Researchers have discovered a hormone that keeps the bones of breastfeeding women strong, and could help heal bone fractures and treat osteoporosis in the general population, which affects more than 200 million people worldwide.
The new study sought to solve the mystery of how breastfeeding women's bones remain intact despite losing calcium to produce milk.
Despite the low estrogen levels, "osteoporosis and bone fractures are very rare," suggesting that something other than estrogen is at play.
Previously, lead researcher Dr. Holly Ingraham, a professor of molecular and cellular pharmacology at the University of California, San Francisco (UCSF), and her colleagues, studying female mice, blocked the estrogen receptor in neurons in a small area of the brain, which led to increased bone mass. They thought the strong bones were linked to a hormone in the blood, but they couldn’t find it.
After an "exhaustive search," they were finally able to identify CCN3, a hormone that behaves differently from other hormones secreted by neurons.
“The idea that a hormone could be secreted directly from the brain is a new idea in the field of endocrinology,” says Dr. Holly. “Our findings make us wonder whether other hormones are secreted through so-called brain windows in response to changing physiological demands, such as lactation.”
According to the press release, they were able to locate CCN3 in the same brain region in lactating female mice, but not the recipient, so far.
In the absence of this hormone, the lactating female mice lost bone mass, and the babies also lost weight. This underscores the importance of this hormone, so they named it Maternal Brain Hormone (MBH).
As CCN3 levels increased in both female and male mice, bone mass and strength improved dramatically within weeks.
Remarkably, CCN3 doubled the amount of bone mass in very old female mice and those deficient in estrogen.
Dr. Thomas Ambrosi, one of the study's co-authors, went on to say that highly mineralized bones aren't always better because they can become weaker and break more easily. However, "when we tested these bones, they turned out to be much stronger than normal."
When they examined bone stem cells, which are responsible for regeneration, they found that when exposed to CCN3, they supported the production of new bone cells. Thus, they concluded that CCN3 could help heal bones.
During the experiments, the team created a hydrogel patch and attached it to a bone fracture, so they could slowly release CCN3 over two weeks.
Typically, bone fractures in older mice don't heal easily or well, but the CCN3 patch actually helped regenerate bone. Even their fracture healing was described as "youthful," with the team noting that fractures repaired at a rate similar to that of two-month-old male mice.
“We have never been able to achieve these types of mineralization and healing results with any other strategy,” Ambrosi said. “We are really excited to pursue it, and perhaps apply CCN3 in the context of other problems, such as cartilage regrowth.”
The researchers now plan to continue studying the molecular mechanisms of CCN3 in breastfeeding women, and its potential to treat bone disease. No side effects have been found so far, the researchers said. However, once they identify the CCN3 receptor, they can survey tissues and cell types that might be affected by the hormone.
Amazing.
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