New technique to selectively and noninvasively turn on
groups of neurons in worms could be boon to science and medicine
(September 15, 2015) Salk scientists have developed a new way to selectively
activate brain, heart, muscle and other cells using ultrasonic waves. The new
technique, dubbed sonogenetics, has some similarities to the burgeoning use of
light to activate cells in order to better understand the brain.
This new method–which uses the same type of waves used in
medical sonograms–may have advantages over the light-based approach–known as
optogenetics–particularly when it comes to adapting the technology to human
therapeutics. It was described September 15, 2015 in the journal Nature
Communications.
“Light-based techniques are great for some uses and I think
we’re going to continue to see developments on that front,” says Sreekanth
Chalasani, an assistant professor in Salk’s Molecular Neurobiology Laboratory
and senior author of the study. “But this is a new, additional tool to manipulate
neurons and other cells in the body.”
In optogenetics, researchers add light-sensitive channel
proteins to neurons they wish to study. By shining a focused laser on the
cells, they can selectively open these channels, either activating or silencing
the target neurons. But using an optogenetics approach on cells deep in the
brain is difficult: typically, researchers have to perform surgery to implant a
fiber optic cable that can reach the cells. Plus, light is scattered by the
brain and by other tissues in the body.
For the first
time, sound waves are used to control brain cells. Salk scientists developed
the new technique,
dubbed sonogenetics, to selectively and noninvasively turn on groups
of neurons in
worms that could be a boon to science and medicine.
Image: Courtesy of
the Salk Institute for Biological Studies
Chalasani and his group decided to see if they could develop
an approach that instead relied on ultrasound waves for the activation. “In
contrast to light, low-frequency ultrasound can travel through the body without
any scattering,” he says. “This could be a big advantage when you want to
stimulate a region deep in the brain without affecting other regions,” adds
Stuart Ibsen, a postdoctoral fellow in the Chalasani lab and first author of
the new work.
Chalasani and his colleagues first showed that, in the
nematode Caenorhabditis elegans, microbubbles of gas outside of the worm were
necessary to amplify the low-intensity ultrasound waves. “The microbubbles grow
and shrink in tune with the ultrasound pressure waves,” Ibsen says. “These
oscillations can then propagate noninvasively into the worm.”