'Biological pacemakers' created to keep heart on beat

Scientists said Wednesday they have used a minimally invasive gene transplant procedure to create "biological pacemakers" that could keep the injured pig heart beating normally.

If proven to work in humans, the technique could one day replace pacemakers, electronic devices that work by sending electrical pulses to the heart if it is beating too slowly or if it misses a beat, according to a paper published in the US journal Science Translational Medicine.

"We have been able for the first time to create a biological pacemaker using minimally invasive methods and to show that the new pacemaker suffices to support the demands of daily life," senior author Eduardo Marban, director of the Cedars-Sinai Heart Institute, told reporters at a teleconference call

Marban said their work is also the first to reprogram a heart cell in a living animal in order to effectively cure a disease.

"This development heralds a new area of gene therapy where genes are used not only to correct a deficiency disorder, but actually to convert one type of cell into another to treat disease, " he said.

Healthy hearts without pacemaker hardware depend on naturally occurring pacemaker cells housed in a tiny region of the heart called the sino-atrial node. The sino-atrial node acts like a metronome to keep the heart pulsing at 60 to 90 beats per minute. People with abnormal heart rhythms lose this sino-atrial node function.

In the new study, Marban and colleagues were able to convert a tiny area of heart tissue that does not normally initiate heartbeats into pacemaker cells using a minimally invasive catheter procedure.

They injected a gene called TBX18 into the hearts of pigs with a defective heartbeat rhythm condition known as complete heart block.

The procedure prevented diseased pigs from developing abnormally slow heart rhythms, without the need for an electronic pacemaker, with the protection lasting two weeks.

The findings could help those who have heart rhythm disorders but suffer side effects, such as infection of the leads that connect the device to the heart, from implanted mechanical pacemakers, the researchers said.

They also said in the future the findings could help infants born with congenital heart block.

"Babies still in the womb cannot have a pacemaker, but we hope to work with fetal medicine specialists to create a life-saving catheter-based treatment for infants diagnosed with congenital heart block," co-author Eugenio Cingolani of the Cedar Sinai Heart Institute, said. "It is possible that one day, we might be able to save lives by replacing hardware with an injection of genes."

The researchers said more experiments have to be performed to study its long-term efficacy and toxicity before they can ethically proceed to trials in humans. "If all goes well, we hope to be able to begin trials in humans within three years," Cingolani said.

According to the researchers, some 300,000 electronic pacemakers are placed in the United States annually with consuming health care costs being estimated at more than $8 billion.