Currently, doctors are forced to perform surgical interventions in the brain to activate neurons in conditions such as Parkinson’s disease (Parkinson’s disease), but the mechanism of ultrasound stimulation of cells promises to change this approach.
In a new study published in the journal Nature Communications, researchers at the Salk Institute for Biological Studies in the United States reported that the mechanism of activating cells using ultrasound has already worked with animal and human cells.
“The transition to wireless networks is the future of just about everything,” says senior study author Srikanth Chalasani, Associate Professor in Salk Laboratory’s Molecular Neurobiology Laboratory. “We already know that ultrasound is safe, and can pass through bones, muscles and other tissues. making it the ultimate tool for treating cells deep within the body.”
For about a decade, Chalasani pioneered the use of ultrasound to stimulate specific populations of cells with genetic markers, and coined the term “acoustic genetics” to describe this medical mechanism.
And in 2015, Chalasani’s research team discovered a protein in a cylindrical worm known as C. elegans, which generally makes cells sensitive to low-frequency ultrasound.
The researchers also recorded this observation when they added the same protein to the nerve cells of the worm, and they were able to activate these cells with a burst of ultrasound, the same used in medical ultrasound imaging.
But when the researchers tried to add the protein to other animal cells, it wasn’t able to make the cells respond to ultrasound, so Chalasani and his colleagues set out to search for an alternative protein that would make cells highly sensitive to ultrasound at 7MHz, the optimal and safe frequency.
After a long and complex search among more than 300 potential proteins, Chalasani and his colleagues succeeded in finding what they wanted in the transporter protein, encoded in humans by TRPA1, which allows cells to respond to the presence of harmful compounds.
In an experiment in mice, brain cells responded to sound waves after adding TRPA1 to a specific group of neurons.
In conditions such as Parkinson’s disease and epilepsy, doctors currently use deep brain stimulation, which involves surgically implanting electrodes into the brain, to activate specific subsets of neurons.
Acoustogenetics could one day replace this approach, Chalasani says, while the next step will be developing a gene therapy delivery method that can cross the blood-brain barrier, something that is already being studied.
Perhaps soon, he adds, “acoustic genetics” could be used to activate heart cells, as a kind of pacemaker that doesn’t require any transplants.
“Gene delivery technologies already exist to get a protein like TRPA1 into the human heart,” Chalasani says. “If we can then use an external ultrasound device to activate those cells, it could really revolutionize pacemakers.”