11 July 2012

Returnees: Grigory Enikolopov, neuroscientist


<url>Russian-American neuroscientist, professor of the famous Cold Spring Harbor Laboratory (whose head was James Watson for a long time)

Grigory Enikolopov told the "Tape.<url>" about how he works in Russia under the megagrant program, what brain stem cells are, what importance they have for astronauts, what antidepressants are useful for, and why running strengthens not only muscles.

"The tape.<url>": You returned to Russia after you won the megagrant competition. You have already managed to form a laboratory (at the Moscow Institute of Physics and Technology - approx. "Tapes.ru"), purchase equipment, assemble a team? Grigory Enikolopov: Yes, we have been working for seven months.

The laboratory has been formed, everything is going pretty rapidly, people are traveling back and forth, we have established an exchange between the American and Russian laboratories. Biology is an experimental science, it takes a lot of time to accelerate, but in this sense everything is going well so far.

Does FZ-94 bother you when purchasing equipment? Many scientists complain that it greatly complicates their lives. It has become easier for the "megagranters", let's say.

Anyway, everything is moving very slowly because of the huge number of administrative and bureaucratic delays.

Do the topics of work in your Russian and American laboratories coincide? They are close.

They don't match, but they are close – we are studying brain stem cells. It's just that at Cold Spring Harbor we do other things as well - for example, we study stem cells in other tissues as well – not just in the brain. We also deal with the effects of nitric oxide (NO) on other stem cells, as well as NO-related diseases.

As for brain stem cells, the two laboratories have slightly different tasks. But I try to keep the work technically on the same level, so that it is easier to establish an exchange of techniques, exchange of experience, and so on. This is exactly how it was planned when I applied for a megagrant.

You are dealing with brain stem cells that can turn into neurons in adults. However, there is a popular opinion that "nerve cells do not regenerate", that they are all formed once and for all in the process of embryonic development. It turns out that this is not quite true? Indeed, the vast majority of cells in the brain are formed during embryonic development.

But, it turned out, there are a significant number of cells that continue to be produced in adulthood. They are formed from brain stem cells, some of which turn into neurons, and others into auxiliary cells (glial cells).

The path of neuroblasts from the place of formation
in the lateral ventricles (LV)
to olfactory bulbs (OB) in rodents.
Image by Jessica B Lennington,
Zhengang Yang and Joanne C ConoverIn the adult brain, stem cells can be found in many areas, but the production of new neurons at a sufficiently high level occurs only in two.

One area is located around the ventricles of the brain. Those stem cells that begin to divide here embark on a very long journey, almost through half the brain, and end their lives in the olfactory bulb (this is the most important part of the brain that is responsible for the sense of smell).

The process of migration of dividing stem cells from the ventricles to the olfactory bulb is very rapid in rodents – mice, rats, and so on, but it is very limited in humans.

The second area of the brain in which constant neurogenesis occurs (although it drops very much with age) is called the hippocampus, or more precisely, the substructure of the hippocampus, the dentate fascia. In the case of the hippocampus, the story is completely different. The new cells remain very close, within literally two to three cell diameters from the mother cell. So this alone suggests that the two processes are based on quite different mechanisms.

The hippocampus attracts the attention of a large number of laboratories, including mine. This is the most important part of the brain, which is responsible for the formation of memory and, as we are now increasingly understanding, for the control and regulation of the emotional sphere.

The first data on this were obtained many years ago during observations of patients with a damaged hippocampus. It has been shown that if it is damaged, say, by strokes, injuries, neurodegenerative diseases like Alzheimer's disease, then the formation of a new memory suffers first of all. Such a patient retains his old memories, but cannot form a new memory about anything.

Therefore, when it turned out that new neurons were being produced in the hippocampus, the thought immediately arose: maybe these new neurons are somehow connected with the known functions of the hippocampus – memory and emotions?

When did such a paradigm shift happen? After all, the opinion about the impossibility of adult neurogenesis lasted for a very long time – it was laid by Ramon y Cajal. Indeed, Santiago Ramon y Cajal at the beginning of the twentieth century first formulated the postulate that all neurons appear during early development, and no new cells are formed in the adult brain.

Ramon y Cajal is the father of modern neuroscience, and he had just brilliant providences, brilliant conclusions, we owe him a lot. But at that time there were no approaches that would allow him to see the areas of the brain where new cells appear. Since these cells, firstly, are very small compared to the entire mass of the brain, and secondly, there were no methods that could identify them, then he did not see them. And although his postulate is still 99 percent correct, it is important that adults have areas of the brain where new neurons are still formed.

In 1962, that is, 50 years after Cajal's work, Joseph Altman from MIT wrote an article in Science in which he described the results of his work on rodents using a radioactive marker. At that time it was a fashionable, unusual method. He took radioactive thymidine and injected it into rats. Thymidine is a nucleotide, so it is embedded in the synthesized DNA. On the brain slices of such rats, you can see cells with increased radioactivity – those where DNA was synthesized after the injection of the marker. The presence of such cells means that they appeared during division – after all, new DNA is not formed at rest. As we now know, these were the very areas on the walls of the ventricles of the brain and in the hippocampus where stem cells divide.

For a very long time, people did not perceive this idea, and not only because of the psychological barrier. It was difficult to prove that those radioactive cells that Altman saw were really neurons. The first proof of this came only in 1983, and from an unusual side.

There is such a wonderful scientist Fernando Nottebom at Rockefeller University, who deals with songbirds: canaries and finches. By this time, it became clear that when songbirds learn new songs, there should be a massive cell division in special areas of the brain that are responsible for learning. There were a lot of these cells and the experimental model turned out to be successful, so Nottebohm really proved that those cells that are formed in the learning process are neurons. It was difficult, but he succeeded.

But birds are a special story, and we are naturally interested in humans and mammals. It took almost ten years to prove that both in the mammalian brain and in the human brain, most of those cells that divide become neurons. These were experiments with terminally ill cancer patients at the Karolinska Institute, in Sweden. They were also given a labeled nucleotide and, with their consent, the brain was analyzed after death. Thus, it was possible to show that the division of cells occurs in the brain of adults, most of which turn into neurons.

At the same time, in the mid-90s, there was information that the rate of this division can be increased, that it depends on the external environment. For example, the rate of neurogenesis was increased in rodents that were kept in large enclosures, where there were many interesting objects. The same was observed in animals that had to engage in physical activity, or those who were given antidepressants.

Thus, the results obtained on rodents suggested that neurogenesis is really quite powerful in adult animals, and therefore high hopes were pinned on the fact that maybe the same thing happens in humans. And in 2005, an article was published in which a new ingenious method was used to determine the age of neurons based on carbon-14 dating. Do I understand correctly that then these hopes were not destined to come true? No, not really.

The fact is that, as I have already said, there are two areas of neurogenesis in mammals and, it turns out, they behave differently. Increased neurogenesis in rodents in an enriched environment, or when running, or as a result of taking antidepressants – all this concerns new neurons in the hippocampus. The last work of Spalding and Friesen in Neuron (Spalding et al., Retrospective Birth Dating of Cells in Humans), which you are talking about, dealt specifically with olfactory bulbs.

These elegant and ingeniously conducted works allow us to state quite definitely that almost all the neurons that exist in the olfactory bulbs in humans, unlike rodents, appear during embryonic development or in infancy. In adulthood, new neurons are not actually formed there. But, I emphasize, this has nothing to do with neurogenesis in the hippocampus. This is a very important distinction, and most of what is written about in scientific or popular articles when it comes to neurogenesis refers to hippocampal neurogenesis. Therefore, we cannot say that these works have dashed the hopes of neuroscientists, on the contrary.

And the work you are talking about answers other and also very interesting questions – for example, how memory is formed related to the sense of smell. For animals, it has been shown that new neurons are needed to form new "memories" for different smells.

For humans, almost nothing is known about the relationship between the appearance of new neurons and the memory of a new smell, and this article says that in adulthood, neurogenesis practically does not occur there.

But even if it was not possible to detect neurogenesis in the olfactory bulb of a person, it must be remembered that modern man has a completely different situation with smells and sense of smell. Our civilization is developing so that we live in a very scented environment. Our culture eliminates a large number of odors, we live in a very sterile atmosphere.

The reviewers who commented on this article for ScienceNOW (No New Neurons for Smell?) were just saying that it would be interesting to look at the same data obtained not on ordinary people, but on humans… Yes, yes, yes, on travelers, on cooks, on perfumers, and so on.

After all, our entire civilization is trying to eradicate odors, with the exception of a few professions – sommeliers, chefs in restaurants or people who constantly go to exotic places with different cultures and different smells.

That is, if the data about the olfactory bulbs in humans rather suggest that neurogenesis does not occur there, then the situation is almost the opposite about neurogenesis in the hippocampus? Yes, more and more laboratories are working to find evidence of this big idea – the idea that the formation of new neurons in the hippocampus is associated with cognitive functions, that it is necessary for these functions.

Maybe it's not as simple as people thought at first, but there are more and more confirmations of this general idea.

There is a lot of data that suggests that some properties of memory formation – not just worse, but better, but some special properties of it - depend very much on new neurons. For example, the ability to distinguish between similar, but nevertheless different contexts. Relatively speaking, as in "Irony of fate, or With a light steam!": the hero comes to the St. Petersburg apartment, and at some point he begins to realize that, although everything around is absolutely the same, the apartment is still someone else's.

That is, it is one thing to form a memory, and another thing is to understand that although something looks like something else, it is not the same. Let's say you come into a room – everything seems to be exactly the same, but last time there was yellow paint, and now it has become, say, blue. That's why, apparently, new neurons are needed to distinguish such similar, but still different, situations.

That is, such a special memory is connected precisely with the work of the hippocampus, and it is the new neurons of the hippocampus? Exactly.

The fact that some facets, properties of memory formation are associated with the hippocampus is one fact. And another fact is that new neurons are needed for this process, and if you crush the process of forming new neurons, then the subtle sensitivity to the context will disappear.

For example, if we talk about a mouse, it will remember that in a certain cage, let's say, it was slightly electrocuted when it rang, and it will start to freeze when it rings. But if it is then transplanted into another cell, where there is also a bell, but it does not shock, and at the same time the cell walls are of a different color, then it will quickly realize that this is a different situation and will stop freezing. But if you suppress the formation of new neurons, the mouse will learn to associate a call with unpleasant sensations as easily as before, but if it is transplanted into an altered cell, it does not realize that it is already another, harmless cell, and will still freeze when it rings.

So she still sees it as an old place? Yes. It is difficult for her to differentiate between two close, but still different contexts.

"The tape.ru" just recently reported about optogenetic experiments, during which light causes activation of neurons. It was shown there that in a mouse that was in a favorable environment, it is possible, by activating just one neuron, to evoke memories of another environment in which it was electrocuted. Such memory neurons were just in the hippocampus, as far as I remember. The hippocampus of transgenic mice.

The bodies of neurons are colored with fluorescent dyes.
Image from the website nikonsmallworld.comYes, these are very interesting works that once again show the role of the hippocampus in memory formation.

However, the fact that the hippocampus is necessary for memory does not mean that memory is necessarily stored there. This simply means that it is necessary for her and, perhaps, in constant negotiations between the cortex and the hippocampus, memory is formed and stored in this process.

But there is no neurogenesis in the cortex? Practically not.

From time to time someone appears and says: "No, we found it!", and everyone would like to have new neurons there, but usually technical complications or flaws are found that do not allow us to believe in the reliability of such results.

But if neurogenesis is important for the formation of memory and cognitive abilities, can it be stimulated in humans? Is it possible to improve your memory, intelligence, if you run in the morning and drink prozac in the evenings? Yes, we are dealing with similar problems.

The fact is that the number of emerging new neurons drops very much with age, and this is due to a drop in the number of stem cells. This is not an obvious statement, because in other tissues, for example, in the bone marrow, the number of stem cells does not fall by the end of life (although their "quality" worsens).

But in the brain, according to our latest data, the number of stem cells drops very much with age, and it drops even more than the number of new neurons. This leads to a somewhat paradoxical, not very intuitive conclusion that with age, stem cells become more effective than in a young brain. There are fewer of them, much fewer, so they cannot compensate for all the loss. But if we consider the efficiency, that is, how many neurons appeared per stem cell, then it grows with age. This is a rather unexpected fact that we managed to discover.

On the other hand, indeed, there are a large number of different effects, such as various medications, physical activity, electrical stimulation of the brain, which enhance neurogenesis. This is one of the most important areas that we are engaged in. We want to understand at what stage there is an increase in the number of new neurons: how running works, what Prozac works on, how therapeutic stimulation of the brain with electrodes affects neurogenesis and whether it can be changed.

So running still works? Yes, absolutely.

But not quite as we expected. Our data show that physical exercise, antidepressants (for example, prozac), brain stimulation with electrodes, which is now used for the treatment of depression, all this leads to the activation of cells– the "daughters" of stem cells, but not the stem cells themselves. This is important, because with each act of division of stem cells, they disappear, turn into astrocytes.So, we have shown that the increase in the number of neurons formed occurs due to the fact that those daughters that are formed during the division of a stem cell themselves divide on average 2.3 times, and after stimulation, say, 2.8 times. That is, there are more neurons, but the number of stem cells themselves does not change.

This suggests that the scenario is a little less optimistic than we would like, right? But not terrible either.

The number of stem cells decreases with age, but, firstly, they become more effective, and secondly, they still respond to stimulation. At the same time, the old brain in this case reacts even more "grateful" than the young one. It can be stimulated by the same means: exercise, prozac, enriched environment.

If these methods do not act on the stem cells themselves, but only on their "daughters", then maybe some kind of external radical intervention would be more effective for stimulating neurogenesis? Like injecting induced stem cells into the brain directly? Theoretically, this is possible, but I think it is very unlikely that such an approach would work.

The fact is that the injected cells will need to properly integrate into the environment, learn to "live by the rules" and so on.

Rather, I pin a lot of hopes on finding some drugs, some factors that would make the cells already existing in the brain multiply better. Not in a cancerous way, of course, but, say, to undergo two or three additional divisions. This is already four to eight times more new neurons.

We are currently working very intensively on this, and, by the way, part of this part of the research will take place in the Moscow laboratory. Experiments are just beginning, so there is no point in talking about it now.

And what else will the work of the Moscow laboratory be devoted to? One of the main topics that we will be dealing with is the effect of very low doses of radiation on brain stem cells.

We live in a civilization in which we all undergo the same medical procedures, tests, scans, tomographs, and so on. We are flying planes more and more, and thus we also get a small dose of radiation. We are talking about such doses that are harmless enough for humans – they are much lower than those established by regulatory documents. But, nevertheless, the long-term effect of such very low doses on the birth of new neurons and, through this, on cognitive abilities has not yet been studied.

I became interested in this when we wrote a grant to NASA. They are very interested in this, because, as you understand, if astronauts fly far away to Mars, they will be exposed to a different type of radioactive background than we experience here on Earth.

With such long-distance flights, the possibility of cancer due to increased radiation levels was naturally realized from the very beginning, this is understandable. However, due to new data on the possible connection between neurogenesis and memory, NASA is also interested in the influence of the cosmic background on the cognitive abilities of astronauts.

And this question concerns not only two or three astronauts, it concerns us all to some extent, because, I repeat, we are more and more faced with radioactivity. It is clear that there has always been a radioactive background on Earth, and all organisms have somehow adapted to this. By the way, this background is not necessarily bad, it can also stimulate some necessary processes. I don't have any ready–made hypotheses yet - are very low radiation levels good or harmful, I just want to emphasize: there is no ready-made answer here. The grant that we received together with Phys Tech is dedicated to this.

Like everyone else, is your grant for two years? For a little more than two years, but now the possibility of extending this program is being discussed.

Stem cells (green) in the mouse hippocampus (the nuclei of ordinary neurons are red).
This photo, obtained in the laboratory of Grigory Enikolopov, won the Bio-Art – 2012 competition.
Grigori Enikolopov/Ann-Shyn Chiang During these two years, we will do the work that we planned, but it will be a sin to finish it all, because we are just going to accelerate and form an actively working team.

This is true not only for us, but also for any megagrant laboratory. It would be very wasteful to finish it, because now very large funds are being introduced there. Of course, the "hardware" will remain – I will buy microscopes and other devices, they will remain standing. But it will be a shame to lose the know-how and scientific and intellectual potential in two years. But the Ministry is fully aware of this and treats it with understanding.

How do you feel about the idea of creating a megagrant program in general? Quite a lot of criticism is being leveled at her about the fact that two years is a very short time to build a functioning laboratory at all. If I had a negative attitude, I would not have written an application.

We are obliged to do everything we have stated in these two years, but, of course, it would be right to extend this program so that the group could fully get back on its feet and work at full strength.

Are there any positive expectations from the Ministry of Education and Science in connection with the appointment of a new minister? This happened recently, so it's hard to say yet.

In principle, most of the "megagranters" talk about the friendly and attentive attitude of those people from the ministry who lead this program.

The difficulties that scientists face arise, rather, because of the general infrastructure. My communication about grants takes place mainly at the institute level, not at the ministry level. There are absolutely wonderful people there who help me a lot and without whom things would not have progressed. But the general bureaucratic infrastructure makes everything difficult: quick purchases of reagents, the ability to directly buy the necessary reagents and devices, and so on. In general, it's all very complicated by the rules, but, I repeat, those people with whom I communicate are just trying very hard to help. Rather, the overall infrastructure is very rigid, rigid and difficult.

Do you feel more freedom within the MIPT than you could get, for example, in the RAS? I don't think so, but it's hard to judge – the holders of mega-grants are in privileged conditions, primarily from the point of view of the huge amount that we received.

Megagrants by megagrants, but the main thing is that "ordinary" good laboratories should be supported by much larger funds and in much larger numbers. Because there are a large number of wonderful groups that often sit on dry rations.

In the story of megagrants, many find such a subtext that can be interpreted as "we will invite the Varangians to raise science, because we have nothing left here." Do you have a feeling that there is still something left in Russia in terms of science? Of course, there are very strong groups in Russia.

But you see, I am the same Varangian, so it's not for me to say whether this is true or not. I think it's good that people from abroad have been invited, this will give an impetus to the development of science, regardless of whether we are talking about people who grew up in the Union, like me, or people who have nothing to do with Russia.

But, of course, it is even more important that all science is maintained at the right level, so that those talented people, groups who are already working or who have great potential are also maintained at a decent level. Megagrant is just one of the mechanisms of pushing science.

It turns out that you are quite optimistic about the situation in Russian science compared to many of those who are now looking at it from the inside. I would probably also look pessimistically if I looked from the inside – they don't give me money, I'm on rations, all these RFBR grants are obscenely small.

I'm not saying that Russian scientists should be happy, on the contrary, I'm saying that their research is still being supported at a completely inappropriate level. But it seems to me that now something is beginning to change in relation to science, and my view is cautious optimism.

Alexander Ershov talked

Portal "Eternal youth" http://vechnayamolodost.ru11.07.2012

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