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Researchers: Ultrasound Can Control Neurons, Bypassing Implants

A Salk team is researching it, not just to control mice but to control cells now controlled by pacemakers, insulin pumps, electrodes, and other therapies
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Light has been used to turn cells on and off for over a decade. The process, called optogenetics, can be therapeutic but because light can’t get through tissues, the light source must be embedded in the skin or beneath the skull. A new method, sonogenetics, which means using sound instead of light to control cells, may show promise in regulating pacemakers and insulin pumps, among other things:

Sreekanth Chalasani

In a new study published today (February 9) in Nature Communications, researchers report they’ve found a way to use ultrasound to noninvasively activate mouse neurons, both in culture and in the brains of living animals. The technique, which the authors call sonogenetics, elicits electrical activity in a subset of brain cells that have been genetically engineered to respond to sound waves.

Natalia Mesa, “Researchers Use Ultrasound to Control Neurons in Mice” at The Scientist (February 9, 2022) The paper is open access.

The main goal is to find less invasive treatments for chronic conditions:

“Going wireless is the future for just about everything,” says senior author Sreekanth Chalasani, an associate professor in Salk’s Molecular Neurobiology Laboratory. “We already know that ultrasound is safe, and that it can go through bone, muscle and other tissues, making it the ultimate tool for manipulating cells deep in the body.”

About a decade ago, Chalasani pioneered the idea of using ultrasonic waves to stimulate specific groups of genetically marked cells, and coined the term “sonogenetics” to describe it. In 2015, his group showed that, in the roundworm Caenorhabditis elegans, a protein called TRP-4 makes cells sensitive to low-frequency ultrasound. When the researchers added TRP-4 to C. elegans neurons that didn’t usually have it, they could activate these cells with a burst of ultrasound—the same sound waves used in medical sonograms.

Salk News, “In a First for “Sonogenetics,” Researchers Control Mammalian Cells with Sound” at Salk (February 9, 2022)

Here’s how sound waves can turn a nematode worm around:

It took the team longer to figure out how to do it with mammalian cells but they found cell lines that were sensitive to sound waves and the experiment has worked in live mice.

Chalasani goes into detail about the benefits:

Clinicians treating conditions including Parkinson’s disease and epilepsy currently use deep brain stimulation, which involves surgically implanting electrodes in the brain, to activate certain subsets of neurons. Chalasani says that sonogenetics could one day replace this approach—the next step would be developing a gene therapy delivery method that can cross the blood-brain barrier, something that is already being studied.

Perhaps sooner, he says, sonogenetics could be used to activate cells in the heart, as a kind of pacemaker that requires no implantation. “Gene delivery techniques already exist for getting a new gene—such as TRPA1—into the human heart,” Chalasani says. “If we can then use an external ultrasound device to activate those cells, that could really revolutionize pacemakers.”

Salk News, “In a First for “Sonogenetics,” Researchers Control Mammalian Cells with Sound” at Salk (February 9, 2022)

For now, they need to study the responsive cell lines more thoroughly, to find out the exact mechanisms by which they respond.

You may also wish to read: Detailed brain mapping outlines what we can — and can’t — know. Your brain, fully mapped, would take up a good part of the internet. And then it would just change again. Living things, even comparatively simple ones, cannot be entirely comprehended by simple measurements.

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Researchers: Ultrasound Can Control Neurons, Bypassing Implants