Signalling pathways that inhibit the capacity of precursor cells for myelin repair

In demyelinating disorders such as Multiple Sclerosis (MS), targets of injury are myelin and oligodendrocytes, leading to severe neurological dysfunction. Regenerative therapies aimed at promoting oligodendrocyte maturation and remyelination are promising strategies for treatment in demyelinating disorders. Endogenous precursor cells or exogenous transplanted cells are potential sources for remyelinating oligodendrocytes in the central nervous system (CNS). Several signalling pathways have been implicated in regulating the capacity of these cell populations for myelin repair. Here, we review neural precursor cells and oligodendrocyte progenitor cells as potential sources for remyelinating oligodendrocytes and evidence for the functional role of key signalling pathways in inhibiting regeneration from these precursor cell populations.

Glial progenitor cell-based treatment and modeling of neurological disease

The diseases of myelin are among the most prevalent and disabling conditions in neurology. These diseases include both the vascular and inflammatory demyelinating disorders of adulthood, as well as the childhood leukodystrophies and cerebral palsy. These fundamentally glial disorders may be amenable to treatment by glial progenitor cells (GPCs), which give rise to astroglia and myelin-producing oligodendrocytes. Given the development of new methods for generating and isolating human GPCs, the myelin disorders may now be compelling targets for cell-based therapy. In addition, the efficient engraftment and expansion of human GPCs in murine hosts has led to the development of human glial chimeric mouse brains, which provides new opportunities for studying the species-specific roles of human glia in cognition, as well as in disease pathogenesis.

Immunotherapy for IgM anti-myelin-associated glycoprotein paraprotein-associated peripheral neuropathies

BACKGROUND

Serum monoclonal anti-myelin-associated glycoprotein antibodies may be pathogenic in some people with immunoglobulin M (IgM) paraprotein and demyelinating neuropathy. Immunotherapies aimed at reducing the level of these antibodies might be expected to be beneficial. This is an update of a review first published in 2003 and previously updated in 2006.

OBJECTIVES

To assess the effects of immunotherapy for IgM anti-myelin-associated glycoprotein paraprotein-associated demyelinating peripheral neuropathy.

SEARCH METHODS

We searched the Cochrane Neuromuscular Disease Group Specialized Register 6 June 2011), CENTRAL (2011, Issue 2), MEDLINE (January 1966 to May 2011) and EMBASE (January 1980 to May 2011) for controlled trials. We also checked bibliographies and contacted authors and experts in the field.

SELECTION CRITERIA

We included randomised or quasi-randomised controlled trials involving participants of any age treated with any type of immunotherapy for anti-myelin-associated glycoprotein antibody-associated demyelinating peripheral neuropathy with monoclonal gammopathy of undetermined significance and of any severity.Our primary outcome measure was change in the Neuropathy Impairment Scale or Modified Rankin Scale at six months after randomisation. Secondary outcome measures were: Neuropathy Impairment Scale or the Modified Rankin Score at 12 months after randomisation; 10-metre walk time, subjective clinical scores and electrophysiological parameters at six and 12 months after randomisation; IgM paraprotein levels and anti-myelin-associated glycoprotein antibody titres at six months after randomisation; and adverse effects of treatments.

DATA COLLECTION AND ANALYSIS

The two authors independently selected studies. Two authors independently assessed the risk of bias in included studies.

MAIN RESULTS

We identified seven eligible trials (182 participants), which tested intravenous immunoglobulin, alfa interferon alfa-2a, plasma exchange, cyclophosphamide and steroids, and rituximab. Only two trials, of intravenous immunoglobulin (with 33 participants, including 20 with antibodies against myelin-associated glycoprotein), had comparable interventions and outcomes, but both were short-term trials.There were no clinical or statistically significant benefits of the treatments used on the outcomes predefined for this review, but not all the predefined outcomes were used in every included trial. Intravenous immunoglobulin showed a statistical benefit in terms of improvement in Modified Rankin Scale at two weeks and 10-metre walk time at four weeks. Cyclophosphamide failed to show any benefit in the trial's primary outcome, and showed a barely significant benefit in the primary outcome specified here, but some toxic adverse events were identified. A trial of rituximab was of poor methodological quality with a high risk of bias and a further larger study is awaited. Serious adverse events were few in the other trials.

AUTHORS' CONCLUSIONS

There is inadequate reliable evidence from trials of immunotherapies in anti-myelin-associated glycoprotein paraproteinaemic neuropathy to form an evidence base supporting any particular immunotherapy treatment. There is very low quality evidence of benefit from rituximab. Large well designed randomised trials of at least six to 12 months duration are required to assess existing or novel therapies, preferably employing unified, consistent, well designed, responsive and valid outcome measures.

[Osmotic demyelination syndrome in patients with hyponatremia caused by neurologic disorders]

Hyponatremia is relatively common in patients with neurologic disorders, while its diagnosis and treatment remain controversial. Osmotic demyelination syndrome (ODS) has shown to be closely associated with hyponatremia. ODS patients often present as central pontine myelinolysis, extrapontine myelinolysis, or both. This article reviews the clinical manifestations, pathogenesis, and risk factors of ODS in patients with hyponatremia caused by neurologic disorders.

Oligodendrogenesis in the subventricular zone and the role of epidermal growth factor

Demyelinating diseases are characterized by an extensive loss of oligodendrocytes and myelin sheaths from axolemma. These neurological disorders are a common cause of disability in young adults, but so far, there is no effective treatment against them. It has been suggested that neural stem cells (NSCs) may play an important role in brain repair therapies. NSCs in the adult subventricular zone (SVZ), also known as Type-B cells, are multipotential cells that can self-renew and give rise to neurons and glia. Recent findings have shown that cells derived from SVZ Type-B cells actively respond to epidermal-growth-factor (EGF) stimulation becoming highly migratory and proliferative. Interestingly, a subpopulation of these EGF-activated cells expresses markers of oligodendrocyte precursor cells (OPCs). When EGF administration is removed, SVZ-derived OPCs differentiate into myelinating and pre-myelinating oligodendrocytes in the white matter tracts of corpus callosum, fimbria fornix and striatum. In the presence of a demyelinating lesion, OPCs derived from EGF-stimulated SVZ progenitors contribute to myelin repair. Given their high migratory potential and their ability to differentiate into myelin-forming cells, SVZ NSCs represent an important endogenous source of OPCs for preserving the oligodendrocyte population in the white matter and for the repair of demyelinating injuries.

Acute urine retention as a clinically isolated syndrome (a case report)

We report a case of 24 years old women with clinically isolated syndrome (CIS) presenting predominantly with acute urine retention. After slight febrile disorder she got acute urine retention. Urologists excluded their nosologies and the patient was sent to our clinic to visit neurologist. At the time of admission the only complain was urine retention. Her neurological and mental status was normal. Her brain and spinal cord MRI revealed pontine demyelination in the right rostral tegmentum (T2se and Flair hyperintensity). Nerve conduction study of lower extremities showed no peripheral nerve lesion. Under the diagnosis of clinically isolated syndrome steroids were prescribed and the patient recovered fully. Urine retention was explained to be a consequence of tegmental demyelinating lesion as it should be a location of Barrington urination centre. Several functional imaging studies confirmed pontine implication in micturition control although the exact site is still missing. Very few cases are reported ascribing unilateral lesion associated with urine retention. We believe our case is one more clear confirmation of unilateral pontine location of supraspinal urination center.

Marburg variant multiple sclerosis - a case report

In this case report we describe the case of a 24 year-old female with a fulminant demyelinating disease of white matter. Disease progression was most probably consistent with the Marburg variant (malignant form) of multiple sclerosis with rapid deterioration of the patient's clinical condition, including bulbar symptoms and epileptic paroxysms and ending with persistent coma and tetraparesis, over the course of 6 months from first symptoms. Repeated Magnetic Resonance Imaging (MRI) examination showed progression of multiple demyelinating lesions culminating in a contiguous focal disorder of the white matter extending both supratentorially and infratentorially. The serial MRI changes closely mapped the deterioration in the patients clinical status. Our patient showed no response to repeated pulse corticotherapy, administration of intravenous immunoglobulins, serial plasmapheresis, and combined high-dose pulse immunosuppression (specify what was used here) and mitoxantrone.

Therapeutic potential of LIF in multiple sclerosis

Therapies for multiple sclerosis (MS) reduce the relapse rate but are unable to stop neurological decline. Here, we evaluate the potential of leukemia inhibitory factor (LIF) as a novel therapeutic in diseases with a neurodegenerative and inflammatory component, such as MS. LIF, which can be a proinflammatory cytokine, can also modulate the immune response in a beneficial way. Recent evidence demonstrates a crucial role of LIF in neuroprotection and axonal regeneration as well as the prevention of demyelination. Finally, LIF is an important survival factor for stem cells and neuronal precursors. Therefore, we propose that LIF is a potential therapeutic candidate for MS.

Cells of the oligodendroglial lineage, myelination, and remyelination

Myelin is critical in maintaining electrical impulse conduction in the central nervous system. The oligodendrocyte is the cell type responsible for myelin production within this compartment. The mutual supply of trophic support between oligodendrocytes and the underlying axons may indicate why demyelinated axons undergo degeneration more readily; the latter contributes to the neural decline in multiple sclerosis (MS). Myelin repair, termed remyelination, occurs in acute inflammatory lesions in MS and is associated with functional recovery and clinical remittances. Animal models have demonstrated that remyelination is mediated by oligodendrocyte progenitor cells (OPCs) which have responded to chemotactic cues, migrated into the lesion, proliferated, differentiated into mature oligodendrocytes, and ensheathed demyelinated axons. The limited remyelination observed in more chronic MS lesions may reflect intrinsic properties of neural cells or extrinsic deterrents. Therapeutic strategies currently under development include transplantation of exogenous OPCs and promotion of remyelination by endogenous OPCs. All currently approved MS therapies are aimed at dampening the immune response and are not directly targeting neural processes.

[Neuromyelitis optica: a clinical update]

INTRODUCTION

Neuromyelitis optica (NMO) or Devic's disease is an autoimmune, inflammatory and demyelinating central nervous system disorder that affects mainly to optic nerve and spinal cord. Recent advances have substantially permitted to expand the knowledge about this entity.

AIM

To present a clinical update on the current understanding of the nature, progression, diagnosis and treatment of NMO.

DEVELOPMENT

Due to its demyelinating nature and its recurrent behavior in most cases, NMO was first considered a form of multiple sclerosis (MS). However, recent findings have led to the conclusion that NMO is a distinct disorder, presenting important immunopathological, clinical, prognostic and therapeutic differences from MS. Fundamental in the under-standing of the disease was the recent discovery of antibodies directed against aquaporin-4 (anti-AQP4, also known as NMO-IgG), which are present in the majority of NMO cases clinically defined, and in a minority of patients with MS. Despite the knowledge on its immunopathogenesis and advances in diagnosis, the treatment of NMO is still challenging.

CONCLUSION

NMO is a demyelinating disease different from MS. Current diagnostic criteria have been enriched with the recent description of the humoral disorder underlying NMO. However, current treatment options for NMO are far from being ideal.

A case of Lewis-Sumner syndrome showing dramatic improvement after plasma exchange

We report a patient with Lewis-Sumner syndrome (LSS) who showed an improvement only with plasma exchange (PE). The patient, 32-yr old man, had progressive multifocal motor-sensory deficits with persistent, multiple conduction blocks and marked slowing of NCVs. Nerve pathology supported a diagnosis of demyelinating neuropathy by revealing marked loss of myelinated fibers with inter- and intrafascicular variation. Although the patient was refractory to treatment with corticosteroid and intravenous immunoglobulin, PE produced a dramatic improvement. Our experience strongly proposes that PE should be tried for refractory LSS.

[Pontine and extrapontine myelinolysis]

INTRODUCTION

Myelinolysis is defined as acute demyelinating disorder, associated with flaccid quadriplegia, speech and swallowing impairment. The pathogenesis is usually related to hydroelectrolytic imbalance, particularly with severe hyponatremia and its rapid correction. The imagiologic diagnostic is commonly done by magnetic resonance imaging.

AIM

The authors present a clinical case focusing on the follow up, rehabilitation program, and giving importance to functionality gains. The main clinical intercurrences related to the late diagnosis are also reported.

CLINICAL CASE

A female patient with documented past psychiatric history and polidipsia was admitted with repeated seizures unsuccessfully controlled by drugs. Hyponatremia was identified and corrected. After the correction, a quadriplegia and a generalized hypotonia were noticed and the patient underwent magnetic resonance imaging. The imaging findings were consistent with the diagnosis of central pontine and extrapontine myelinolysis.

Robust generation of oligodendrocyte progenitors from human neural stem cells and engraftment in experimental demyelination models in mice

BACKGROUND

Cell-based therapy holds great promises for demyelinating diseases. Human-derived fetal and adult oligodendrocyte progenitors (OPC) gave encouraging results in experimental models of dysmyelination but their limited proliferation in vitro and their potential immunogenicity might restrict their use in clinical applications. Virtually unlimited numbers of oligodendroglial cells could be generated from long-term self-renewing human (h)-derived neural stem cells (hNSC). However, robust oligodendrocyte production from hNSC has not been reported so far, indicating the need for improved understanding of the molecular and environmental signals controlling hNSC progression through the oligodendroglial lineage. The aim of this work was to obtain enriched and renewable cultures of hNSC-derived oligodendroglial cells by means of epigenetic manipulation.

METHODOLOGY/PRINCIPAL FINDINGS

We report here the generation of large numbers of hNSC-derived oligodendroglial cells by concurrent/sequential in vitro exposure to combinations of growth factors (FGF2, PDGF-AA), neurotrophins (NT3) and hormones (T3). In particular, the combination FGF2+NT3+PDGF-AA resulted in the maintenance and enrichment of an oligodendroglial cell population displaying immature phenotype (i.e., proliferation capacity and expression of PDGFRalpha, Olig1 and Sox10), limited self-renewal and increased migratory activity in vitro. These cells generate large numbers of oligodendroglial progeny at the early stages of maturation, both in vitro and after transplantation in models of CNS demyelination.

CONCLUSIONS/SIGNIFICANCE

We describe a reliable method to generate large numbers of oligodendrocytes from a renewable source of somatic, non-immortalized NSC from the human foetal brain. We also provide insights on the mechanisms underlying the pro-oligodendrogenic effect of the treatments in vitro and discuss potential issues responsible for the limited myelinating capacity shown by hNSC-derived oligodendrocytes in vivo.

[Remyelination properties of human embryonic nerve cells in conditions of long-term culture]

We have examined the mitogenic and differentiation potential and remyelination properties of human embryonic nerve cells in culture. After 1 month of cultivation without differentiation agents CNP-positive cells (the mitotically-active precursors of oligodendrocytes) were expanded at 3,6 times. At the same time the amount of GalC-positive cells (mature oligodendrocytes) remained low. So, the remyelination properties of embryonic nerve cells can be explained by high concentration of oligodendrocytes precursors. Cell population after cultivation maintained the increased remyelination potential by increasing the number of CNP-positive cells that was confirmed by using experimental demyelination.

Neonatal chimerization with human glial progenitor cells can both remyelinate and rescue the otherwise lethally hypomyelinated shiverer mouse

Congenitally hypomyelinated shiverer mice fail to generate compact myelin and die by 18-21 weeks of age. Using multifocal anterior and posterior fossa delivery of sorted fetal human glial progenitor cells into neonatal shiverer x rag2(-/-) mice, we achieved whole neuraxis myelination of the engrafted hosts, which in a significant fraction of cases rescued this otherwise lethal phenotype. The transplanted mice exhibited greatly prolonged survival with progressive resolution of their neurological deficits. Substantial myelination in multiple regions was accompanied by the acquisition of normal nodes of Ranvier and transcallosal conduction velocities, ultrastructurally normal and complete myelination of most axons, and a restoration of a substantially normal neurological phenotype. Notably, the resultant mice were cerebral chimeras, with murine gray matter but a predominantly human white matter glial composition. These data demonstrate that the neonatal transplantation of human glial progenitor cells can effectively treat disorders of congenital and perinatal hypomyelination.

Inflammatory demyelinating neuropathies and neuropathies associated with monoclonal gammopathies: treatment update

This review focuses on recent data regarding inflammatory demyelinating neuropathies and neuropathies associated with monoclonal gammopathies. We describe both acute and chronic inflammatory neuropathies, and we discuss conditions ranging from mostly cell-mediated to antibody-mediated disorders. These diseases are characterized by proximal and distal sensory motor involvement. Treatments are based on immune-modulation and/or immune-suppression. Work-up sequence and therapeutical modes are discussed in the light of recently published data, with a special interest on new treatment modalities.

An unsuccessful trial of immunomodulatory therapy in delayed posthypoxic demyelination

INTRODUCTION

Delayed posthypoxic demyelination may rarely complicate an episode of severe hypoxia, with or without exposure to carbon monoxide. Following recovery from initial coma, progressive neurologic deterioration ensues with outcomes ranging from death to full recovery. Delayed posthypoxic demyelination is hypothesized to be immunemediated, with support coming from recent animal experiments.

METHODS

We report a 46-year-old man who developed progressive cognitive deficits with abulia approximately 3 weeks after recovering from coma related to alcohol and morphine intoxication.

RESULTS

Despite treatment with high-dose steroids and plasmapheresis, he continued to deteriorate and remained in a vegetative state until his death under hospice care more than 2 months after his initial hypoxic insult. Serial brain imaging and postmortem examination showed bilateral necrosis of the globi pallidi and extensive demyelination in the centrum semiovale and corona radiata.

CONCLUSIONS

Based on an immune-mediated model of disease and given a lack of effective treatments, future use of immunomodulatory therapy may still be worth considering early in the course of this rare and potentially devastating condition.

Myelin repair: the role of stem and precursor cells in multiple sclerosis

Multiple sclerosis is the most common potential cause of neurological disability in young adults. The disease has two distinct clinical phases, each reflecting a dominant role for separate pathological processes: inflammation drives activity during the relapsing-remitting stage and axon degeneration represents the principal substrate of progressive disability. Recent advances in disease-modifying treatments target only the inflammatory process. They are ineffective in the progressive stage, leaving the science of disease progression unsolved. Here, the requirement is for strategies that promote remyelination and prevent axonal loss. Pathological and experimental studies suggest that these processes are tightly linked, and that remyelination or myelin repair will both restore structure and protect axons. This review considers the basic and clinical biology of remyelination and the potential contribution of stem and precursor cells to enhance and supplement spontaneous remyelination.

Cellular approaches for stimulating CNS remyelination

Myelination is critical for the normal functioning of the vertebrate nervous system. In the CNS, myelin is produced by oligodendrocytes, and the loss of oligodendrocytes and myelin results in severe functional impairment. Although spontaneous remyelination occurs in chronic demyelinating diseases such as multiple sclerosis, the repair process eventually fails, often resulting in long-term disability. Two distinct general approaches can be considered to promote myelin repair. In one the target is stimulation of the endogenous myelin repair process through delivery of growth factors, and in the second the target is augmentation of the repair process through the delivery of exogenous cells with myelination potential. In both cases, effective treatment of diseases such as multiple sclerosis requires modulation of the immune system, since demyelination is associated with specific immunological activation. Recent studies have shown that some populations of stem cells, including mesenchymal stem cells, have the capacity of promoting endogenous myelin repair and modulating the immune response, prompting an assessment of their use as therapy in demyelinating diseases such as MS. Other types of demyelinating disorders, such as the leukodystrophies, may require multiple repair strategies including both replacement of dysfunctional cells and delivery or supplementation of growth factors, immune modulators or metabolic enzymes. Here we discuss the use of stem cells for the treatment of demyelinating diseases. While the current number of stem cell-based clinical trials for demyelinating diseases is limited, this is likely to increase significantly in the next few years, and a clear understanding of the applicability, limitations and underlying mechanisms mediating stem cell repair is critical.

Applicability and limitations of MR tracking of neural stem cells with asymmetric cell division and rapid turnover: the case of the shiverer dysmyelinated mouse brain

LacZ-transfected C17.2 neural stem cells (NSCs) were labeled with the superparamagnetic iron oxide formulation Feridex prior to ICV injection in shi/shi neonates. Feridex labeling did not alter cell differentiation in vitro and in vivo. Initially, MR images obtained at 11.7T correlated closely to NSC distribution as assessed with anti-dextran and anti-beta-galactosidase double-fluorescent immunostaining. However, at 6 days postgrafting there was already a pronounced mismatch between the hypointense MR signal and the histologically determined cell distribution, with a surprisingly sharp cutoff rather than a gradual decrease of signal. Positive in vivo BrdU labeling of NSCs showed that significant cell replication occurred post-transplantation, causing rapid dilution of Feridex particles between mother and daughter cells toward undetectable levels. Neural differentiation experiments demonstrated asymmetric cell division, explaining the observed sharp cutoff. At later time points (2 weeks), the mismatch further increased by the presence of non-cell-associated Feridex particles resulting from active excretion or cell death. These results are a first demonstration of the inability of MRI to track rapidly dividing and self-renewing, asymmetrically dividing SCs. Therefore, MR cell tracking should only be applied for nonproliferating cells or short-term monitoring of highly-proliferative cells, with mitotic symmetry or asymmetry being important for determining its applicability.

[Past hepatitis B virus infection and demyelinating multiphasic disease: casual or causal relationship?]

INTRODUCTION

The relationship between hepatitis B virus and hepatitis B vaccine with central nervous system demyelinating diseases is controversial.

CASE REPORTS

We describe two male patients, who in their 70's developed recurrent pictures of acute demyelinating diseases. The first one had recurrent acute disseminated encephalomyelitis (diplopia, paraparesis and urinary retention) and the second one recurrent transverse myelitis (paraparesis and urinary retention).

RESULTS

The cerebrospinal fluid test showed mononuclear pleocytosis with negative oligoclonal bands in both patients. Visual evocated potentials were normal. Magnetic resonance imaging (T2-WI and FLAIR) showed hyperintense lesions located in the brain and spinal cord in the first case and only in the spinal cord in the second. With negative antigenemia, antibodies against hepatitis B core and hepatitis B surface antigens were positive in both patients. No patient had been vaccinated for nor had suffered symptomatic hepatic disease. In the second patient, there was an almost total remission of the symptoms with periodic treatment with immunoglobulins.

CONCLUSIONS

We recommend hepatitis B virus infection investigation in all patients with central nervous system demyelinating disease.

Remyelination of the central nervous system: a valuable contribution from the periphery

The loss of myelin, a major element involved in the saltatory conduction of the electrical impulse of the nervous system, is a major target of current research. Serious long-term disabilities are observed in patients with demyelinating disease of the central nervous system, such as multiple sclerosis. New therapeutic strategies aimed at overcoming myelin damage and axonal loss focus on the repair potential of myelin-forming cells. This review examines the use of peripheral myelin-forming cells, the Schwann cells, to promote myelin repair.

Endogenous or exogenous oligodendrocytes for remyelination

The relative merits of endogenous and exogenous oligodendrocyte progenitor cells (OPCs) for remyelination are compared in terms of their ability to repopulate OPC-depleted tissue and generate remyelinating oligodendrocytes. Exogenous neonatal OPCs can repopulate OPC-depleted tissue 5-10 times faster than endogenous cells and as a result are capable of more extensive remyelination. Both endogenous and exogenous cells will only repopulate normal tissue if there is extensive depletion of the local OPC population and both show reduced ability to generate remyelinating cells in the absence of acute inflammation. When endogenous OPCs are depleted by X-irradiation during cuprizone intoxication, where there is a combination of astrocytosis and acute demyelination, endogenous but not exogenous embryo-derived OPCs fail to repopulate the OPC-depleted cortex.

Mechanisms of disease: inherited demyelinating neuropathies--from basic to clinical research

The hereditary motor and sensory neuropathies (also known as Charcot-Marie-Tooth disease or CMT) are characterized by a length-dependent loss of axonal integrity in the PNS, which leads to progressive muscle weakness and sensory deficits. The 'demyelinating' neuropathies (CMT disease types 1 and 4) are genetically heterogeneous, but their common feature is that the primary defect perturbs myelination. As we discuss in this Review, several new genes associated with CMT1 and CMT4 have recently been identified. The emerging view is that a range of different subcellular defects in Schwann cells can cause axonal loss, which represents the final common pathway of all CMT disease and is independent of demyelination. We propose that Schwann cells provide a first line of axonal neuroprotection. A better understanding of axon-glia interactions should open the way to therapeutic interventions for demyelinating neuropathies. Transgenic animal models have become essential for dissecting CMT disease mechanisms and exploring novel therapies.