Tim Radford
Wounds might be persuaded to heal without scarring, and limbs persuaded to grow again after amputation, according to scientists in Philadelphia. They have found a race of laboratory mice whose livers regenerate after surgery and whose tails grow again after being severed.
Amphibians can lose limbs and grow new ones. Mammals, however, cannot. Unborn and newborn babies heal perfectly after surgery, but thereafter human wounds close leaving a scar, and lost limbs stay lost.
Professor Ellen Heber-Katz, of the Wistar Institute in Philadelphia, went into a laboratory to check on the progress of an experiment on mice.
Like some farm animals, they were supposed to be identified by holes punched in their ears. But the mice, used for studying auto- immune conditions such as lupus, turned out to have perfectly sound ears.
Heber-Katz repunched the holes, but two weeks later they had almost disappeared again.
The mice were a standard laboratory type, bred for experiment and sold commercially. They showed no sign of the original injury, and no scarring. The self-repairing mice have provided researchers with a completely new tool that could answer questions about why wounds leave scars.
They also open a window to the tantalising possibility of limb regeneration for accident victims.
The body’s billions of cells all carry the blueprint for everything in the body, but adult cells of skin or bone or muscle cannot turn the clock back and start again, to form new outer skin and the different layers underneath that would constitute proper healing.
This seems to be because of certain bits of the immune system machinery called T-cells.
“One of the things missing from amphibians is a complex immune system, and we found that if you eliminate a population of T- cells, you can get better regeneration than before, so it is possible that the T-cell population that has developed in mammals is blocking regeneration,” she says.
Heber-Katz and her colleagues have identified seven places in the DNA where strange genes might lurk that would provide an answer to the puzzle. If so, these could be used in some way to help injury victims.