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US study on lab mice provides another clue in the search for a longer life -

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ELEANOR HALL: Now to a scientific discovery that may mean we'll live not only longer but healthier lives.

In research published in the journal Nature, US-based scientists show how they've extended the lives of mice, simply by removing old and worn-out cells.

But as Barney Porter explains, they caution they haven't yet found the fabled fountain of youth.

BARNEY PORTER: The research has been carried out by Dr Jan van Deursen and Assistant Professor Darren Baker, molecular biologists at the Mayo Clinic in Minnesota.

Professor Baker says they stumbled on their finding by accident.

DARREN BAKER: The way we came into ageing in the first place, we started with a model that was supposed to be a cancer model and instead ended up looking, the mouse looked awful at five months of age, and so that was where our entry into the ageing field came from.

BARNEY PORTER: The researchers focused on old and damaged cells that are no longer able to divide.

Known as senescent cells, they accumulate with age in our body, and release molecules that can harm nearby tissues.

Professor Baker says they've been linked to diseases of old age such as kidney failure and type two diabetes.

DARREN BAKER: We knew that senescent cells were accumulating with age and natural tissues and the thought was let's just start removing these things starting at mid-life in mice and see what the consequences were.

BARNEY PORTER: How they did that was to genetically engineer the mice so that their senescent cells would die off when the rodents were injected with a drug, effectively triggering a suicide gene.

DARREN BAKER: There were really no negative consequences, the only thing that we actually found were either no effect in some tissues, but for the most part we found beneficial impacts in a variety of tissues.

BARNEY PORTER: Dr van Deursen says the mice whose senescent cells were killed off over six months were healthier than a control group of mice, whose cells were allowed to build up.

JAN VAN DEURSEN: So we started at mid-life and continued until they died a natural death, and what we observed is that the mice were healthier, that their organs were better functional, organs such as the heart and kidney who are two vital organs and we found that the mice were protected against cancer.

BARNEY PORTER: And the crucial question, did they live longer?

Professor Baker again.

DARREN BAKER: We found that all of the mice that were treated to remove their senescent cells had a lifespan extension neighbouring from 25 to 35 per cent.

In all cases we found that there is a significant health and lifespan extension.

BARNEY PORTER: But hold on folks, Professor Baker says the drug can't simply be used on humans.

DARREN BAKER: Even filling you or I with as much of this particular drug as we used in the study, it's going to have no impact because we don't have the suicide gene within us.

BARNEY PORTER: Their research is one of many attempts to find that elusive, fabled fountain of youth.

Professor David Le Couteur is a professor of medicine at the University of Sydney, and has had a long interest in the ageing process, how it causes disease and intervention strategies.

DAVID LE COUTEUR: Ageing really has been a hard nut to crack, but we now know pretty much the causes of ageing at the molecular and cellular level, and around the world different strategies have been developed to attack different things that go wrong with ageing.

So the particular thing in the Mayo Clinic paper that's been published recently relates to something that goes wrong with ageing called cellular senescence, and in their animal model they've been able to get rid of the cells that become senescent and in that process make animals live longer, but also prevent them from getting cancer, from getting heart disease, from getting kidney disease and improving their brain function.

So it's a pretty good proof that if you've got an intervention that delays ageing you won't just prevent one disease or one problem, you'll prevent the whole package of issues that go wrong with people as they get older.

BARNEY PORTER: In the meantime, Dr van Deursen is urging patience.

JAN VAN DEURSEN: So the next step is really to have a safe drug go into humans in the form of a clinical trial and to test these drugs for safety and efficacy.

But usually these things take a little bit of time.

ELEANOR HALL: That's Dr Jan van Deursen from the Mayo Clinic in Minnesota ending that report by Barney Porter.