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    The Pacemakers of the Future Will Keep Your Heart Beating With Light

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    Lex Berko

    Contributor

    A person collapses from a heart attack. Medics arrive and hastily produce a defibrillator from the back of their ambulance. “Clear!” The paddles are placed on the ailing person’s chest and zap! The victim is shocked and brought back from the brink of death.

    Scenes like this are pretty common in movies and television shows. In these tense cinematic moments, the defibrillator has almost a magical quality to it, operating in a vacuum with little to no adverse effects, other than possibly not working. But in reality, electrical stimulation devices like defibrillators and pacemakers have notable injurious consequences.

    Misuse of defibrillators may result in a disruption of the heart’s normal rhythm, increased mortality, and some psychological trauma, while pacemakers can in certain cases go so far as to cause heart failure and even death.

    Concerned about these damaging side effects, Natalia Trayanova, a professor of biomedical engineering at Johns Hopkins University, started looking for a safer option. Collaborating with a set of researchers out of Stony Brook University, Trayanova is focused on a surprising potential alternative to conventional electrical stimulation: light.

    Trayanova has turned to optogenetics, a relatively young technique developed about a decade ago. While you may not have heard of it quite yet, it has already shown significant promise in neuroscience by helping scientists understand how brains work.

    As you might imagine, optogenetics is not as easy as simply shining a light on someone to fix her irregular heartbeat. It’s more complicated than that. The process involves inserting special light-sensitive proteins, called opsins, into cells. When exposed to light, opsins change the ion balance in and outside of the cell, giving scientists some degree of control over cellular activity.

    More research needs to be done to arrive at the point where we might see light-based heart stimulation devices, but Trayanova and her team have made headway by developing a sophisticated computer model of the heart to better understand how this might all play out.

    “The goal of this optogenetics virtual reality is to accelerate experimental research significantly by testing various scenarios of light application to the heart and narrowing the options that are most promising and should be tested experimentally,” she told me.

    Image via Patrick M. Boyle, one of Trayanova's colleagues and a postdoctoral fellow at the Institute for Computational Medicine.

    To that end, her model offers multiple vantage points, “from the level of the protein to the level of that of the entire organ,” to examine the effects of light. In a research paper published in Nature Communications yesterday, the Johns Hopkins team reported on the development of their new tool and its successful application in probing different opsin delivery mechanisms and potential pacemaking targets.

    When I asked Trayanova how far off we are from having light-based defibrillators and pacemakers, she said it’s still too early too tell.

    “Optogenetics in the heart is in its nascent stage,” she said. “There might be numerous implantation difficulties and concerns that might arise as we progress.” So electrical stimulation will remain the norm for the time being.

    However, of the two, an optogenetic pacemaker seems more likely to come to fruition sooner than a defibrillator, because pacemaking is a simpler process. “A light-based pacemaker would pretty much look like a conventional, electrical pacemaker because the objective would be the same—initiate a heartbeat from a single site,” Trayanova explained. “The electrical circuitry in a pacemaker lead could be augmented with fiber optics, thus replacing current output with light output.”

    But while the devices may look the same to an outsider, they certainly won’t act the same.

    “The exciting difference is that unlike electrical pacing, if a particular tissue area is lit up, only cells that have been treated to express the light-sensitive protein will respond,” she said. This is drastically different from the current electrical method. According to Trayanova, "optogenetics will allow us to initiate pacemaking from specific, specialized heart tissue structures leading to more and more natural paced heartbeats. This level of selectivity cannot be obtained conventionally.”

    So although cardiological optogenetics is in its infancy, there may come a day when our lives are saved by the mild wavelengths of light instead of the harsh buzz of an electrical jolt. I don't know what that means for screenwriters, but I presume all those defibrillator scenes will become a little less dramatic.

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