MUSCLE tissue can be renewed by chemically resetting its biological clock to an earlier stage of development, a study has shown.
Scientists believe the technique may pave the way to reversing muscle loss due to disease or natural ageing.
It may also be extended to repairs of other kinds of tissue, such as brain and liver.
US researchers used molecular signals to separate mature muscle tissue into individual "progenitor" cells called myoblasts.
These were then successfully used to repair the damaged muscles of injured mice.
"The research opens the door to the development of new treatments to combat the degeneration of muscle associated with muscular dystrophy or ageing," said study leader Dr Irina Conboy, from the University of California at Berkeley.
Crucially, the technique does not rely on the creation of "pluripotent" stem cells - immature cells that can differentiate into virtually any kind of tissue.
Previous attempts to regenerate muscle using pluripotent embryonic stem cells or reprogrammed adult cells have led to uncontrolled growth and tumours.
The new approach, described in the journal Chemistry & Biology, avoids this danger by not returning cells to an embryo-like state through genetic reprogramming.
Instead, it uses specific inhibitor chemicals that coax muscle back one stage of of development but no further.
Skeletal muscle tissue is composed of elongated bundles of "myofibres" composed of individual myoblasts that have fused together.
The Berkeley scientists succeeded in returning the myofibres back to their previous state as separate myoblast cells.
"Muscle formation has been seen as a one-way trip, going from stem cells to myoblasts to muscle fibre, but we were able to get a multi-nucleated muscle fibre to reverse course and separate into individual myoblasts," said Dr Conboy.
"For many years now, people have wanted to do this, and we accomplished that by exposing the tissue to small molecule inhibitor chemicals rather than altering the cell's genome (genetic code)."
But sometimes, as occurs in people with Duchenne muscular dystrophy, the repair process stops working. Natural ageing also makes it harder to replace lost muscle tissue.
The scientists turned the clock back on muscle fibres using one chemical that transmits signals for cell division, and another that prevents cells dying.
"We basically brainwashed the cells to go into the cell cycle, to divide, and also not die in the process," said Berkeley bioengineer Dr Preeti Paliwal.