Be regular my beating heart

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Biology / Health / Medicine

Thanks to a specialised group of cells called pacemaker cells, your heart keeps beating, and at a regular pace. There are a few thousand of these cells in your heart and they send out the electrical signals that initiate each heartbeat.

But if you suffer from a condition called heart block, these signals are disrupted and your heart may skip beats or beat too slowly. These abnormal heart rhythms may just leave you feeling light-headed and woozy but they may also lead to full-blown cardiac arrest. This is when the heart doesn’t contract properly and the brain and rest of the body don’t get enough oxygen delivered to them. Without fast treatment, brain damage can occur.

Enter the man-made pacemaker

Heart block can occur at any age, even in unborn babies, and current treatment is to fit an electrical pacemaker device. The pacemaker monitors the heart’s rhythm and if the heart slows down or skips a beat, the pacemaker sends out an electric pulse to get the heart back on track. This surgery obviously isn’t an option for an unborn baby and heart failure due to heart block is thought to be the cause of some stillbirths. Even in adults, pacemakers last only seven years and the process of implanting the device carries its own risks, mostly of infection. This week, researchers from the Cedars-Sinai Heart Institute in Los Angeles announced in the journal Science Translational Medicine that they had used a gene called TBX18 to coax ordinary heart cells into becoming new specialised pacemaker cells. TBX18 usually plays a role during development before birth, when the heart’s original pacemaker cells are being formed.

Electronic pacemaker. Image credit: Steve Wintor [CC] via Flickr

Electronic pacemaker. Image credit: Steve Winton via Flickr.

Pig pacemakers

Researchers injected the gene into the hearts of pigs with heart block (pigs hearts are very similar to human hearts). Within 48 hours, this little patch of cells, about the size of a peppercorn, had begun to act as pacemaker cells, delivering electrical signals to the rest of the heart. And the process of injecting the gene wasn’t anywhere near as invasive as the surgery required to fit a pacemaker and could conceivably be done to an unborn baby. They only monitored the pigs for the next two weeks but during that time the new pacemaker cells kept working and the scientists are hopeful that the cells might keep doing their new job permanently. The aim is to be trialing this technique, dubbed the biological pacemaker, in humans within three years. This is a very cool example of what’s called gene therapy — using DNA effectively as a drug to treat disease. Let’s hope those pigs’ hearts stay regular.

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