Bone weakness is a significant problem for astronauts, but a unique biological process that occurs in hibernating bears could be the basis for a new therapy

This article is more than 5 years old

This article is more than 5 years old

Astronauts could protect themselves against bone wastage by harnessing a unique biological process that allows black bears to maintain their skeletons during hibernation.

A study has revealed that bears protect their bones from degrading, despite hardly moving for up to six months, by suppressing the usual constant release of calcium from the bones into the blood. Such a lengthy period of inactivity in humans would lead to a severely weakened bone structure.

“This could be the basis for a new therapy for astronauts, or people with a bone-related chronic illness,” said Meghan McGee-Lawrence, assistant professor in cellular biology and anatomy at Georgia Regents University in Augusta, and an author of the study.

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Reduced movement in humans, and other mammals, can cause significant health problems. This is due to the body responding to inactivity by decreasing bone formation and increasing calcium release, leading to bone loss and increased risk of breaks and fractures.

One of the major side-effects of prolonged weightlessness is spaceflight osteopenia, a condition where reduced stress on the bones triggers bone loss. Astronauts on the Mir space station, for example, lost on average 1-2% of their bone mass each month. The condition can be a limiting factor for the length of missions that astronauts can endure.

Exercise has been used as the main strategy to overcome, this but has limited success, according to Dr Lewis Dartnell, an astrobiologist at the University of Leicester.

“Astronauts spend a huge amount of their time strapped to running machines with bungees, but it’s not particularly effective,” he said.

“If we can look to nature and try to understand how existing biological systems, such as those in hibernating black bears can overcome bone loss, we can use this knowledge to protect our own species in space.” he added.

The study, published in the Journal of Experimental Biology, found that bears are able to suppress the process of calcium release through the changes in levels of two specific enzymes.

“We know that hibernation is controlled by the brain. Our next step is to understand how these proteins and enzymes get turned down by a bear’s brain to reduce bone loss,” said McGee-Lawrence.

The scientists studied 13 female bears between 2006 and 2009, collecting blood and bone samples before, during and after hibernation and measuring enzyme and hormone levels.



The researchers found that levels of a protein called cocaine and amphetamine regulated transcript (CART), which reduces the quantity of bone minerals being broken down into the blood, increased 15-fold during hibernation.

Two other enzymes known to contribute to new bone generation, bone-specific alkaline phosphatase (BSALP) and tartrate-resistant acid phosphatase (TRACP) fell when the bears were hibernating. Levels of bone-regenerating cells, called osteoblasts, also fell significantly, from 2% before hibernation to just 0.15% during hibernation.

According to the researchers, these changes show that black bears are able to maintain their skeletal structure and strength by suppressing bone loss during hibernation, rather than by generating new bone material.

Finding a solution to bone degeneration is seen as a crucial challenge for long distance space travel. “It’s particularly important when we send people to Mars,” said Dartnell.

“If astronauts have flown for six months, and their skeletons have become weak during the journey, they may suffer significant health problems when they get to Mars, even though the gravity there is less than that on earth.”