A new technology to stimulate heart muscle cells with low-energy light raises the possibility of a future light-controlled pacemaker, according to a new study.

Researchers at Stony Brook University (NY, USA), developed a tandem cell unit (TCU) strategy, using nonexcitable cells to carry exogenous light-sensitive ion channels which were electrically coupled to cardiomyocytes, producing optically excitable heart tissue. The TCU strategy, which is based on optogenetics, was validated in vitro in cell pairs with adult canine myocytes (for a wide range of coupling strengths) and in cardiac syncytium with neonatal rat cardiomyocytes. A stable light sensitive channelrhodopsin2 (ChR2) expressing cell line was developed, characterized, and used as a cell delivery system.

The researchers were also able to combine optical excitation and optical imaging to capture images of light-triggered muscle contractions and high-resolution propagation maps of light-triggered electrical waves that were found to be quantitatively indistinguishable from electrically triggered waves. The study revealed that optical pacing used less energy, offered superior spatiotemporal control, and allowed remote access.

According to the researchers, the technique could form the basis for a new generation of light-driven cardiac pacemakers and muscle actuators. The study was published in the August 2011 issue of Circulation: Arrhythmia & Electrophysiology.

“Electronic cardiac pacemakers and defibrillators are well established and successful technologies, but they are not without problems, including the breakage of metal leads, limited battery life, and interference from strong magnetic fields,” said senior author Emilia Entcheva, PhD, an associate professor of biomedical engineering. “Eventually, optical stimulation may overcome some of these problems and offer a new way of controlling heart function.”

Optogenetics is the combination of genetic and optical methods to control specific events in targeted cells of living tissue, even within freely moving mammals and other animals, with the temporal precision--on the millisecond-timescale--needed to keep pace with functioning intact biological systems.

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