ScienceHub # 05: Biophysics of Excitable Systems

    In the new issue of ScienceHub, we talked with Konstantin Agladze, candidate of physical and mathematical sciences, professor at the Moscow Institute of Physics and Technology and the head of the laboratory "Nanoconstruction of membrane-protein complexes for monitoring cell physiology" at the Moscow Institute of Physics and Technology about biophysics, modern approaches to studying the heart and how rat cells differ from human.

    What is biophysics

    It is clear that this is the area where two disciplines are combined - physics and biology, that is, when the objects of biology are investigated, but by the methods of physics. Konstantin Agladze prefers that it is physicists who are engaged in biophysics, rather than classical biologists, and preferably physicists who have been educated in Russia or the USSR.
    How can physicists help biologists: study the subtle structures of cell interaction, cell ensembles, understand how they work using the tools of physics and mathematics.

    Konstantin Agladze: “For example, there may be a physical approach to the population. The population dynamics is described by just nonlinear equations. This all correlates very well. For example, the mathematical apparatus correlates well with that used to study, say, processes in excitable tissues (such as the heart and nerve tissue. The small area that we deal with is the study of excitable systems. That is, our laboratory is called "(it has historically been given this name), nanoconstruction of protein complexes to control cell physiology. But in fact, we simply call it the laboratory of physics of excitable systems."

    In the laboratory, Agladze deals specifically with cardiac tissues. To increase life expectancy and avoid heart disease, you need to understand how the heart works.

    K. A.: “What happens to the heart? Excitation waves travel along it and make a very large number of cells work as a single ensemble, pumping blood through the body. What is it? This task, on the one hand, is bionically interesting. There is such a science of bionics, which originates in biological objects and tries to make narrow objects in this way. This in itself is interesting. See how to pump viscous fluids very effectively, for example. But it's not that. And to see why this pumping system suddenly starts to give failures? ”


    An electrophysiological study of the heart, as a direction that arose more than 100 years ago, has now been developed and allows us to understand how excitation spreads throughout the heart. This became possible only after the discovery of the optical electrical determinants of the waves of excitation of the heart.

    K. A.: “We put the electrode on the heart tissue, and we can see that the wave ran under the electrode. But we want to see the entire front of the wave. So we have to put a lot of electrodes. And if we want to see the position of the front at different points in time, then we must put not just a comb of these electrodes, but already a matrix of these electrodes. And if with a good resolution, then there should be thousands of electrodes .

    What breakthroughs were in this area: 20 years ago, dyes were developed that help track the excitation in the cell. And in parallel, cameras capable of seeing these fluorescences were developed. At the same time, the first ones showed the propagation of an excitation wave, the appearance of vortex waves, which made it possible to understand that the concept of rotating vortices leads to sudden death.

    K. A.: “Any attempts at multi-electrode recording required a very thorough decryption, some kind of speculation, that is, extrapolation. And there always arose the question that maybe this is an extrapolator's fantasy. And here it became visible. That is, it turned out to be possible to see it. "

    The second breakthrough was when we learned to make a tissue culture and optical mapping on it. This made it possible to understand

    K. A .: “The question always arises, or maybe the wave runs here so that a special heart, and not because there are such paths? Therefore, it was necessary to learn how to simplify the system. They simplified it, made it a fabric structure. And they saw that there, too, you can see the propagation of waves and see why these waves under the influence of some chemicals lose stability, can break and form harbingers of developing arrhythmia. Further, our job was to go the opposite way. We started to complicate. Then the question arises: well, all the same, this heart is not isotropic, it has a fiber structure. And let's see what happens if we have not just an isotropic, but not an isotropic medium, that is, the cell will come out in one direction, what are the opportunities for spreading excitement there? Here we are tormented by this. This is what we are doing now. Plus, we can now make a controlled three-dimensional system. It’s still quite thin. But still, it’s not just one layer, but several layers of cells, and move in this direction. ”

    The future in the laboratory "Nanoconstruction of membrane-protein complexes to control cell physiology"

    The research prospects are as follows - a transition to rat human cells is needed. Of course, it is impossible to simply get them, but thanks to the work of Shinya (Xinya) Yamanaka, who learned to make pluripotent cells from ordinary cells, you can make them in such quantities as to make artificial heart tissue, and see what happens in human heart tissue.

    K. A.: “On the one hand, we understand that there is much in common between a rat heart and a human one. If this were not common, then cardiac biophysics would not exist. But the fact is that there is a big difference. And we, for example, ourselves, came across this difference. My Japanese graduate student who did this work, used an ordinary Japanese diarrhythmic, gave it to the rat’s heart cell culture, to see what would happen, he didn’t see anything. And when we began to deal with this, it turned out that the very widely used third-class diarrhythmics would work only on human cells, because they have special ion channels that are blocked by these diarrhythmics. But rats do not have these ion channels. It would seem a pretty obvious thing, but it received such unexpected confirmation. I.e,

    New specialists. Who is it?

    Who should do this research at all? Konstantin believes that physicists with good biological training are more likely because the study of excitation waves is a very physical task.

    K. A.: “Of course, the expertise of molecular biologists is extremely important. For example, for working with pluripotent cells and for routine work. Although this is a very complex and delicate process. To differentiate them into cardiac cells, competent molecular biologists are needed in the first place. But for the next stage, physicists need to work with these heart vortices.

    If we talk about specialists who are trained to work in our laboratory, then this is a very difficult question. Because, speaking specifically, let's say, about those guys - my graduate students, who will be the first to defend themselves here at the physics and technology department, these are people who are engaged in the science that maybe a dozen more people in the world are doing. That is, this is not a wide audience. On the other hand, they are excellent specialists in the same fluorescence microscopy, because they had to master it at the highest level. These are people who work great with computerized data collection systems. And these are people who, of course, routinely studied tissue engineering. Therefore, wherever specialists in this area are needed, they can fully work. On the other hand, I have a feeling that in the near future we will have to prove that our method is extremely effective in the selection of medical devices. And I really hope that then it will simply be in demand in most pharmaceutical companies. What is it about? To do this, you need to see how pharmaceutical companies work. Since the successes of molecular biology were very strong and everything descended to the level of molecular machines, in fact now it all works at the level of ion channels. Excitable cells work due to the fact that ion channels work. And when the pharmacists work out something, they look at the effect of the substance on a single channel and say: “Well, we blocked this channel. Lower excitability. And so this medicine will work. ” This is a perspective. After this is proved in these experiments, single cells, animal experiments are underway. ”

    Unresolved issues:

    The main task is to understand, due to what, what happens when wave breaks occur, and how the vortices behave:

    K. A .: “It is completely unknown now, the vortex excitations that cause fibrillation in the end, how much these waves themselves stable. That is, do they stabilize on homogeneity or can they stably exist on their own, being reborn, multiplying and somehow supporting their existence? That is, many things related to the dynamics of these vortices are still unknown in reality. Therefore, there is still a large field for activity. ”

    For fans of the video format, an interview with Konstantin Agladze is available here.

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