Damaged human limbs could one day regrow by themselves after scientists found the genetic key to repairing tissue.

Experts discovered creatures such as salamanders, that can reproduce amputated legs, lack a gene mammals have which stops injured cells growing back.

They believe that temporarily switching off the gene, called p21, in humans could leave limbs to repair themselves.

The exciting breakthrough came during tests on mice in Philadelphia.

Scientists bred them without p21 and found they could repair and regenerate damaged tissue. Lead researcher Professor Ellen heber-Katz said: "Much like a newt that has lost a limb, these mice will replace missing

"While we are just beginning to understand the repercussions of these findings, perhaps, one day we'll be able to accelerate human healing by temporarily inactivating the p21 gene."

The discovery came when a hole in the ear of mouse without the gene repaired itself.

Mammals have only a limited ability to heal themselves apart from hair and skin so the discovery shocked them. Further tests found the mouse could also repair its heart and spine and form the first signs of a limb.

Without p21, cells behaved more like stem cells.

p21 GENE Appears to act as a blocker that stops mammal cells from turning cancerous