24 | New Scientist | 5 February 2022ZoologyADULT frogs can regrow a leg
if they are treated with a device
containing a silk gel infused with
five regenerative chemicals. The
new limbs can apparently move and
sense as well as the original legs.
Although tadpoles and young
froglets can regenerate their
hindlimbs, adult frogs lack the
capacity to do this.
To overcome this, Nirosha
Murugan at Algoma University in
Ontario, Canada, and her team used
a small cylindrical device, called a
BioDome. This is made of a silicone
outer layer with an inner layer of
silk processed and incorporated
into a polymer called a hydrogel.
They amputated the right hindleg
of 115 frogs (Xenopus laevis). The
frogs were then placed into one
of three groups. Those in the first
group wore a BioDome over thewound site that had been loaded
with a cocktail of five drugs known
to help cells regenerate. Frogs in
the second group wore BioDomes
without the drug cocktail and the
third group received no treatment
at all. The frogs that wore a
BioDome did so for one day.
After 18 months, frogs that
received a BioDome containing the
drug cocktail had regrown legs with
digit-like structures. Each frog could
use its new leg to stand on, swim
and push off walls. The other frogs
didn’t regrow limbs. The new legs
carried nerves, blood vessels and
bone in patterns similar to those
in the original legs (Science
Advances, doi.org/hd4p).
The researchers are now testing
the approach in mammals. Murugan
thinks it may have the potential to
be tested in humans. Carissa WongCocktail of chemicals allows
frogs to regrow lost limbs
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News In brief
TAKING supplements of vitamin D
prevents some people developing
an autoimmune disease, at least
for those aged over 50, in a study
providing the first evidence of
a causal link between the two.
Previous studies on the effect
of vitamin D on autoimmune
conditions have looked at those
with an autoimmune disease or
those who go on to develop one.
Other studies have hinted at the
supplement’s beneficial effects
on the immune system, but no
studies had proven the link.
To remedy this, Karen
Costenbader at the Brigham and
Women’s Hospital in Boston and
her colleagues randomly split
nearly 26,000 people in the US
who were 50 or over into two
groups, giving them either
vitamin D supplements or a
placebo. The team tracked the
participants for around five yearsHealth^to measure the development
of autoimmune conditions,
including rheumatoid arthritis,
autoimmune thyroid disease
and psoriasis.
This revealed that a dose of
2000 international units (IU) of
vitamin D per day reduced the
development of autoimmune
disease by 22 per cent, compared
with the placebo (British Medical
Journal, doi.org/gn9xdm). This
is a larger dose than the 400 IU
recommended by health bodies
such as the UK’s Department
of Health and Social Care.
It is unclear how vitamin D
prevents autoimmune disease,
but we know it is processed in the
body to produce an active form
that can alter the behaviour of
immune cells.
The team is now extending the
trial to see how long the benefits
last and hopes to start a new trial
in younger people.
“I’m very excited and really
quite bowled over by the results,”
says Costenbader. CWoOlder adults boosted
by vitamin D tabletsTODAY, HIV can be controlled,
but for most people there is no
cure because the virus can become
dormant so HIV medicines have
no effect. This could change, now
that progress has been made in
waking up dormant viruses.
People with HIV can take
antiviral medicines that stop the
virus from reproducing, giving
them nearly normal lifespans. But
HIV inserts copies of its geneticVirusesmaterial into human immune
cells, which then become dormant.
As a result, people have to take the
antivirals for life because if they
stop, viruses inside the cells wake
up and start infecting more and
more immune cells.
The idea that dormant viruses
could be reactivated before being
destroyed is sometimes known
as a “kick and kill” strategy. In the
latest work on this, Sharon Lewin
at the University of Melbourne,
Australia, and her team studied
people with HIV who were also
being treated for cancer with a
fairly new drug: pembrolizumab,
an antibody (pictured). They found
the drug also makes HIV inside
dormant immune cells wake up.
In 32 people given pembrolizumab,
HIV levels in their blood rose
1.6-fold (Science Translational
Medicine, doi.org/hd4v).
But the approach needs further
work, as strategies to kill immune
cells with replicating HIV, such as
vaccines and antibodies, are still
MO in development. Clare WilsonLEKUUL.BE/ALAMYCancer drug could be
way to clear out HIV