Lop off a newt’s leg or tail, and it will grow a new one. The creature’s cells can regenerate thanks to built-in time machines that revert cells to early versions of themselves in a process called dedifferentiation.

Researchers who study this mechanism hope one day to learn how to induce the same “cell time travel” in humans. If the cells go back far enough, they become stem cells, which researchers believe hold promise for treating many diseases. Stem cells, which are often taken from embryos, are unformed and have the ability to become many different types of cells. If researchers succeed in inducing this cell time travel, they will also eliminate the ethical issues surrounding embryonic stem-cell research, because no embryos would be destroyed to obtain the cells.



The research is in its infancy, but a 2001 discovery jump-started the field of study. Mark Keating, Christopher McGann and Shannon Odelberg applied a protein extract derived from newts to mouse muscle cells. To their surprise, the protein extract transformed those muscle cells into stem cells in just 48 hours, which means the mouse cells would have the ability to regenerate.



No one expected the experiment to work. Previously, scientists believed that once mammalian cells became muscle, bone or any other type of cells, that was their fate for life — and if those cells were injured, they didn’t regenerate, but grew scar tissue.



But Keating’s experiment introduced the possibility that, under the right circumstances, humans — who are 99 percent genetically similar to mice — might one day be able to regenerate their own cells. Those regenerated cells could be used to treat disease.



“For those of us who want to understand what happens in dedifferentiation, our ultimate goal is to be able to form a pool of stem-cell-like cells that would be able to repopulate the organ or tissue you’re trying to repair,” said Catherine Tsilfidis, a scientist at the Ottawa Health Research Institute who has reproduced Keating’s findings, which she describes as “beautiful.”



In newts and some other animals with the ability to regenerate, cells at the site of an injury can revert to their embryonic stem-cell stage and can become another type of cell in that creature’s body. In other words, a skin cell can dedifferentiate into a stem cell, then regenerate into a muscle cell or another completely different type of cell.



Tsilfidis and her colleagues are now trying to pinpoint which genes are responsible for kick-starting newt dedifferentiation. They published findings in the March 23 issue of Developmental Dynamics identifying 59 DNA fragments that seem to play a role in newt forelimb regeneration, and Tsilfidis believes many of those gene fragments have counterparts in humans.



“Whether (those genes) can actually induce dedifferentiation is yet to be determined,” Tsilfidis said. While the genes were active during maximum dedifferentiation activity, she said, so much is going on in cells after a newt’s forelimb is cut off that it’s difficult to pick out specific dedifferentiation genes.



While some cells are dedifferentiating, others have already begun regenerating and differentiating, or becoming specialized cells. They’re performing activities like healing wounds or growing blood vessels, so it’s difficult to pin certain genes to specific activities.



Researchers are trying to learn similar lessons from other creatures that have the ability to regenerate, including starfish, zebrafish, earthworms and lobsters.



Adult human bodies do contain some stem cells, but they are rare.



More here.

0