Wired Science (July 1, 2009)
"By tracking individual cells in genetically modified salamanders, researchers have found an unexpected explanation for their seemingly magical ability to regrow lost limbs.
"Rather than having their cellular clocks fully reset and reverting to an embryonic state, cells in the salamanders' stumps became slightly less mature versions of the cells they’d been before. The findings could inspire research into human tissue regeneration.
" 'The cells don't have to step as far back as we thought they had to, in order to regenerate a complicated thing like a limb,' said study co-author Elly Tanaka, a Max Planck Institute cell biologist. 'There's a higher chance that human or mammalian cells can be induced into doing the same thing.'..."
The article gives a pretty good overview of the research: what scientists thought the stumps of severed salamander legs did as they re-grew legs; how the researchers made glow-in-the-dark genes for the salamanders, and what they discovered when they tracked the limb regeneration on a cell-by-cell level.
Their finding - that the salamander cells are quite restricted in what sort of tissue they grow into - may help solve one problem with limb regeneration in people.
At this point, we're able to make cells from an adult organism act as if they were stem cells: become pluripotent, able to turn into any sort of cell. The good news is that such cells will grow into whatever sort of tissue was lost. The bad news is that sometimes the new cells turn cancerous.
Turns out, salamander leg stumps don't have pluripotent cells.
"...Contrary to expectation, skin cells that joined the blastema later divided into skin cells. Muscle became muscle. Cartilage became cartilage. Only cells from just beneath the skin could become more than one cell type...."We're probably a long way off from being able to have people regrow amputated limbs or damaged organs, but this research may be bringing us a lot closer.