New Scientist - USA (2021-10-30)

30 October 2021 | New Scientist | 13

News

A CLINIC in Belgium has been
given the go-ahead to reimplant
frozen testicular tissue to obtain
sperm for fertility treatments. The
hope is that this will allow those
whose fertility was destroyed by
cancer treatments before they
reached puberty to have children.
“Our protocol has been
approved by the ethical
committee, and now we are
waiting for the first case,” says
Ellen Goossens at the Free
University in Brussels (VUB). 
Cancer treatments such as
chemotherapy or radiotherapy
can sometimes make people
infertile. In those old enough
to produce sperm, samples can
simply be frozen for later use for
IVF. For prepubescent children
who don’t produce sperm yet,
this isn’t an option, but their testes
do contain spermatogonial stem
cells, which later produce sperm.
These can be preserved by
removing small pieces of the
testes and freezing them.
After animal studies suggested
that it might be possible to derive
mature sperm from such cells,
Goossens’s group began offering

testicular tissue banking in 2002.

A growing number of centres

worldwide are following suit, and

a survey in 2019 found that testes

tissue had been collected from

more than 1000 individuals.

A breakthrough in the animal

studies came recently, says Rod

Mitchell at the University of

Edinburgh in the UK, who wasn’t

involved in the work. A US team

froze testicular tissue from rhesus

macaques and reimplanted it in

the scrotum or under the skin of

the back. All the grafts produced

testosterone and mature sperm,

which were extracted and used

to fertilise eggs. In 2019, the team

reported that the process led to

the birth of a healthy macaque.

“This is proof of principle in the

primate that the whole process

from obtaining tissue, storing

tissue, generating sperm and

being able to generate offspring

with those sperm is feasible,”

says Mitchell. Now, several centres

have begun preparing to try

reimplanting testicular tissue into

the individuals from whom it was

taken. Goossens’s group is likely

to be the first.

“Since we were the first

worldwide to offer testicular tissue

banking to prepubescent boys,

we now have the oldest cohort,

including patients in their mid-

twenties,” she says. Some of them

may now want to start families

and find that natural conception

isn’t possible, says Goossens.

These first attempts will be

done as part of a clinical trial,

says Mitchell. It may be several

years before the procedure is

tried in other countries.

Researchers are also exploring

other ways of generating sperm

from the frozen tissue. One is to

try to grow the stem cells in the

lab and generate sperm without

reimplanting tissue into the body.

On 19 October, researchers in

the US reported that they had

fertilised rhesus macaque eggs

with sperm generated from

stem cells. Another possibility is

reimplanting the stem cells into

the tubes of the testes in a way that

spurs normal sperm production. ❚

Fertility

Michael Le Page

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Male fertility could be restored with

frozen testicular tissue implants

A cross-section

of human testicular

tissue

Machine learning

AN ARTIFICIAL intelligence algorithm
can transform still images into a
high-resolution, explorable 3D
world, with potential implications
for film effects and virtual reality.
By feeding the neural network
a selection of images of a scene
and a rough 3D model of the
scene created automatically using
off-the-shelf software called
COLMAP, it is able to accurately
visualise what the scene would

look like from any viewpoint.

The neural network, developed

by Darius Rückert and colleagues

at the University of Erlangen-

Nuremberg in Germany, is different

to previous systems because it is

able to extract physical properties

from still images.

“We can change the camera

pose and therefore get a new

view of the object,” says Rückert.

The system could technically

create an explorable 3D world from

just two images, but it wouldn’t be

very accurate. “The more images

you have, the better the quality,”

says Rückert. “The model cannot

create stuff it hasn’t seen.”

Some of the smoothest examples

of the generated environments use

between 300 and 350 images

captured from different angles

(arxiv.org/abs/2110.06635).

Rückert hopes to improve the

system by having it simulate how

light bounces off objects in the

scene to reach the camera, which

would mean fewer still images are

needed for accurate 3D rendering.

“The rendering quality is

unparalleled,” says Tim Field,

founder of New York-based

company Abound Labs, who

works on 3D capture software.

“It’s proof that automated

photorealism is possible.”

Field believes the technology

will be used for generating visual

effects in films and virtual reality

walkthroughs of locations.

“It’s going to accelerate the

already-hot research field of

machine learning-based rendering

for computer-generated imagery,”

he says. ❚

AI can turn collection

of 2D images into an

explorable 3D world

“ The rendering quality is

unparalleled. It is proof

that photorealism is

possible” Chris Stokel-Walker

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