[intro music]
Host – Dan Keller
Hello, and welcome to Episode Seventy-five of Multiple Sclerosis Discovery, the podcast of the MS Discovery Forum. I’m Dan Keller.
Today's interview features Elaine Kingwell, a research associate at the University of British Columbia in Canada. She and her colleagues have gathered and recently published incidence and prevalence figures for people with MS in the province. I spoke with Dr. Kingwell at the ECTRIMS meeting in Barcelona in October to find out the reason for the study and to explore the changing trends she found and their significance.
Interviewer – Dan Keller
What prompted you to do this study?
Interviewee – Elaine Kingwell
In British Columbia, we know that Canada has got a high incidence and prevalence rate of MS, but we don't actually have the numbers, so we've been doing a lot of research on MS in British Columbia for many, many years. But we don't have the incidence numbers for BC, and also the prevalence is out of date – the estimates that we have – so it really was time to get an idea on how many people we have in BC. And also, we wanted to look at change over time, and we have access to some amazing administrative databases in BC and also had some algorithms that we could use that have been validated, so that we could identify people with MS in the databases.
MSDF
Why are these numbers important?
Dr. Kingwell
It's important for lots of different reasons. For instance, it's important to monitor trends over time. We're able to do that in BC, because we have data going back several years. And so, it's important to see if populations are changing, so that we can get some clues about whether environmental factors might be changing. And also, for the prevalence estimates, it's important to know how many people have MS in the province, so that healthcare planning can be done wisely and resources.
MSDF
How do you go about looking at this?
Dr. Kingwell
So as I mentioned, we did use the health administrative databases in BC, which are big databases that collect data on the whole population. A number of different databases were combined, including hospital admissions and physician visits. It's all claims data, so that when someone goes to see their physician, a billing claim gets put in with their diagnosis. So we use these codes to identify people with MS. And we basically estimated the number of people with MS [over] several years – one year at a time – so that we could look at change over time for prevalence. And we also estimated the incidence, the number of new cases each year, starting in '96 right up until 2008.
MSDF
What did you find in terms of incidence and prevalence?
Dr. Kingwell
Well we found the incidence and prevalence are both high. The incidence was around 7.8 per 100,000 per year, and the prevalence was around 180 to 200 per 100,000 in 2008. So they were both high, what is relatively high compared to other places in the world and similar to rates that have been found in Europe, in Northern Europe, and other parts of Canada, as well.
MSDF
And the prevalence is increasing over time?
Dr. Kingwell
Yeah, we found that it increased quite significantly by about 4.7% per year, so a big increase. It also shifted in the predominant age of people, so that the peak prevalence age was around in the mid-40s in the 1990s, and it's now shifted up into the mid-50s. So the population of people with MS is getting older in BC. We also saw with incidence … quite differently, the incidence was not changing over time, so it stayed relatively stable; it did fluctuate as incidence always does. But over time, on average, it stayed the same.
MSDF
Are those two pieces combined—increasing prevalence and older age—good news?
Dr. Kingwell
I don't know if any of it's good news. It means that we have an older population that are probably requiring more care, as they get older, for the MS, as well as, of course, comorbidities they may have. So, it's certainly something that healthcare planners need to be aware of. And we have an aging population, in general, in Canada, as we do in other parts of the world, but we have a lot more people with MS at an older age.
MSDF
But doesn't that mean they're surviving longer?
Dr. Kingwell
That's the good news part, yeah. And it does mean that, because we're not seeing a change in incidence, the most likely explanation is that the survival is better. People are surviving longer with MS. We're seeing an increase in survival for the whole population, but we're also seeing an increase in survival for people with MS.
MSDF
What about the gender ratio in terms of prevalence but also in terms of survival?
Dr. Kingwell
We're seeing a gradual increase in the number of women relative to men in prevalence. That's most likely due to the fact that women do survive longer than men, on average, of course that's highly variable. But on average, they survive longer than men. And so, if you've got an aging population and three-quarters of the people with MS are women, then you're going to find the number of women are increasing.
MSDF
How did the socioeconomic status affect the findings?
Dr. Kingwell
Yeah, so we did actually look at socioeconomic status. It was measured at the neighborhood level, so not the individual level. It's linked into the databases by postal code. We did find that there were more people with MS in the higher levels of socioeconomic status, but the absolute differences were not that great. And, when we looked at this, it was not linked or adjusted for other factors. So there's so many things that can be attached to socioeconomic status and, of course, age is one of them, and your age is greatly related to whether you have MS or not. And so, there are other possible explanations, so we don't put a lot of emphasis on that. When we look at socioeconomic status, we really think that you need to design a study specifically to look at that.
MSDF
Could you look at the use of disease-modifying drugs according to socioeconomic status?
Dr. Kingwell
We could, and we have actually looked at that in other studies. Again, as a kind of an adjustment factor or something to bear in mind when we're looking at lots of variables at once, we find there's the same kind of trend that people in the higher levels tend to be on drug more often. But again, the absolute numbers are very small, and it could totally be related to age or other factors that are not adjusted in.
MSDF
Were the data there to be able to look at early initiation of disease-modifying drugs and any effects it may have had?
Dr. Kingwell
Well for this particular study – in the incidence and prevalence study – we looked at just whether people had ever had drug. We looked at the incident population to see if they'd had it in the last three years or so—that's the three years from their first claim, which is close to when they're first diagnosed or recognized as having MS. And for the prevalent population, we looked at whether they'd ever had MS. So we were able to tell that about a third of the cases had had a disease-modifying drug. And this study did start way back in the early 90s and then mid-90s for the incidence cases. So, you would expect it to be a lower rate because the drugs were just starting to become available in the mid-90s. So we didn't look at the actual start date of the drug for this particular study; we certainly are able to look at that because we have access to the databases to look at those kinds of questions, and we are looking at those kinds of questions in other studies.
MSDF
Can you put your findings in context to other studies at other latitudes, locals, healthcare systems?
Dr. Kingwell
Yeah, that's a complicated question. Certainly as studies are similar to the findings from some other studies. In particular, in Canada, there's been some very similar studies done in Manitoba and Nova Scotia where we've used exactly the same algorithm that was validated in those provinces led by Dr. Ruth Ann Marrie from the University of Manitoba. So, we found that prevalence and incidence estimates are very similar, and the findings and the change over time are also very comparable. When we look at some of the other countries, there are some similar findings in other places, but they vary a lot. When it comes to latitude, of course, we didn't have a big latitude gradient in our study; we were just looking in BC, and most of the people in BC live in one area around they're concentrated in the south of the province. But certainly there's a lot of variation in findings. But in order to get a look at the change over time, you really need to look within the same population on more than one occasion rather than comparing between populations over time. It's really difficult to make that comparison.
MSDF
Do you have a particularly good situation in BC in that you can link databases of diagnostic codes, physician visits, hospitalizations, pharmacy benefits, things like that that may not exist in other places with a less coordinated system?
Dr. Kingwell
Yeah, definitely. We are in a situation where we have access to some amazing databases. Many of the provinces in Canada have the same or similar databases, so it is like that. We also have the great situation that we have a clinical database in BC too where we've been collecting data on MS patients over a very long period of time. And we can link that data into the administrative databases, so we have the depth of the clinical data that we can link in the breadth of the administrative data, which has really put us in a very strong position to look at these long-term followup studies.
MSDF
Is it pretty smooth to be able to delve into these databases, or do you have any regulatory barriers like, in the US, we have all these HIPAA things. Do you have a problem with de-identifying or anything like that?
Dr. Kingwell
It's certainly not smooth. It can actually take us several years to access this data. It's a long process. It's a lot of paperwork for all of the reasons that…or some of the reasons you just mentioned. The data is actually all handled through…when we're at UBC, it's handled through Population Data BC, which is kind of the center between the Ministry of Health and the databases. And they strip all the identifiers off, so that by the time we receive any data … we, of course, have to go through a lot of privacy concerns and justification before we get any data sets. All the names and the numbers are removed, so that we don't know who anybody is in our database. Even when we're linking our clinical data, of course, everything is completely anonymized by the time we work on anything like that.
MSDF
What kind of conclusions can you draw from what you've found so far?
Dr. Kingwell
One of the main conclusions, I think, is that the incident population has leveled off, apparently, in BC. We started measuring incidence in 1996, and it's possible there were changes in incidence before that, but we can say that in the last 13 years – up to 2008 – that the number of cases has leveled off, which is good news it's not increasing. We also can say that the number of prevalent cases, on the other hand, is increasing a lot, so that the services need to be aware of that that there's going to be a demand on the healthcare system, there already is. And also that our results are very similar to as seen in other parts of Canada and comparable.
The other main conclusion I would draw is that this study really shows how you can utilize these types of databases and reliable algorithms and ways of identifying people with MS in order to monitor the number of people and also changes over time. And also can give us some information about the people with MS and what kinds of drugs they're taking because we're linked into the PharmaNet databases, and we can do that too. So there's lots of questions we can answer about the population in British Columbia.
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MSDF
Thank you for listening to Episode Seventy-five of Multiple Sclerosis Discovery. This podcast was produced by the MS Discovery Forum, MSDF, the premier source of independent news and information on MS research. MSDF’s executive editor is Carol Cruzan Morton. Msdiscovery.org is part of the nonprofit Accelerated Cure Project for Multiple Sclerosis. Robert McBurney is our President and CEO, and Hollie Schmidt is Vice President of Scientific Operations.
Msdiscovery.org aims to focus attention on what is known and not yet known about the causes of MS and related conditions, their pathological mechanisms, and potential ways to intervene. By communicating this information in a way that builds bridges among different disciplines, we hope to open new routes toward significant clinical advances.
[outro music]
We’re interested in your opinions. Please join the discussion on one of our online forums or send comments, criticisms, and suggestions to editor@msdiscovery.org.
For Multiple Sclerosis Discovery, I'm Dan Keller.
[intro music]
Host – Dan Keller
Hello, and welcome to Episode Seventy-four of Multiple Sclerosis Discovery, the podcast of the MS Discovery Forum. I’m Dan Keller.
Today's interview features Dr. Markus Reindl, an Associate Professor of Neuroscience at Innsbruck Medical University in Innsbruck, Austria. We discuss autoantibodies to myelin oligodendrocyte glycoprotein, or MOG, a protein component of myelin. These anti-MOG antibodies are particularly important in pediatric demyelinating diseases.
Interviewer – Dan Keller
First of all, why don't you define MOG for our audience.
Interviewee – Markus Reindl
MOG is myelin oligodendrocyte glycoprotein, and it's a myelin protein which was discovered about 30 years ago. It is of enormous interest to people working in neuroimmunology, because it's one of the main autoantigens used in experimental models for multiple sclerosis. And about 20 to 30 years ago, a lot of people started to work on autoantibodies against MOG in the field of MS because it was suspected to be a key autoantigen. And at that time, there were a lot of papers published with somewhat contradictory results.
About five years, six years ago, the interest of MOG was rediscovered again when people developed more specific assays to detect these antibodies. And surprisingly, it was found that they're not present in classical multiple sclerosis but rather in pediatric demyelinating diseases, such as acute disseminated encephalomyelitis, ADEM, or neuromyelitis spectrum disorders.
MSDF
And what does finding anti-MOG antibodies tell you?
Dr. Reindl
At the moment, it just tells you that if you have these antibodies the risk that you develop MS is minor. So it points to the direction of a different demyelinating disease, which is in most cases monophasic with a good outcome. Or if it's recurrent, it's often recurrent optic neuritis on multiphasic ADEM. Altogether, all this with a good recovery from relapse. Severe disease causes are rare.
MSDF
So in the early stages of MS – something like clinically isolated syndrome – does MOG tell you which direction to go in if you find it?
Dr. Reindl
Usually if you have a clinically isolated syndrome that fulfills the current criteria for multiple sclerosis, looking at the MRI or at the cerebrospinal fluid, it will typically be negative for MOG and autoantibodies, so it's just an exclusion criteria. If you look at the CIS [clinically isolated syndrome], whether it could go to the direction of multiple sclerosis or not, if MOG antibodies are present, the answer would be rather not.
MSDF
Does it fit into neuromyelitis optica, especially seronegative, where there's no anti-aquaporin-4 antibodies?
Dr. Reindl
Yes, it can also be observed in cases with neuromyelitis optica that are aquaporin-4 antibodies negative, particularly in pediatric cases, and often in cases that present with simultaneous optic neuritis and transverse myelitis at onset. So the classical description of neuromyelitis optica by Devic back in the 19th century would rather have been a MOG antibody positive case than an aquaporin-4 antibody positive case. And the pathology of both diseases is entirely different. So in aquaporin-4 mediated neuromyelitis optica, you have an astrocytopathy under high risk of future relapses and disease deterioration. Whereas in the case of MOG antibodies, it's often monophasic, and the recovery is much better.
MSDF
So it sounds like anti-MOG antibodies are not just a marker, but they're actually pathognomonic or pathogenic of the disease.
Dr. Reindl
This is currently under investigation. So what we know from neuropathology there are currently five cases – if I'm correct, or as far as I know – that have been analyzed for neuropathology. These were in most biopsies/autopsies where MOG antibodies were present. And their pathology was in multiple sclerosis type II pathology, which points to the direction of antibody-mediated pathology. So from a neuropathological point of view, looks like MS. If you look at the clinical criteria that are currently valid for multiple sclerosis, it's clearly not MS.
If you look at the pathogenesis, this is currently under investigation. From the in vitro studies, we know that these antibodies can, of course, activate compliment. They also have an affect on oligodendrocyte cell function. In vivo models are currently ongoing, and I expect there to be more results by next year on this.
MSDF
What is the clinical utility at this point? Is it ready for clinical use, or what more needs to be done?
Dr. Reindl
I think particular people working in the pediatric field are using it more and more. Because if you look, for an example, at ADEM, earlier this year we published a study that children with ADEM that are positive for MOG antibodies they have certain features in neuroradiology but also in their clinical presentation and their clinical recovery, which could aid the clinician. In particular, in the European countries, many laboratories are now setting up assays for MOG antibodies and using it in clinical routine. What has to be done now is better development of the assay, a comparison of the assays like it has been done for aquaporin-4 antibodies, like international validation experiments. We're currently setting up such an experiment for next year, together with the people in Oxford and other centers. But, my expectation would be that this antibody would have a similar use like aquaporin-4 antibody has. Also, aquaporin-4 antibodies are more specific for a specific type of disease.
MSDF
You've discussed anti-MOG antibodies in terms of diagnosis. You mentioned prognosis, better course. Can they be useful for following therapy? Do the antibodies actually disappear with immunosuppression, or are they always present?
Dr. Reindl
The point is in the monophasic cases the antibodies disappear anyway. So, I guess in 70% to 80% of all patients – particular the pediatric patients – they have these antibodies at disease onset at high titers, and with time they disappear. They only are persistent if there is a bad recovery or if there's a recurrent disease cause, like recurrent optic neuritis would be an excellent example for this. If you look at therapies, of course, therapies like plasma exchange or corticosteroid used at high doses will lead to a disappearance or a drop of antibody titers. I think we have no really long-term experience, at the moment, because these antibodies were just discovered a few years ago, until long-term studies are ongoing.
MSDF
Is there any work on what triggers these antibodies; whether there's exposure of antigens, what agents may be involved—environmental, genetic, viral?
Dr. Reindl
This is the $100 million question. Of course, we would be happy to know it. It's the similar situation like with aquaporin-4 antibodies. Also there we still don't know it. What is particular interesting is that this is most frequently observed in children at the age under 10 years. These are children that are frequently exposed to infections – the respiratory infections and other infection – therefore it's highly likely that the underlying cause is infectious. But at the moment, as far as I know, there were a couple of studies, at least, but no real systematic study using a lot of patients and with a good epidemiological setup.
MSDF
If there's an infectious agent, is it that it is causing damage to myelin, which is exposing antigens, or there's some crossreactivity with the infecting agent itself?
Dr. Reindl
Both things I think could be possible. The animal models tell us a lot of this. This is work published by Hartmut Wekerle’s group three years ago where they discovered that in transgenic animals – animals that are transgenic for MOG T cells – gut bacteria activate these T cells that go into the brain, and then MOG is released, transported out by dendritic cells to the cervical lymph nodes. And at this stage, the antibodies are induced and built. So it's a rather secondary phenomenon, which is caused by T-cell damage and T-cell destruction. I could imagine that a similar phenomenon could also help in the human situation, particularly if you consider ADEM, which has large lesions, a lot of inflammation going on there. I think it's highly likely that antigen is released, and MOG is one of the most antigenic components of the central nervous system.
MSDF
So what are the big lines of research right now – two or three of them – or the big questions that people are approaching?
Dr. Reindl
At the moment, of course, a better developmental definition of the assay—I guess this is one of the most important—is we're working together – a lot of laboratories, a couple of groups – to improve our assays to come to a common standard and to develop an assay which could be used by different laboratories in the world.
The second is, of course, to better define the clinical and neuropathological diagnosis of the patients presenting with these antibodies. Because at the moment, it's rather diffuse. You have children with ADEM, you have children with optic neuritis, children with myelitis. You have adults with NMO-like symptoms. And to put this together in a better way is, of course, highly challenging, and this is work ongoing at the moment. I think we will have more results of this by the next year.
And of course, the third thing is just to look better at the long-term prognosis of these patients. How these antibodies fits in their long-term prognosis, if they are rather beneficial or not. And this is also work that only can be clarified using larger cohorts of patients and international studies.
MSDF
So is it fairly rare to find anti-MOG antibodies?
Dr. Reindl
In adults, yes. In children, no. So if you look at children presenting with demyelinating syndromes, from our own ongoing study cohort in Germany and Austria—we know it's about a third of all children presenting with demyelinating syndromes—more than a third have these antibodies. If you look at adults, it's much more rare. I guess it's about 5% or less.
MSDF
Well, thank you very much.
Dr. Reindl
You're most welcome.
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MSDF
Thank you for listening to Episode Seventy-four of Multiple Sclerosis Discovery. This podcast was produced by the MS Discovery Forum, MSDF, the premier source of independent news and information on MS research. MSDF’s executive editor is Carol Cruzan Morton. Msdiscovery.org is part of the non-profit Accelerated Cure Project for Multiple Sclerosis. Robert McBurney is our President and CEO, and Hollie Schmidt is vice president of scientific operations.
Msdiscovery.org aims to focus attention on what is known and not yet known about the causes of MS and related conditions, their pathological mechanisms, and potential ways to intervene. By communicating this information in a way that builds bridges among different disciplines, we hope to open new routes toward significant clinical advances.
We’re interested in your opinions. Please join the discussion on one of our online forums or send comments, criticisms, and suggestions to editor@msdiscovery.org.
For Multiple Sclerosis Discovery, I'm Dan Keller.
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Full Transcript:
[intro music]
Host – Dan Keller
Hello, and welcome to Episode Seventy-three of Multiple Sclerosis Discovery, the podcast of the MS Discovery Forum. I’m Dan Keller.
Today's interview features Donna Osterhout, a cell biologist at Upstate Medical University in Syracuse, New York, USA. Dr. Osterhout talks about a new way of looking at myelin-making cells, which move and change shape in dramatic ways. Current MS drugs take aim at preventing new immune damage. In the future, researchers hope to figure out how to repair myelin and restore function.
But first, let’s look at new content on MS Discovery Forum. Spring brings rain, flowers, and a bouquet of scientific meetings related to multiple sclerosis. See the list at msdiscovery.org under the tab “professional resources.” MSDF sent the only journalist to cover the recent meeting of the American Society of Neurochemistry in Denver, but you can count on a blitz of news from the media pack at the next meeting on the calendar – the American Academy of Neurology in April, happening this year in Vancouver, BC, Canada. The number of research papers about multiple sclerosis has doubled in the last 10 years, and many findings are first reported at meetings before publication.
Moving on, let’s sample a few of the new papers we found in our weekly PubMed search of the world’s largest medical library, the National Library of Medicine. You can link to each week’s list of curated papers at msdiscovery.org.
Related to this week’s podcast, a new paper reviews the latest research about the molecular cues that allow precursor cells to mature and go through the stages of making myelin. These cues come from axons and from other surrounding tissue. Clinical drug development efforts focus on overcoming inhibitory cues, such as with the experimental agent anti-LINGO-1, now completing phase 2 clinical trials for MS and acute optic neuritis by Biogen. The review authors suggest future drugs to repair myelin could boost permissive and promotional cues, which may go wrong in disease. The paper is published by researchers at the Virginia Commonwealth School of Medicine in the journal Experimental Neurology.
Another report updates the Cochrane systematic review on teriflunomide, a daily oral medication for relapsing remitting MS marketed under the brand name Aubagio by Sanofi Genzyme. Cochrane’s systematic reviews are ranked among the highest level of medical evidence, because of the rigorous independent analysis of multiple studies, including randomized controlled trials. The authors write that, as a single drug, the high dose of teriflunomide was as effective as interferon beta 1-a, while the low dose was less effective. They recommended longer follow-up analyses and noted that the available evidence was low-quality, as well as subject to bias, in part because all studies were sponsored by pharmaceutical companies. In general, side effects were mild to moderate and do not usually lead to treatment being stopped, but the higher dose is more prone to cause these side effects. The study is available in the Cochrane Library.
The final editor’s pick this week takes a fresh look at how medical images transform a patient’s view of her own body. The paper describes an artistic collaboration between Devan Stahl, a bioethicist at Michigan State University with multiple sclerosis, and her sister Darian Goldin Stahl, a printmaker. The resulting art – some of it life sized – superimposes Devan’s narrative and MRI images with body photos. Devan wrote in the paper that the art collaboration has made it easier to talk about her MS. The paper is published in the journal Medical Humanities. If you're in town for the big Neurology meeting, you can catch Darian’s artist talk on April 17 at 2 pm at Malaspina Printmakers in Vancouver, Canada.
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And now to our interview. We caught up with Donna Osterhout in Denver, Colorado at the March meeting of the American Society for Neurochemistry. She organized a symposium that told a new story about myelin-making cells. In different labs, researchers started looking for clues in the radical shape changes that occur in the cells in their normal process of making myelin. These oligodendrocyte precursor cells sprout “arms” to reach out and touch neighboring axons. Then they push out slabs of fatty membrane and wrap them around and anchor them to the axons. In multiple sclerosis and other demyelinating diseases, the immune system attacks this myelin wrap, and the cells cannot keep up with repair. The unprotected axons may be damaged or destroyed, causing the worsening disability of MS. Learning how the cells make myelin may pave the way toward new therapeutic agents to repair demyelinated axons and restore function. Dr. Osterhout spoke with our executive editor, Carol Cruzan Morton.
Interviewer – Carol Cruzan Morton
So we are here, in Denver, at the annual meeting of the American Society for Neurochemistry, and you've put together a very interesting panel on a new way of looking at myelin. So can you sort of set the scene for us when you're talking about the myelin research that you're working on?
Interviewee – Donna Osterhout
Well, myelin is a specialized membrane that is wrapped around axons; it occurs in the last step of development. And oligodendrocyte progenitor cells are the cells that form myelin. They are going to migrate out through the developing brain and they're going to extend processes that come in contact with axons that need to be myelinated. And when they get the appropriate signals, they are going to start a process by which they synthesize and extend a large membrane, which wraps around this axon many times and compacts and forms myelin.
The way that this happens has been a mystery thus far, but recent research suggests that there has to be a lot of rearrangements of the internal cytoskeleton for this to happen. And so the symposium was organized to talk about how the cytoskeleton might be changing to allow for this membrane wrapping and myelin formation.
MSDF
Can you tell me more about the cytoskeleton?
Dr. Osterhout
The cytoskeleton is comprised of specialized proteins within cells, and every cell has a cytoskeleton; it gives it shape, but it also allows it to migrate, differentiate, and extend processes, so cells wouldn't be able to do much without a cytoskeleton. And in the case of oligodendrocytes, there are a lot of cytoskeletal rearrangements that occur to allow for myelination.
MSDF
Can you tell me more about the emerging view about how myelination may be working based on this new way of looking at it?
Dr. Osterhout
Initially, we know that there are early signals that trigger extensive process outgrowth from these cells. Once the axon sends a signal to the oligodendrocyte progenitor cell, they start to put out many, many processes, synthesize myelin proteins, and make this big membrane that will wrap around the axon. What winds up happening is that in the past everybody thinks that we've needed a driving force so that something pushes this forward, and it had been thought that perhaps the actin cytoskeleton was the driving force behind this.
The newer research indicates that initially you have to have signals that trigger the process outgrowth, but this is followed by an actual disassembly of the actin cytoskeleton. So it's somewhat opposite of what we had thought previously.
MSDF
Can you tell me more about the steps that are involved in the process of myelinating that you and your colleagues have been discovering?
Dr. Osterhout
Well, the initial step is the activation of a cellular kinase called Fyn tyrosine kinase; this is the earliest step in the differentiation of these progenitor cells. Fyn will be activated by any number of signals from the axon including, for example, glutamate that's released. And once Fyn is active, it initiates a rearrangement of cytoskeletal proteins called microtubules in order to facilitate process outgrowth so we can extend processes to form this membrane.
In later stages, then we have Fyn helping to trigger the synthesis of myelin proteins, and then you start to get other proteins active that will disassemble the actin cytoskeleton. There is even some evidence that perhaps myelin basic protein can do this. So Fyn signaling will turn on early and promote the synthesis of myelin basic protein, and then myelin basic protein will proceed down these processes and help to disassemble the actin cytoskeleton so the membrane can wrap around the axon.
MSDF
Can you describe what the cells look like when they're going through this process?
Dr. Osterhout
Well, this is really interesting to study, especially in vitro. You can set up myelinating cultures of oligodendrocyte progenitor cells. They're very simple cells, they're like bipolar, two to three processes, and that's the earliest progenitor that we might look at. But once you trigger differentiation, they start to put out processes in a somewhat predictable manner. They will first extend five processes, and then these five processes start branching And they produce these intricate branches. At some point these mature cells will actually look like a lace doily; they are spectacular with the cell body in the center and all these highly branched processes surrounding it. And then you see a transformation of these processes into this huge membrane sheet, and in the absence of an axon it's just going to cover the tissue culture dish; it's amazing how large this can get. But if you had an axon in the culture, this membrane sheet would just form myelin. They would form a myelin segment wrapping around the axon.
MSDF
That’s so interesting. And then can you say, adding to that picture, the steps that are happening in those process that you and your colleagues have been discovering?
Dr. Osterhout
So when you have the initial process outgrowth, you have Fyn tyrosine kinase active, and that facilitates the initiation and that extensive process outgrowth. But the transition between the process outgrowth and the formation of membrane sheets is going to be the disassembly of the actin cytoskeleton.
MSDF
And that's the big news is that the actin cytoskeleton is breaking down instead of pushing the myelin forward as it's making its multiple wraps around?
Dr. Osterhout
Yes, this seems to be the way that this is happening mechanistically. The formation of that myelin membrane requires the actin disassembly, and two of the speakers that we had in our symposium gave evidence to this, using several different experimental systems. And then ultimately when you're going to anchor this myelin sheath, and you can get some specializations in the axonal membrane, and this is what one of the speakers talked about, anchoring the perinodal loops, kind of the ends of the myelin segment. And so we have a process by which we have extensive process outgrowth triggered by Fyn. Then once you get the process outgrowth, you have actin disassembly and you form these membrane sheets, and then they would wrap around the axon, forming myelin, and then you would stabilize it with special proteins in the axon that stabilize the ends at the perinodal loops.
MSDF
So what does this have to do with diseases like multiple sclerosis?
Dr. Osterhout
That's a very good question. If we understand what goes on in development, then we might be able to predict how we could facilitate this process in a demyelinating disease like multiple sclerosis. We do have oligodendrocyte progenitor cells in our brain and spinal cord. They persist as a population throughout adulthood. And any time you have a lesion or a trauma to the brain, and especially if you get demyelination, then you'll have these cells migrate to the area of demyelination. And if we can encourage them to remyelinate, they would undergo the same steps.
We have shown evidence that the inflammation and other conditions in a demyelinating disease upregulates chondroitin sulfate proteoglycans, and these can actually inhibit the process outgrowth and remyelination by oligodendrocytes, because they ultimately inhibit the activation of Fyn kinase.
So if you're considering a disease process, you want to stimulate these steps. And you want to look for agents that might trigger and make sure that these steps proceed, or neutralize things that would be present in the lesion that would inhibit this.
MSDF
One interesting aspect of your work, and perhaps of science more generally, is that some of these discoveries with relevance to multiple sclerosis come from your work on spinal cord injury. Can you talk about how that works in science?
Dr. Osterhout
Well, spinal cord injury is another type of lesion, it's a specialized lesion; you have damage to axons as well as demyelination due to trauma. But in diseases in general in the brain and the spinal cord, whenever you have an injury process or inflammation or some kind of destruction of tissue, you get an inflammation and immune influx, and you will get a process called reactive gliosis. And this is common to many diseases that you see in the brain. For example, you can see it easily in spinal cord injury, it's been well documented. You can see these proteoglycans' reactive gliosis in multiple sclerosis, you can see it in Alzheimer's disease, Parkinson's disease, and other conditions, because they all have a common element that you've got some kind of inflammation occurring and tissue destruction occurring at a specific place.
MSDF
Getting back to multiple sclerosis and the work on how cells myelinate axons, what are the next big questions that you and your colleagues are asking?
Dr. Osterhout
Well, there still are a lot of questions about exactly how this myelination process is accomplished even during development; we don't fully understand all of the triggers that would activate this process. And, likewise, we don't always understand things that might inhibit this process. So we need to more fully characterize what's going on in development so that we can take a look at it in the remyelinating situations, either in spinal cord injury, or multiple sclerosis, or any other demyelinating condition.
MSDF
Well, that's really interesting. Well, thank you for taking the time to explain the research.
Dr. Osterhout
And thank you for your interest; it's been my pleasure.
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MSDF
Thank you for listening to Episode Seventy-three of Multiple Sclerosis Discovery. This podcast was produced by the MS Discovery Forum, MSDF, the premier source of independent news and information on MS research. MSDF’s executive editor is Carol Cruzan Morton. Msdiscovery.org is part of the nonprofit Accelerated Cure Project for Multiple Sclerosis. Robert McBurney is our President and CEO, and Hollie Schmidt is Vice President of Scientific Operations.
Msdiscovery.org aims to focus attention on what is known and not yet known about the causes of MS and related conditions, their pathological mechanisms, and potential ways to intervene. By communicating this information in a way that builds bridges among different disciplines, we hope to open new routes toward significant clinical advances.
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