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(https://directorsblog.nih.gov/2024/08/01/maternal-brain-hormone-key-to-strengthening-bones-could-help-treat-osteoporosis-bone-fractures/) Maternal Brain Hormone Key to Strengthening Bones Could Help Treat Osteoporosis, Bone Fractures
Aug 1st 2024, 09:00

Credit: Donny Bliss/NIH

More than 200 million people around the world have (https://www.nia.nih.gov/health/osteoporosis/osteoporosis) osteoporosis, a condition that weakens bones to the point that they break easily. Women are at especially high risk after menopause due to declining levels of the hormone estrogen, which helps keep bones strong. While osteoporosis rarely has noticeable symptoms, it can lead to serious injuries when otherwise minor slips and falls cause broken bones that in turn can lead to further fracture risk and fracture-related mortality. So, I’m pleased to share NIH-supported research suggesting a surprising candidate for strengthening bones: a maternal hormone produced in the brain.

The study in mice reported in (https://www.nature.com/articles/s41586-024-07634-3) Nature shows that this newly discovered hormone maintains and rebuilds bone strength in lactating females, even as estrogen levels dip and calcium is lost to the demands of milk production. 1 The findings suggest this hormone—or a drug that acts similarly—could be key to treating osteoporosis and preventing and healing broken bones.

The findings come from a team led by (https://profiles.ucsf.edu/holly.ingraham) Holly Ingraham, University of California, San Francisco. The researchers knew from studies in mice and humans that a protein related to parathyroid hormone, which is made in the mammary glands, is the main driver for stripping calcium from maternal bones for milk production. As a result of this process, nursing mothers tend to lose a lot of bone. In humans, this bone loss is 10% on average, compared to nearly 30% in mice. Fortunately, these losses are reversed after lactation ends, suggesting to the researchers there must be some other bone-strengthening factor in play.

Previous (https://www.nature.com/articles/s41467-018-08046-4) work in Ingraham’s lab, also supported by NIH, offered other clues. The researchers found that in female mice, blocking a certain estrogen receptor in select neurons in a small area of the brain led to the development of bones that were exceptionally dense and strong. 2 This was an early hint that an unidentified hormone might have a role. The team’s search in this latest study led them to brain-derived communication network factor 3 (CCN3).

The new findings showed that, in lactating female mice, CCN3 is produced in the same brain area identified in the previous study. When the researchers prevented the brain from making CCN3, lactating female mice rapidly lost bone. The researchers also found that male and female young adult and older mice gained a considerable amount of bone mass and strength when their levels of circulating CCN3 were boosted over a two-week period. In fact, in some female mice that were very old or completely lacked estrogen, the hormone more than doubled their bone mass. Tests showed that the animals’ bones weren’t just denser, but also stronger.

Further studies conducted by co-author (https://urldefense.com/v3/__https:/profiles.ucdavis.edu/thomas.ambrosi__;!!LQC6Cpwp!pxycGr8Uw5wGQGUsrsRkTDGI68nq-qPNsEyGr-X7sqrqFlx972_zXgOUViYb7G6vFaHu_oM6EYSR8mD5ps59-gXgrF9rDOJd%24) Thomas Ambrosi, University of California, Davis, revealed that bone stem cells were responsible for receiving signals and generating the new bone. When those cells were exposed to CCN3, they ramped up bone production even more. When the researchers applied a hydrogel patch containing CCN3 to the sites of bone breaks, this spurred the formation of new bone. As a result, the researchers saw rapid bone healing in older mice comparable to what would be expected in much younger mice.

In future studies, the researchers want to gain insight into the underlying mechanisms of CCN3. They also plan to explore the hormone’s potential for treating bone loss in people at increased risk, including postmenopausal women, breast cancer survivors taking estrogen blockers, and those with other conditions leading to unhealthy bone mass, such as genetic bone disorders, chronic kidney disease, or premature ovarian failure. They suggest that more immediate local uses for CCN3 include fracture repair, cartilage regeneration, and bone improvements for anchoring dental implants. It’s a great example of how finding an answer to a scientific puzzle—like how maternal bones stay strong during breastfeeding—can potentially lead to advances that help many more people.  

References:

[1] Babey ME, et al. (https://pubmed.ncbi.nlm.nih.gov/38987585/) A maternal brain hormone that builds bone. Nature. DOI: 10.1038/s41586-024-07634-3 (2024).

[2] Herber CB, et al. (https://pubmed.ncbi.nlm.nih.gov/30635563/) Estrogen signaling in arcuate Kiss1 neurons suppresses a sex-dependent female circuit promoting dense strong bones. Nature Communications. DOI: 10.1038/s41467-018-08046-4 (2019).

NIH Support: National Institute of Diabetes and Digestive and Kidney Diseases, National Institute on Aging, National Institute of General Medical Sciences, National Institute of Arthritis and Musculoskeletal and Skin Diseases

Forwarded by:
Michael Reeder LCPC
Baltimore, MD

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