Аuthor: Аibulova Diana
Editor: Аibulova Diana
Electric pacemakers save many people from life-threatening conditions: according to statistics, more than 3 million people around the world carry such devices - their use is associated with certain inconveniences. A pacemaker, or an artificial pacemaker, helps restore normal heart rate and rhythm. In order for the rhythm driver to function properly, his electrodes need to be inserted into the heart tissue, the wires from them are connected to a pulse generator, which is inserted subcutaneously.
Over time, the pacemakers have improved: their size is smaller and the electrode wires are thinner. However, all the above mentioned advantages do not cover the fact of the need for periodic battery replacement. In addition, electrodes with wires that reach to the heart can wear out and need to be changed from time to time.
Udi Nusinovich and Lior Gepstein from the Israeli Institute of Technology "Technion" offered a kind of model of pacemaker, which has no wires or electrodes or batteries, and which works in the literal sense of light. In fact, there is no stimulator in the form of an external device: the researchers introduced an optogenic modification into the heart cells, which allowed to control heart beats. The general sense of the optogenetic methods is that a gene of a photosensitive protein is introduced into the cell - such a protein, embedded in the cell membrane, in response to a light pulse opens ionic channels in the membrane. And as we know, it is the redistribution of ions on both sides of the membrane that creates the electrochemical pulse. Optogenetics has found the widest use in neurobiology: by introducing a light-sensitive protein into the neuron, we can randomly generate a signal in the chain of neurons using light signals.
But the heart rhythm also depends on electrochemical impulses (remember that although the heart has autonomic nervous system fibers, some special myocardial cells can generate rhythmical signals themselves, forming the so-called conductive system of the heart). And there is nothing to prevent the optogenic mechanism from entering the heart.
Researchers used a special "domesticated" virus to inject the algae light-sensitive protein ChR2 (channelrhodopsin-2), which reacts to blue light, into the ventricles of rat hearts. For single celled green algae like chlamydomonade, this protein helps to look for more illuminated areas. In an article in Nature Biotechnology, the authors write that they could adjust the heart rate of the animals with blue flashes. The virus allows you to deliver the protein to a variety of different areas of the heart muscle, so you can control the heart with greater efficiency, because the external signal here respond to many cells from different places.
You don't need any electrodes to "turn on" the optocouplers: the blue light from outside, although it penetrates quite badly through living tissue, can still reach the heart. But only if we are talking about a rat. In a larger animal, not to mention human, the heart lies deeper, so you need to think about how long the light wave can reach it, and therefore what kind of light-sensitive protein is needed. Here, the red and infrared regions of the spectrum could fit, and if it comes to experimenting with primates, these are the waves that will be used.
It is worth noting, however, that there are other approaches to creating a wireless pacemaker. However, despite their existence, the optogenic approach looks the most radical, humane and convenient, because there is no need to implant electrodes into the heart tissue.
