascular problems and other ailments in humans.
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Frøbert’s effort to understand the mystery of a bear’s veins is just one of many studies of hibernating animals. Space agencies and militaries fund hibernation research to capitalize on discoveries.
“We really have a lot to learn from nature and animals, more than we realize,” says Manuela Thienel, a cardiologist at Ludwig Maximilian University of Munich who worked with Frøbert and led the new research on hibernating bears.
A hibernating bear’s heart rate drops below 10 beats per minute
Many drugs, treatments and medical studies are tested on mice in the laboratory. This study turns to the traditionally understudied ‘hibernators’ and tries to understand the strange workings of their bodies. “I was a bit bored with the traditional way we do medical research,” says Frøbert. For him, a hibernating brown bear is a ‘living library of biological solutions’.
For brown bears, sleep is a big deal. After gaining weight in the fall, the furry giants hibernate, sometimes for up to eight months. But what would happen if a human tried to sleep that long? Muscles atrophy, bones weaken and skin scabs over with bedsores.
Of course, hibernation is not a form of ‘sleep’ as we humans know and experience it. It is something much more extreme: a kind of energy-saving mode. For example, a grizzly bear’s heart rate drops below 10 beats per minute.
As a cardiologist, Frøbert is interested in blood. For humans, just taking a transatlantic flight increases the risk of blood clots. But when bears emerge from their dens after months of sleep, they are fresh and ‘clot-free’.
Frøbert and Thienel teamed up with bear researchers in Sweden to try to understand the underlying causes. The team followed 13 grizzly bears by helicopter over the summer and monitored their burrows for blood in winter.
Because blood cells deteriorate rapidly outside the body, they had to transport centrifuges and other lab equipment from Germany to a country house in Sweden to do the analysis. “If you work with blood and platelets, you have to be really fast,” says Tobias Petzold, another cardiologist on the project.
According to the article published in the journal Science, the study found that some proteins, such as HSP47, were much less common in blood samples taken in winter than in summer. This protein, found on the surface of platelets, helps blood cells stick together. Clots that form after a cut stop the body from bleeding and aid healing. But when blood clots inside blood vessels and does not dissolve naturally, it can be fatal.
The team focused on people with spinal cord injuries to see if the protein has the same effect in humans. Like hibernating bears, these patients don’t show much blood clotting, suggesting that their bodies have found a way to reduce the presence of the protein after injury. The team found that these patients had much less HSP47 than uninjured people.
Some animals take hibernation even further than bears. Every fall, for example, 13 striped ground squirrels burrow into the ground, curl up into a little ball of fluff and fall asleep. During hibernation, the rodents’ body temperature drops to just above freezing. It wakes up every one or two weeks. This made veterinarian and scientist Ashley Zehnder curious and prompted her to ask herself the following question:
What does the squirrel do to repair its body over and over again after almost freezing to death?
Zehnder, founder of Fauna Bio, and colleagues analyzed tissue samples taken at different times during hibernation. The team found genes activated in the squirrels’ cells that protect and repair the heart. Now scientists are working on a compound that aims to mimic this reaction in humans. Clinical trials of the potential treatment to help restore damaged heart function will begin soon.
Falling costs of genome sequencing and greater sharing of data are allowing science to go beyond the model organisms often studied. Earlier this year, for example, more than 100 scientists sequenced and analyzed the genomes of 240 mammals.
Hannah Carey, a professor at the University of Wisconsin, and colleagues discovered that squirrels’ gut microbes recycle waste chemicals and turn them into amino acids, which they use to maintain muscle. This discovery could not only help the elderly and those suffering from muscle wasting, but also help astronauts stay strong in zero gravity.
“This is an exciting time for the biology of hibernation. Many people want to collaborate,” says Carey.
NASA funds ‘hibernation’ research
At first it was difficult for Frøbert to find funding for the brown bear study due to ‘conservatism in the medical research community’. But eventually his team began working with both NASA and the German Aerospace Center.
NASA and other space agencies fund such research with the idea of putting space travelers into a hibernation-like state for long missions and resistance to cosmic radiation. This is because ‘hibernators’ – animals that hibernate – are resistant to radiation. For the moment, no one knows exactly why.
Now Frøbert and his colleagues are looking for ways to develop a new blood thinner with fewer side effects than existing drugs. According to him, a new drug could be available in five to 10 years. “For these crazy projects, we need a little more time,” he says.
Excerpted from a Washington Post article
