What if something as simple as light could be transformed into a way to power the human heart?
A research team at Stony Brook University has been developing a new technique in optogenetics, a combination of genetically modified cells and light used to control specific events in living tissue.
The research team has calculated that the new light-based system might require lower energy for stimulation, and if applied to pacemakers, “may potentially translate to life-long batteries.”
Light stimulation also offers a method to induce a more focused stimulation as opposed to the wider and generalized stimulation of an electrode. The non-viral approach also allows for donor cells from a patient’s bone marrow or skin to be cultured and modified to respond to light, reducing the possibility of an immune system rejection of the tandem cells.
Their methods involve a tandem unit cell (TCU) strategy that uses light to control excitation and contraction in cardiac muscle cells.
The research team, led by Emilia Entcheva, associate professor in the departments of biomedical engineering, physiology and biophysics, and the division of cardiology in medicine at Stony Brook University, has recently published their findings in the online edition of Circulation: Arrhythmia & Electrophysiology: “Stimulating Cardiac Muscle by Light: Cardiac Optogenetics by Cell Delivery.” The lead author of the study is Zhiheng Jia, a biomedical engineering Ph.D. student from Entcheva’s lab.
Ira Cohen, lead professor of the department of physiology and biophysics, director of the Institute of Molecular Cardiology and member of Entcheva’s research team, explains that it was the combination of all those involved that led to their success.
“A good idea can be executed if you have a good team in place that works seamlessly together and in this case it did,” Cohen said. He and Entcheva worked closely withPeter Brink, professor and chair of the department of physiology and biophysics.
Originally, Entcheva’s lab experimented with different transfection techniques, such as viruses, to bring a gene, known as ChR2, capable of coding for light-activated ion channels, into cardiac cells. Upon collaboration with Brink and Cohen, a more effective, non-viral strategy was formed: TCU. The TCU strategy involves the use of cells that have been engineered to emit an electric charge via ChR2 in the presence of light. These cells are coupled together with cardiac cells, allowing signals to pass between them. When light is flashed, an inward current is generated and spread from cell to cell, causing the cardiac tissue to contract as it would for a heartbeat.
“A group is more than the sum of its parts,” says Cohen who, along with Zongju Lu, a research assistant professor in his laboratory, was responsible for testing the light-sensitive ion channels of the ChR2 modified cells. Brink and his colleague research assistant professor Virginijus Valiunas studied the connectivity of the ChR2 modified cells with cardiac cells. It was found that light-stimulated heart muscle contractions were indistinguishable from electrically-stimulated contractions.
“In a nutshell, we have a person with an idea and the drive to execute the idea,” Cohen said. As of now, the new technique is viewed as a research tool to study how heart excitability can be controlled and what is necessary to control cells. According to Cohen, a future application may make it possible to terminate cardiac arrhythmias.