Often when it is dark, we go for a flashlight or our phone to see where we are going. What if I told you that is much the same in science. Light is used in almost every field to visualize things that we normally cannot see.
The body utilizes light in many ways. It actually induces a chemical reaction in certain proteins in your eyes, which allows you to see things. In the medical field, light is used in many different ways. An X-ray is the easiest example. X-rays use high-frequency light to visualize dense areas in our bodies (bones, organs, etc.). Some researchers want to combine these two things and use light-inducible proteins in next-generation medical techniques. This field of study is called optogenetics.
In a recent study out of the University of Colorado in Aurora, a team sought to use the light-sensitive protein opsin to create a sort of “light switch.” This switch would be applied to cells of the vagus nerve, a critical modulator of passive heart rate, to regulate heart rate in patients. To get it into the cells, the team would utilize adeno-associated virus (AAV) technology, an up-and-coming genetic delivery tool.
The study centered around in vivo mouse and in vitro cell studies. The opsin switch worked wonders, with the team able to activate them with a light beam and regulate the heart rate of mice. The issue came in delivering the opsin to the cells of the vagus nerve. AAV suffers from a lack of specificity and tends to affect cells and tissue outside the target area. In this case, there was evidence showing that the AAV delivered genes to other tissues beyond the vagus nerve, which could result in side-effects and toxicities. They could not get consistent activation levels either, suggesting that it could be due to inconsistent delivery of the genes by AAV.
Although the AAV treatment used in this study had some issues with both specificity and potency, the selective stimulation of the vagus nerve tissue with light was a success. The team’s future efforts would seek to apply the AAV to certain parts of the heart, hopefully solving off-target AAV issues. All in all, this study shows some positive results for light as a switch to activate the vagus nerve.
The study concludes, “The present study provides an initial demonstration of retrograde opsin delivery in an organ-specific manner to facilitate peripheral nerve photomodulation. Results showed the feasibility of perturbing organ function with this technique.”
Sources: Nature Scientific Reports, Addgene