Representative image of an arm in a cast.
Researchers from the University of California at San Francisco (UCSF) and UC Davis discovered a hormone that keeps breastfeeding women’s bones strong, and it could help heal fractures, too.
The new study sought to solve the mystery of how women’s bones remain unaffected even though they lose calcium to produce milk. Though estrogen levels are low, “osteoporosis and bone fractures are much rarer,” as per a press release, suggesting that something other than estrogen is at play.
And they found it: a new hormone named CCN3.
Previously, senior author Dr. Holly Ingraham and collaborators, in studying female mice, blocked an estrogen receptor in neurons in a small area of the brain, and their bone mass increased. They thought that strong bones were linked to a hormone in the blood, but they couldn’t find it.
After an “exhaustive search,” they finally identified CCN3, a hormone that behaved differently than others that neurons secrete.
“The notion that a hormone can be secreted directly from the brain is a new concept in the field of endocrinology. Our findings leave us wondering if other hormones are secreted from the so-called ‘windows of the brain’ in response to changing physiological demands, such as lactation.”
As per the press release, they were able to locate CCN3 in the same brain region in lactating female mice, but not the receptor, as of yet.
In the absence of this hormone, lactating female mice lost bone mass, and the babies lost weight as well. This confirmed how vital this hormone is, so they named it the Maternal Brain Hormone (MBH).
In increasing the levels of CCN3 in female and male mice, their bone mass and strength improved in weeks, and dramatically. Remarkably, CCN3 doubled the amount of bone mass in very old female mice and those lacking estrogen.
Further testing proved just how strong the bones were.
Dr. Thomas Ambrosi, a project collaborator, went on to say that highly mineralized bones aren’t always better as they can become weaker and break more easily. However, “when we tested these bones, they turned out to be much stronger than usual.”
When he examined the stem cells in the bones, responsible for regeneration, he found that when exposed to CCN3, they supported the production of new bone cells. Thus, they concluded that CCN3 could possibly assist in bone healing.
They created a hydrogel patch and attached it to the bone fracture, so they could slowly release CCN3 for two weeks. Normally, bone fractures in older mice don’t heal easily or well, but the CCN3 patch actually helped to regenerate the bone. The healing of their fracture was even described as “youthful.”
“They essentially repair at the rate of young two-month-old male mice,” researchers told IE.
“We’ve never been able to achieve this kind of mineralization and healing outcome with any other strategy,” Ambrosi said. “We’re really excited to follow it up and potentially apply CCN3 in the context of other problems, such as regrowing cartilage.”
Now, researchers intend to continue studying the molecular mechanisms of CCN3 in breastfeeding women, and its potential to treat bone conditions. No side effects have been found yet, as researchers told IE. However, once they identify the receptor for CCN3, they can survey which tissues and cell type might be affected by this hormone.
With osteoporosis impacting more than 200 million people worldwide, which is classified as a weakened bone structure, thus making them susceptible to fracturing, women, after menopause, are at a particularly high risk.
A decrease in estrogen levels was thought to be the cause, which is true. However, while breastfeeding, researchers found this loophole, as they don’t lose any bone mass. So, they found the hormone that they can now apply to help women later in life.
But this study also stands to support breast cancer survivors, as they have to take hormone blockers, female athletes, and older men who statistically have a lower survival rate after a hip fracture than women.
“It would be incredibly exciting if CCN3 could increase bone mass in all these scenarios., Ingraham said.
Lastly, interestingly enough, “one of the remarkable things about these findings, Dr. Ingraham said in the press release, is that female mice aren’t used in biomedical research, which is why the hormone had never been discovered.
“It underscores just how important it is to look at both male and female animals across the lifespan to get a full understanding of biology.”
The study was published in Nature.
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Maria Mocerino Originally from LA, Maria Mocerino has been published in Business Insider, The Irish Examiner, The Rogue Mag, Chacruna Institute for Psychedelic Plant Medicines, and now Interesting Engineering.
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