A single gene, inserted into the apex of the heart, can convert normal cardiac muscle cells into those that control its electrical function, a study found.

The findings from laboratory experiments and work with guinea pigs are a step toward creating a “biological pacemaker” for humans with failing hearts, said Hee Cheol Cho, director of cellular electrophysiology at Cedars-Sinai Heart Institute in Los Angeles. Almost 10 percent of muscle cells exposed to the gene started spontaneously firing, behaving the same way as the rare pacemaker cells, the researchers said.

It will be years before doctors may be able to use the approach to treat people with weakened hearts who currently rely on electronic pacemakers, Cho said. Additional studies in larger animals are needed to confirm the results and ensure the therapy is safe and lasting for humans, he said. The findings appeared Sunday in the journal Nature Biotechnology.

“This is the culmination of 10 years of work in our laboratory to build a biological pacemaker as an alternative to electronic pacing devices,” Eduardo Marban, director of the Cedars-Sinai Heart Institute, said in a statement.

Previous work that focused on electrical currents allowed heart muscle cells to beat, though they didn’t fully behave like pacemaker cells, the researchers said. Cho compared that approach to adding an external motor to a bicycle. The addition removes the need to pedal, though the machine is a still a bicycle.

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“In this study, we discovered that this gene could reprogram all major parts of the heart muscle cells to those of native pacemaker cells,” Cho said. “The bicycle transformed into a Harley.”

The heartbeat starts in the sinoatrial node. It is a small structure located on top of the right atrium that contains fewer than 10,000 pacemaker cells, a tiny portion of the heart’s 10 billion cells. When the pacemaker cells fail to generate electrical activity, either because of age or disease, the heart muscle cells used to create contractions lapse into inactivity.

Patients typically rely on pacemakers from companies including Medtronic Inc., Boston Scientific Corp., and St. Jude Medical Inc. Pacemakers in general are limited because they run on batteries that must be replaced, Cho said. Patients can also develop complications, including breakage, damaged wires that connect the devices to the heart, and infections, he said.

“All these problems could be solved by a biological pacemaker, which is microscopic in scale and free of all hardware,” he said.

Copyright 2012 Bloomberg News