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 multi-university 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 team leader professor Natalia Trayanova of Johns Hopkins. "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." Light-sensitive cells are already being used to control certain brain activities. Trayanova and other bioengineers at Stony Brook and Johns Hopkins plan to give this technique a cardiac twist so that in the near future doctors can use low-energy light to solve serious heart problems such as arrhythmia. Her team plans to accomplish their less painful method by using biological lab data and intricate computer modeling. To achieve this, Trayanova's team is diving into the field of optogenetics — 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. 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 reported that they had successfully tested the light-based tactic on the computer-modeled heart. Trayanova's team will use this 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 will also try to gauge how much light is needed to activate the healing process. The Stony Brook collaborators 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 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. 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" protein (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 that triggers a healthy heartbeat. Courtesy of Patrick M. Boyle. "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 postdoctorate 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." After the technology is honed through the computer modeling tests, it could be incorporated into light-based pacemakers and defibrillators. The research was published Aug. 28 in the online journal Nature Communications. For more information, visit: www.jhu.edu