No gym needed? Scientists in China develop self-exercising muscle grafts

Scientists in China have developed a groundbreaking method to create self-exercising muscle grafts, which could potentially benefit bedridden individuals by providing the health advantages of exercise without any physical effort. By injecting muscle cells beneath the skin, these cells autonomously assemble into muscle grafts that enhance whole-body muscle mass in mice and improve various health aspects, such as bone density, endurance, liver function, and cognitive health.

The innovative "myografts" could offer the benefits of exercise to patients suffering from age-related conditions like Alzheimer's and osteoporosis, and could also be used by individuals simply seeking to build muscle without visiting the gym. Although the long-term safety and pharmacological profile of these autologous myografts need further investigation in human trials, the researchers' preclinical studies in mice mark a significant milestone in this field.

According to study author Ng Shyh-Chang, a professor at the Chinese Academy of Sciences' Institute of Zoology, these myografts have the potential to distill the positive aspects of exercise while eliminating its negative effects on the heart and joints. Moreover, they can act as a living biofactory, producing targeted therapeutic proteins within the body, including GLP-1, which aids in managing diabetes and weight loss.

During exercise, skeletal muscle releases hundreds of proteins that contribute to the multi-organ benefits of physical activity and help combat age-related diseases and obesity. However, those who require exercise the most often face the greatest challenges in performing it.

Initially, the researchers attempted to transplant lab-grown muscle organoids into mice, but these efforts failed due to the large size of the 3D cell structures, which hindered nutrient diffusion. To overcome this challenge, the team resorted to a more straightforward approach: introducing cells under the skin, allowing them to form the organoid gradually.

By using myocytes derived from mouse muscle stem cells and embedding them in a supportive gel scaffold, the researchers achieved self-organizing, mature myografts capable of spontaneous contractions without external stimuli.

The myografts not only improved muscle mass in ageing and obese mice but also showed positive outcomes in strength and mobility tests. The researchers are currently investigating the substances secreted by the myografts to understand their various health benefits, which may be comparable to or even exceed the effects of a single hour of acute exercise. The muscle fibres in the grafts are also younger or immature, potentially allowing them to secrete higher concentrations of beneficial factors than mature muscles.

Over time, the grafts integrate with local blood vessels while remaining stable and avoiding tumour-like growth. Ng expressed confidence in the safety of the myografts, stating that no signs of toxicity or negative health impacts have been observed so far. However, he emphasized the necessity of clinical trials to confirm their safety.

The team is contemplating trials with intensive care unit patients and plans to expand testing to broader patient populations once safety and efficacy are confirmed. Ng also noted that while the grafts were initially implanted shallowly in mice for easy visual tracking, human skin is thicker, and the transplant site would be carefully chosen to avoid obvious movement of the grafts.