With age, bones become less dense and more fragile. Mesenchymal stem cells in the bone marrow play a key role in this process, as they can transform into either bone tissue or fat cells. With a lack of physical activity, these cells are more likely to form fat tissue, which accelerates bone weakening and initiates a process of bone degradation that is difficult to reverse.
In experiments on mice and human stem cells, scientists identified the Piezo1 protein, located on the surface of mesenchymal stem cells. It acts as a kind of "physical activity sensor," detecting mechanical signals generated by movement and stress. Activation of Piezo1 reduces fat accumulation in bone marrow and stimulates the formation of new bone tissue.
When this protein is absent or inactive, the process is reversed: fat cell formation increases and bone loss accelerates. Furthermore, pro-inflammatory signals (Ccl2 and lipocalin-2) are activated, further interfering with bone repair. Blocking these signals can partially restore the cells' ability to form healthy bone tissue.
The study's leader, Professor Xu Aiming, noted that the team has effectively deciphered how the body converts movement into bone strengthening at the molecular level. This will enable the development of drugs that activate the Piezo1 pathway and "trick" the body, mimicking the effects of exercise without the actual impact.
Bone loss is a particularly pressing issue for older adults and those with limited mobility, with women being significantly more susceptible. According to the World Health Organization, fractures related to weak bones occur in one in three women and one in five men over 50. In Hong Kong, osteoporosis is diagnosed in 45% of women and 13% of men over 65.
Scientists believe that these "exercise mimics" could be a breakthrough in the treatment of osteoporosis in the elderly, bedridden patients, and patients with chronic diseases. The team is currently working to translate the research findings into clinical practice and develop new methods for preserving bone mass and quality of life in vulnerable populations.
