ScAm

ADVANCES

14 Scientific American, April 2020

LENTINK LAB

Stanford University

Illustrations by Thomas Fuchs

B I O L O G Y

Therapy

for Cells

Cognitive-behavioral therapy

improved cellular aging markers

in people with social anxiety

Depression, anxiety and other psychiatric

disorders can also influence physical health;

they are linked with increased risk of heart

disease, for example, and shorter life expec-

tancy. Recent research suggests this may

be related to accelerated aging—and new

work finds that a form of purely psychologi-

cal therapy can have a protective physio-

logical effect.

A study led by clinical psychologist Krist-

offer Månsson of the Karolinska Institute in

Sweden showed that cognitive-behavioral

therapy (CBT), a common psychotherapy

technique, not only reduced anxiety levels in

people with social anxiety disorder but also

improved cellular aging markers for some

patients. This finding could ultimately help

clinicians personalize treatments.

Telomeres, short DNA sequences that

cap chromosomes’ ends to protect them

from damage, indicate cellular age. Each

time a cell divides to drive growth and

repair, its telomeres shorten. The enzyme

telomerase maintains them to an extent, but

eventually they shorten so much that cells

can no longer divide, and signs of bodily

aging appear. Telomeres also shorten

through cellular damage caused by highly

oxidizing molecules called free radicals.

Many studies link stress with shorter

telomeres. And in 2015 researchers led by

clinical psychologist Josine Verhoeven of

Amsterdam University Medical Center

found that patients with an active anxiety

disorder had shorter telomeres than those

in remission or healthy controls.

In the new study, published last Decem-

ber in Translational Psychiatry, the scientists

first took two blood samples, nine weeks

apart, from 46 people with social anxiety dis-

order. They measured the subjects’ telomere

length as well as levels of telomerase and

glutathione peroxidase (GPx), an antioxidant

enzyme that counteracts free radical dam-

age. The participants received nine weeks

of online CBT and then gave another sample.

All measures remained largely unchanged

over the two samples prior to therapy. But

afterward, the subjects had increased GPx

into their flier. Motion-capture footage
showed how pigeons do this primarily by
opening and closing their wrist joints.
Once the researchers built a prototype—
a foam-board body with onboard electronic
guidance systems and elastic bands control-
ling real pigeon feathers—they first flexed
its wings in a wind tunnel to determine if it
could function in blustery real-world condi-
tions. It worked, paving the way for gliding
and turning tests outside the laboratory.
Chang piloted PigeonBot from the ground
and describes it as an incredibly nerve-
wracking experience: “[When] we had
landed in one piece, I do remember collaps-
ing on the ground afterward in this sense of
relief,” he says. The scientists published their
results in January in Science Robotics.
Pigeon feathers can automatically
attach to their neighbors to form a smooth,
flexible flying surface, and PigeonBot’s mak-
ers had to figure out exactly how. Like many
bird species, pigeons accomplish this with
microscopic structures called lobate cilia,
which ornithologists documented early in
the 20th century. But partly because of the
limits of light microscopy at the time, they
assumed birds’ lobate cilia worked by sim-
ply increasing friction between feathers,
much like rubbing pieces of sandpaper
together, says Teresa Feo, a zoologist at

the Smithsonian National Museum of Nat-

ural History, who contributed to a second

paper from the team in Science, also in Jan-

uary. “What we discovered is the actual

mechanism of those lobate cilia—that it is

not friction, but hooking,” Feo says. The

team demonstrated how these cilia release

when birds fold their wings and grab each

other again when the wings are extended.

Their new understanding was made

possible by modern analytic techniques

such as scanning electron and x-ray micro s-

copy and CT scans, says study co-author

Laura Mat loff, a mechanical engineer at

Stanford. “We’re the first to really revisit

[lobate cilia] with this new instrumenta-

tion,” she says.

But there are still mysteries about how

natural feathers work. The research group

found that the cilia are notably absent

from feathers of barn owls and nightjars,

two species that stalk prey at night. Like

Velcro, the microstructures are noisy when

they detach; in these stealthy hunters,

evolution may have favored silent flight

over feather connectivity. “It’s pretty clear

that this is an example of convergent evo-

lution, where there was a trade-off,” says

Julia Clarke, a paleontologist at the Univer-

sity of Texas at Austin, who was not involved

in the studies. Clarke is intrigued by the cil-

ia’s evolutionary history, although she says

the tiny structures may be hard to find in

the fossil record.

Emulating features that help make flying

surfaces soft but sturdy could be invaluable

in designing artificial morphing wings—

a key step to building next-generation

drones. Typical quadcopter-style drones

are maneuverable and adept at hovering

in place, but Chang says winged drones

could be faster and quieter. The Stanford

team is looking at how to best design not

just “an actual wing shape that gives you

more efficiency, but [the ability] to change

that wing shape very dynamically” for

streamlined flight, he says.

The research “points the way to new

forms of biomimetic flying robots that could

have a lot of useful applications,” says Phil

© 2020 Scientific American