Borrowed Time: The Science of How and Why We Age

by Sue Armstrong

Horvath's results were remarkable: overall, his biological clock was able to estimate a person's chronological age accurately to within 3.6 years on average.

Saliva, for example, gave a prediction to within 2.7 years, some white blood cells to within 1.9 years, and brain cells to within 1.5 years.

By contrast, the clock showed a huge imbalance between biology and chronology in the cancerous tissue samples, which were an average of 36 years older tha...

can we do anything to reverse ageing by artificially manipulating the natural switches on our genes?

have developed an epigenetic clock for mice – one that, like Horvath's, is based on changes over time in the methylation patterns of DNA, but that uses 329 different reference sites on the mouse genome from those used in the human clock.

This depletion of the raw materials for repair is known as ‘stem cell exhaustion’. It's one of the classic hallmarks of ageing

At birth, we humans have around 10,000–20,000 of these white blood specialists, packed away mostly in our bone marrow, and every day around 1,300 of them are actively involved in topping up the system.

When you run out of maintenance materials through stem-cell exhaustion, says Campisi, the only solution is to create new stem cells, and there the promise is transplantation.

A big challenge here, she says, is delivery.

researchers, also pairing old mice with much younger ones, obtained strong evidence of extended lifespan.

the old serum dominated the picture, inhibiting activity in stem cells from whatever source.

It is not the stem cells that age, she suggested, but the environment in which the cells live that becomes depleted so that they no longer get the stimulation they need to do their job.

‘For all of these tissues there was profound rejuvenation of stem cells and regenerative capacity in the old mouse,’ said Irina. ‘And there was noticeable decline in the young mouse.’

another factor in old blood that causes harm. This is TGF-beta (transforming growth factor), a molecule which is overproduced as mice (and humans) get older.

The researchers also identified one of the factors circulating in young blood that helps to rejuvenate old tissues. This is oxytocin,

Once a week for four weeks they received injections of plasma from volunteer blood donors aged between 18 and 30 years, or else a saline solution as a placebo.

no improvement was found in the cognitive function of those who remained; and only mild improvements in performing everyday tasks were reported by caregivers.

old liver was somewhat rejuvenated by young blood, while young liver was prematurely aged by old blood.

‘Old blood appears to have inhibitors of brain-cell health and growth, which we need to identify and remove if we want to improve memory.’

‘Our study suggests that young blood by itself will not work as effective medicine,’

‘It's more accurate to say that there are inhibitors in old blood that we need to target to reverse ageing.’

Resveratrol is known to affect many different cellular mechanisms, including RNA splicing,

‘Our data suggests that using chemicals to switch back on [the RNA splicing factor genes] that are switched off as we age might provide a means to restore function to old cells.’

nearly 5,000 people in more than 60 clinical trials to gain approval,

Only around one in 1,000 compounds that looks promising in the lab even gets the go-ahead in the first place to set off on the road to the clinic.