Abstract:
Bone plays important roles in the human body such as supporting the body, storing calcium, and producing blood cells, but scientists have now discovered that it may also have a previously underestimated function: by sensing mechanical stress, it releases proteins that can protect other organs, thereby affecting the aging process of the entire body.
A new study by a Chinese research team found that regularly applying gentle, regular mechanical pressure to the tibia of mice not only improves bone health, but also has a positive impact on the brain, liver, muscles and immune system. The median lifespan of treated older mice increased by an average of 9.4%, equivalent to an increase of approximately 80 days.
This study was led by scientists from Guangzhou Southern Medical University, focusing on a type of bone cell that can sense mechanical force - Osteocytes. They are widely distributed inside bone tissue, can sense the pressure and deformation of bones, and help bones adapt to exercise and body load by regulating bone tissue metabolism.
The researchers found that PIEZO1 protein levels in bone tissue of both mice and humans gradually decreased with age. PIEZO1 is a mechanosensitive ion channel that can convert external mechanical stimuli into biological signals within cells and plays an important role in the process of bone cells sensing stress.
To further understand this mechanism, the researchers first chemically destroyed the PIEZO1 channel in adult mouse bone cells. It was found that these mice showed significantly accelerated signs of aging, and the effects were not limited to the bones themselves. Multiple organs such as the brain, liver and muscles were also affected, with the median lifespan shortened by about 11% in female mice and 13% in male mice.
This discovery led the research team to raise a new question: If weakening the ability of bones to sense mechanical pressure will accelerate aging, can conversely, actively applying moderate pressure to bones delay aging?
To test this idea, the researchers designed a specialized mechanical loading device to apply slight, rhythmic pressure on the tibia of mice starting from the age of 20 months. This age is considered an old age for mice. In the experiment, the mice were treated under anesthesia, and the researchers repeatedly applied small loads to the tibia through the device and observed changes in their bodies.
The results were surprising. Mice that received mechanical stimulation of their bones not only lived longer, but also had improved blood sugar regulation and bone structure. The researchers also found that inflammation indicators and cellular aging markers in multiple organs of these mice decreased. The immune system, which was already showing signs of aging, also showed a more youthful state. In particular, there were positive changes in the tissue responsible for making blood cells in the bone marrow.
The research team then further searched for the specific mechanism by which bones transmit signals to other organs.
They transferred the plasma of mice that received mechanical bone stimulation to other older mice and found that the latter also experienced some health improvements. This shows that after bones are mechanically stimulated, bioactive substances that can affect systemic tissues may appear in the blood.
One substance that has received a lot of attention is pigment epithelium-derived factor (PEDF). This is a protein with multiple tissue protective effects. The study found that PEDF levels in the blood of mice increased significantly after bones were subjected to mechanical loading. Further experiments showed that directly injecting this protein into elderly mice could also improve a number of aging indicators and improve their cognitive abilities and physical activity performance.
This means that bones may not only be passive supporting structures in the locomotor system, but also participate in systemic physiological regulation through mechanosensing and protein secretion. The health benefits of exercise may also come in part from chemical signals released by bones to other organs, beyond just improvements in muscle activity and cardiopulmonary function.
This finding is an interesting echo of another study earlier this year. At that time, scientists observed improvements in metabolism, bone density and other health markers in mice by implanting tiny muscle tissue that could contract on its own. The two studies together point to a direction worthy of attention: muscles and bones are not only responsible for allowing the body to move, but also release biological signals that affect other tissues during movement.
However, the researchers emphasized that the current results cannot directly infer that humans can extend their lifespan by squeezing bones. This experiment was completed on mice. It has not been proven that the same mechanical stimulation method can produce similar effects in humans, and there is no evidence that this method can extend human life span by nearly 10%.
Additionally, researchers have not determined whether PEDF is necessary for mechanical stimulation of bone to produce the full anti-aging effects. Other proteins, immune system changes, and different cell signaling pathways may also be involved.
Research also doesn't prove that applying stress to your shins twice a week can replace the overall health benefits of walking, swimming, or strength training. New Atlas points out that the real concern is not that bones are squeezed in some special way, but that this study further reveals the deep connection between physical activity and bone mechanical perception.
If future research can confirm this mechanism in humans, scientists may be able to develop treatments targeting the bone mechanosensory system, providing new health intervention avenues for people who have difficulty engaging in regular exercise due to disease, mobility impairment, or physical decline.
Relevant research results have been published in the journal "Cell Metabolism". This study provides a new biological explanation for understanding why exercise can delay aging. It also suggests that bones may be far more active than traditional cognition. They not only support the body, but may also participate in maintaining the health of the entire body by releasing chemical signals.
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