Hui Yee, LOH
Picture: Two newts compared 40 days after limb amputation: The newt on the right received the nAG protein, the newt on the left was part of a control group and did not receive nAG. (Adapeted from http://www.news.softpedia.com/)
Amphibians such as salamanders can regenerate a missing tail, legs and even eyes. Don’t we wish that we had the same power of regeneration like salamanders do?
A few developmental biologists claimed that humans and amphibians share as much as 90% of the same genes, so it is possible that adult human can have the ability to regenerate lost limbs, organs and tissues.
“What fascinating about this is that a salamander’s limb is basically a miniature of our limbs,” says the Panagiotis Tsonis of the University of Dayton(Ohio).
According to Dr. Stephen Badylak, the researcher of University of Pittsburgh, the genes that allow animals such as newts to regenerate their limbs exist in human, but are inactive. The researchers now think they can find what to turn on the dormant genes so that people who lost an arm might be able to generate a new one.
A new research by a British team showed that a protein called newt anterior gradient (nAG), secreted by nerve and skin cells, play a central role in forming a cluster of immature cells, known as a blastema, which then form the missing body part. The importance of nAG was demonstrated by the fact that even when a nerve was severed below the stump tip, which would normally prevent regrowth, the scientists were able to coax regeneration by artificially making cells produce the protein.
The new research published in the November 2 issue of the journal Science shown that nAG protein enhanced the multiplication of stem cells that ultimately generate new limbs in red-spotted newts (Notophthalmus viridescens). When the newt loses a limb, local cells experience de-diffentiation to stem cells, which form at the tip of the stump left by the limb a mass of cells named blastema. Cells grow and divide and they give rise to the structures that have been removed. If a newt’s leg is severed at the ankle, the stem cells will re-grow a foot; if you amputate at the shoulder, they'll give rise to an arm.
However, humans may have a different regenerative mechanism. It can only happen when our cells de-differentiate to produce blastema together with nAG protein, Stocum suggests.
The team of Stocum amputated the red-spotted newts' limbs and then attached the nerves. Nerves are essential for triggering the synthesis of the nAG protein. Then they stimulated the stumps with electrical pulses so that the tissues could release DNA comprising genes for the protein nAG.
Brockes suggests that the nerve's insulating sheath discharge nAG, probably in response to chemical signals from the nerve. Even when the researchers blocked the nerve and sheath from regrowing, adding nAG to the stem cells was sufficient to cause the cells to resume dividing and to fully regenerate the limb.
Ellen Heber-Katz, professor of immunology at the Wistar Institute has created a miracle mouse that can regenerate amputated limbs or badly damage organs except brain. Ellen discovered this miracle while she was carrying out an experiment of autoimmune diseases. She punched a hole in the MRL mice ear as marker, and was shocked that there were no ear holes on the mice ear after three weeks. As mice has the similar gene as human, her discoveries raise the prospect that human could one day be given the ability to regenerate lost or damage limbs, opening a new era in medicine.
Indeed, when we consider all that we have learned about regeneration from studies in various animal models, the surprising conclusion is that we may be only a decade or two away from a day when we can regenerate human body parts. Soon, humans might be able to harness this truly awesome ability ourselves, replacing damaged and diseased body parts at will, perhaps indefinitely.
Main article:
1. E.Heber-Katz, J.Leferovich, K.Bedelbarva, D.Gourevitch and L.Clark, 2004, ‘The scarless heart and the MRL mouse’, The Royal Society, vol. 359, pp. 785-793.
(http://rstb.royalsocietypublishing.org/content/359/1445/785.full.pdf+html)
2. Jamie, IM, Sara, L, He, P, Simon, A, 2005, 'Salamander limb regeneration involves the activation of a multipotent skeletal muscle satellite cell population', The Journal of Cell Biology', vol. 172, no. 3, pp. 433-440.
(http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2063652&rendertype=abstract)
Related links:
1. http://today.msnbc.msn.com/id/21584381/
2. www.technologynews.com.au/human-limb-regeneration-breakthrough/
3. www.sciam.com/article.cfm?id=regrowing-human-limbs
