Why muscles heal more slowly with age

With increasing age, it takes longer for muscles to recover from injury. Muscle stem cells make a kind of biological decision as we age - they ensure their own survival, but lose some of their repair capacity in the process.

Muscle stem cells are essential for the renewal and repair of our muscles. When we are young, they react quickly to injuries, divide and help to replace damaged muscle tissue. As we age, however, these cells change. As recent experiments by Kang et al. at the Stanford University School of Medicine show, they produce more of a protein called NDRG1, which makes them more resistant.

The catch: this protective strategy makes the cells more sluggish. They become active more slowly when a muscle is injured and contribute less effectively to the healing of the muscle. "The cells survive longer, but are functionally limited," says von Maltzahn, summarising the results.

Particularly exciting in connection with work from other research groups, including Stanford: although the number of subgroups of muscle stem cells does not change with age without injury, functionality is limited. This means that the cells are still there - they just no longer react as flexibly as they used to. Instead of a complete loss, it is therefore a biological compromise: safety takes precedence over performance.

These new findings are changing the way we look at ageing. They show that age-related limitations are not simply caused by "wear and tear", but by active adaptations of the cells themselves. In the long term, this knowledge could help to develop new therapies that maintain or improve the regenerative capacity of muscles in old age - with the aim of ensuring mobility, independence and quality of life into old age.