Stem cells play a key role in repairing muscle
Scientists have found a way to give old, tired muscles a new lease of life.
They tweaked biochemical signals in mice to boost the ability of the animal's stem cells to repair damaged tissue, restoring its youthful vigour.
The breakthrough raises hopes of new treatments for age-related degenerative diseases such as Alzheimer's and Parkinson's.
The study, by the University of California, Berkeley, is published in the journal Nature.
Adult stem cells play a key role in helping to repair the mature, differentiated cells that make up the body's working tissues.
The Berkeley team identified two key regulatory pathways that control how well adult stem cells carry out their repair work.
They were then able to modify the way stem cells reacted to those biochemical signals to revive the ability of muscle tissue in old mice to repair itself nearly as well as the muscle in the mice's much younger counterparts.
Using adult stem cells to rejuvenate tissue would eliminate the ethical controversy surrounding the use of cells taken or derived from embryos.
Researcher Dr Morgan Carlson said: "We are one step closer to having a point of intervention where we can rejuvenate the body's own stem cells so we don't have to suffer from some of the debilitating diseases associated with ageing."
The Berkeley team compared muscle regeneration capacity of two-year-old mice - comparable in age to a human aged 75-85 - to that in two-month old mice, comparable to a human aged 20-25.
As expected, they found the muscle tissue in the young mice easily replaced damaged cells with healthy new cells, while areas of damaged muscle in the older animals was full of scar tissue.
But when they effectively disabled the "ageing pathway" by blocking production of a key protein called TGF-beta, the level of cellular regeneration in the older animals was comparable the much younger mice.
However, the researchers warned that closing down the ageing pathway completely could run a risk of many health problems, for instance the ability to suppress cell division is key to controlling the development of cancer.
Lead researcher Dr Irina Conboy said the key was to find the right balance between the biochemical pathway which promoted healing, and that which promoted ageing.
"We need to find out what the levels of these chemicals are in the young so we can calibrate the system when we're older.
"If we can do that, we could rejuvenate tissue repair for a very long time."
Rebecca Wood, of the Alzheimer's Research Trust, said: "Since Alzheimer's causes brain cells to gradually die, research into ways to regenerate them could eventually lead to revolutionary new treatments for this devastating disease.
"More research is needed as this study was conducted on muscle tissue rather than the complex nerve cells in the brain and there are many health problems associated with the suppression of cell division."
Dr Susanne Sorensen, of the Alzheimer's Society, said the research was interesting as it had recently been shown that stem cells in the brain might be able to help create new tissue after damage has been done.
"This new research gives further hope that our own stem cells can be used to help regenerate cells in the body."