Gene Therapy in Pigs Creates Temporary ‘Biological Pacemaker’

A pacemaker that may no longer be needed if the new gene therapy technique works. By Rachael Rettner, Senior Writer for LiveScience 2014-07-17 22:15:37 UTC

Electronic pacemakers can be lifesaving for people with abnormal or slow heart rhythms, but not everyone who needs a pacemaker is able to have an electronic device implanted in their heart.

Now, in experiments in pigs, researchers have come up with a new method for making a "biological pacemaker" that might one day serve as an alternative to electronic ones, the researchers said.

Making this pacemaker involves injecting a gene into heart muscle cells, which transforms these normal heart cells into special cells that can initiate a heartbeat.

This method could be useful for certain patients, such as those who develop infections from electronic pacemakers and need to have the devices temporarily removed, or fetuses with life-threatening heart disorders who cannot have an electronic pacemaker implanted, the researchers said.

"Babies still in the womb cannot have a pacemaker," study researcher Dr. Eugenio Cingolani, director of the Cardiogenetics-Familial Arrhythmia Clinic at Cedars-Sinai Heart Institute in Los Angeles, said in a statement. "It is possible that one day, we might be able to save lives by replacing [electronic] hardware with an injection of genes."

The researchers previously showed that this method worked in rodents, but pig hearts are similar to human hearts in their size and the way that they work, so there's reason to think the new findings could translate to humans. Still, more research is needed before the method could be tested in people to better understand the treatment's safety and effectiveness, the researchers said. The method relies on a virus to insert the gene into the heart cells, and although this virus cannot replicate itself or integrate into the genome, the pig experiments showed that a small amount of virus did end up in other organs in the animals besides the heart, according to the study published July 16 in the journal Science Translational Medicine.

In healthy people, a small region of the heart, called the sinoatrial node, fires the electrical impulses that determine heart rate. If this region is not working properly, people can develop heart rhythm problems, and have symptoms such as fatigue, fainting or even cardiac arrest. Such patients may have electronic pacemakers put in to monitor the heart rhythm, which sends electrical pulses to keep the heart beating normally.

In the study, the researchers used pigs with a condition called complete heart block, in which the heart beats very slowly. The researchers injected a gene called TBX18 into a small area of the heart muscle. This gene converted this area of heart muscle cells into sinoatrial node cells.

"In essence, we create a new sinoatrial node in a part of the heart that ordinarily spreads the impulse, but does not originate it," study researcher Dr. Eduardo Marbn, director of the Cedars-Sinai Heart Institute, said in news conference about the findings. "The newly created node then takes over as a functional pacemaker, bypassing the need for implanted electronics and hardware."

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Gene Therapy in Pigs Creates Temporary 'Biological Pacemaker'