When taking long international flights, we are often advised to walk around and stretch our legs to avoid deep venous thrombosis, or blood clots, from forming due to our immobility.  However, hibernating bears experience even longer periods of immobility without the danger of developing these kinds of blood clots.  Scientists have recently uncovered what it is about hibernating bears that protects them, and how that phenomenon is paralleled across different mammals, including pigs, mice, and humans. 

To study this phenomenon, scientists at Ludwig Maximilian University of Munich, led by Manuela Thienel and Tobias Petzold, collected blood samples from thirteen bears during their hibernating months as well as during their more active spring months.  In comparing the blood from different seasons, Thienel and colleagues discovered that HSP47, a protein involved in platelet adhesion and clot formation, was less prevalent in the blood of hibernating bears.  This pattern suggests that having less HSP47 protects hibernating bears from blood clot formation.  To further examine the role of HSP47 in blood clots, they compared mice that have platelets with HSP47 to mice that have platelets without HSP47.  It was found that those mice not expressing HSP47 were protected from blood clot formation.

Similar to hibernating bears, human patients with spinal cord injuries (SCI) and paralysis also are not at a higher risk for blood clot formation.  Blood samples from SCI patients were found to have lower levels of HSP47 compared to healthy patients.  They even saw the same difference in comparing healthy volunteers who underwent 27 days of bed rest.  Thienel and colleagues also compared blood collected from pigs that have recently given birth with blood collected from free ranging pigs, as lactating pigs routinely have limited mobility for approximately 28 days.  The same difference in HSP47 was found, showing that this kind of protective effect may be seen across other mammalian species.  While it’s still not known what it is about processes such as hibernation that prompts the body to make less HSP47, this study shows a promising target for future medicines in the treatment and prevention of blood clots.

This study was led by Manuela Thienel at Ludwig Maximilian University of Munich in the Department of Cardiology, University Hospital, Munich Germany.

Managing Correspondent: Stacey Yu

Press Articles: Hibernating bears don’t get blood clots. Now scientists know why. sciencenews.org

Original Journal Article: Immobility-associated thromboprotection is conserved across mammalian species from bear to human Science

Image Credit: Pixabay

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