California, Feb 17 (IANS): Scientist have identified for the first time a process by which older muscle stem cell populations can be rejuvenated to function like younger cells.

This promises a new therapeutic target that could be used to help elderly patients repair muscle damage.

Researchers discovered why normal aging is accompanied by a diminished ability to regain strength and mobility after muscle injury.

Over time, stem cells within muscle tissues dedicated to repairing damage become less able to generate new muscle fibres and struggle to self-renew.

“In the past, it's been thought that muscle stem cells themselves don't change with age, and that any loss of function is primarily due to external factors in the cells' environment,” said Helen Blau, professor at Stanford University's School of Medicine in California.

When the scientists isolated stem cells from older mice, they found that they exhibit profound changes with age.

“In fact, two-thirds of the cells are dysfunctional when compared to those from younger mice, and the defect persists even when transplanted into young muscles,” added Blau.

The findings identify a defect inherent to old muscle stem cells and how to overcome that defect, she added.

The new treatment does not turn the clock back on dysfunctional stem cells in the aged population.

“Rather, it stimulates stem cells from old muscle tissues that are still functional to begin dividing and self-renew,” explained lead author Benjamin Cosgrove from University of Toronto.

The researchers found that, when transplanted back into the animal, the treated stem cells provide a long-lasting stem cell reserve to contribute to repeated demands for muscle repair.

“In mice, we can take cells from an old animal, treat them for seven days during which their numbers expand as much as 60-fold and then return them to injured muscles in old animals to facilitate their repair,” Blau added.

This opens a whole new avenue to enhance the repair of specific muscles in the elderly, especially after an injury, said the study published in the journal Nature Medicine.