'Biological pacemaker' restores heartbeat in pigs

Injecting a gene directly into the heart may be able to replace the need for an electronic pacemaker, according to new research by scientists at the Cedars-Sinai Heart Institute.

Tested in pigs, the minimally invasive gene transplant procedure turns unspecialized heart cells into "biological pacemaker" cells that keep the heart beating at a steady pace.

For people who suffer side effects like infection from implanted mechanical pacemakers, the therapy could be a potentially safer, biological alternative. About 300,000 U.S. patients receive pacemakers every year.

"While electronic pacemakers generally work well, there are people who desperately need a pacemaker but can't get one safely," said Cedars-Sinai Heart Institute Director Dr. Eduardo Marbán, who led the research team, on a call with reporters.

In regular hearts, a tiny, highly specialized region called the sinoatrial node is responsible for initiating the heartbeat like a metronome, Marbán said. In hearts without a functional sinoatrial node, the heart beats very slowly or not at all, which can cause symptoms varying from dizziness in minor cases or cardiac arrest in serious instances.

The method developed by Marbán and his team, detailed in today's print issue of Science Translational Medicine, requires the transplant of a single gene into the pumping chambers of the heart. This site is not typically responsible for starting a heart rate. But the injection of the TBX18 gene turns this part of the heart into one that can beat automatically by converting ordinary heart cells into specialized sinoatrial node cells, which number in the thousands compared to the billions of regular heart cells that exist in the heart.

Using a basic catheter procedure, Marbán and his colleagues injected the TBX18 gene in pigs with complete heart block. Two days after the procedure, the pigs who received the gene had significantly faster heartbeats than pigs who did not receive the gene. The pigs that received the therapy had a stronger heartbeat that persisted throughout the 14-day study.

"In essence, we create a new sinoatrial node in a part of the heart that ordinarily spreads the impulse but does not originate it. The newly created node then takes over as the functional pacemaker, bypassing the need for implanted electronics and hardware," Marbán said.

- see the study abstract
- read the press release

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