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Myelin

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The effects of age on remyelination in MS are reversible(03/10/14)

Like conducting an errant orchestra to play together, researchers are guiding processes that go awry in multiple sclerosis to repair themselves.

The conductor walks to the stand and takes his place in front of the orchestra. He raises his baton and, with a dramatic flourish, one hundred individuals come to life. From nowhere, the stillness becomes a beautiful harmony as each member takes their part in a complex symphony.

Consider the workings and structure of the human brain – our most complicated organ – in terms of this orchestra. When it works, it is capable of something more remarkable than the greatest musical compositions in human history, but when it is affected by a condition such as multiple sclerosis (MS), "the brain's tightly orchestrated biological functions become discordant – the conductor begins to fail at their job and several instruments go out of tune," said Professor Robin Franklin, Head of Translational Science at the Wellcome Trust-Medical Research Council (MRC) Cambridge Stem Cell Institute and Director of the MS Society Cambridge Centre for Myelin Repair.

His research team and those led by other Stem Cell Institute researchers Drs Thóra Káradóttir, Mark Kotter and Stefano Pluchino are each looking at a different aspect of this errant orchestra. They hope that their collective knowledge will one day help 're-tune' the brains of MS patients to self-repair.

In its simplest terms, MS is a disease in which the immune system turns on itself, destroying the oligodendrocytes that make a protective sheath called myelin, which encases nerve fibres. This halts the transmission of neural messages, and eventually leads to nerve fibre damage, resulting in a progressive loss of movement, speech and vision for the 100,000 people in the UK who have MS. However, the complexities of treating the disease go beyond simply stopping the destruction of myelin, said Franklin: "The myelin damage causes a build-up of debris, which needs removing, and the environment surrounding the cells needs to be conducive to regenerating the sheath. When we think about repairing the damage, we need to be considering several different biological phenomena at the same time."

Although there are drugs available for modifying the early stages of MS – including alemtuzumab (Lemtrada), developed in Cambridge – there are no treatments that regenerate the damaged tissue. Moreover, although the disease evolves over decades, with periods of remission followed by relapses, there is no treatment once patients have reached the progressive stage (estimated to be about 50% of current patients).

Oligodendrocytes – the master manufacturers of myelin – are formed by a type of stem cell in the brain called oligodendrocyte progenitor cells (OPCs), and are responsible for re-wrapping, or remyelinating, the bare axons with myelin in response to injuries or diseases. But this regenerative ability decreases with age and MS. "As the disease progresses, the need for intervention that galvanises the natural healing process becomes ever more important," explained Franklin. "Working with colleagues at the Harvard Stem Cell Institute, we've shown that the effects of age on remyelination are reversible, which gives us some confidence that we can use the brain's own OPCs for myelin regeneration."

However, to understand how to stimulate the brain's own repair mechanisms first requires an understanding of how the brain detects injury and initiates repair.

Thóra Káradóttir believes that one way the brain 'senses' problems are afoot is through the drop in how fast neural messages are passed across the brain. "The difference in speed between an intact neuron and a damaged one can be like comparing the speed of a cheetah to a tortoise," she said. "I'm eavesdropping on the information superhighway by attaching electrodes to neurons and OPCs." Her findings show that damaged fibres release a molecule called glutamate. "It's their 'cry for help' to OPCs. If it doesn't happen, or if the OPCs don't 'hear', then repair is reduced." She is working with Numedicus, a company that specialises in developing secondary uses for existing drugs, to test drugs that she hopes will be able to amplify this signal and increase the repair process.

Meanwhile, Robin Franklin's team has shown that it's possible to kick-start OPCs, driving the formation of oligodendrocytes and sheath formation, using a drug that targets retinoid X receptor-gamma, a molecule found within OPCs. The results are positive and clinical trials will shortly commence in collaboration with Dr Alasdair Coles from the Department of Clinical Neurosciences and the MRC Centre for Regenerative Medicine at the University of Edinburgh.

What's interesting about the rejuvenation of remyelination is that the treatment primarily affected inflammation in demyelinating lesions, and specifically the recruitment of cells called macrophages. These are the body's 'big eaters' – their role is to search out and gobble up rubbish. "We have identified myelin debris as a potent inhibitor of stem cells. Learning how it is being sensed by stem cells enabled us to overcome this inhibition by using drugs such as ibudilast. A clinical trial to test these effects is currently undergoing preparation," explained Mark Kotter. Franklin and Kotter's work is representative of an interesting turn in MS research within the field. Increasingly, investigators are looking at how the environment around the damage can be improved to help natural remyelination. "It's a curious paradox," said Franklin. "MS is caused by the immune system but components of the immune system are also key to its recovery."

Stefano Pluchino's team, for instance, has shown that injecting brain stem cells into mice with MS works in a surprising way. Instead of making new oligodendrocytes (or other brain cells), the cells seem to work by re-setting the damaging immune response, creating better conditions for the brain's own stem cells to replace or restore what has been damaged. He is now developing more-efficient stem cells and new drugs, including nanomedicines, to foster the healing of the damaged brain.

Given the complex landscape of abnormal activities happening in the MS brain, will combination therapies be the way forward? "Certainly," said Franklin. "Over the next ten years we will see an increased understanding of the fundamental biology in MS, we will identify more targets which may yield effective drugs and we'll have more-refined strategies for running clinical trials. What makes Cambridge rare is the spectrum of skills here – from understanding the fundamental biology of myelin repair through to clinical trials."

Source: Medical Xpress © Medical Xpress 2011-2014, Science X network (03/10/14)

Olfactory dysfunction is common in multiple sclerosis (22/09/14)

Olfactory Pathology in Central Nervous System Demyelinating Diseases.

DeLuca GC, Joseph A, George J, Yates RL, Hamard M, Hofer M, Esiri MM.

Abstract

Olfactory dysfunction is common in multiple sclerosis (MS). Olfactory bulb and tract pathology in MS and other demyelinating disease remains unexplored.

A human autopsy cohort of pathologically confirmed cases encompassing the spectrum of demyelinating disease (MS; n=17), neuromyelitis optica (NMO); n=3), and acute disseminated encephalomyelitis (ADEM); n=7)) was compared to neuroinflammatory (herpes simplex virus encephalitis (HSE); n=3), neurodegenerative (Alzheimer's disease (AD); n=4), and non-neurologic (n=8) controls.

For each case, olfactory bulbs and/or tracts were stained for myelin, axons, and inflammation. Inferofrontal cortex and hippocampus were stained for myelin in a subset of MS and ADEM cases.

Olfactory bulb/tract demyelination was frequent in all demyelinating diseases (MS 12/17 (70.6%); ADEM 3/7 (42.9%); NMO 2/3 (66.7%)) but was absent in HSE, AD, and non-neurologic controls.

Inflammation was greater in the demyelinating diseases compared to non-neurologic controls.

Olfactory bulb/tract axonal loss was most severe in MS where it correlated significantly with the extent of demyelination (r=0.610, P=0.009) and parenchymal inflammation (r=0.681, P=0.003).

The extent of olfactory bulb/tract demyelination correlated with that found in the subjacent adjacent inferofrontal cortex but not hippocampus.

We provide unequivocal evidence that olfactory bulb/tract demyelination is frequent, can occur early and be highly inflammatory, and is specific to demyelinating disease.

Source: Brain Pathol. 2014 Sep 17. doi: 10.1111/bpa.12209. [Epub ahead of print] & Pubmed PMID: 25230202 (22/09/14)

Myelin measure in MS tracks patient disability(12/09/14)

Whole-brain measures of myelin water fraction (MWF) -- reflecting the amount of myelin present in brain tissue -- correlated significantly with disease duration and disability levels in multiple sclerosis, supporting a role for MWF in patient management and as an outcome in clinical trials, a researcher said here.

In a cross-sectional study of 141 MS patients and 10 neurologically healthy controls, the "skew" of one of two peaks seen in the distribution of MWF across the brain, including normal-appearing white matter as well in MS-type lesions, was associated with Expanded Disability Status Scale (EDSS) score (P=0.000039) and with the number of years since symptom onset (P=0.012), said Elizabeth Monohan, of Weill Cornell Medical College in New York City.

"To date, our study is the first to demonstrate an approach to modeling white matter myelin water fraction to explore clinical variables that may be driving myelin content," she said at the European Committee for Treatment and Research in Multiple Sclerosis annual meeting, held jointly this year with its North American counterpart.

"These observations promote the use of myelin water fraction as a biomarker for myelin," she added, noting that the relationship between MWF on the one hand and EDSS and disease duration on the other suggests that "myelin loss is accumulated during the disease and perhaps contributes to the progressive nature of MS."

Demyelination is the chief pathology in MS and is believed to be the driving force behind the physical disabilities that mark the disease in its later stages. Nerve fibers are sheathed in a protective layer of proteins dominated by myelin; its progressive loss leaves nerve axons vulnerable to various insults such that eventually they break down, leading to loss of nerve function.

However, this process has been impossible to witness or measure directly in human patients. Recently, MWF -- measurable with MRI scans as the amount of water within myelin versus the total amount of water in the tissue scanned -- has emerged as a quantitative marker of myelin that can be assessed noninvasively in living patients.

Up till now, though, its clinical applicability has been uncertain, Monohan explained, because it was unclear whether focusing on MWF in lesioned areas was sufficient and also because the scans took a long time to perform and data analysis was difficult.

She said her group had developed a more practical approach to the scans that cut the image acquisition time to just 10 minutes for the whole brain. Moreover, she and her colleagues determined that scanning the whole brain was the right way to go, because there was no solid evidence to indicate that the clinically relevant demyelination occurs only in lesions.

The whole-brain MWF measurement, Monohan said, provides an "unbiased approach" for studying myelin dynamics.

An important finding in the study was that patients showed a "bimodal" distribution in histograms of MWF values -- a small spike in relatively low values and another larger spike in mid-range values. Monohan said that 94% of the patients showed this type of pattern, compared with just one of the 10 controls.

It was the shape of this spike in low values -- primarily the skew, but also its width -- that was most strongly correlated with EDSS and disease duration, she reported. The shape of the larger mid-value spike was associated with EDSS score but not disease duration.

Monohan said her group is pursuing additional studies to look at a broader patient population, with a wider range of EDSS scores and disease durations. Another goal is to examine MWF in patients undergoing treatment with current MS drugs.

Also, longitudinal studies to track within-patient changes in MWF over time will be necessary to determine how it may correlate with lesion evolution and, importantly, disease progression.

The study was funded by the National Multiple Sclerosis Society and the National Institutes of Health.

Study investigators had relationships with Biogen Idec, Teva, Questcor, Genzyme, EMD Serono, Novartis, and Acorda.

Primary source: ECTRIMS-ACTRIMS
Source reference: Monohan E, et al "Clinical disease burden predicts myelin water fraction in multiple sclerosis" ECTRIMS-ACTRIMS 2014; Abstract YI1.3.

Source: Medpage Today © 2014 MedPage Today, LLC. (12/09/14)

People with multiple sclerosis lose myelin in grey matter(10/09/14)

People with multiple sclerosis (MS) lose myelin in the grey matter of their brains and the loss is closely correlated with the severity of the disease, according to a new magnetic resonance imaging (MRI) study. Researchers said the findings could have important applications in clinical trials and treatment monitoring. The study appears online in the journal Radiology.

Loss of myelin, the fatty protective sheath around nerve fibres, is a characteristic of MS, an inflammatory disease of the central nervous system that can lead to a variety of serious neurological symptoms and disability. MS is typically considered a disease of the brain's signal-conducting white matter, where myelin is most abundant, but myelin is also present in smaller amounts in grey matter, the brain's information processing center that is made up primarily of nerve cell bodies. Though the myelin content in grey matter is small, it is still extremely important to proper function, as it enables protection of thin nerve fibers connecting neighbouring areas of the brain cortex, according to Vasily L. Yarnykh, Ph.D., associate professor in the Department of Radiology at University of Washington in Seattle.

"The fact that MS patients lose myelin not only in white but also in grey matter has been proven by earlier post-mortem pathological studies," he said. "However, the clinical significance of the myelin loss, or demyelination, in grey matter has not been established because of the absence of appropriate imaging methods."

To learn more about associations between MS and demyelination in both white and grey matter, Dr. Yarnykh and colleagues used a refined MRI technique that provides information on the content of biological macromolecules - molecules present in tissues and composed of a large number of atoms, such as proteins, lipids and carbohydrates. The new method, known as macromolecular proton fraction (MPF) mapping, has been hampered in the past because of the length of time required for data collection, but improvements now allow much faster generation of whole-brain maps that reflect the macromolecular content in tissues.

"The method utilises a standard MRI scanner and doesn't require any special hardware-only some software modifications," Dr. Yarnykh said. "MPF mapping allows quantitative assessment of microscopic demyelination in brain tissues that look normal on clinical images, and is the only existing method able to evaluate the myelin content in grey matter."

The researchers looked at 30 MS patients, including 18 with relapsing-remitting MS (RRMS), the most common type of MS initially diagnosed, and 12 with the more advanced type of disease known as secondary progressive MS (SPMS). Fourteen healthy control participants were also included in the study. Each participant underwent MRI on a 3-Tesla imager, and the researchers reconstructed 3-D whole-brain MPF maps to look at normal-appearing white matter, grey matter and MS lesions. The researchers further compared the results of their imaging technique with clinical tests characterising neurological dysfunction in MS patients.

The results showed that MPF was significantly lower in both white and grey matter in RRMS patients compared with healthy controls, and was also significantly reduced in both normal-appearing brain tissues and lesions of SPMS patients compared to RRMS patients with the largest relative decrease in grey matter. MPF in brain tissues of MS patients significantly correlated with clinical disability and the strongest associations were found for grey matter.

"The major finding of the study is that the loss of myelin in grey matter caused by MS in its relative amount is comparable to or even larger than that in white matter," said Dr. Yarnykh. "Furthermore, grey matter demyelination is much more advanced in patients with secondary-progressive MS, and it is very strongly related to patients' disability. As such, we believe that information about grey matter myelin damage in MS is of primary clinical relevance."

The improved technique has potentially important applications for MS treatments targeted to protect and restore myelin.

"First, this method may provide an objective measure of the disease progression and treatment success in clinical trials," Dr. Yarnykh said. "And second, assessment of both grey and white matter damage with this method may become an individual patient management tool in the future."

Dr. Yarnykh and colleagues are currently conducting additional research on the new method with the support of the National Multiple Sclerosis Society and the National Institutes of Health.

"This study was done on the participants at a single point in time," he said. "Now we want to compare MS patients with control participants to see how myelin content will evolve over time. We further plan to extend our method to the spinal cord imaging and test whether the combined assessment of demyelination in the brain and spinal cord could better explain disability progression as compared to brain demyelination alone."

Source: News-Medical.Net Copyright 2000-2014 AZoM.com Limited (10/09/14)

Remyelination promoted by phosphatidic acid(12/08/14)

Cyclic phosphatidic acid treatment suppress cuprizone-induced demyelination and motor dysfunction in mice.

Yamamoto S, Gotoh M, Kawamura Y, Yamashina K, Yagishita S, Awaji T, Tanaka M, Maruyama K, Murakami-Murofushi K, Yoshikawa K.

Abstract

Multiple sclerosis is a chronic demyelinating disease of the central nervous system leading to progressive cognitive and motor dysfunction, which is characterised by neuroinflammation, demyelination, astrogliosis, loss of oligodendrocytes, and axonal pathologies.

Cyclic phosphatidic acid (cPA) is a naturally occurring phospholipid mediator with a unique cyclic phosphate ring structure at the sn-2 and sn-3 positions of the glycerol backbone. cPA elicits a neurotrophin-like action and protects hippocampal neurons from ischemia-induced delayed neuronal death.

In this study, we investigated the effects of cPA on cuprizone-induced demyelination, which is a model of multiple sclerosis.

Mice were fed a diet containing 0.2% cuprizone for 5 weeks, which induces severe demyelination, astrocyte and microglial activation, and motor dysfunction.

Simultaneous administration of cPA effectively attenuated cuprizone-induced demyelination, glial activation, and motor dysfunction.

These data indicate that cPA may be a useful treatment to reduce the extent of demyelination and the severity of motor dysfunction in multiple sclerosis.

cPA is a potential lead compound in the development of drugs for the treatment of this devastating disease.

Source: Eur J Pharmacol. 2014 Jul 30. pii: S0014-2999(14)00577-9. doi: 10.1016/j.ejphar.2014.07.040. [Epub ahead of print] & Pubmed PMID: 25084219 (12/08/14)

Tapping UCSF invention, Roche and Versant dive into myelin repair(23/06/14)

When mice chew through the insulation that protects a house’s wires, an electrician can repair the wires. People with multiple sclerosis, whose immune systems malfunction and attack the insulation of their own neural wires, don’t have that option. Helping them could be a very big deal in MS care.

Swiss drug giant Roche, tapping into an unorthodox business model created by a San Francisco venture group, wants to find treatments to help. Roche and Versant Ventures have created the oddly named Inception 5—we’ll explain the name later—to house a promising new way to look for multiple sclerosis drugs, a high-throughput screen developed at the University of California, San Francisco.

Roche will contribute its vast libraries of compounds to test in the UCSF assay, and a seasoned team of drug discovery scientists in the employ of Versant’s Inception group will also try to design new compounds.

Repairing the neural insulation is called remyelination. Myelin is the substance that makes up the sheaths, and it’s also what the immune system mistakes for a pathogen. The attack leaves holes in the myelin, and like a house with faulty wiring, the patient’s nervous system starts to short-circuit, leading to a wide and unpredictable range of neurological symptoms.

While drug makers have produced improvements with drugs that tamp down the immune system’s attack, nothing is available to reverse the actual myelin damage. (Two monoclonal antibody therapies, one from Biogen Idec, Anti-LINGO-1, and another from Acorda Therapeutics, rHIgM22, are in the clinic.)

The UCSF assay, created by neurology professor Jonah Chan, is an innovative way to get at a thorny problem: It’s really hard to build tests that demonstrate remyelination. Neurons, the cells that need to be remyelinated, are finicky to grow in the lab. Also a problem: oligodendrocytes, the cells that produce myelin, don’t wrap their myelin around the axons of neurons in an easily measurable way. (Axons are the branching arms of neurons that transmit electrical signals.)

There are other reasons, too, but Chan created a work-around: Build tiny silica cones that encourage oligodendrocytes to wrap their myelin cleanly. In other words, he built axons from pure glass. And when those silica cones (which Chan calls “micropillars”) are lined up in a testing plate, their cone shape allows measurement of the myelin thickness as it wraps around. Imagine reading the myelin as if it were the rings in the cross-section of a tree.

“Jonah’s done a great job,” said Jay Tung, chief research officer of the Myelin Repair Foundation in Saratoga, CA, which has worked with Chan in the past. “We are ecstatic about pharma, academics, startups, anyone moving the field forward. This is exactly what we want to see.”

“My view is that the missing link for finding candidate therapies for myelin repair has been the lack of a platform for efficient high-throughput screening of agents,” said Timothy Coetzee, chief research officer at the National Multiple Sclerosis Society in New York. The nonprofit funded much of Chan’s work that went into the micropillars. “The complexities of co-culture systems just don’t lend themselves to HTS. Jonah’s technology fills that critical gap.”

With the screening platform, researchers can test how thousands of drugs spur oligodendrocytes to produce myelin. That’s exactly what Inception 5 plans to do.

The group is part of a Versant initiative to keep its own drug-discovery team in-house at a company called Inception Sciences, led by a group of scientists who, at the Merck-Frosst labs in Montreal, had a string of successes including the painkiller rofecoxib (Vioxx)—later withdrawn from the market for safety concerns—and the asthma drug montekulast (Singulair). One of those scientists, Peppi Prasit, and Versant teamed up to create Amira Pharmaceuticals, which they sold in 2011 for $475 million.

Prasit and Versant managing director Brad Bolzon (right) immediately pivoted to launch Inception Sciences, which describes itself as a “small-molecule pharmaceutical incubator.” It is wholly owned by Versant and has two labs, one in San Diego, another in Vancouver. A third is about to open as well.

Instead of turning Inception Sciences into a sprawling biopharma, Versant uses a few million dollars at a time to fund Inception spin-offs that it partners with outside drug companies. (Hence the Inception 5 name; there are four other spinoffs, with more soon to be announced, according to Bolzon.) With Inception 5, Roche is paying for the research and has the option to buy the company outright once the Inception team files an IND, which is industry shorthand for asking the Food and Drug Administration permission to test a drug in humans.

Chan told Xconomy his work had drawn a lot of industry interest, but meeting the Inception scientists at their San Diego facility last year “hooked him.” Two people in particular, the medicinal chemist Brian Stearns and the biologist Daniel Lorrain, were “very impressive,” said Chan. “They’re so focused on developing products and new drugs. It made perfect sense.”

Chan also liked the idea of a third party like Inception between his work and Roche, which previously had asked him directly to screen their compounds in his lab. “That wasn’t appealing,” he said. “I didn’t want to be a service provider for companies.”

Instead, Chan and his students can get back to basic research and leave the screening work to others. “I’m just a lab rat,” he said. “It’s up to the drug hunters to take the next steps.”

Chan and his fellow UCSF neurology professor Ari Green, also an MD who treats multiple sclerosis patients, are among Inception 5’s founders and have an undisclosed equity stake. (Versant is the main owner, and Inception’s employees also take equity in each spinout.)

Even as the micropillar screen goes over to Inception 5, Green is overseeing a 50-person trial at UCSF with a drug he and Chan found with the screen. Like much of the work surrounding myelin repair, Green is taking a creative tack to measure the drug’s effect. The trial measures the speed at which light shone in a patient’s eye is converted into a signal in the brain. Myelin damage to the optic nerve slows that conversion. Patients whose speed improves during the trial might be experiencing myelin repair.

Data could be ready by the end of the year, but the trial isn’t meant to get a new drug on the market. They’re testing an off-patent, over-the-counter antihistamine, and its drowsy effect on patients rule out its potential as an MS drug. “Fatigue is the number-one issue for MS patients,” said Green. “But if this trial goes well, we’ll pursue funding for a large scale clinical trial, because even if it doesn’t lead to development of a therapeutic, it’ll help advance the field.”

It’s a field full of unknowns. As promising as Chan’s micropillars are, they’re synthetic. They only approximate how myelin would wrap around real axons, and they lack the complicating factor of inflammation in the micro-environment. Tung of the MRF says his group has an “intense focus” to move toward a high-throughput screen without using a synthetic material. Inception 5 will work on next-generation assays, too, says Green.

If Roche pulls the trigger and buys Inception 5, it will take the micropillar screen with it, which doesn’t sit well with Tim Coetzee of the NMSS. “If this platform technology got walled off from rest of the world, I’d be worried,” said Coetzee. “This is about MS, but we’re also starting to see defects in myelin in Alzheimer’s, ALS, and other diseases. It’s not as profound right now as MS, but there are other places this technology could have relevance.”

Source: Xconomy © 2007-2014, Xconomy, Inc (23/06/14)

Myelin repair in mice enhanced using stem cells and other novel approaches(17/06/14)

Two teams of researchers report success in stimulating the repair of nerve-insulating myelin in mouse models of MS. Myelin is a major target of immune attacks in MS, and although these are early results and further work is needed, these findings show some promise for strategies to repair damage and restore function for people with multiple sclerosis.

Background: In MS, myelin, the material that surrounds and protects nerve fibers, is damaged in the brain and spinal cord, and so are the cells that make myelin, called oligodendrocytes. Though the replacement cells that could repair myelin, called oligodendrocyte precursor cells (OPCs), exist in the brain, in MS they cannot adequately repair the damaged myelin.

Stem Cell Study: Lu Chen, PhD, Thomas Lane, PhD (University of California, Irvine) and colleagues report that administering neural precursor cells (nerve stem cells) to mice with MS-like disease reduced inflammation, decreased myelin damage, and increased myelin repair. (Stem Cell Reports, published May 15, 2014)

The team injected the stem cells into the spinal cord of mice with an MS-like disease induced by a virus. Although the stem cells were rejected by the body, and were not detectable within eight days after transplant, they were effective nevertheless in reducing the disease. Improvements in motor abilities of the treated mice were still apparent after six months.

The team noted that improvements went along with an increase in a type of immune cell called “regulatory T cells,” or “Tregs.” To test whether the Tregs contributed to the improvements, they blocked Tregs activity, which reduced the stem cells treatments’ impact.

The team speculates that the stem cells may be stimulating the immune environment in a way that activates mouse OPCs, even though the stem cells themselves do not turn into myelin-making OPCs. They are now investigating this idea further to discover the factors released by the stem cells. Ultimately, this information could contribute to the development of stem cell therapies and even cell-free therapies that stimulate recovery in people with MS.

Stimulating Resident Cells: Jessica Williams, PhD, Robyn S. Klein, MD, PhD, and colleagues (Washington University School of Medicine) report that targeting a signaling receptor (docking site) called “CXCR7” on immature oligodendrocytes in mice enhances myelin repair (Journal of Experimental Medicine, published April 14, 2014).

Dr. Klein’s team focused on a messenger protein (chemokine) that interacts with the immature OPCs. They studied mice that were given a toxin called cuprizone, which mimics myelin damage that occurs in the brain during MS. Once cuprizone is withdrawn, myelin repair occurs. The team found that CXCR7 activity increased during myelin damage, and then reduced with myelin repair. When the team administered an experimental compound that inhibits CXCR7, the numbers of OPCs, as well as mature oligodendrocytes, increased within myelin-damaged areas. Myelin repair was enhanced.

These data suggest that CXCR7 might serve as an important therapeutic target to promote myelin repair. Since these studies were conducted in mice, further research is necessary to ultimately determine whether this approach might be an effective approach for stimulating myelin repair in people with MS.

Conclusion: Achieving success in the Society’s priority area of nervous system repair would provide life-changing advances for people with MS. Read more about this research strategy.

Source: US National MS Society (17/06/14)

MS drug candidate shows positive results for myelin repair in cell culture assay(27/05/14)

Bionure Inc. has announced its drug candidate, BN201, was shown to promote myelination — the cellular process of repairing the protective sheath surrounding nerves that is damaged in people with multiple sclerosis (MS). The pre-clinical study was conducted in a novel cell-culture assay developed by the Myelin Repair Foundation (MRF) and assessed at the Foundation’s Translational Medicine Center under a previously announced collaborative agreement.

Bionure and the Myelin Repair Foundation are working together to evaluate BN201 as a potential myelin repair candidate for treating acute optic neuritis and the severe MS relapses that occur in some patients. Acute optic neuritis is a severe inflammation of the optic nerve that may lead to blindness in people with MS. Using the Foundation’s co-culture assay, the collaboration’s scientists were able to show BN201 promotes myelination in animal cells.

“We are working closely with scientists at the Myelin Repair Foundation’s Translational Medicine Center to advance the commercialization of BN201,” said Albert G. Zamora, CEO at Bionure, Inc. “The MRF’s myelin repair assay provided the confidence and independent validation to help us propel BN201 into clinical trials to determine its efficacy in humans. As a result, Bionure will now expand upon the intellectual property that we have for this compound.”

“We are delighted to collaborate with Bionure to advance a potential myelin repair therapeutic for MS and optic neuritis towards commercialization,” said Jay Tung, Ph.D., chief research officer at the Myelin Repair Foundation. “Our collaboration with Bionure exemplifies the value that our Translational Medicine Center brings to industry partners. Our goal is to leverage our non-profit status to partner with industry and accelerate the drug development of potential MS therapeutics that promote myelin repair.”

Source: MarketWatch Copyright © 2014 MarketWatch, Inc (27/05/14)

Better understanding of remyelination pathway offers promise for new MS treatments(02/05/14)

Real hope for modifying the disease course of multiple sclerosis (MS) may come from strategies to remyelinate damaged neurons and brain cells, says Catherine Lubetzki, MD, of the Pierre and Marie Curie University and Pitie-Salpetriere Hospital in Paris, France. Speaking on April 30, 2014, at the American Academy of Neurology’s 2014 annual conference in Philadelphia, PA, Lubetzki mapped out the pathway her lab is building from basic science to drug development for new MS agents.

She told the audience that treatments effectively targeting the inflammatory component of MS are still lacking. Pilot and phase 2 studies are underway with agents aimed at reducing inflammation, enhancing neuroprotection, and encouraging remyelination; however, the remyelination pathway in particular has not been well understood. Currently, the SPRINT-MS study for ibudilast in relapsing-remitting and primary progressive MS is underway with 250 patients planned to enroll. The phase 2 MS-SMART study of secondary progressive MS will enroll 440 patients in one of four treatment arms to receive riluzole, amiloride, ibudilast, or placebo.

Even given the current and emergent treatment landscape, remyelination, when it does occur, is insufficient to overcome chronic axonal damage and resultant disease progression. To understand why remyelination fails, the processes involved in oligodendrocyte precursor cell (OPC) activity must be made clear. These cells, which migrate to areas of plaque, mature, and eventually wrap around axons to remyelinate, do so through a four-step process. First, the cells are activated; then, they are recruited to migrate. Next, they achieve maturation before finally completing their wrap and myelination of the axon.

Lubetzki’s lab has used a mouse model to examine the transition from quiescent to activated OPCs, and to achieve a better understanding of the transcription profile of mature OPCs. Her group’s work shows that demyelination-induced activation of adult OPCs makes the cells revert to a less mature gene cell, providing cues to promote OPC motility, necessary for activation and recruitment of these cells to the demyelinated areas with plaque burden.

OPCs must then receive guidance for targeted migration to demyelinated areas. Two genes have been identified which seem to have opposing effects on OPC recruitment and remyelination rates. Overexpression of the Sema 3F gene has been associated with increased OPC recruitment and with increased remyelination rates, while overexpression of netrin has the opposite effect, decreasing OPC recruitment and reducing the rate of remyelination. Thus, a primary focus is to target Sema 3F at the lesion site, increasing the rate of remyelination by increased (and targeted) OPC recruitment. Critically, this must be accomplished early in the disease process, when axonal damage may still be reversible.

Lingo-1 has also been identified as a down-regulator of OPC activation and recruitment; researchers are also attempting to achieve early remyelination through use of an anti Lingo-1 monoclonal antibody. Two trials are currently underway examining this drug. The SYNERGY trial plans to follow 400 patients with relapsing-remitting MS over 18 months, while the RENEW trial for sufferers of optic neuritis (another inflammatory demyelinating disorder) will examine the drug’s effects on 80 patients over six months.

Fielding questions from the overflow crowd following the presentation, Lubetzski discussed the outcome measures under consideration to measure efficacy of these drugs in humans. In addition to using magnetic resonance imaging to show remyelination and to follow brain atrophy, positron emission tomography using a myelin ligand may become clinically useful. However, she also emphasized the primacy of maintaining a patient-centered focus, and the critical importance of paying attention to improvement in clinical endpoints.

Source: HCP Live Copyright HCPLive 2006-2014 (02/05/14)

Could CXCR7/ACKR3 help remyelination in MS?(29/04/14)

Targeting CXCR7/ACKR3 as a therapeutic strategy to promote remyelination in the adult central nervous system

Abstract

Current treatment modalities for the neurodegenerative disease multiple sclerosis (MS) use disease-modifying immunosuppressive compounds but do not promote repair. Although several potential targets that may induce myelin production have been identified, there has yet to be an approved therapy that promotes remyelination in the damaged central nervous system (CNS).

Remyelination of damaged axons requires the generation of new oligodendrocytes from oligodendrocyte progenitor cells (OPCs). Although OPCs are detected in MS lesions, repair of myelin is limited, contributing to progressive clinical deterioration.

In the CNS, the chemokine CXCL12 promotes remyelination via CXCR4 activation on OPCs, resulting in their differentiation into myelinating oligodendrocytes. Although the CXCL12 scavenging receptor CXCR7/ACKR3 (CXCR7) is also expressed by OPCs, its role in myelin repair in the adult CNS is unknown. We show that during cuprizone-induced demyelination, in vivo CXCR7 antagonism augmented OPC proliferation, leading to increased numbers of mature oligodendrocytes within demyelinated lesions.

CXCR7-mediated effects on remyelination required CXCR4 activation, as assessed via both phospho-S339-CXCR4-specific antibodies and administration of CXCR4 antagonists.

These findings identify a role for CXCR7 in OPC maturation during remyelination and are the first to use a small molecule to therapeutically enhance myelin repair in the demyelinated adult CNS.

Williams JL, Patel JR, Daniels BP, Klein RS.

Sources: J Exp Med. 2014 Apr 14 & Pubmed PMID: 24733828 (29/04/13)

Harvard neuroscientists present new view of myelin(22/04/14)

Harvard neuroscientists have made a discovery that turns 160 years of neuroanatomy on its head.

Myelin, the electrical insulating material long known to be essential for the fast transmission of impulses along the axons of nerve cells, is not as ubiquitous as thought, according to a new work lead by Professor Paola Arlotta of the Harvard Stem Cell Institute (HSCI) and the University's Department of Stem Cell and Regenerative Biology, in collaboration with Professor Jeff Lichtman, of Harvard's Department of Molecular and Cellular Biology.

"Myelin is a relatively recent invention during evolution," says Arlotta. "It's thought that myelin allowed the brain to communicate really fast to the far reaches of the body, and that it has endowed the brain with the capacity to compute higher level functions." In fact, loss of myelin is a feature of a number of devastating diseases, including multiple sclerosis and schizophrenia.

But the new research shows that despite myelin essential roles in the brain, "some of the most evolved, most complex neurons of the nervous system have less myelin than older, more ancestral ones" Arlotta, co-director of the HSCI neuroscience program, says.

What this means, Arlotta says, is that the higher in the cerebral cortex one looks - the closer to the top of the brain, which is its most evolved region - the less myelin one finds. Not only that, but "neurons in this part of the brain display a brand new way of positioning myelin along their axons that has not been previously seen. They have 'intermittent myelin' with long axon tracts that lack myelin interspersed among myelin-rich segments.

Arlotta continues: "contrary to the common assumptions that neurons use a universal profile of myelin distribution on their axons, the work indicate that different neurons choose to myelinate their axons differently. In classic neurobiology textbooks myelin is represented on axons as a sequence of myelinated segments separated by very short nodes that lack myelin. This distribution of myelin was tacitly assumed to be always the same, on every neuron, from the beginning to the end of the axon. This new work finds this not to be the case."

The results of the research by Arlotta and post doctoral fellow Giulio Srubek Tomassy, the first author on the report, are published in the latest edition of Science, the journal of the American Association for the Advancement of Science.

The paper is accompanied by a "Perspective" by R. Douglas Fields, of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, at the National Institutes of Health, who says that Arlotta and Tomassy's findings raise important questions about the purpose of myelin, "are likely to spark new concepts about how information is transmitted and integrated in the brain."

Arlotta and Tomassy collaborated closely on the new work with postdoctoral fellow Daniel Berger of the Lichtman group, which generated one of the two massive electron microscopy data bases that made the work possible.

"The fact that it is the most evolved neurons, the ones that have expanded dramatically in humans, suggests that what we're seeing might be the "future". As neuronal diversity increases and the brain needs to process more and more complex information, neurons change the way they use myelin to "achieve" more", says Arlotta.

It is possible, said Tomassy, that these profiles of myelination "may be giving neurons an opportunity to branch out and 'talk' to neighboring neurons". For example, because axons cannot make synaptic contacts when they are myelinated, a possibility is that these long myelin gaps may be needed to increase neuronal communication and synchronize responses across different neurons. Perhaps, he and Arlotta postulate, the intermittent myelin is intended to fine-tune the electrical impulses traveling along the axons, in order to allow the emergence of highly complex neuronal behaviors.

Source: News-Medical.Net (22/04/14)

Slightest change makes myelin come unglued(06/03/14)

For a healthy nervous system, axons—the long projections of our nerve cells that run throughout our bodies—must be properly insulated.

Much like conventional power cords need electrical insulators around the conducting wires for efficient and effective transfer of current, axons rely on multiple bilayers of myelin to maintain a rapid and optimal transfer of impulses between, for instance, brain and organ, or spinal cord and muscle. These bilayers are composed of lipids (fat molecules), protein, and water.

“Basically, myelin is this multiple stacking of lipid bilayers,” says Dong-Woog Lee, a researcher in the chemical engineering department at the University of California, Santa Barbara. “They need to be compact, and with very little water between the bilayers.”

Lee and colleagues found that even the slightest change in the composition of these myelin bilayers affect their ability to insulate axons. Their findings could offer insights into demyelinating diseases, such as multiple sclerosis.

Stick Like Glue

To observe and measure the characteristics and differences between healthy and diseased myelin bilayers, they studied the ability of these layers to adhere to each other.

The researchers used a highly sensitive instrument, called the surface forces apparatus, that can measure interactions between membranes. The deposited a lipid bilayer on a mica substrate on each of the two opposing surfaces of the apparatus.

Then they immersed the setup in a buffer solution containing myelin basic protein (MBP), a biomolecule commonly found in myelin that gives them adhesive properties and plays a role in maintaining the optimal structure of the myelin sheath.

They brought the two bilayers close together, allowing them to stick to each other, and then pulled them apart, measuring the strength of the adhesion brought about by the MBP “glue” between the bilayers, and also the MBP’s adsorption—the ability of the MBP molecules to stick to the bilayers’ surfaces.

They performed this experiment with both healthy myelin and with “disease-like” myelin bilayers.

“A lipid bilayer simulating a normal or healthy myelin membrane adsorbs this protein much better than a lipid bilayer simulating a multiple sclerosis-type of myelin membrane,” says UC Santa Barbara researcher Kai Kristiansen, “meaning that the protein attaches more strongly to the lipid bilayer and can make two apposing lipid bilayers adhere more firmly to each other and at a smaller distance—which is highly desirable for a well functioning myelin around a neuron.”

Swelling and Multiple Sclerosis

One common characteristic of diseased myelin is swelling, due to various causes such as the autoimmune responses associated with multiple sclerosis and its variants, or in cases of infection or exposure to certain chemicals. Genetics also play a role in the health of myelin.

“When the disease progresses, people can see that they swell and eventually vesiculate, creating scars,” says Lee, who is lead author of the study published in the Proceedings of the National Academy of the Sciences.

The MBP layer between the lipid bilayers also swells with water that seeps in between the double lipid layers. Instead of being a compact, molecule-thick film, the MBP layer becomes more gel-like.

“And since there’s more water between the bilayers, their insulation property decreases,” says Lee. From there, impulses slow down along the axon, or dissipate before they reach their destinations, causing paralysis and loss of function.

Disease–related changes in the lipid domain structures’ size and distribution also causes irregular adsorption of MBP onto the lipid bilayers and weakens their adhesion properties. This in turn also leads to lower nerve insulation.

The next step, according to Jacob Israelachvili, professor of chemical engineering and of materials, is to develop a user-friendly bench-top instrument that could be used in hospitals and clinics to visualize the membranes of certain cells, both healthy and pathological, whose domain structure can be an indicator of the progression of a disease.

“We are currently planning a collaboration with a local hospital to provide us with such membranes, for example, from leukemic blood cells, that we would tag with a suitable fluorescent dye to enable this imaging,” he says.

Source: Futurity © 2014 Futurity (06/03/14)

Protein may repair brain tissue damaged by Multiple Sclerosis(10/02/14)

Multiple Sclerosis is an autoimmune disease that affects the brain and spinal cord, destroying tissue and cells along the way. Previous research and practices have found that therapies can help with relapses of MS, but cannot help repair the tissue and cells that have been affected.

After MS has affected the body and caused cell damage, the brain produces new cells to repair the old ones. However, a majority of cases has shown that there are unknown factors that hinder the cells from completely repairing, thus creating a permanent loss. The brain inflammation caused by MS leads to the destruction of myelin, which is the fatty insulation for the axon nerve fibers in the brain, thus destroying brain cells. A molecule known as Endothelin-1 (ET-1) is known to inhibit the repair of the myelin.

Yesterday, Gallo and his team of researchers reported their findings in Neuron and cited the effectiveness of a certain protein that could help fully repair previously damaged cells. This protein, known as "ET-R antagonist PD142,893" can be used therapeutically to promote remyelination and effectively block ET-1 from inhibiting cell repair.

"We demonstrate that ET-1 drastically reduces the rate of remyelination," Gallo said. "ET-1 is potentially a therapeutic target to promote lesion repair in deymyelinated tissue. It could play a crucial role in preventing normal myelination in MS and in other demyelinating diseases," Gallo said.

Source: Science World Report (10/02/14)

Vitamin A's potential benefits for multiple sclerosis patients studied(07/01/14)

Some 2.5 million people around the world have multiple sclerosis (MS), a potentially debilitating disease in which the body's immune system destroys the protective sheath (myelin) that covers nerves.

This damage interferes with the communication between the brain, spinal cord and other parts of the body, causing symptoms that can range from a mild weakness to an inability to walk or speak clearly. There is no cure for MS, but there are some preliminary data showing that Vitamin D, retinoic acid or Vitamin A, may help alleviate these symptoms.

To determine if Vitamin A could help, the Conrad N. Hilton Foundation recently awarded the Los Angeles Biomedical Research Institute (LA BioMed) a $900,000 grant to study the role of serum Vitamin A in halting – or at least slowing – disease progression in people with Relapsing-Remitting MS. About 80% of MS patients have Relapsing-Remitting MS, in which new symptoms flare up and then go into remission.

"This grant will jump start this area of research in the United States," said Bijal Mehta, MD, MPH, the lead researcher for the LA BioMed study into Vitamin A. "This will be the first large-scale study of whether higher levels of Vitamin A in the bloodstream may lead to improved outcomes for people who have Relapsing-Remitting MS. If the study finds MS patients with higher levels of Vitamin A have reduced progression of the disease, we could then examine using Vitamin A as an additional treatment."

LA BioMed researchers plan to recruit 100 volunteers with Relapsing-Remitting MS to measure the Vitamin A levels in their blood. The researchers also will study Vitamin A's role in promoting repair to the myelin sheaths, which cover the nerves, a process known as remyelination. The research will examine Vitamin A's effectiveness in correlation with two commonly used MS medications: interferon-beta (Avonex, Rebif and Betaseron) or glatimer acetate (Copaxone).

Source: Phys Org © Phys.org™ 2003-2014 (07/01/14)

Study finds clues to understanding MS(02/01/14)

Scientists at the Sanford-Burnham Medical Research Institute have found a possible explanation for the loss of nerve function caused by multiple sclerosis and similar neurodegenerative diseases. The research provides a new approach to finding potential therapies.

A protein called contactin-1 is required to wrap nerves with myelin, a protective sheathing that enables proper function, the scientists found. When myelin is worn away, as in multiple sclerosis, nerves in the brain and spinal cord become damaged and don’t properly transmit sensory and motor signals.

Multiple sclerosis is considered an autoimmune disease, in which the body’s own immune system attacks the nerves for some unknown cause.

Contactin-1 acts like a messenger coordinating a construction crew. It directs myelin formation around axons, the long strands that carry impulses down nerve cells, said Barbara Ranscht, who led the research. Without the protein, myelin-producing cells called oligodendrocytes don’t do their jobs.

The study was published in the Proceedings of the National Academy of Sciences. Ranscht was senior author; Gülsen Çolakoglu was first author.

Working in mice, the researchers found the protein was produced in both the oligodendrocytes and the axons during myelination.

The researchers also inactivated the gene for making contactin-1 in mice. The offspring died shortly after birth, displaying a greatly reduced production of myelin. Moreover, what myelin was produced wasn’t functional, because it wasn’t attached to the axons, Ranscht said.

Myelin formation takes many steps that must be performed in harmony, Ranscht said.

“First of all, the axons need to be there, then the oligodendrocytes come to the axons. They proliferate, they make more cells, then the cells align nicely along the axons, then they get signals from the axons to make the myelin,” she said. “The axons get signals from the oligodendrocytes to be myelinated. It’s a constant cross-talk between the two different cells. What we show in the paper is that contactin is absolutely necessary for this cross-talk.”

Although the study was performed in animals, there’s evidence of the protein’s role in people. A 2011 paper in PNAS found that contactin-1 is involved in development of precursor cells to the myelin-forming oligodendrocytes. Moreover, a 2009 study also in PNAS found that a related molecule called contactin-2 is targeted in an autoimmune response in multiple sclerosis patients.

The study is impressive, said P. Hemachandra Reddy, a neuroscientist at Oregon Science & Health University who published his own research on multiple sclerosis Dec. 26. Reddy and colleagues found that an antioxidant called MitoQ reverses symptoms in mice with an MS-like demyelinating disease.

“This is a very well-executed study,” Reddy said. “I am excited to see this paper.”

The paper described the function of contactin-1 in the optic nerve, providing an explanation for why multiple sclerosis patients may experience blurred vision, Reddy said.

“We did not look at the contactin protein levels in our study; we are going to look at it now, because it makes a lot of sense,” he said. “Maybe MitoQ is enhancing contactin levels.”

Ranscht emphasized that the Sanford-Burnham study represented basic research, and years of further work would be needed before any potential drug could be found. But on the positive side, the research provides a clear guide about what to look for, namely a drug that restores contactin functioning.

“This is something that is a top priority on our research list. ... Is this really the molecule that might help to restore myelin in a demyelinating disease?” Ranscht said. “It’s exciting, because we have a candidate now to look for. That’s where we are. We don’t have a cure.”

Source: U-T San Diego © 1995-2014 The San Diego Union-Tribune (02/01/14)