Optogenetics could work to correct life-threatening arrhythmias

Bursts of electric current from a pacemaker or defibrillator can cause pain, tissue damage, and other serious side effects in ailing hearts, such as arrhythmias. Recognizing this, a team of researchers from Johns Hopkins University (California, MD) and Stony Brook University (Stony Brook, NY) are turning to optogenetics to help control abnormal heart behavior noninvasively.

Related: Optogenetics, optical imaging combine to stimulate heart muscle by light

Related: Optogenetics tools address a growing range of applications

Pioneered by scientists at Stanford University in California, optogenetics refers to the insertion of light-responsive proteins called opsins into cells. When exposed to light, these proteins become tiny portals within the target cells, allowing a stream of ions—an electric charge—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.

In their paper published in the journal Nature Communications, the research team reported that they had successfully tested this same technique on a heart—one that "beats" inside a computer. Natalia Trayanova, a professor of biomedical engineering at Johns Hopkins, has spent many years developing highly detailed computer models of the heart that can simulate cardiac behavior from the molecular and cellular levels all the way up to that of the heart as a whole. At Johns Hopkins, she also directs the Computational Cardiology Lab within the Institute for Computational Medicine.

As detailed in the journal article, the Johns Hopkins computer model for treating the heart with light incorporates biological data from the Stony Brook lab of Emilia Entcheva, an associate professor of biomedical engineering. The Stony Brook collaborators are working on techniques to make heart tissue light-sensitive by inserting opsins into some cells. They also will test how these cells respond when illuminated.

"Experiments from this lab generated the data we used to build our computer model for this project," Trayanova says. "As the Stony Brook lab generates new data, we will use it to refine our model."

In Trayanova's own lab, her team members will use this model to conduct virtual experiments. They will try to determine how to position and control the light-sensitive cells to help the heart maintain a healthy rhythm and pumping activity. They will also try to gauge how much light is needed to activate the healing process. The overall goal is to use the computer model to push the research 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," says Patrick M. Boyle, a postdoctoral fellow in Trayanova's lab and lead author of the paper. "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."

After the technology is honed through the computer modeling tests, it could be incorporated into light-based pacemakers and defibrillators. It is interesting to note that it was a Johns Hopkins electrical engineering researcher, William B. Kouwenhoven, who developed the closed-chest electric cardiac defibrillator, which has been used since the 1950s to save lives.

For more information on the research team's work, please visit http://www.nature.com/ncomms/2013/130828/ncomms3370/full/ncomms3370.html.

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