Currently, devices such as pacemakers and deep brain stimulation electrodes must be surgically implanted into patients.However, such implants may one day be replaced by cells activated by ultrasound, according to a new study.
Back in 2015, researchers from the Salk Institute for Biological Studies in California showed that when a protein called TRP-4 is added to the neurons of the roundworm Caenorhabditis elegans, these neurons can be activated by external application of ultrasonic pulses are activated. Lead scientist Associate Professor Sreekanth Chalasani calls the technique “acoustogenetics”.
But unfortunately, TRP-4 was found to have no such effect on mammalian cells — meaning the technology cannot be applied to humans.
With this in mind, Chalasani and colleagues set out to try nearly 300 different proteins on a human research cell called HEK. They eventually found that a naturally occurring protein — named TRPA1 — made HEK cells respond to ultrasound at a 7-MHz frequency, which is considered safe.
To see if the protein works on other types of mammalian cells, the researchers used gene therapy to add the gene for human TRPA1 to specific groups of neurons in the brains of living mice. When the mice were exposed to bouts of ultrasound, the only neurons that were activated were those with the TRPA1 gene.
Now researchers hope to eventually be able to add the TRPA1 gene to cells in the heart and brain (and elsewhere) of human patients. When activated by an external ultrasound-emitting device, these cells can perform the same function as a pacemaker or brain-implanted electrodes that are currently used to treat conditions such as epilepsy and Parkinson’s disease.
Scientists are now studying the precise way TRPA1 senses ultrasonic waves, with the aim of tuning the protein to increase its sensitivity. They are also looking for proteins that inactivate cells to ultrasound.
A paper on the research was recently published in the journal Nature Communications.