A 'Viral Pacemaker' : Teaching a Virus New Tricks

We all know that the human heart is a tireless pump. Biologists tell us that this wonderful organ is made up of billions of cells. But its steady "rhythm of life" is kept up by the electrical pulses produced by a collection of just about 10,000 cells that make up the Sino-atrial Node. These pacemaker cells are formed in the embryonic stage itself. With time, they naturally lose their precision with age and disease. The result? Their pulses might speed up, slow down, become irregular, or, God forbid! even stop. These are the instances when heart surgeons would implant an artificial, battery-powered pacemaker to serve as a substitute. But these 'foreign' devices bring with them the risks of breakdowns, power loss and infections, not to speak of a comparatively short life span on account of the limitations of technology.

The ideal solution, then, would be a replacement pacemaker that is built and powered by the body. Researchers at the Cedars-Sinai Heart Institute are on their way to creating just such a thing. They have succeeded in teaching a few good tricks to viruses and have deployed them as pacemakers.

When pacemaker cells are developing in the embryo, a particular gene—Tbx18—is also activated. Researchers inserted this Tbx18 gene into a virus and inserted that virus into normal, adult guinea pig heart cells. In a matter of days, these cells morphed into pacemaker cells and began sending heartbeat signals of their own. The approach is similar to the reprogramming of heart scar tissue to function like normal heart cells, but in this case the researchers were reprogramming the heart’s pacemaker, thus controlling the beating of all other heart cells.

Another good thing was that the effects lasted even after the Tbx18 had faded away. Researchers are confident that the structural change is permanent and might offer long-term treatment for patients with heart rhythm irregularities. At this point, though, the research, which was published in Nature Biotechnology, is far from human trials.

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