Healing in Hibernating Bears May Hold Clues for Human Injury Recovery


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Study of wound healing in black bears may yield better treatment for humans: Photo courtesy of: UFSWS Public Gallery

Scientists studying black bears during hibernation in Minnesota noticed something unusual: Injured bears healed during their winter hibernation – why is this odd? A bear’s low body temperatures during hibernation should inhibit healing. Researchers believe that they have discovered the reason for the bear’s ability – could this be applied to humans as well?

In a recent study, scientists discovered that two compounds found at higher levels in bear plasma during hibernation may contribute to that healing. That finding, in turn, may be useful for human patients such as diabetics, who tend to have delayed wound healing.

Hypothermia Usually Delays Wound Healing

In most instances, low body temperatures delay wound healing. Diabetics, for example, tend to have cold extremities due to poor blood circulation – this causes their wounds to heal very slowly. Bears in hibernation maintain a body temperature of 4 to 5°C below their active body temperature, and their extremities may be an additional 3 to 4°C cooler. In an interview with Decoded Science, Dr. Iaizzo, lead author of the study conducted at the University of Minnesota, said that, rather than finding the animals becoming septic from untreated injuries as he would expect, the wounds healed remarkably quickly and cleanly.

Why Do Bears Heal So Well During Hibernation?

Bears are unusual in that their metabolic rate remains higher, they lose less body weight and skeletal muscle tone, and they maintain a higher body temperature than most other hibernating species. Bears also have daily isotonic, isometric, and shivering muscular activity which may account for them maintaining better muscle tone. The localized warming caused by this activity may even play some role in the healing process.

Studying a Bear’s Healing During Hibernation

In this recent study, natural wounds occurring in the wild before hibernation, and/or biopsy sites, were either left open to heal or sutured. The wounds were examined several months into the hibernation period – all healed with minimal scarring, no evidence of infection, and minimal hair follicle damage. Although muscle activity may play a role in the healing process, there appear to be other factors involved.

During hibernation, bears have elevated levels of Hibernation Induction Trigger (HIT), a delta-opioid receptor agonist, and ursodeoxycholic acid (UDCA), a bile acid found in the plasma.  How HIT and UDCA function is not completely understood, but in another study, Dr. Iaizzo found that plasma from hibernating bears helped lessen damage to muscle tissue, caused by reduced blood flow during surgery.

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