Immortal worms defy aging

Feb 27, 2012
Polycelis felina, a freshwater planarian. Image: Eduard Sola, Wikipedia.

Researchers from The University of Nottingham have demonstrated how a species of flatworm overcomes the ageing process to be potentially immortal.

The discovery, published in the , may shed light on the possibilities of alleviating ageing and age-related characteristics in .

Planarian worms have amazed scientists with their apparently limitless ability to regenerate. Researchers have been studying their ability to replace aged or damaged tissues and cells in a bid to understand the mechanisms underlying their .

Dr Aziz Aboobaker from the University's School of Biology, said: "We've been studying two types of planarian worms; those that reproduce sexually, like us, and those that reproduce asexually, simply dividing in two. Both appear to regenerate indefinitely by growing new muscles, skin, guts and even entire brains over and over again.

"Usually when stem cells divide — to heal wounds, or during reproduction or for growth — they start to show signs of ageing. This means that the stem cells are no longer able to divide and so become less able to replace exhausted specialised cells in the tissues of our bodies. Our ageing skin is perhaps the most visible example of this effect. Planarian worms and their stem cells are somehow able to avoid the and to keep their cells dividing."

One of the events associated with ageing cells is related to telomere length. In order to grow and function normally, cells in our bodies must keep dividing to replace cells that are worn out or damaged. During this division process, copies of the genetic material must pass on to the next generation of cells. The genetic information inside cells is arranged in twisted strands of DNA called chromosomes. At the end of these strands is a protective 'cap' called a telomere. Telomeres have been likened to the protective end of a shoelace which stops strands from fraying or sticking to other strands.

Each time a cell divides the protective telomere 'cap' gets shorter. When they get too short, the cell loses its ability to renew and divide. In an immortal animal we would therefore expect cells to be able to maintain telomere length indefinitely so that they can continue to replicate. Dr Aboobaker predicted that planarian worms actively maintain the ends of their chromosomes in adult stem cells, leading to theoretical immortality.

Dr Thomas Tan made some exciting discoveries for this paper as part of his PhD. He performed a series of challenging experiments to explain the worm's immortality. In collaboration with the rest of the team, he also went some way to understanding the clever molecular trick that enabled cells to go on dividing indefinitely without suffering from shortened chromosome ends.

Previous work, leading to the award of the 2009 Nobel Prize for Physiology or Medicine, had shown that telomeres could be maintained by the activity of an enzyme called telomerase. In most sexually reproducing organisms the enzyme is most active only during early development. So as we age, telomeres start to reduce in length.

This project identified a possible planarian version of the gene coding for this enzyme and turned down its activity. This resulted in reduced telomere length and proved it was the right gene. They were then able to confidently measure its activity and resulting telomere length and found that asexual worms dramatically increase the activity of this gene when they regenerate, allowing to maintain their telomeres as they divide to replace missing tissues.

Dr Tan pointed out the importance of the interdisciplinary expertise: "It was serendipitous to be sandwiched between Professor Edward Louis's yeast genetics lab and the Children's Tumour Research Centre, both University of Nottingham research centres with expertise in telomere biology. Aziz and Ed kept demanding clearer proof and I feel we have been able to give a very satisfying answer."

However, what puzzled the team is that sexually reproducing planarian worms do not appear to maintain telomere length in the same way. The difference they observed between asexual and sexual animals was surprising, given that they both appear to have an indefinite regenerative capacity. The team believe that sexually reproductive worms will eventually show effects of telomere shortening, or that they are able to use another to maintain telomeres that would not involve the telomerase enzyme.

Dr Aboobaker concluded: "Asexual planarian demonstrate the potential to maintain telomere length during regeneration. Our data satisfy one of the predictions about what it would take for an animal to be potentially immortal and that it is possible for this scenario to evolve. The next goals for us are to understand the mechanisms in more detail and to understand more about how you evolve an immortal animal."

Professor Douglas Kell, BBSRC Chief Executive, said: "This exciting research contributes significantly to our fundamental understanding of some of the processes involved in ageing, and builds strong foundations for improving health and potentially longevity in other organisms, including humans."

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User comments : 22

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kevinrtrs
1.2 / 5 (15) Feb 27, 2012
Our data satisfy one of the predictions about what it would take for an animal to be potentially immortal and that it is possible for this scenario to evolve. The next goals for us are to understand the mechanisms in more detail and to understand more about how you evolve an immortal animal.

Surely the researcher is confusing terms here. Is "evolution" a planned thing or is the researcher saying that they'd like to know how it is that the planarian just happens to have none-shortening telomeres, i.e. how did they get to that state from some other non-ideal state via the process of "evolution"?
XQuantumKnightX
5 / 5 (12) Feb 27, 2012
Kev, the researcher is not confused! To answer your question, to evolve the results of their findings to the next stage where it becomes applicable to human cells is what the researcher was referring to! It's called scientific method and when a researcher's hypothesis have been supported partially or completely with facts through experiment, the next step is to "evolve" the original hypothesis and/or assumptions towards a higher value goal! In this case the goal would be to find the biological mechanisms that will allow for humans to regenerate continuously with out over expression of cell division (a.k.a Cancer). This in my book would be the world's greatest achievement of all times; although we may shed skin and hair more:)
Sanescience
5 / 5 (5) Feb 27, 2012
So in a couple tens of millions of years these will be the ancestors of elves!

Seriously though, there is a lot of possible connections between the advantages of sexual reproduction and generation-churn that seems to bias against immortal individuals. In the meta view, many species as a whole are "immortal", were just stuck in a reductionist view point of an individual.
ibuyufo
1 / 5 (3) Feb 27, 2012
I'll play the devil's advocate and say that although it's nice to be immortal but at what cost in terms of world population. Eventually if no one dies the population will outstrip food sources as well as other natural resources such as land. All those extra people will produce more carbon dioxide which traps heat.
Are we as a society going to stop the progression of this research when we find out how to stop cancer? When do we stop?
aroc91
5 / 5 (8) Feb 27, 2012
Once again, kevin unsuccessfully tries to make trouble surrounding evolution where there is none.
bredmond
not rated yet Feb 27, 2012
planarians likely also dont have trouble with their eyes aging: http://www.nytime...tml?_r=1
bob456789
1 / 5 (2) Feb 27, 2012
I'll play the devil's advocate and say that although it's nice to be immortal but at what cost in terms of world population. Eventually if no one dies the population will outstrip food sources as well as other natural resources such as land. All those extra people will produce more carbon dioxide which traps heat.
Are we as a society going to stop the progression of this research when we find out how to stop cancer? When do we stop?


The consequences of modern medicine are never debated and need serious attention. People living a couple of hundred years is not that far off. The implications are staggering.
enigma13x
1 / 5 (1) Feb 27, 2012
@ ibuyufo

its quite simple really soylent green solves all these problems in a handy hi-energy wafer
Telekinetic
1 / 5 (4) Feb 27, 2012
It's just a matter of time before scientists develop the elixir that elongates human lifespan. I see these advancements as a fulfillment of visions of the nightmare future described by screenwriters- Sprawling cities with mile-tall, twisting into-the-sky high-rises, where its residents are armed to the teeth and barricaded in, except that instead of guys that look like Clooney or Crowe wielding the automatic electro-magnetic pulse weapon, it'll be thousands upon thousands of great-grandpa-looking geezers. Unless of course, this elixir keeps you looking like the rake you were in college. Then, gentlemen, count me in.
Tausch
1 / 5 (1) Feb 27, 2012
Polycelis felina is 'immune' to over expression?

Is there a cancerous state that exists for Polycelis felina?
Naturally or induced?

If so, what are the forms of malignant cancers that Polycelis felina can maintain, induce, support, or express until premature demise due to a cancerous state?

The following is one of the best synopsis out there to give you a path in the molecular jungle of genetics:
http://employees....NA1.html

Birger
not rated yet Feb 28, 2012
Tausch got it right -cancer is the enemy of very long-lived individuals.
And among higher vertebrates, we have the problem of dementia.

If you are interested in immortality, I advise you to invest in research on vitrification. Then you can freeze yourself for a couple of centuries while the intractable problems of senescence and cancer are slowly untagled... :-)
antialias_physorg
3 / 5 (2) Feb 28, 2012
Unfortunately conserving telomere length does not confer immortality in humans. There's a reason that telomeres grow shorter when dividing and, when too short, initiate planned cell death (apoptosis).

Cells accumulate damage in the DNA (through copy errors when dividing, mutations via radiation, and exposure to chemical/bacterial mutagens). These mutations get passed on upon division.

The more divisions the more errors (and the less likely that the cell is still operative - i.e. that a newly divided liver cell still is able to perform the functions a liver cell is supposed to)

So it's in our interest that cells that are likely to be non-functional die. Cells in the human body where, through some defect, telomeres don't shorten, eventually become immortal and non-functional have a name: cancer.
antonima
not rated yet Feb 28, 2012
When they mention evolution, it may mean they are doing an artificial evolution experiment in their lab. Planarian worms are small enough for it to work in an artificial environment in the laboratory.
C_elegans
3 / 5 (2) Feb 28, 2012
Hmm antialias, what then is the purpose of stem cells that give rise to your germ line? You'd better believe that those cells, too, are immortal, or else you would be the last antialias to roam the Earth. While stem cells are much more slowly dividing, they are in fact immortal.
Pressure2
not rated yet Feb 28, 2012
I would like to know how many divisions these worms went through and how long they actually carried out the experiment on a single line of worms?
wealthychef
5 / 5 (1) Feb 28, 2012
This is interesting. Sometimes when you ask, should humans live forever, the response is no, we won't have room, we'll be overcrowded! Well, here is a species that lives forever, and yet has managed to not decimate the earth by overpopulation.
C_elegans
4 / 5 (2) Feb 28, 2012
This species has predators. What's a human predator?
enigma13x
1 / 5 (1) Feb 28, 2012
mmmmmmm long pork sweeeet
mosahlah
not rated yet Mar 03, 2012
I'll play the devil's advocate and say that although it's nice to be immortal but at what cost in terms of world population. Eventually if no one dies the population will outstrip food sources as well as other natural resources such as land. All those extra people will produce more carbon dioxide which traps heat.
Are we as a society going to stop the progression of this research when we find out how to stop cancer? When do we stop?


Don't worry. Sooner or later, nature will reach an equilibrium. War always was and always will be. The immortals cannot survive a bullet.
Tausch
1 / 5 (1) Mar 04, 2012
C elegans
Rating error from me - the highest rating was intended, the lowest given in error for the comment highlighting the immortality of human stem cells.
kaasinees
1 / 5 (1) Mar 04, 2012
Imagine combining this with a virus. Vampires might become a reality. Or zombies ala resident evil.
antialias_physorg
1 / 5 (1) Mar 04, 2012
War always was and always will be.

War has never significantly affected population numbers (even WWII had 'only' 55 million casualties. Unless we're talking global thermonuclear war that will not be a corrective measure.

The only thing that has really put a (small) dent in the human population - as a percentage - was the black plague in the 1400's