“Bearing” Good News for Osteoporosis Treatments: What Black Bears Can Teach Us About Bone Strength

When biomedical student Seth Donahue ran into a black bear while hiking in California’s Sierra Nevada Mountains, he felt inspired rather than frightened.  He wondered how the Ursus americanus, which hibernates for up to seven months a year, can wake with bones that are just as strong as they were when it first settled down for a snooze.  Taking a long nap might sound like a great plan, but if a human were to do the same for only two weeks, its bones would begin to wear down from disuse.

The Sierra Nevada Mountains of California support a healthy population of black bears.

The Sierra Nevada Mountains of California support a healthy population of black bears.

Throughout our lifetimes, our bones are constantly being rebuilt.  Over time, we lose more bone than we replace.  As a result, many elderly people suffer from osteoporosis, the significant bone loss that can increase the risk of fracture.  This disease affects more than 10 million Americans and is the underlying cause behind 1.5 million fractures every year (Jennings et al., 2011).  Rather than develop osteoporosis, these black bears’ bodies have made evolutionary adjustments to prevent bone loss during disuse.

But how?

Tapping into the reason behind this bone restoring mechanism could offer new treatments for osteoporosis.  That’s exactly what Seth Donahue, a biomedical engineer at Michigan Technological University, hypothesized.

An American black bear such as this one inspired Donahue to take on a potentially dangerous bone project.

An American black bear such as this one inspired Donahue to take on a potentially dangerous bone project.

For over a decade, Donahue and a team of research scientists have been investigating the secret behind the integrity of bears’ bones (Jennings et al., 2011).  They have discovered that in bears, the trabecular, or spongy, bone that forms tissue does not lose density or volume.  Working with bears was tricky, however.  In an interview with the Wall Street Journal, Donahue said that bears are “not like rats where you can get 100 animals and bring them into the lab…” (Oransky et al., 2008).  Donahue relied on colleagues at Virginia Tech and Washington State University to obtain samples from anesthetized hibernating bears.

These samples showed that black bears have a uniquely strong form of parathyroid hormone (PTH), which regulates the levels of blood calcium (Donahue et al., 2006).  In both humans and bears, PTH is 84 amino acids long.  When Donahue’s team sequenced the gene for PTH, they found nine differences in the amino acid sequence (Jennings et al., 2011).  They believe that the bears evolved their distinct amino acid sequence to protect against the debilitating effects of bone disuse during hibernation.  Additionally, bears maintain a constant level of PTH in their bodies throughout their dormancy, increasing the hormone’s beneficial effect.

Continuing to investigate hormonal effects on black bear bones during hibernation, the lab measured PTH in bear blood, cloned the gene for bear PTH, and used synthetic and recombinant PTH to reverse bone loss in rodent models of osteoporosis (Jennings et al., 2011).  Notably, mice that received bear PTH injections over a period of weeks developed stronger bones.  This suggests that a treatment of bear PTH could also help humans with diseases, like osteoporosis, that involve bone atrophy.

What are the next steps for getting black bear PTH available to patients suffering from osteoporosis?  A 5-year-old Kalamazoo-based biotechnology company, Aursos Inc., has been developing a drug based upon Donahue’s technology.  The company plans to target the smaller market of people suffering from Duchenne’s muscular dystrophy (DMD) before making its product, bear PTH1-84, available to the millions of people with osteoporosis.  DMD is an inherited neuromuscular disease that has harmful consequences for muscle and bone, causing osteoporosis.  Clinical trials on patients with this rare disease may show the efficacy of the bear PTH1-84 treatment.

People who are affected by osteoporosis lose density in their spongy bone. Finding a more effective treatment could mean fewer fractures.

People who are affected by osteoporosis lose density in their spongy bone. Finding a more effective treatment could mean fewer fractures.

If black bear PTH passes the test of DMD treatment, it could compete with currently available osteoporosis drugs.  These include biphosphonates and calcitonin, which can reduce bone loss and fracture risk (Kerriem-Norwood et al., 2011).  A synthetic PTH drug, Forteo, builds new bone, but comes with black box warnings for cancer risks.

If the bear PTH treatment with its unique amino acid sequence is more effective in humans than Forteo, a smaller and less dangerous dose can be delivered.  The scientific study of black bears could aid patients who suffer from age, disease, or disuse-related osteoporosis.

As Ursus americanus hunkers down this fall, it can only dream of the possibilities it has created for new DMD and osteoporosis treatments.

In Brief:

  • Researchers from Michigan Technological University are learning how black bears can hibernate without waking up with brittle bones.
  • They have identified parathyroid hormone as a potential reason for the bears’ strong bones.
  • This research could lead to improved osteoporosis treatments.

This article was written by cYw4. As always, before leaving a response to this article please view our Rules of Conduct. Thanks! -cYw Editorial Staff

Works Cited


19 thoughts on ““Bearing” Good News for Osteoporosis Treatments: What Black Bears Can Teach Us About Bone Strength

  1. Great Article, well written with good references! Animals have always taught us and it is good to read about this bridge into scientific research. I think we can also learn a lot from for example chimps because of their close relation to us especially when considering the aging process and the diseases that come with it (parkinson etc) ot those affecting brain development.

  2. This blog is very interesting and is almost enlightening, except for the fact we don’t know to how close this is to becoming reality. Is there any clarification on when a treatment or preventative measures could be taken to prevent osteoporosis? How close do you think the scientific community is to finding the cure? I think that it is very interesting that we are in a sense taking some of their genes to make us better. Overall great job!

    • Response from the author:
      I agree that sometimes research seems idealistic and far from reality. Many times it takes decades to turn a concept into a researchable topic into a marketable drug. I am not sure how close the scientific community is to finding a cure, but perhaps this website could give you some ideas. http://www.nof.org

  3. Overall I think that your blog was very well researched and written. The information about the black bear study was very informative and detailed. I think that this was an important topic to write about, due to the number of people suffering from osteoperosis. Animals have always played a huge role in our medical and scientific advancements. If this bear treatment works, I think that this will open the door to many other advances in the medical field. Researchers and scientists will be able to move forward from this, maybe even finding other treatments to bone related diseases.

  4. Well done on the article! It is amazing how much we can learn from other organisms. Our bone structure is one of the most important systems and we need to take care of it. There should be a lot more research going on that can help improve our skeletal system. I like how you pointed out that bears are not like lab rats and research is limited. It is also more difficult becuase the number of bears reduces every year due to hunting and poaching. If the new PTH passes it will help millions of people. Again good job on the article, it was very informative.

  5. Very well written article with excellent information. I like how valuable facts were italicized and bullet points were used to conclude the entire article in simple sentences as well as links to terms such as PTH. However, why hasn’t this treatment become well publicized or come into common use? I still see commercials regarding Osteoporosis as if it is still a major problem out there, what is hindering the widespread use of the PTH? There are a few synthetic treatments, as said in the article, but heed warnings of possible cancer development, why produce it if it could potentially cause more bodily damage on top of bone damage? Overall, I like how this article provided a peek into the future of our medical advancements, and I hope this treatment becomes a solution to this problem.

    • Response from the author:
      I think that the treatment still has to go through clinical trials before it can become publicized. Many times researchers and pharmaceutical companies do not want to promote a drug until they are absolutely sure that it is going to be marketable and effective. Otherwise, they face the risk of having to recall drugs and face backlash. Sometimes the treatment of osteoporosis may be worth the risk of developing cancer. Many treatments have side effects, and it is the trade-off between the function of the drug and the side effects that the drug user must decide on. For instance, several chemotherapeutic drugs cause adverse effects such as weakness and fatigue.

  6. Cool Article! I really think that this study looks very promising for the future of osteoporosis treatment. I never thought about the bodily effects that hibernation has on animals like black bears, and this article really shed some light on that topic. I would love to know more about what happens during hibernation, and how the researchers extracted information from these bears while in this sleep state. I hope that this project is succesful!

  7. You made really good connections with your findings. You have solid information! Your post is informative and you have a creative layout. Having you put a “in brief” box was very helful because it lets the viewer see the important key concepts.

  8. You did a great job creating an informative article that was interesting to read. I liked how you incorporated pictures with captions and a summary of the information. It was nicely laid out and I liked how you included scientific information. It is fascinating what research has lead us to discover. Where is this research headed in the future?

  9. This treatment for osteoporosis seems like it will help a lot of people. It is interesting to see how close, but so different our genes are to bears. But how do scientist make this medicine? Do they extract it from bears directly?

  10. It’s incredible to think that the possibility of this breakthrough has been practically staring us right in the face. It is difficult to comprehend how similar the amino acid sequences of bears and humans are. I would be interested in learning more about how DMD and osteoporosis are related.

  11. Wow, what a great blog post! I was wondering if humans would react to the PHT injections the same way the rodents did. Aren’t the bone structures between humans and rodents different? Thus, if the injections worked for them, it could not work for us? Also, it would be helpful if the hyperlinks opened up in a different tab so thatI could read it and refer back to the blog post.

    • dbradster speaking:
      Which internet browser are you using? I have it set to open up in new tabs, and it seems to be working just fine for Chrome and Safari.

      Response from the author:
      Thanks for the advice. We will look into that. Mice are used for many preliminary drug tests since they are mammals and genetically show many similarities with humans. However, it is true that there exist many differences between the mouse and the human. Research can be fine-tuned with a mouse model, and then further research can be done with less risk with humans in clinical trials. While the following link talks about addiction, there are many insights we can find about why animals are used in research.

      • I was using internet explorer when I first read it. But now on Google Chrome it opens up in different tabs. Sorry about that.
        The human brain is significantly similar to that of mice, as I saw on the webpage you linked. Also, there is a list of different organisms and the number of genes they have. The first organism on that list was chimpanzees, stating they have the same number of genes as humans. According to National Geographic, humans and chimps are 96% identical. Whereas mice and humans are only 85% identical (National Human Genome Research Institution). Also humans and chimps are both apart of the same order of classification known as Primates. While mice as well as rats are apart of the order Rodentia. In the Nation Geographic article it stated, “the number of genetic differences between humans and chimps is ten times smaller than that between mice and rats”. Do you think chimps would make a better product tester than mice?


      • When I first read the article, it was through internet explorer, but now I’m on Google Chrome and it works just fine. Sorry about that!
        That article you linked was extremely informative. The similarities between mice and human brains are enormously. But if you look on the side of the link, it states chimps (and rats as well) have the same number of genes as humans. So I looked into it and according to the U.S Department of Energy Office of Science, mice and humans are 85% genetically identical. Whereas National Geographic stated that “humans are 96 percent similar to the great ape species”. Not only that, but chimpanzees and humans are apart of the same scientific order classification called “Primates”. But mice, as well as rats, are apart of the “Rodentia” order. To top it all off the amount of “genetic differences between humans and chimps is ten times smaller than that between mice and rats”. Meaning chimps and humans are more closer related than mice and rats, nevertheless mice and humans. Do you think that chimpanzees would make better test subjects than mice for the PHT injection then mice?


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