What stimulates limb regeneration?

Research looks at amphibians' unique capability and the implications for humans

By Anne LeBold

mphibians have the unique capability to regenerate limbs -- and zoology professor Steven Scadding has dedicated his 25-year research career to finding out why. His is one of only a dozen laboratories in the world studying the factors that control limb regeneration. He works on a species of salamanders called axolotls.

Scadding has found a clue in a substance called retinoic acid (RA), a form of vitamin A that seems to "switch on" certain genes, triggering specific growth patterns. Different concentrations of RA in various areas on the blastema (the bud that grows out from the stump of the limb) regulate how the limb grows.

Scadding has found that in general, there is more RA in the posterior part of the limb. But how the regenerating cells communicate with one another and disperse RA is unclear. He is investigating the possibility that "tunnels" called "gap junctions," which allow cells to communicate with each other, may regulate the movement of RA between cells.

One of Scadding's goals is to discover why axolotls can regenerate and higher animals cannot. His vision is to see limb regeneration apply to humans.

"If amphibians can do it, and they have an arrangement of bones, muscles and cells similar to ours, there should be the potential for humans to do it, too."

This research is sponsored by the Natural Sciences and Engineering Research Council.