Why people can not regenerate limbs?




The idea that some form of modest life on the planet – jellyfish, coral and so on – in fact immortal, it seems very convincing. Fans of “Star Trek” in 1969 may remember an episode of the 5000-year-old man, born in ancient Mesopotamia, who met Kirk and the team, because he could not die. The effect is the same. These “immortal” beings are not included twice in the same river – they were there and will be.

Not long ago, scientists alarmed study by the National University of Ireland regenerative medicine on Hydractinia echinata, or hairy snails.

Hairy snail – is the mass of pink spikes, tentacles and polyps from 20 to 30 millimeters in length, making it small enough that it can be attached to the carapace of hermit crabs on the Irish and British coasts. Hairy snail looks ordinary, except for one thing: in the words of Uri Frank, a scientist from the institute, the creation of “in theory live forever.” In the above image hairy snail “sitting” on the back of a normal crab.

Immortality, it is worth noting, even in the animal world is a concept rather rare. At the time, New York Times much trumpeted approval of the Japanese scientist that Cho Turritopsis dorhnii, species of jellyfish, also lives forever. But Frank just wanted to say that hairy snails have the ability to completely regenerate body parts. Regeneration is not too rare in the animal kingdom – hearts could ever recover his head along with the memories . The same with the snail:

“It sounds awful, but if you bite off her head for a few days to grow another,” – said the scientist.

This is not quite what it was with the guy in the “Star Trek”, and to some extent even looks like a complete upgrade of the car and the computer – they, too, will be eternal, as long as you change them apart. But agree, grow replacement limbs, when you need them, it’s quite a neat trick.

Hairy snail (snail fur) – not only being able to do so. Earthworms, starfish, lobsters, snails, salamanders, and many other creatures can produce their own bodies and replace them limb. Some mammals can regenerate itself in less degree. Several species of African spiny mice can regrow lost sweat glands, skin and cartilage.

Well, if the lizard can grow a new tail myself, why can not we restore the arm, leg, kidney, or heart when they become irreparably damaged? Fortunately, 3D-printed organs gives good hope for the future.

For the answer we need to look at how we grow our bodies in the first place. Even in the belly of a man going to pieces of human embryonic stem cells, which are very well divide and create other types of cells – from the nerve to the blood.

Creatures that regenerate limbs and organs, store stem cells that provide this capability throughout the life cycle. If a salamander leg cut, stem cells enter the fray and form a rapidly growing mass of undifferentiated cells – the blastema, which eventually forms a new limb.

But like many mammals, by the time we are born, these cells are replaced by somatic “adult stem” cells, which are stored in limited quantities in their limbs. Adult stem cells in the bone marrow, for example, are capable of creating new blood cells and skin – to recover its layers. They can also grow scar tissue for sealing wounds. People also have some regenerative abilities. We can not grow a lost limb, but in an article for Nature in 2013, wrote that children can sometimes grow accidentally lost a finger. In the adult human liver regenerate if damaged, at least part of it.

Why do we and other mammals have lost much of the ability to grow new limbs or organs remains unclear. Some scientists believe that this is a natural consequence of the increasing complexity of our bodies.

Perhaps the genetic mechanisms of our body trying to prevent the development of cancer and, consequently, the formation of a blastema. Enrique Amaya, a biologist at the University of Manchester in the United Kingdom recently suggested another possible explanation.

“If the amphibian will chew one of his paws, she can go for weeks without food and shelter to regenerate,” – he said BBC News. – “For an animal with a high metabolism, which constantly need to be fed, it can be a daunting task.”

As soon as scientists come to understand how some of the animals recovered, they have the hope that one day they will manipulate the human body, growing limbs and organs directly from it.

Here, he writes researcher David M. Gardiner:

“We have a genetic program of growth of limbs in our genome, and we use this program to grow arms and legs, as embryos. The task of regenerative medicine – to learn how to activate the internal program. ”

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