{"id":8553,"date":"2016-11-24T13:47:27","date_gmt":"2016-11-24T12:47:27","guid":{"rendered":"https:\/\/news.embl.de\/?p=8553"},"modified":"2024-03-25T10:07:20","modified_gmt":"2024-03-25T09:07:20","slug":"1611-what-would-it-take-to-regrow-an-arm","status":"publish","type":"post","link":"https:\/\/www.embl.org\/news\/science\/1611-what-would-it-take-to-regrow-an-arm\/","title":{"rendered":"What would it take to regrow an arm?"},"content":{"rendered":"\n

If you were to attempt to regrow an arm, there would be two ways to go about it, says James Sharpe. You could either coax the body into regenerating the limb, or you could produce an arm in the lab and graft it on. Of course, neither option is as straightforward as it may sound.<\/p>\n\n\n\n

Sharpe is Coordinator of the Systems Biology Programme<\/a> at the Centre for Genomic Regulation (CRG) in Barcelona, where his lab tries to understand precisely how limbs are formed. \u201cWe know quite a bit more about limb development than about some other systems or organs,\u201d says Sharpe. Unlike the heart or the brain, limbs are not essential for life. From a scientist\u2019s standpoint, this makes them ideal: while they are still just tiny buds of tissue, barely 1mm across, you can interfere with them without destroying their \u2018life-support system\u2019 \u2013 the rest of the embryo. So as early as the 1940s scientists were opening chicken eggs and studying how a chick\u2019s wing is formed. Like us, chickens are vertebrates, so a lot of what was learnt in those early studies probably holds true for humans. Over the years, thanks to advances in genetics and microscopy, our knowledge of how limbs form has grown in leaps and bounds.<\/p>\n\n\n\n

making sense is not the same thing as being true<\/p><\/blockquote>\n\n\n\n

Scientists now know many of the molecules that sculpt a mass of embryonic cells into a functioning arm, hand and fingers. They have uncovered gradients, where a particular molecule is found in high concentrations near the body, and diffuses out so that the further away from the body a cell is, the less it is exposed to that molecule. Like markers by the side of the road, these gradients tell cells how far along the arm they are, so that cells know when to stop growing and start making a hand. In the hand, Sharpe and others have found an interplay of \u2018activating\u2019 and \u2018repressing\u2019 molecules that seems to define the strips of cells that will become fingers, and those that will be chiselled away to create the spaces in between.<\/p>\n\n\n\n

\"Computer
Computer simulation of how different genes shape the limb bud into upper arm, forearm, hand and fingers over a two day period during development. IMAGE: Xavier Diego & James Sharpe<\/figcaption><\/figure><\/div>\n\n\n\n

\u201cWe have a lot of information, but we\u2019re coming to the conclusion that a lot of our stories about how this system works, based on that knowledge, are probably dramatically simplistic,\u201d Sharpe warns. \u201cThey make sense, but making sense is not the same thing as being true.\u201d Nevertheless, Sharpe is confident that the truth \u2013 however convoluted \u2013 is within reach. \u201cI think we\u2019re in the perfect situation that maybe 10 years from now we will have a really confident view about the complexity of all this,\u201d he says.<\/p>\n\n\n\n

Getting the arm to grow back<\/h2>\n\n\n\n

Nadia Rosenthal is similarly excited about the prospects of regenerative medicine. \u201cI think the next decade is going to be very exciting,\u201d she says with a smile. \u201cNow that the field is really thinking about what a tissue needs to regenerate itself, we\u2019re going to come up with ingenious ways to make that happen.\u201d<\/p>\n\n\n\n

We know that salamanders can do this, so the question is why can\u2019t we?<\/p><\/blockquote>\n\n\n\n

Rosenthal was Head of EMBL\u2019s site in Monterotondo from 2001 to 2012, Scientific Head of EMBL Australia from 2010-2015 and is now Scientific Director at The Jackson Laboratory for Mammalian Genetics<\/a>, USA, and Chair in Cardiovascular Science at Imperial College London<\/a>. Her lab investigates how muscles regenerate. Rosenthal is interested in teasing out the differences and similarities between the skeletal muscles that you show off when you flex your arm and the heart muscle that beats in your chest. As anyone who\u2019s pulled a muscle can attest, skeletal muscle can regenerate. The heart, on the other hand, has much less regenerative capacity. Rosenthal and her labs use mice as a proxy for humans, but they also look at animals that can<\/em> grow back an arm: salamanders.<\/p>\n\n\n\n

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