Working their way towards energy-efficient pacemakers that use light pulses to control the beating of the heart, scientists at New York's Stony Brook University recently developed optogenetic heart tissue - it contracts when exposed to light. More specifically, they took donor cells that had been modified to respond to light, and coupled them to conventional heart cells. A team from California's Stanford University, however, has now created actual optogenetic heart cells.

The researchers started by inserting DNA encoding a light-sensitive protein called channelrhodopsin-2 (ChR2) into human embryonic stem cells. These were then transformed into cardiomyocytes, the cells that cause the heart to beat by contracting. When the cells were exposed to a specific wavelength of blue light, the ChR2 caused tiny channels on their surface to open, allowing electrically charged sodium to flow in. The cells proceeded to contract, as the presence of the sodium ions is what would cause regular cardiomyocytes to contract under normal conditions, also.

Using a computer model, the scientists determined at which points on the heart the pacemaking cells should be injected, in order for it to contract in a natural fashion. A pacemaker emitting pulses of the proper wavelength of light would need to be located either within the heart, or in its immediate vicinity.

Light-based pacemakers should theoretically use less battery power (so they could stay in longer), be more reliable, and wouldn't incorporate traditional pacemakers' electrodes, which can cause damage to the heart tissue in which they're implanted.

Although such devices may still be years away, Stanford project leader Oscar Abilez stated the optogenetic heart cells could also be valuable for research.

The team's findings were published today in Biophysical Journal.

The video below shows one of the pacemaking cells responding to light.