How Bears Hibernate without Getting Blood Clots - Scientific American
▻https://www.scientificamerican.com/article/how-bears-hibernate-without-getting-blood-clots
The biologists collected blood samples from 13 hibernating bears in their dens during the winter. In the summer the biologists collected additional blood from the same bears after shooting tranquilizer darts at them from a helicopter.
[…] The platelet protein with the largest disparity between active and hibernating bears was heat shock protein 47 (HSP47).
HSP47 recruits an enzyme called thrombin that helps platelets stick together and form clots. In active bears, HSP47 helps patch up cuts and stop bleeding. But hibernating bears, which are safely snug in their dens, have little use for this clotting protein. On average, hibernating bears’ platelets produced 55 times fewer HSP47 proteins than those of active bears.
“We hadn’t heard much about this protein, and we were completely surprised to discover that it has such a large impact,” says Manuela Thienel, the paper’s lead author, also at the German Center for Cardiovascular Research. Thienel says that decreasing the levels of this particular protein likely reduces the platelets’ penchant for clumping together and restricting blood flow.
[…]
To determine if a similar mechanism prevents blood clotting in chronically immobile humans, the researchers compared blood samples from patients who had suffered debilitating spinal injuries with samples from their active counterparts. Like that of hibernating bears, the blood of chronically immobile patients had fewer circulating HSP47 proteins. “Downregulation of HSP47 during hibernation of bears or chronically immobilized patients reduces thromboinflammation” and thus reduces the risk of blood clots, Schattner says.
