Salamander- “The Super Hero of Regeneration”

Salamander has always been my favourite animal. This small amphibian has the capacity to regain the exact copy of its lost body organs(other than the CNS and major organ like heart) like Limbs, tail etc. The regeneration is not like that of lizard. Lizard, as we all know, looses its tail whenever it senses danger and then grows a new tail, but scientific studies has shown that the newly formed tail looses a large part of its sensitivity, and as we all have seen the tail is not the exact replica. Regeneration is also seen in invertebrates like flatworms, but what Salamander has is truly unique and complicated phenomenon. They can grow their lost limbs, tails like the original one and do it repeatedly, if needed.

The salamander is a superhero of regeneration, able to replace lost limbs,eyes, damaged lungs, sliced spinal cord even bits of lopped off brain. They have a quite robust regenerative system. Unfortunately for them, this tends to mean that many of them spend their lives in tanks in laboratories across the world, getting bits chopped off of them while biologists try to figure out how it works.

It was before the X-Files (a TV serial that once screened salamander like regeneration in human using the salamander stem cell) days, it was before the pre-internet days I read a sci-fi story about salamander regeneration that made it my favourite animal. In that story a Indian genitist who lost his legs during accident regenerated them using
salamander cells. It was the story of late ’90s. Humans have always been fascinated with the salamander’s ability to regenerate lost limbs.

Now scientists studying salamander genes have discovered that the process isn’t quite as complicated as once thought.Scientists had long credited the diminutive
amphibious creature’s outsized capabilities to "pluripotent" cells that, like human
embryonic stem cells, have the uncanny ability to morph into whatever appendage, organ or tissue happens to be needed or due for a replacement. Based on experiments on genetically modified axolotl salamanders, the researchers show that cells from the salamander’s different tissues retain the "memory" of those tissues when they regenerate, contributing with few exceptions only to the same type of tissue
from whence they came.

Standard mammal stem cells operate the same way, albeit with far less dramatic results they can heal wounds or knit bone together, but not regenerate a limb or rebuild a spinal cord. What’s exciting about the new findings is they suggest that harnessing the salamander’s regenerative wonders is at least within the realm of possibility for human medical science. "I think it’s more mammallike than was ever expected," said Malcolm Maden, a professor of biology, member of the UF Genetics Institute, and author of the paper. "It gives you more hope for being able to someday regenerate individual tissues in people."

Also, the salamanders heal perfectly, without any scars whatsoever, another ability people would like to learn how to mimic, Maden said. When an axolotl loses, for example, a leg, a small bump forms over the injury called a blastema. It takes only about three weeks for this blastema to transform into a new, fully functioning replacement leg not long considering the animals can live 12 or more years.During limb regeneration adult tissue is converted into a zone of undifferentiated progenitors called the blastema that reforms the diverse tissues of the limb.

Moreover it is not to be confused that salamander regeneration is not due to the stem
cells but cell-type-specific pluripotent cells that develops into blastema cells. Stem cells can develop into any type of cells but it is not so in this case. Only ‘old’ muscle cells make ‘new’ muscle cells, only old skin cells make new skin cells, only old nerve cells make new nerve cells, and so on. The only hint that the axolotl cells could revamp their function came with skin and cartilage cells, which in some circumstances seemed to swap roles’, Maden said.

Note: The source of this article is based on the coverage of salamander limb generation in Nature, July ’10 issue.

Here is another link I found that is useful, “Salamander like regeneration, not just the X-Files anymore”