| 1 | California Institute for Regenerative Medicine | Neural Stem Cells in the Adult Human Brain: Spotlight on Basic Researc... | 14579 | 127 | 2 | 53.9 | positive | 23:55 | Our second speaker is Arturo Alvarez-Bullia. Arturo is a professor of neurologic surgery and a principal investigator in the brain tumor research center at the Eli and Edith Brode Center of Regeneration at UCSF here in San Francisco. Arturo received his PhD degree from Rockefeller University where he continued his post-doc research and training. He has an international reputation in his work in developmental neuroscience and stem cell neurobiology research. His research includes interest in the mechanisms of production of different types of adult brain cells including neurons and the possible connection between these progenitors and brain cancer. This includes research and neurogenesis of the adult mammalian brain, the assembly of the brain, brain tumors and repair and the ontogeny and phylogeny of behavior. His expertise encompasses the field of developmental biology, developmental neuroscience, neurobiology, molecular and cellular neurobiology and learning and plasticity. He's an innovator and inventor as well as a phenomenal scientist. Dr. Alvarez-Bullia has designed a device for mounting tissue sections on histological slides, a digital stereo-taxic apparatus for mice and songbirds, a computer-based mapping system for tissue sections and multiple fluorescent-staining techniques. Please join me in welcoming Dr. Alvarez-Bullia. Thank you so much. It's really a pleasure to be here and to give you a little bit of my views of how in my own experience, really basic science makes a huge difference and actually can save us time to go to the clinic. I've been in this field of neural stem cells for about 25 years and I have witnessed with admiration and also surprised sometimes how the field has grown and actually taken a whole new level of interest from the public. We began this, actually, we were just basically interested in the basic mechanisms of development and especially of formation of new nerve cells. I actually have admired Earth's work for many, many years and I wish we had the ability as in a liquid or tissue like Earth has of transplanting cells and been able to reestablish whole lineages in the beautiful way that he has done. But without working the brain as is the case for many other solid tissues, we have a huge challenge and it's not only the ability to generate the appropriate cells but then the problem of integrating those cells into functional circuits in the case of the brain or plugging them in a way that they can benefit disease. And I am actually, even though I think it's a huge challenge, I'm actually very, very optimistic that this is going to happen and it's not going to happen very far away from where we are now. So the brain is basically formed by three cell types, that you have them illustrated there and all of them I think are going to be target for some kind of disease and cell therapy. The top ones are the most frequent cells in the brain, they are the astrocytes and they are very interesting cells in many ways. The middle cells are the neurons, the nerve cells that actually form the circuits and the bottom cells is the cells that we are learning more and more about them. They were thought to be originally very related to the top cells but they are actually now many, many studies that suggest that they are much more related to neurons than to astrocytes and they are colloligo dendrocytes. And in the words of Cajal, they were the third element, he was disputed the idea that these cells existed for many years but these cells are essential for myelination and they are probably going to have a very important role in cell therapy. These kinds of cells are attacked in multiple sclerosis and actually there are trials ongoing to begin using these cells for transplantation, the progenitor cells for transplantations. So the cells that I am most interested in are the middle ones because they are the most challenging and because they are the cells that die in actually many diseases. These cells actually were thought not to be forming adulthood, they were thought to be formalian deembreon and actually the progenitor that come from that NE that's the neuropeethyl cells that gave rise to them were thought to disappear during development and were gone by adulthood. So it was widely spread 25 years ago and still studying some schools and impressing some textbooks that you are born with the number of neurons that you have and then anything happens is just cell death and loss of neurons. So these are actually these cells and you have an illustration from Ramonika Halt who actually defined these cells as single elements on the left. These are these cells that die in many diseases. In the case of heart and stones, Alzheimer's, in epilepsy and it is likely that defects in the formation of these cells are death of a specific population of these cells also responsible for other psychiatric diseases like autism, schizophrenia and depression. So neurons are largely formed during neural development and one very important concept to understanding the solid tissue that is the brain is that they are produced in a sequential manner, sort of forming a pyramid where cells are building on top of other cells. So when you lose some of these cells become very difficult to think how you are going to be able to replace cells that were born years ago when you were an embryo and that replacing those cells in a way that they can remake the connections and reestablish the kind of circuitry that slows in patients. But one thing that happens when these cells are born is that you create imbalances within the brain so that some circuits become hyper excited at the expense of these cells that were normally regulated in those circuits and that is very clearly happening in Parkinson's the C is an epilepsy, it is perhaps easier to understand an epilepsy where the loss of some inhibitory neurons is sufficient to create a hyper excited region especially in the hippocampus that then triggers four side of seizures that then spread throughout the brain. So what we do with pharmacological intervention is try to ameliorate these imbalance by putting drugs that bring back neurotransmitters that are low and by creating that environment you ameliorate these symptoms but you are really not curing the disease. So I believe that all of these loss of cells diseases require a cell therapy and I am very very enthusiastic that this is really going to happen and you will see some of the ways that we think that is going to happen. Now the challenges are that during development these cells are formed by a complex process that involves progenitors, incredible journeys of young cells migrating through the brain to get to the right places and you will see why these migrations are required and then the differentiation and integration of these cells into a appropriate circuit. Each one of these I think is a challenge and I will try to convince you that the last one in terms of cell therapy is a very, very important challenge and sometimes we should begin there then I will start thinking about progenitors and generating the right cells when we don't have a way of putting those cells back in the disease case. So I came into the field through a very interesting phenomenon and it is the discovery that some neurons do continue to be produced in the adult brain and this created an incredible hope and actually it is a field that took about 30 years to change the way people were thinking and I won't go through the details but it was discovered that actually germinal centers, sorry, germinal centers do exist in the adult brain that low neuronal migration can actually occur in adult brain and takes cells to vary these locations and then actually some cells do integrate and form circuits within areas of the brain that are already functional and this is something that we still do not understand because these circuits are already you know working yet you are taking some cells away and plugging new ones. So all of these discoveries, even before this field exploded like exploded, triggers some people to think that this really should change the way we think about the brain and fix the idea that everything is fixed, everything is terminated, nothing can change. So in New York in actually 1985 there was a conference in the Walghar Historia Hotel called Hope for Neul neurology where some of these ideas were pushed forward and actually one of the ideas that was pushed forward is that the brain might have itself the progenitors that it requires for cell repair so the idea of brain cell required was brought there and the idea that you could introduce and replace cells within circuits that have lost neurons due to the C-cell which are trauma. So there was a huge interest in this process and I'll tell you just very briefly because isn't this is not a basic science talk, how this happens in one part of the brain that we've been studying in a lot more detail. So the largest germinal region in the adult brain and this is a roden brain and in light blue you see the walls of the lateral ventricle, the cavities that are filled with spinal fluid inside the brains lies the largest reserve of these germinal cells in the adult brain in the neural stem cells and most of these cells give rise to neurons that migrate rosary to that place where you see the spots in the front that is the olfactory bulb or region that process of function and their cells are continuously replaced and I could we could go at length why these cells are continuously replaced there. The other region where near genus occurs the hippocampus that little V group like a structure where the unures are born very close to where they would work and those cells actually are very important for things like memory and depression and other processes. So there's a lot of interest in these processes. So one thing that actually trigger a lot of interest is that from the walls of the lateral ventricle you could isolate cells that have the qualities that are just mentioned of cell renewal plus differentiation into those three main cell types neurons, astrocytes and oligodendrocytes and these are usually called nearest fears and these triggers even more exciting in the field because then people said well not only we have these cells in the brain but we can induce them to grow in very very large numbers. Well we also then over the years learned which were these stem cells and working the laboratory by a student Fiona Dodge identified those blue cells as stem cells more recently some one years a day has found that those cells have epithelial characteristics they both touch the wall of the ventricle plus the blood vessels and they interact closely with the cells around them creating a niche for near genesis. We went on to learn also that similar cells do exist in the adult human brain on the walls of the lateral ventricles and you can take these cells in the neutron, mirror steers and grow them so the excitement can grow and you know these cells are going to be really wonderful and maybe able to replace cells that die from the seas. We also learned that cells can migrate incredibly long distances and as I told you in the beginning this is a requirement to repair brains because you need to get these cells to the right place to get incorporated into those circuits that have lost cells and this is one process that was described also in the lab years ago called chain migration by which cells you know accumulate along each other and move over very long distance at very fast speeds. Plus at the very end we could follow these cells and we could find that they would form beautiful neurons with their processes and forms synapses into the circuits where they get integrated and one of the amazing things that these cells could not only form one type of neuron but actually could form at these six different types of neurons that have different morphologies and different connectivity and different expression. So again the hope was building up and very big claims were made during the 90s there were papers all supporting this idea that some ventricular zones were cells were going to be able to cure Parkinson and it was proposed at TGF might induce a panninurgic differentiation of these cells, is this cells like some close to this triatum it would be wonderful cells for replacement of the panninurgic cells within that region. The same thing for Huntington it was suggested BDNF and Noggin would induce the replacement of these cells for stroke even without giving anything it was suggested that giving a stroke close to where these stem cells were would induce these cells to go to the stroke side and replace the cells that had been born and even there was suggested that some of these cells could go into zero cortex and form long projection neurons that go all the way down to the thalamus or to the spinal cord. So this was really surprising and it was created the idea during the 90s that we have cells in our brains that are capable of repairing cells depend on the environment so these cells are able to read out what's needed and somehow magically they turn into these cells that fix the disease. So here I think is where very important role of basic science comes in. If you look carefully both in work that we had done in the lab and others, if you take cells from the subentricular zone that thin layer and you breath them back into the subentricular zone, these cells give beautiful cells that go to the olfactory bulb just like they do normally. But if you take these cells and put them in hippocampus, cortex, cerebellum or estriatum, all science where people wanted to repair, they don't differentiate into neurons, they largely differentiate into astrocytes and the few neurons that you get are actually neurons that look very much like those that you get in the olfactory bulb. You don't get these cells that you wanted to replace in those regions. So basic science began telling us that we should be a little bit more cautious and that there might be something very basic about these cells that we just didn't know yet and actually a clue was there from the very beginning. Cells are not born and some fortunate they have a point here but you see that all that blue area is a very large germinal area, it occupies millimeters, it's a big fraction of the adult brain. You don't need only a very small fraction of that area to generate sufficient cells for the olfactory bulb where cells are normally replaced. Yet cells were born to one of that very vast area and we didn't know why. It was amazing because some of the cells way back close to the hippocampus actually have to migrate many more millimeters to get to the olfactory bulb. So all of that hope was going on while a very important piece of evidence was already there in our noses and really it was basic science that solved the problem. And the solution was that even though there were stem cells throughout that wall, stem cells within different regions of that wall were different and there were stem cells because they were able to be raised to oligod, the exercise, astrocytes and neurons. But when it came to make neurons, each side was peculiar. Each side had their own taste of what kinds of cells they wanted to make. So cells in the front actually made those orange cells in the surface of your olfactory bulb and so there was a beautiful map of organization of stem cells within that wall. So what we learned is that the neural stem cells actually are multipotent, they can give rise to multiple lineage, they can sell remu but they are heterogeneous in terms of the types of neurons that they make. Actually we went on to learn that these cells are actually determined during development by a cell autonomous process and we know this from transplantation of cells from one side to another. So I think this was a very important lesson that the cells just like that, I don't think are going to be just useful for brain repair like people were claiming. And if it wasn't for basic science, we could have lost millions of dollars and a lot of effort just trying to make these cells just like they were to do what they needed to do. Yet I think there was something important about these that is very important for therapy, but again basic science was telling us that replacement could happen, that migration could happen, it was just a matter of finding the right cell and that these cells were not going to be the cells or at least directly where they were not going to be the right cells for repair. So the view that emerged is that stem cells are actually coming in different colors and each one produce different types of neurons and that's why you need this long migration because you need these cells then to get to the appropriate places yet they're producing very specific factors within the brain. These reverberates on a lot of basic work, some of which has been done on Pioneer here at UCSF from the work of John Rubenstein and many others, especially at Columbia University, showing that the brain, that germinal epithelium is subdivided into little domains, little territories, specialized factories for the production of different neurons. So within those areas there might be cells that might be useful for repair and that's what we have been doing during the last 10 years, looking for the right cells for repair. And it turns out that we think that ventral region, you see the blue region, the lower partners to the red one, there is a specific domain of cells that produce all the inhibitory neurons for the cerebral cortex and these are very important cells for therapy. So these cells actually migrate from the MG and invade the cortex in an amazingly long migration in the embryo and form all the inhibitory circuits that actually shape that cortex to function throughout life. So we then found, a rather student in a Victor lead that's now Professor at Columbia found that you could take these cells out from the MG and graph them into postnatal animal, including an adult animal. And these cells did exactly what they did in the embryo, they migrated and they incorporated into circuits. Now these works, unlike other neurons, because these interneurons are the last cells that come into the circuits are the top of the pyramid. So I think these cells are likely to have a very important function in therapy. So you can see the difference in behavior between three different populations of cells. In the left you have the cortical progenitors and they stay put like many people have described in graphs that really do not integrate. On the center you have another germinal region called the LG and these cells are very good at giving the migration going to the olfactory ball but when you put them in cortex these cells really do not disperse and do not integrate. And in the right you have the amazing behavior of the MG cells that actually disperse anywhere that you put them in cell and form this inhibitory cells. And actually the picture is just remarkable. This is 30 days after transplantation into an adult animal and you can see that these cells have migrated and they just look like normal cells, normal inhibitory cells. So the point I want to make here is again basic science is guiding us to the right cells that are going to be appropriate for repair. And now we have to find how we can modify these cells or how we can use them as they are for fixing disease brain. And this is something that we are doing at UCSF in collaboration with a group that we call the UCSF MG group that includes Arnold Cricks thing. This is called Baravan and John Rubenstein. So we are using these cells or trying to use these cells to replace cells that are lost during different diseases. And I can tell you that actually these cells are incredibly good at making cortical intern neurons. You have here the cortex of a mouse. On the right side all of the red cells have been grafted. We can add up to 30% of cells and you can see how beautifully they have this person throughout the cortex. And actually the green cells are the host cells. So the host cells are not affected by the incorporation of the new cells. We have preliminary data actually published this month suggesting that actually transplantation of these cells can greatly ameliorate the seizure activity in an animal model of that's actually a human relevant disease, maybe one mutation that affects excitability in neurons and produce a seizures, very severe seizures that are not killing the animal. Well these animals the degree of the size of the seizures and the frequency of the seizures is greatly ameliorated. So this is one of the things that we are very interested in doing. So with this I just want to end by telling you what I think that basic science is doing for us. I think that cell therapy will happen in the brain and will actually bring us a totally new world of therapeutic intervention that we cannot achieve with pharmacological intervention because neurons know how to tickle other neurons and they know how to integrate into the circuits. But we need to solve the problem of cell birth, migration and integration into adult tissues. So I think it's better to start at the end on cells that we know how to integrate and then work backwards and produce these cells specifically and that's something that we're not trying to do with the MG cells. So as I said one of the biggest challenges is achieving anatomical and functional integration of grafted progenitors. This is partly now a problem of basic science but something that probably are ready to move into a larger species but at least we needed the beginning with the basic science information. We need to select the right cells and for this we need to develop ways to develop these cells directly from large sources like IPS cells or neural stem cells. And something that we know very literally in which I think CRM could play a big role we know very little about human brain development and I think this is true for many other tissues. So we're in very many things from what we have learned from Rovens but I think there's a big column that's what I put in red that this is something where again basic science could guide and save us in 12 amount of money in terms of knowing some very basic things that could happen relatively quickly in terms of the molecules and the regions that are involved in developing structures in humans in order to make the right move for the translation. So I would make the point again on translation and basic science go inside by hand, they actually go hand by hand. It prevents premature heavy investment on approaches that are not likely to work and I think this is something that we're going to see one time and again in this stem cell field. And I think they're going to guide us to new approaches. I think the revolution of IPS cells as we see it as a technique to make the report in cells is just one step in a long sequence of basic science including the discovery of of Oc4 which was a basic science discovery of SOX2 and many other genes that are involved in the reprogramming of cells. And I think there's many of these clues that are essential and if you just push immediately to translate you're going to miss the opportunity to invest just a little bit more to give the right clues to get the right things solved. So that's what I wanted to tell you today. Thank you. Thank you Arturo. I think everyone would agree that our two speakers have really hit the mark on the spotlight and not only told us what basic science can do but hopefully re-energized all of our producers to get to work on the RFA that we'll be addressing later this morning. To ask everyone here just to thank our two speakers again for a wonderful time. Thank you very much for an extraordinary session on basic science. I'd like us to convene immediately. We have a challenging session and it is remarkable. The clear and continuing role in new discoveries, startling discoveries at times that basic science can bring us. Thank you. | ↗ |