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Light-powered hearts?

With a blue laser and a swarm of fruit flies, researchers have put a new spin on the phrase "light of my life."

Adopting a technique used to study brain cells, researchers at Harvard Medical School and Lehigh University in Pennsylvania have manipulated the heartbeat of fruit flies using bursts of light. It's a tentative step toward what could be a noninvasive human pacemaker that operates with light instead of electricity.

The method, described this month in the journal Science Advances, employs a new technique for imaging fruit fly hearts over time. It could power a new wave of heart development studies and provide a platform to test how therapies like pacemakers affect growing hearts.

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In fruit flies, "we can stimulate the heart without even touching it," says Chao Zhou of Lehigh University, senior author of the study. "It's a completely noninvasive procedure."

In the past, researchers used light to control heart cells during open-heart surgery in mice and in young zebrafish, before their tissues thickened and prevented light from reaching the heart.

In fruit flies, however, the heart is close to the surface of the animal's skin, so it can be bathed in light without surgery and during adulthood. And the insects have similar early stages of heart development to vertebrates, including humans, making them a good laboratory model.

The procedure relies on genetically engineered fruit flies bred by Airong Li at Harvard. By introducing a gene for a light-sensitive protein into the heart cells of the flies, she was able to make the heart beat in response to pulses of blue light. At Lehigh University, Zhou and colleagues developed a noninvasive, high-speed microscopy system to pace and view the beating hearts over time. Putting the two together, they were able to observe and manipulate fruit fly hearts throughout stages of development.

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Using this method in a separate study, the team discovered that the heart of an immature fruit fly actually stops beating for nearly a day, yet the fly is still alive and develops normally.

"The attraction is that you can do this over time and study the heart function in a live system," says Emilia Entcheva, a biomedical engineer at Stony Brook University in New York, who was not involved in the research. "It's a great basic science tool."

For now, the technique could be used in medicine to measure how pacemakers and other pacing therapies affect heart development, but a light-driven human pacemaker remains decades away. The technique requires gene therapy, inserting a stretch of DNA into heart cells, which is still considered risky in humans.

MEGAN SCUDELLARI