Although brown bears hibernate for more than half of the year in the extreme cold,Ursus Arctos) remains very healthy. These lazy giants rarely suffer from ailments such as blood clots, which can occur in humans experiencing only temporary bouts of immobility and can be fatal. Patients who are admitted to the hospital with a heart attack are usually more likely to develop thrombosis,” says Tobias Petzold, a cardiologist at the German Center for Cardiovascular Research. “By contrast, brown bears that have been lying down for months do not develop blood clots.”
In a new study published Thursday in the journal chemistryPetzold and his colleagues identified a protein that helps hibernating bears avoid dangerous clotting that can impede blood flow during their long winter sleep.
To figure out how dormant bears keep pumping blood during months of lethargy, Petzold and his colleagues partnered with biologists studying brown bear populations in Sweden. Did. The biologist took blood samples from his 13 bears as they hibernated in their dens during the winter. In the summer, biologists shot a tranquilizer dart from a helicopter to sample additional blood from the same bear.
The researchers then put these samples through a series of blood tests. They found that the abundance of over 150 proteins varied significantly between the blood of hibernating and active bears and was concentrated in platelet proteins, the components of blood that cause clotting. The platelet protein that showed the greatest discrepancy between active and hibernating bears was heat shock protein 47 (HSP47).
HSP47 recruits an enzyme called thrombin that helps platelets stick together and form a clot. In active bears, HSP47 helps repair cuts and stop bleeding. But this clotting protein is of little use to hibernating bears as they lounge safely in their dens. On average, hibernating bear platelets produced 55 times less HSP47 protein in her than in active bear platelets.
“I hadn’t heard much about this protein, but I was completely surprised to find that it had such a big impact,” says Manuela, lead author of the paper and also of the German Cardiovascular Research Center. Tinel said. Lowering levels of this particular protein likely makes platelets less prone to clumping and restricting blood flow, says Thienel.
Mirta Schattner, a biologist at the Immunobiology Laboratory of Experimental Thrombosis and Inflammation at the Institute of Experimental Medicine in Argentina, agrees. “This cellular interaction [of HSP47 proteins] Beneficial when limited, [also] It’s very important for containing infections and inflammation, says Schattner, who was not involved with the research team but wrote a comment on the new study. chemistry.
To determine whether similar mechanisms prevent blood clotting in chronically immobile humans, researchers compared blood samples from patients with debilitating spinal cord injuries to those from their active counterparts. Similar to the blood of hibernating bears, the blood of chronically immobile patients had less circulating HSP47 protein. reduces thrombo-inflammation,” thus reducing the risk of blood clots, says Schattner.
The team also drew blood from several healthy individuals before participating in a month-long space flight simulation study conducted by NASA and the German Aerospace Center. After the participant experienced his 27 days of head-down bed rest, the researchers collected another round of samples to see how prolonged immobilization affected physiology. Did. The team found that the participant’s platelets began to significantly reduce her HSP47 production during the experimental fixation process.
Researchers found similar patterns in the blood of restricted-movement pigs and lab-raised mice. They argue that reducing HSP47 protein expression, a mechanism used throughout mammals, may prevent coagulation during long periods of rest. seems to take a long time. In humans, people experiencing short-term immobility due to illness or injury are more likely to clot than those chronically immobile due to spinal cord injury.
Petzold says the new findings highlight how understanding the biology of bears and other animals can provide insight into how the human body works. It may also stimulate fine-tuned therapies to prevent clotting in patients experiencing temporary immobility. So we know that humans do the same to prevent blood clots,” he says.
