Aging Muscles and the Hidden Survival Switch

Aging often means recovering more slowly from muscle injuries, but a new study from UCLA has uncovered an important reason why this happens. Researchers have discovered a hidden survival switch that may be responsible for the decline in muscle repair with age.

According to the study, published in the journal Science, aging muscle stem cells build up high levels of a protein called NDRG1. This protein slows down the cells’ ability to spring into action and repair damaged tissue. At the same time, NDRG1 appears to help the cells endure the challenging conditions found in aging muscle.

The researchers, led by Dr. Thomas Rando, found that levels of NDRG1 rose dramatically with age, reaching concentrations 3.5 times higher in older cells. NDRG1 functions like a brake inside the cell, suppressing a signaling pathway called mTOR, which normally helps drive cell activation and growth.

To determine whether NDRG1 was contributing to slower muscle recovery, the scientists studied mice that had aged naturally to roughly the equivalent of 75 human years. When they blocked NDRG1 activity, the older muscle stem cells quickly regained youthful behavior, becoming more active and improving muscle repair after injury.

However, the improvement came with a drawback. Without the protective effects provided by NDRG1, fewer stem cells remained alive over time. As a result, the tissue became less capable of regenerating after repeated injuries.