Light used to control heart rhythm

Researchers have for the first time used light to precisely control electrical waves that regulate the rhythm of our heartbeat.
Both cardiac cells in the heart and neurons in the brain communicate by electrical signals, and these messages of communication travel fast from cell to cell as 'excitation waves'.
For heart patients there are currently two options to keep these waves in check: electrical devices (pacemakers or defibrillators) or drugs (eg beta blockers).
However, these methods are relatively crude: they can stop or start waves but cannot provide fine control over the wave speed and direction.
Researchers from Oxford and Stony Brook universities set out to find ways to steer the excitation waves, borrowing tools from the developing field of optogenetics, which so far has been used mainly in brain science.

"When there is scar tissue in the heart or fibrosis, this can cause part of the wave to slow down. That can cause re-entrant waves which spiral back around the tissue, causing the heart to beat much too quickly, which can be fatal. If we can control these spirals, we could prevent that," said Dr Gil Bub from Oxford University.

"Optogenetics uses genetic modification to alter cells so that they can be activated by light. Until now, it has mainly been used to activate individual cells or to trigger excitation waves in tissue. We wanted to use it to very precisely control the activity of millions of cells," said Bub.

A protein called channelrhodopsin was delivered to heart cells using gene therapy techniques so that they could be controlled by light.
Then, using a computer-controlled light projector, the team was able to control the speed of the cardiac waves, their direction and even the orientation of spirals in real time - something that has never been shown for waves in a living system before.
In the short term, the ability to provide fine control means that researchers are able to carry out experiments at a level of detail previously only available using computer models.
They can now compare those models to experiments with real cells, potentially improving our understanding of how the heart works.

"Precise control of the direction, speed and shape of such excitation waves would mean unprecedented direct control of organ-level function, in the heart or brain, without having to focus on manipulating each cell individually. This ideal therapy has remained in the realm of science fiction until now," Dr Emilia Entcheva, from Stony Brook University, said.
The research was published in the journal Nature Photonics.