Electrical signals in the heart are responsible for regulating its pumping action. Investigators from the German Center for Cardiovascular Research (DZHK) have for the first time succeeded in visualizing these signals in the beating heart. To do so, they use a fluorescent protein which they inserted into the genome of mice.
The protein, a so-called voltage sensor, emits light when the heart muscle cells are electrically stimulated. The method was originally developed in nerve cells in cell culture and is meanwhile increasingly used to map electrical activity in living organisms. Investigators have long been able to record the electrical activity of cells in culture with the help of voltage-sensitive dyes. These dyes emit light depending on the membrane potential of the cell, however, they are often toxic.
A team of researchers led by Wolfram Hubertus Zimmermann from the University Medical Center Göttingen have, for the first time, genetically engineered mice so that they form this one non-toxic voltage-sensitive sensor in the cells of the heart muscle. Using high-resolution camera systems and fiber optic cables the investigators are then able to produce a cardiogram of the electrical stimulation in the beating heart.
The researchers hope this will lead to a better understanding of cardiac arrhythmia, among other things. By carrying out experimental simulations they were able to demonstrate that the sensor can, in theory, also be applied in humans.
Sensing Cardiac Electrical Activity with a Cardiomyocyte Targeted Optogenetic Voltage Indicator, Circulation Research 117:401-412 (August 2015).