23 DECEMBER 2016 • VOL 354 ISSUE 6319 1519 SCIENCE sciencemag.org
Killing old cells to stay young
Pricey plastic surgery won’t stop you from getting old. Nor will dietary supplements, testosterone injections, or those wrinkle creams that imply they’ll make
you look 21 again. But this year, researchers demonstrated one way to postpone
some ravages of time—at least in mice. When they selectively weeded out rundown cells, the animals lived longer and remained healthier as they aged.
The infirm cells the scientists targeted had undergone a partial shutdown
The first study showing that eliminating senescent cells can produce health
known as senescence, in which they lose the ability to divide. Researchers think
senescence may prevent worn-out, cancer-prone cells from initiating tumors,
but it may also promote aging. As we grow older, more and more cells stop
reproducing, potentially robbing our tissues of the ability to replace dead or
injured cells. Senescent cells also discharge molecules that can cause problems
such as abnormal cell growth and inflammation.
and longevity benefits, at least in middle-aged mice, came out in February.
Deterioration of the animals’ hearts and kidneys slowed, and they didn’t sprout
tumors until later in their lives. Some age-related declines, such as in memory
and muscle coordination, didn’t abate. Nonetheless, the rodents outlived their
contemporaries by more than 20%.
In October, the same research team took aim at senescent cells from the
immune system that amass in artery-clogging plaques and may drive their formation. Removing these cells from mice that are prone to atherosclerosis reduced
the amount of fatty buildup in the animals’ arteries by 60%, even though the
rodents gorged on fat-laden food.
The multibillion-dollar question: Will taking out senescent cells help humans
stay young longer? Both studies used genetically modified mice that clear away
their senescent cells in response to a particular compound—a technique that
isn’t feasible in humans. But researchers have created several so-called senolytic
drugs that slay senescent cells without genetic tinkering. Next year, scientists will
launch the first clinical trial of one of those drugs in people who have arthritis.
learning algorithm. Then AlphaGo played
against itself—or, rather, slightly different
versions of itself—over and over, fine-tuning its strategies with a technique
called deep reinforcement learning. The
final result is AI that wins not just with
brute-force calculation, but with something
that looks strikingly like human intuition.
Most of the things we want AI to master
involve a seemingly unmanageable number of possible decisions—walking a robot
safely through a crowded room, routing
driverless cars, making small talk with
passengers. Because hard-coded rules fail
for such tasks, AlphaGo’s triumph shows
just how powerful deep reinforcement
learning can be. —John Bohannon
An artist’s concept of
Proxima b orbiting the red
dwarf Proxima Centauri.
Removing worn-out cells might delay the buildup of artery-clogging plaques.
BREAKTHROUGH OF THE YEAR | RUNNERS-UP 2016