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  • Light to the heart to restore healthy beats

BioPhotonics
Nov 2013
BALTIMORE – When a person’s heart slows or stops, the current practice is to jump-start it with a blast of electricity from a pacemaker or defibrillator. But a multiuniversity team aims to put an optogenetic twist on the procedure by replacing the violent jolt of electricity with gently applied light.

“Applying electricity to the heart has its drawbacks,” said Natalia Trayanova, a professor at Johns Hopkins University and team leader of a group of biomedical engineers from Johns Hopkins and Stony Brook University. “When we use a defibrillator, it’s like blasting open a door because we don’t have the key. It applies too much force and too little finesse. We want to control this treatment in a more intelligent way. We think it’s possible to use light to reshape the behavior of the heart without blasting it.”


Natalia Trayanova


In optogenetics, light-sensitive proteins called opsins are already being inserted into cells to control certain brain activities. When exposed to light, these proteins become tiny portals within the target cells, allowing a stream of ions to pass through. Early researchers have begun using this tactic to control the bioelectric behavior of certain brain cells, forming a first step toward treating psychiatric disorders with light.

The researchers plan to give the technique a cardiac twist so that, in the near future, doctors can use low-energy light to solve serious heart problems such as arrhythmia. They plan to accomplish their less-painful method by using biological lab data and intricate computer modeling.

Trayanova has spent many years developing highly detailed computer models of the heart, simulating whole cardiac behavior as well as molecular and cellular behavior. The researchers report that they have successfully tested the light-based tactic on the computer-modeled heart.


In this illustration, the optrode at left delivers blue light to the heart via a fiber optic tip. In the enlargement at right, a heart cell (large red oval) contains an implanted light-sensitive opsin (blue oval) that works alongside the heart’s own proteins (yellow ovals). This teamwork allows the cell to convert light energy into an electric kick to trigger a healthy heartbeat. Courtesy of Patrick M. Boyle.


The Johns Hopkins researchers will use the model to conduct virtual experiments, trying to determine how to position and control the light-sensitive cells to help the heart maintain healthy rhythm and pumping activity. They also will try to gauge how much light is needed to activate the healing process.

Collaborators at Stony Brook are working on techniques to make heart tissue light-sensitive by inserting opsins into cells. They also will test how these cells respond when illuminated. The goal is to use the computer model to move closer to the day when doctors can begin treating their heart patients with gentle light beams. The researchers say it could happen within a decade.

“The most promising thing about having a digital framework that is so accurate and reliable is that we can anticipate which experiments are really worth doing to move this technology along more quickly,” said postdoctoral fellow Patrick M. Boyle. “One of the great things about using light is that it can be directed at very specific areas. It also involves very little energy. In many cases, it’s less harmful and more efficient than electricity.”

The research was published in Nature Communications (doi: 10.1038/ncomms3370). After the technology is honed through the computer modeling tests, it could be incorporated into light-based pacemakers and defibrillators.


GLOSSARY
optogenetics
A discipline that combines optics and genetics to enable the use of light to stimulate and control cells in living tissue, typically neurons, which have been genetically modified to respond to light. Only the cells that have been modified to include light-sensitive proteins will be under control of the light. The ability to selectively target cells gives researchers precise control. Using light to control the excitation, inhibition and signaling pathways of specific cells or groups of cells...
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