Using microbubbles to transduce ultrasound into mechanical deformations capable of activating neurons genetically sensitized to membrane stretch

Abstract

Ultrasound is an ideal modality to stimulate neurons due to its ability to focus through deep tissue. To facilitate the selective ultrasound activation of neurons within a dense network, we have developed a new method called sonogenetics where we genetically sensitize individual neurons to respond to the mechanical deformations created by an ultrasound pulse. This was done by misexpressing the TRP4 mechanotransduction ion channel in select neurons. As a model system, we used Caenorhabditis elegans nematodes which were allowed to freely move on the surface of an agar gel. We found that ultrasound alone did not create enough mechanical deformation at the surface of the agar to activate the TRP4 channels. To overcome this challenge, we introduced stabilized microbubbles to the system by plating them on the gel surface where they naturally surrounded the worms. The interaction between the microbubbles and the ultrasound created mechanical deformations that propagated into the body of the worm and successfully activated the expressed TRP4 causing subsequent neural activation. Activation was confirmed using calcium dependent fluorescent dyes and by quantifying whole worm behavioral changes. This technique can be a valuable tool for future applications in mammalian neural systems aimed at understanding complex neural circuits.Ultrasound is an ideal modality to stimulate neurons due to its ability to focus through deep tissue. To facilitate the selective ultrasound activation of neurons within a dense network, we have developed a new method called sonogenetics where we genetically sensitize individual neurons to respond to the mechanical deformations created by an ultrasound pulse. This was done by misexpressing the TRP4 mechanotransduction ion channel in select neurons. As a model system, we used Caenorhabditis elegans nematodes which were allowed to freely move on the surface of an agar gel. We found that ultrasound alone did not create enough mechanical deformation at the surface of the agar to activate the TRP4 channels. To overcome this challenge, we introduced stabilized microbubbles to the system by plating them on the gel surface where they naturally surrounded the worms. The interaction between the microbubbles and the ultrasound created mechanical deformations that propagated into the body of the worm and successfully...