With age, muscle stem cells in mice cease to be a uniform population: some retain the ability to effectively restore tissue, while others sharply lose this function. Researchers from UCLA under the leadership of Thomas Rando discovered that the key cause of this division is the level of glutathione — the cell's main antioxidant.
At a young age, all muscle stem cells demonstrate high activity and respond quickly to damage. Over time, old mice develop a second subpopulation of cells with low glutathione content, which copes poorly with regeneration. It is the metabolism of this substance, as experiments have shown, that determines whether a cell will remain "young" in function or transition into a weakened state.
The scientists tested the cause-and-effect relationship directly. When cells with low glutathione were given a drug that raises its level, their regenerative ability was restored. Conversely, artificial reduction of glutathione in young cells turned them functionally old. These results were published in the journal Cell Metabolism.
The study was performed on mice and so far has no direct analogues in clinical trials on humans. Funding came from the Glenn Foundation for Medical Research, the US National Institutes of Health, and the Department of Veterans Affairs. The authors emphasize that glutathione is only one of the drivers of age-related changes, and not a universal solution to the problem of tissue aging.
Imagine a cell as a workshop where glutathione acts as a protective filter against the oxidative "smoke" of everyday work. When the filter becomes clogged or there is not enough of it, some workshops begin to work at half strength, while others continue to cope. Restoring the filter returns the second group to its former pace, but does not make the entire workshop new.
The discovery shows that stem cell aging is not simply a general slowdown, but the emergence of heterogeneous subpopulations with different metabolic profiles. Similar mechanisms may explain why tissue regeneration deteriorates unevenly and why some people retain muscle strength longer than others.
The question now is whether it will be possible to safely and selectively maintain a high level of glutathione in the needed human cells over decades without disrupting the body's other metabolic balances.
