The “Turritopsis dohrnii” jellyfish cheats death! It reverses the ageing process to ensure it can regenerate and recover from injuries.
Would you want to live forever?
What is ageing?
It happens to all of us, and it starts the moment we're conceived. We all age, some faster, some slower. But what actually is ageing? On a cellular level, it's the death of senescent (old) cells. But what makes a cell old and what determines its lifespan?
In your youth, new cells are constantly forming so that you can grow bigger and develop. But once you reach adulthood, you don’t need loads of new cells, so your body slows down a bit and only replaces the ones that have died.
The growth and replacement is achieved by a process called mitosis, where a cell divides into two identical cells. Here's a short animation to show what happens:
The thing is, cells can’t keep dividing forever. We know that a piece of DNA on the end of each chromosome (called a telomere) gets shorter each time the cell divides. Young cells have long telomeres and old cells have short telomeres. Once the telomeres are too short, the cell stops dividing and commits suicide in an orderly way (this is called 'apoptosis'). A person dies when too many cells are dead or sick.
But does the only signal for a cell to die come from the telomeres? Or is there more to it than that?
Theories about ageing
There are a few theories about why we age.
One is to do with mutations (changes) in our DNA. These happen as a result of mistakes when our DNA is copied or due to environmental factors such as exposure to ultra-violet light from the sun. Mutations in our DNA also mean mutations in our proteins. When this happens, a cell stops working properly.
Another theory is the free radical theory. Toxins such as tobacco smoke, pollution, poisons, and even the chemical processes that happen in your cells (such as processing sugar), cause molecules called free radicals to damage DNA and other parts of the cell. If the cell can’t convert enough of the free radicals into safe molecules quickly enough then damage occurs and the cell will commit suicide. Or it may become a cancer or another type of diseased cell.
So, ageing is basically the loss of function of cells, or more cells dying than are replaced.
Another important issue to consider is how our immune systems are affected by ageing.
As we grow older, we're less able to fight off illness since our immune system weakens over time. On top of this, our body's response to inflame (swell, become irritated and redden etc.) is triggered more easily. This is known as 'inflamm-aging' - a term introduced by Prof. Claudio Franschechi (University of Bologna) in 2000.
And so in a kind of vicious circle, we're less able to protect ourselves from infection at the same time as our bodies being more sensitive to any changes it experiences.
Scientists are continuing to research into this complex process to improve our understanding of it.
How to prevent ageing
So are there ways for us to prevent ageing? Well, increased sanitation (i.e. access to cleaner water and toilet facilities), better medicines and better food have already increased human lifespan in some countries by about 50% in the past hundred years or so.
But for many people, the last few years of life are filled with health problems. So how can we grow older but stay healthy for longer too? Are there any therapies in the pipeline?
There are a few things we can do to slow down the ageing of our cells. The first is to do with nutrition.
To avoid free radicals causing increased damage to your cells, it's best to aim for a balanced, healthy diet. Taking regular exercise, and avoiding illegal drugs and cigarettes helps too.
In particular, studies have shown the benefits of the 'Mediterranean diet' which includes lots of fruit, vegetables, olive oil, nuts, beans and cereal grains, some fish, and eating less meat.
As the name suggests, this diet originates from countries bordering the Mediterranean Sea such as Italy, Greece and Spain. A 2013 study found that people following a Mediterranean diet had a 30% lower risk of heart disease and stroke.
Scientists have done tests on mice to see if they can find ways to make them live longer, and one way was to reduce the amount of food the mice ate.
They reduced the mice’s calories by 40%, and this doubled their lifespan. They thought that this may be due to the lower amount of metabolism in the mice, which would make fewer free radicals.
However, this method of increasing lifespan for humans has not been researched much, not least because it would be a very long-term study, and the people in the study would have to be hungry for about 40 years!
Gene therapy is when faulty or missing genes are replaced.
Gene therapy for ageing is not a common procedure, but one woman underwent gene therapy to lengthen her telomeres. The telomeres of her leucocytes (white blood cells) grew by an equivalent of 20 years of extra life. But no-one knows yet whether this will translate into a real increase in her lifespan.
In mice, increasing telomere length increased their lifespan and delayed diseases like cancer, but it’s uncertain what would happen in humans.
There is even a trial underway where old people are injected with the plasma (the part without the red blood cells) from young people’s blood to keep them looking and feeling younger after a study in mice showed that older mice appeared rejuvenated after this treatment. But, this study has raised various questions, because people have to pay to participate in the trial.
Stem cell therapy
When stem cells, which are responsible for creating new cells, get old, the organism loses the ability to regenerate and repair tissues properly.
Stem cell therapy is when stem cells are used to regenerate and repair tissues and organs in the body, but there is not a lot of evidence to prove that this can prevent ageing. Also, there is the risk that stem cells can go out of control and cause cancer.
Gene therapy and stem cell therapy raise ethical questions. Firstly, because some stem cell therapy requires embryonic cells (cells from an unborn baby in the early stages of development).
And secondly, because some people say we have too many people on the planet already and believe that ageing is “natural”, so we shouldn’t try to stay young forever!
What do you think?
Human embryonic stem cells. Image credit: Nissim Benvenisty via Wikicommons
A couple of drugs have been tested for their effects on longevity. These are called: resveratrol and rapamycin.
Resveratrol, found in vegetables and wine, targets cancer and other diseases of old age, and mice have lived longer in some studies. There are no proven effects in humans yet.
Rapamycin targets cell growth and multiplication, and has extended lifespan in mice, mainly because it prevented cancers that develop in old age.
While these drugs show some promise, they are far from ready for market.
Nature is incredible and some animals don’t seem to age! And so scientists are studying some of them to see what it is about them that allows them to live so long.
Some lobsters, tortoises, whales, clams and mussels can live 200-500 years! What has been noticed about them is that their DNA is very stable, so perhaps they don’t get the build up of mutations (cell changes and mistakes) that we do.
Some other animals are able to regenerate a new leg, or a new head or tail. Imagine if we could grow new organs or limbs like this?!
Until we can, it looks like we will have to make do with a healthy lifestyle to try to increase our lifespans.
Bowhead Whales can live to over 200 years old. Image credit: Kate Stafford via Wikicommons.
The challenges of our ageing population
By 2020 half of Europe’s population will be over 50. This video by The Oxford Institute of Population Ageing takes a look at the wide-ranging effects of ageing on a growing world population.
But who actually wants to live forever?
Dr George Leeson (Oxford Institute of Population Ageing) poses another big question: what do we want out of growing old? We may be living for longer but illness and loneliness remain concerns for the elderly, is there a way to find an effective compromise?
One of the greatest achievements of humankind has to be that as many people as possible are living as long as possible. But is this a good thing?
Around the world, new generations can expect to live longer than previous generations, and the rate of increase is surprisingly strong and constant.
Let's take the example of life expectancies at birth in England and Wales. This increased from 48 years for women and 44 years for men in 1900 to 71 years and 66 years respectively by 1965 and to 84 years and 80 years respectively in 2014.
Data from the Office for National Statistics in the UK reveal that by the turn of the next century, life expectancies at birth are predicted to be 93 years for men and 95.6 years for women in England and Wales.
It's not the same for everyone
The evidence for our increasingly long lives, however, is accompanied by less positive evidence of increasing inequalities.
If we look at life expectancies at any age, we find inequalities in death everywhere, between countries, between regions within countries and between different socio-economic groups within a region.
For example, in Glasgow life expectancy at birth is 71.6 years for men, nearly seven years below the national figure of 78.2 years, and 78 years for women, over four years below the national figure of 82.3.
According to the World Health Organization in 2008, life expectancy at birth for men in the Calton area of Glasgow was just 54 years. This is the same as the life expectancy of men in Burundi, East Africa (a part of the developing world).
And while we continue to live longer and longer, the infrastructures around us (e.g. hospitals, workplace, housing, transport, social care), designed to support us as we age, seem to be crumbling or at best struggling to keep up with our increasing years.
And suddenly, the success story is turning sour.
So how do we want to age?
Essentially, we need to ask ourselves: what do we want out of growing old?
Do we simply want to live as long as possible (quantity)? Or do we want to remain healthy, active and independent - dying not as old as science can achieve for us (quality)?
Death is being pushed back. So why then does the media seem to be full of depressing stories of loneliness and neglect of older people, when we should be celebrating the success of such long-lived lives?
Has the science that has successfully extended our lives also produced an old age of such length that effectively it has no purpose, no content?
To learn more about this topic, take a look at the interview with Dr Leeson below:
200 countries, 200 years in 4 minutes!
The late statistician, Prof. Hans Rosling, plots life expectancy against income for 200 countries across 200 years. He shows how the world we live in is very different from the world most of us imagine.
The “Turritopsis dohrnii” jellyfish cheats death! It reverses the ageing process to ensure it can regenerate and recover from injuries.
5 other species that live “forever”
- American Lobsters
As humans and most other animals develop, our bodies grow to a pre-defined adult size and then stop. One of the reasons we don’t get any bigger is that the cells that make up our arms and legs, our skin and veins and muscles, can only divide into two cells (by a process called mitosis) a certain number of times. Where does the restriction come from? The answer is in bits of DNA called telomeres. Telomeres are DNA sequences that protect the ends of all chromosomes (pieces of DNA) in the nuclei of our cells. When cells divide, each chromosome must be duplicated so that one copy can go to each resulting cell. But telomeres get a little bit shorter every time this happens until eventually, they are too short to work anymore. American lobsters override this problem by using an enzyme called Telomerase to make telomeres longer again, meaning their cells can keep dividing over and over. So a lobster’s cells are biologically immortal, but does that mean they live forever? Unfortunately for the lobsters, the energy it takes to grow bigger and bigger – to keep producing larger shells and take in enough food – is too high for them to keep growing indefinitely. So, while not actually immortal, lobsters can still outlive humans to over 140 years old.
- Sea Sponges
What do you think of when someone says the word “animal”? Something with eyes and a mouth perhaps? Maybe fins or a tail? Or wings and antennae? How about a sponge that sits at the bottom of the seabed? Despite looking like plants, sea sponges win the award for being the longest living animals on earth – one type called a glass sponge is estimated to live for up to 15,000 years! While what we usually think of as an “animal” might spend its day catching prey or finding partners to mate with, sea sponges spend their whole existence not moving, attached to the sea floor. Some would say this doesn’t make for a very interesting life, but it does give them a big advantage when it comes to life expectancy. Because some glass sponges are so old, they can even be used to tell us about what the earth’s climate was like thousands of years ago. The next oldest animal we have found was a quahog clam called Ming, who died in 2006 at age 507. The oldest mammals, on the other hand, live to be around 200 – a bowhead whale was found in 2007 with a harpoon from the 1880s still embedded in its skin.
- Turtles and tortoises
- Turtles and tortoises are well-known for living to a grand old age. You might have heard of some famous examples: there’s Harriet the tortoise who died in an Australian zoo in 2007 at the predicted age of 176, or Lonesome George, the last tortoise of his subspecies, who died on the Galapagos Islands in 2012 at the age of 102. It turns out that the reason for their long lives is that these animals have the ability to stay “young forever”. As humans get older, our body parts don’t work as well as they used to and the way we look changes too. We also can’t keep having children once we get over a certain age. For turtles, the story is completely different. As a 100-year-old, their organs look the same as when they were a young adult. And they can keep breeding right up until they die. In fact, when their lives do come to an end, it is not usually because they have aged, but instead because of disease or predator attack. How they stay so physically young is a bit of a mystery, but it could relate to the fact that their hearts don’t need to beat continuously like ours: if you can give your organs a rest when they are not needed, maybe you can stay like-new for longer.
- Bristlecone Pine
- One big problem when we age is that our DNA takes on lots of changes called mutations. And the rate at which we take on new mutations gets quicker as we get older. Some changes don’t have any effect on our bodies but others can make our cells work less well or even give us diseases like cancer. Amazingly, bristlecone pine trees have found a fix for this problem. If you compare the pollen and seeds from different bristlecone pine trees up to 4700 years old, there is no significant increase in the mutation rate with age. Scientists think this could be due to a small group of cells in the meristem called the quiescent centre. By dividing very slowly, these cells avoid getting new mutations. On the outside, bristlecone pines get damaged like any other living thing, but on the inside, their cells stay healthy and like-new.
- As we get older as humans, our complicated bodies have a lot of problems to deal with. We are constantly faced with damage to our tissues, like diseases that affect certain organs or physical damage when we hurt ourselves. Compared to lots of long-lived organisms out there, we live an extremely fast-paced life where we have to fix these kinds of problems all the time. This puts our stem cells (the cells that can replace old tissue cells when they get damaged) under a lot of stress. Instead of trying to maintain a large, complicated body, colonial animals like corals are made up of lots of simple repeated units called polyps. Polyps divide asexually – they can make multiple copies of themselves that carry the same DNA, like clones – and expand to make a colony where individual polyps are connected by a large exoskeleton. So the complete coral is a collection of identical polyps: if one gets damaged, any one of the others can reproduce to replace it. Together as a colony, corals can exploit this strategy to live for thousands of years.
Would you want to live forever?
See the world
Think about all the places you’d go, and the things you’d see! Living forever means you can learn everything you’ve ever wanted to know and achieve everything you’ve ever dreamed of doing (in theory). Even better – if your family and friends lived forever too, you’d be able to experience all these great things with them!
Quality over quantity
Do we simply want to live as long as possible (quantity)? Or do we want to remain healthy, active and independent (quality)? The media seems to be full of depressing stories of loneliness and neglect of older people. Plus, some retired people come out of retirement so they can be seen to be making a ‘contribution’ to society. Dr George Leeson (Oxford Institute of Ageing) questions: "Has the science that's successfully extended our lives also produced an old age of such length that effectively it has no purpose, no content?" Would it not be better to have higher quality, shorter lives, than to live forever without a purpose?
Live longer, healthier and happier
Increased sanitation (i.e. access to cleaner water and toilet facilities), better medicines and better food have already increased human lifespan in some countries by about 50% in the past hundred years or so. Scientists are constantly developing technology and medicine, like gene and stem cell therapy that can help us live longer, more comfortable lives. If we were to live forever, we could be pretty confident that scientific developments would keep us happy and healthy.
Young people make the world go round
Our population is ageing rapidly. Life expectancy is increasing by five hours a day in the UK and childbirth rates across the globe are falling (for example, Hong Kong has the lowest rate in the world with less than one child per woman). Fewer young people in society presents a huge problem as young people contribute more to the economy (they tend to produce, consume and save more than older people) and they provide vital care to older generations.
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