Old mouse muscle cells can act young again, but fewer survive
A protein that rises with age slows repair, but it keeps the repair crew alive.
Science Daily · Old muscle stem cells can act young again but there’s a catchOld muscle stem cells in mice can act young again when scientists release a brake that builds up inside them, but then fewer of the cells survive.
The brake is a protein called NDRG1. In older mice, levels ran 3.5 times higher than in young animals. It dampens a signal that normally tells reserve repair cells to wake up, multiply, and fix injured muscle.
When researchers blocked NDRG1 in mice roughly as old as 75-year-old people, old stem cells woke more readily and repaired muscle better after injury. Without the brake, though, fewer stem cells stayed alive over time, and muscle fared worse after repeated injuries.
The researchers call it a cellular survivorship bias. Cells with too little of the protein disappear, leaving a slower but tougher pool. Sluggish healing, in other words, may be the price of keeping any repair crew at all.
Questions people ask
What do muscle stem cells actually do?
Muscle stem cells are reserve cells tucked along muscle fibers. When muscle is injured by exercise, a fall, or a cut, they wake up, multiply, and turn into new muscle cells to patch the damage.
What is the mTOR signal the protein brakes?
mTOR is a central control signal inside cells that tells them to grow and divide when conditions are good. In muscle stem cells, turning it up helps them activate quickly, while turning it down keeps them quiet and conserves them.
Could blocking this protein become an anti-aging treatment?
Not yet. The work was done in mice, and the catch is important: making old cells act young depleted the stem cell supply. Any future therapy would need to boost repair without using up the reserve, and researchers have not shown how to do that in people.