Scientists have found a way to temporarily regulate a pig’s heart using an injection of genes meant to reprogram cells in the heart. This gene therapy creates a “biological pacemaker” that, if successful in testing, could one day replace the need for electronic pacemaker implants in some patients.

A healthy heart regulates its own beating through a small area known as the sino-atrial node. This area only contains a few thousand cells that contribute to maintaining heart rate. When these cells aren’t functioning properly, or cannot communicate well with other cells, the heart rate becomes irregular or dangerously slow.

In the United States, 300,000 people each year rely on pacemaker implants to counteract these irregularities. Of these people, roughly two percent develop complications, such as infections, that sometimes require the pacemaker to be removed temporarily. It is thought that this small group of people will benefit from the gene therapy most immediately.

Another group that may benefit would be unborn babies who have been identified as having a heart complication known as congenital heart block. This occurs when the sino-atrial node is completely disconnected from the rest of the heart. A fetus in utero would not be able to receive a pacemaker implant, but the gene therapy could be delivered using a catheter.

The therapy is at least three years away from being tested on human subjects but preliminary testing on pigs has proven encouraging. Scientists have isolated the gene TBX-18 as potentially important to the sino-atrial nodes functioning. They concluded this after observing its presence in the developing hearts of embryos. Following this observation, they injected the gene into the hearts of seven of 12 pigs with complete heart block. The other five pigs were used as controls and given electronic pacemakers.

The pigs injected with the TBX-18 gene showed a marked improvement in their heart rates. Their hearts were able to regulate their beats, even in response to changes in physical activity. This effect lasted for about 11 days before the therapy began to wear off. Current testing is looking into whether or not there could be longer lasting therapies and if there are safety concerns involved in the treatment.