Genes important for forming muscle cells in embryos and newborns are not needed in adult muscle stem cells to regenerate muscles after injury, find scientist.

The discovery challenges the current course of research into muscular dystrophy, muscle injury, and regenerative medicine, which uses stem cells for healing tissues.

The finding also favors using age-matched stem cells for therapy. Christoph Lepper and colleagues from Carnegie Institute's Department of Embryology report their findings in the journal Nature.

Previous studies have shown that two genes, Pax3 and Pax7, are essential for making the embryonic and neonatal muscle stem cells in the mouse.

To get a better understanding of their function, Lepper and colleagues studied these genes at various stages of development in mice.

"I thought that if they are so important in the embryo, they must be important for adult muscle stem cells. Using genetic tricks, I was able to suppress both genes in the adult muscle stem cells. I was totally surprised to find that the muscle stem cells are normal without them," Lepper said.

The researchers then looked at whether the same was true in injured muscles, when muscle stem cells go to work making new muscle tissue.

To study this, they injured mouse leg muscles between the knee and ankle, and found the muscle stem cells were able to make new muscle, even without the two key embryonic muscle stem cell genes.