Growth factors and myelin regeneration in multiple sclerosis

A Unique Multiplex ELISA to Profile Growth Factors and Cytokines in Cerebrospinal Fluid

Multiplex arrays designed for enzyme-linked immunosorbent assays (ELISAs) are robust and cost-effective for profiling biomarkers. Identification of relevant biomarkers in biological matrices or fluids helps in the understanding of disease pathogenesis. Here, we describe a sandwich ELISA-based multiplex assay to assess growth factor and cytokine levels in cerebrospinal fluid (CSF) samples derived from multiple sclerosis patients, amyotrophic lateral sclerosis patients, and control subjects without any neurological disorder. Results indicate that multiplex assay designed for the sandwich ELISA method is a unique, robust, and cost-effective method for profiling growth factors and cytokines present in CSF samples.

Newly Identified Deficiencies in the Multiple Sclerosis Central Nervous System and Their Impact on the Remyelination Failure

The pathogenesis of multiple sclerosis (MS) remains enigmatic and controversial. Myelin sheaths in the central nervous system (CNS) insulate axons and allow saltatory nerve conduction. MS brings about the destruction of myelin sheaths and the myelin-producing oligodendrocytes (ODCs). The conundrum of remyelination failure is, therefore, crucial in MS. In this review, the roles of epidermal growth factor (EGF), normal prions, and cobalamin in CNS myelinogenesis are briefly summarized. Thereafter, some findings of other authors and ourselves on MS and MS-like models are recapitulated, because they have shown that: (a) EGF is significantly decreased in the CNS of living or deceased MS patients; (b) its repeated administration to mice in various MS-models prevents demyelination and inflammatory reaction; (c) as was the case for EGF, normal prion levels are decreased in the MS CNS, with a strong correspondence between liquid and tissue levels; and (d) MS cobalamin levels are increased in the cerebrospinal fluid, but decreased in the spinal cord. In fact, no remyelination can occur in MS if these molecules (essential for any form of CNS myelination) are lacking. Lastly, other non-immunological MS abnormalities are reviewed. Together, these results have led to a critical reassessment of MS pathogenesis, partly because EGF has little or no role in immunology.

Brain Regeneration Resembles Brain Cancer at Its Early Wound Healing Stage and Diverges From Cancer Later at Its Proliferation and Differentiation Stages

Gliomas are the most frequent type of brain cancers and characterized by continuous proliferation, inflammation, angiogenesis, invasion and dedifferentiation, which are also among the initiator and sustaining factors of brain regeneration during restoration of tissue integrity and function. Thus, brain regeneration and brain cancer should share more molecular mechanisms at early stages of regeneration where cell proliferation dominates. However, the mechanisms could diverge later when the regenerative response terminates, while cancer cells sustain proliferation. To test this hypothesis, we exploited the adult zebrafish that, in contrast to the mammals, can efficiently regenerate the brain in response to injury. By comparing transcriptome profiles of the regenerating zebrafish telencephalon at its three different stages, i.e., 1 day post-lesion (dpl)-early wound healing stage, 3 dpl-early proliferative stage and 14 dpl-differentiation stage, to those of two brain cancers, i.e., low-grade glioma (LGG) and glioblastoma (GBM), we reveal the common and distinct molecular mechanisms of brain regeneration and brain cancer. While the transcriptomes of 1 dpl and 3 dpl harbor unique gene modules and gene expression profiles that are more divergent from the control, the transcriptome of 14 dpl converges to that of the control. Next, by functional analysis of the transcriptomes of brain regeneration stages to LGG and GBM, we reveal the common and distinct molecular pathways in regeneration and cancer. 1 dpl and LGG and GBM resemble with regard to signaling pathways related to metabolism and neurogenesis, while 3 dpl and LGG and GBM share pathways that control cell proliferation and differentiation. On the other hand, 14 dpl and LGG and GBM converge with respect to developmental and morphogenetic processes. Finally, our global comparison of gene expression profiles of three brain regeneration stages, LGG and GBM exhibit that 1 dpl is the most similar stage to LGG and GBM while 14 dpl is the most distant stage to both brain cancers. Therefore, early convergence and later divergence of brain regeneration and brain cancer constitutes a key starting point in comparative understanding of cellular and molecular events between the two phenomena and development of relevant targeted therapies for brain cancers.

Phelan McDermid Syndrome: Multiple Sclerosis as a Rare but Treatable Cause for Regression-A Case Report

Phelan McDermid syndrome (PMcD) is a neurogenetic disease associated with haploinsufficiency of the SHANK3 gene due to a spectrum of anomalies in the terminal region of the long arm of chromosome 22. SHANK3 is the abbreviation for SH3 domain and ankyrin repeat-containing protein, a gene that encodes for proteins of the postsynaptic density (PSD) of excitatory synapses. This PSD is relevant for the induction and plasticity of spine and synapse formation as a basis for learning processes and long-term potentiation. Individuals with PMcD present with intellectual disability, muscular hypotonia, and severely delayed or absent speech. Further neuropsychiatric manifestations cover symptoms of the autism spectrum, epilepsy, bipolar disorders, schizophrenia, and regression. Regression is one of the most feared syndromes by relatives of PMcD patients. Current scientific evidence indicates that the onset of regression is variable and affects language, motor skills, activities of daily living and cognition. In the case of regression, patients normally undergo further diagnostics to exclude treatable reasons such as complex-focal seizures or psychiatric comorbidities. Here, we report, for the first time, the case of a young female who developed progressive symptoms of regression and a dystonic-spastic hemiparesis that could be traced back to a comorbid multiple sclerosis and that improved after treatment with methylprednisolone.

Investigation of Neuregulin-1 and Glial Cell-Derived Neurotrophic Factor in Rodent Astrocytes and Microglia

Growth factors play a crucial role during de- and remyelination of the central nervous system (CNS) due to their neurotrophic functions. We have previously shown that the growth factors neuregulin-1 (Nrg-1) and glial cell-derived neurotrophic factor (Gdnf) are upregulated during the first 2 weeks after induction of toxic demyelination in the CNS. Nevertheless, the factors responsible for Nrg-1/Gdnf upregulation and their effects on glia cells are unknown. We investigated the effect on Nrg-1 and Gdnf expressions after stimulation of primary mouse microglia or astrocytes with various pro- and anti-inflammatory factors. Additionally, primary cells were incubated with NRG-1 and/or GDNF followed by determining the gene expression level of their receptors, chemokines, and other growth factors. We demonstrate that inflammatory stimuli have a distinct impact on the expression of Gdnf, Nrg-1, and their receptors in astrocytes and microglia. In microglia, LPS or simultaneous treatment with IFNγ plus TNFα led to downregulation of Nrg-1, whereas LPS treatment slightly increased Nrg-1 expression in astrocytes. Furthermore, Gdnf was slightly upregulated after TFG-β treatment in microglia, while Gdnf was significantly upregulated after LPS treatment in astrocytes. In contrast, treatment with GDNF or/and NRG-1 did not alter any measured gene expression in microglia or astrocytes. Taken together, our in vitro studies show that Nrg-1, Gdnf, and their receptors are differently regulated in astrocytes and microglia upon inflammatory stimuli. The lack of response of astrocytes and microglia to NRG-1 and GDNF suggests that both factors exert their effects directly on neurons.

PDGF Modulates Synaptic Excitability and Short-Latency Afferent Inhibition in Multiple Sclerosis

Maintenance of synaptic plasticity reserve is crucial to contrast clinical deterioration in MS and PDGF plays a key role in this phenomenon. Indeed, higher cerebrospinal fluid PDGF concentration correlates with improved clinical recovery after a relapse, and the amplitude of LTP-like cortical plasticity in relapsing-remitting MS patients. However, LTP-like cortical plasticity varies depending on the individual level of inhibitory cortical circuits. Aim of this study was to explore whether PDGF-CSF concentration correlates with inhibitory cortical circuits explored by means of transcranial magnetic stimulation in patients affected by relapsing-remitting MS. We further performed electrophysiological experiments evaluating GABAergic transmission in the experimental autoimmune encephalomyelitis (EAE) hippocampus. Our results reveal that increased CSF PDGF concentration correlates with decreased short afferent inhibition in the motor cortex in MS patients and decreased GABAergic activity in EAE. These findings show that PDGF affects GABAergic activity both in MS patients and in EAE hippocampus.

A pilot study of recombinant insulin-like growth factor-I in seven multiple sclerosis patients

The purpose of this open-label, crossover study was to determine the safety and efficacy of recombinant insulin-like growth factor-I (rhIGF-I) using magnetic resonance imaging (MRI) and clinical measures of disease activity in seven multiple sclerosis (MS) patients. Monthly clinical and MRI examinations were performed during a 24-week baseline and a 24-week treatment period with rhIGF-I. The primary outcome measure was contrast enhancing lesion (CEL) frequency on treatment compared to baseline. Secondary outcome measures included clinical and MRI measures of disease activity including. white matter lesion load (WMLL), magnetization transfer ratio (MTR), TI-Hypointensity volume, cervical spine cross-sectional area and proton magnetic resonance spectroscopic (MRS) imaging for determining regional metabolite ratios. rhIGF-I (Cephalon) was administered at a dose of 50 mg subcutaneously twice a day for 6 months. rhIGF-I was safe and well tolerated with no severe adverse reactions. There was no significant difference between baseline and treatment periods for any MRI or clinical measures of disease activity. Although rhIGF-I did not alter the course of disease in this small cohort of MS patients, the drug was well tolerated. Further studies using rhIGF-I alone or in combination with other therapies may be of value because of the proposed mechanism of action of this growth factor on the oligodendrocyte and remyelination. Multiple Sclerosis (2002)8,24-29

Novel functional polymorphism in IGF-1 gene associated with multiple sclerosis: A new insight to MS

BACKGROUND

Interactions between several genes and environment may play a role in susceptibility to multiple sclerosis (MS). The IGF-1 plays a key role in proliferation, maintenance and survival of nerve cells. Therefore, we hypothesized that IGF-1 may be a target for prediction and control MS. We aimed to analysis IGF-1 gene promoter sequence, to investigate the effect of the single nucleotide variants on IGF-1 expression and its association with MS.

METHODS

We enrolled 339 MS patients and 431 healthy controls. A specific region in IGF-1 gene promoter was investigated by SSCP analysis. All samples were genotyped by SSP-PCR. In-vitro and in-vivo IGF-1 production was measured by ELISA assay. IGF-1 expression in PBMCs was measured using real-time PCR.

RESULTS

We identified a T to C single nucleotide substitution at position -1089 and a C to T at position -383 from transcription start site in the IGF-1 gene promoter. There was a significant association between MS and genotypes IGF-1(-383) C/T (p=0.001) and IGF-1(-383) C/C (p<0.001). There was also a significant association between IGF-1(-383) allele C and MS (p=0.001). In-vitro and in-vivo IGF-1 level showed that IGF-1 production in samples with genotype IGF-1(-383) C/C significantly was less than T/T (p=0.004) but not T/C (p=0.220).

CONCLUSION

According to IGF-1 roles in CNS and our results, this study suggests that low IGF-1 level may be associated with susceptibility to MS.

Role of C16, angiopoietin-1 and regeneration gene protein 2 in attenuating inflammation in an experimental rat model of autoimmune encephalomyelitis

Multiple sclerosis (MS) is a chronic neurological disorder that affects the central nervous system (CNS), and results in CNS inflammation and damage to myelin. In this study, we examined the possible synergistic effects of C16, angiopoietin-1 (Ang-1) and regeneration gene protein 2 (Reg-2) in alleviating inflammation in an acute experimental autoimmune encephalomyelitis (EAE) model. We employed multiple histological, morphological and iconographic assays to examine the effect of those drugs on disease onset, clinical scores and behavioral deficits. Our results demonstrated that triple combination therapy was more efficient than the monotherapy in EAE treatment. The triple therapy significantly delayed the onset of motor symptoms, reduced disease severity, attenuated inflammatory cell infiltration and suppressed the secretion of proinflammatory cytokines. Additionally, treatment increased anti-inflammatory cytokines expression, inhibited reactive astrocytes proliferation, reduced demyelination and axonal loss, and finally reduced the neural death. Specifically, Reg-2 administration rescued oligodendrocytes and neuronal axons mainly by direct neurotrophic effects, while C16+Ang-1 (C+A) mainly improved the inflammatory milieu. In conclusion, our study suggests a possible synergistic effect through targeting a variety of pathways in relieving the clinical symptoms of inflammation in acute EAE model. Therefore, using molecules that target different molecular pathways can be beneficial for exploring novel therapeutic approaches for MS treatment.

Reg-2, A Downstream Signaling Protein in the Ciliary Neurotrophic Factor Survival Pathway, Alleviates Experimental Autoimmune Encephalomyelitis

Ciliary neurotrophic factor (CNTF), originally described as a neurocytokine that could support the survival of neurons, has been recently found to alleviate demyelination, prevent axon loss, and improve functional recovery in a rat model of acute experimental autoimmune encephalomyelitis (EAE). However, poor penetration into the brain parenchyma and unfavorable side effects limit the utility of CNTF. Here, we evaluated the therapeutic potential of a protein downstream of CNTF, regeneration gene protein 2 (Reg-2). Using multiple morphological, molecular biology, and electrophysiological methods to assess neuroinflammation, axonal loss, demyelination, and functional impairment, we observed that Reg-2 and CNTF exert similar effects in the acute phase of EAE. Both treatments attenuated axonal loss and demyelination, improved neuronal survival, and produced functional improvement. With a smaller molecular weight and improved penetration into the brain parenchyma, Reg-2 may be a useful substitute for CNTF therapy in EAE and multiple sclerosis (MS).

A monoclonal natural human IgM protects axons in the absence of remyelination

BACKGROUND

Whereas demyelination underlies early neurological symptoms in multiple sclerosis (MS), axonal damage is considered critical for permanent chronic deficits. Intracerebral infection of susceptible mouse strains with Theiler's murine encephalomyelitis virus (TMEV) results in chronic induced demyelinating disease (TMEV-IDD) with progressive axonal loss and neurologic dysfunction similar to progressive forms of MS. We previously reported that treatment of chronic TMEV-IDD mice with a neurite outgrowth-promoting natural human antibody, HIgM12, improved brainstem NAA concentrations and preserved functional motor activity. In order to translate this antibody toward clinical trial, we generated a fully human recombinant form of HIgM12, rHIgM12, determined the optimal in vivo dose for functional improvement in TMEV-IDD, and evaluated the functional preservation of descending spinal cord axons by retrograde labeling.

FINDINGS

SJL/J mice at 45 to 90 days post infection (dpi) were studied. A single intraperitoneal dose of 0.25 mg/kg of rHIgM12 per mouse is sufficient to preserve motor function in TMEV-IDD. The optimal dose was 10 mg/kg. rHIgM12 treatment protected the functional transport in spinal cord axons and led to 40 % more Fluoro-Gold-labeled brainstem neurons in retrograde transport studies. This suggests that axons are not only present but also functionally competent. rHIgM12-treated mice also contained more mid-thoracic (T6) spinal cord axons than controls.

CONCLUSIONS

This study confirms that a fully human recombinant neurite outgrowth-promoting monoclonal IgM is therapeutic in a model of progressive MS using multiple reparative readouts. The minimum effective dose is similar to that of a remyelination-promoting monoclonal human IgM discovered by our group that is presently in clinical trials for MS.

Changes of CXCL12, CXCL14 and PDGF levels in the brain of patients with idiopathic demyelinating optic neuritis and neuromyelitis optica

The CXC chemokines (CXC-motif ligand 12 and CXC-motif ligand 14) and platelet-derived growth factor are suggested to modulate remyelination in the course of many demyelinating diseases. The present study compared the difference in the brain levels of these chemokines between patients with idiopathic demyelinating optic neuritis (IDON) and neuromyelitis optica (NMO) by measuring their concentrations in the cerebrospinal fluid using an enzyme linked immunosorbent assay. Our data indicate that the prognosis of neuritis depends on the remyelinating process that is impaired due to decreased chemokines. The much lower levels of chemokines would specifically indicate the severe neuritis, such as NMO.

Targeting insulin-like growth factor 1 leads to amelioration of inflammatory demyelinating disease

In patients with multiple sclerosis (MS) and in mice with experimental autoimmune encephalomyelitis (EAE), proliferating autoreactive T cells play an important role in the pathogenesis of the disease. Due to the importance of these myelin-specific T cells, these cells have been therapeutic targets in a variety of treatments. Previously we found that Lenaldekar (LDK), a novel small molecule, could inhibit exacerbations in a preclinical model of MS when given at the start of an EAE exacerbation. In those studies, we found that LDK could inhibit human T cell recall responses and murine myelin responses in vitro. In these new studies, we found that LDK could inhibit myelin specific T cell responses through the insulin-like growth factor-1 receptor (IGF-1R) pathway. Alteration of this pathway led to marked reduction in T cell proliferation and expansion. Blocking this pathway could account for the observed decreases in clinical signs and inflammatory demyelinating disease, which was accompanied by axonal preservation. Our data indicate that IGF-1R could be a potential target for new therapies for the treatment of autoimmune diseases where autoreactive T cell expansion is a requisite for disease.

Growth factors and synaptic plasticity in relapsing-remitting multiple sclerosis

During multiple sclerosis (MS) inflammatory attacks, and in subsequent clinical recovery phases, immune cells contribute to neuronal and oligodendroglial cell survival and tissue repair by secreting growth factors. Animal studies showed that growth factors also play a substantial role in regulating synaptic plasticity, and namely in long-term potentiation (LTP). LTP could drive clinical recovery in relapsing patients by restoring the excitability of denervated neurons. We recently reported that maintenance of synaptic plasticity reserve is crucial to contrast clinical deterioration in MS and that the platelet-derived growth factor (PDGF) may play a key role in its regulation. We also reported that a Hebbian form of LTP-like cortical plasticity, explored by paired associative stimulation (PAS), correlates with clinical recovery from a relapse in MS. Here, we explored the role of PDGF in clinical recovery and in adaptive neuroplasticity in relapsing-remitting MS (RR-MS) patients. We found a correlation between the cerebrospinal fluid (CSF) PDGF concentrations and the extent of clinical recovery after a relapse, as full recovery was more likely observed in patients with high PDGF concentrations and poor recovery in subjects with low PDGF levels. Consistently with the idea that PDGF-driven synaptic plasticity contributes to attenuate the clinical consequences of tissue damage in RR-MS, we also found a striking correlation between CSF levels of PDGF and the amplitude of LTP-like cortical plasticity explored by PAS. CSF levels of fibroblast growth factor, granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor did not correlate with clinical recovery nor with measures of synaptic transmission and plasticity.

Recognition of the kind of stress coping in patients of multiple sclerosis

BACKGROUND

Investigations have shown that some factors like stress can increase the recurrence and severity of multiple sclerosis (MS). Considering the direct influences of depression and anxiety on our body immunity system, and also the relation between stress and factors, such as Insulin Growth Factor (IGF-1), involved in neurogenesis and myelin repairing, it is an essential issue to identify the most common method used in relieving stress by such patients.

OBJECTIVE

To identify the type of common coping methods for stressful situation.

MATERIALS AND METHODS

This case-control study was performed on 50 patients of both the genders with MS in Esfahan (Esfahan MS Association). The data were collected and then analyzed using analysis of variance (ANOVA) method with the help of SPSS software version 15. P value less than 0.05 was considered as statistically significant.

RESULTS

In our study, coping method for stressful situation was significantly different in MS patients versus the healthy group (P=0.02). Descriptive indices showed that these patients use avoidant method more commonly than the control group (mean=45.01, SD=8.9 vs. mean=40.8, SD=11.8, respectively).

CONCLUSION

Due to the different methods used by MS patients to cope with stressful situation in comparison with the healthy ones, more appropriate techniques can be introduced to modify them, and hence, less stress-induced side effects could be expected in this population.

Neonatal and adult O4(+) oligodendrocyte lineage cells display different growth factor responses and different gene expression patterns

Oligodendrocytes are the myelinating cells of the central nervous system. Although the CNS possesses the ability to repair demyelinating insults, in certain cases, such as the chronic lesions found in multiple sclerosis, remyelination fails. Cycling cells capable of becoming oligodendrocytes have been identified in both the developing and the adult mammalian forebrain. Many studies have focused on differences in gene expression profiles as oligodendrocyte progenitors differentiate into myelinating oligodendrocytes by isolating cells at different developmental stages from animals at a single age. However, few have studied the differences that exist between the progenitors of the neonatal CNS and those of the adult CNS. This study examined the response of neonatal and adult O4(+) cells to platelet-derived growth factor-AA, basic fibroblast growth factor, and insulin-like growth factor-1 and revealed marked differences. Whereas adult cells readily differentiated in vitro, the majority of neonatal progenitors remained immature. Microarray analysis was used to examine differences between acutely isolated neonatal and adult progenitors further. Gene expression profiles showed that the adult O4(+) cells are more developmentally mature than neonatal cells. Neonatal cells expressed higher levels of genes involved in proliferation. Adult O4(+) cells expressed higher levels of transcripts for genes involved in cell death and survival. Therefore, O4(+) cells from the adult differ greatly from those of the neonate, and the developmental stage of the animal models utilized must be taken into consideration when applying principles from neonatal systems to the adult.

Is multiple sclerosis a mitochondrial disease?

Multiple sclerosis (MS) is a relatively common and etiologically unknown disease with no cure. It is the leading cause of neurological disability in young adults, affecting over two million people worldwide. Traditionally, MS has been considered a chronic, inflammatory disorder of the central white matter in which ensuing demyelination results in physical disability. Recently, MS has become increasingly viewed as a neurodegenerative disorder in which axonal injury, neuronal loss, and atrophy of the central nervous system leads to permanent neurological and clinical disability. In this article, we discuss the latest developments on MS research, including etiology, pathology, genetic association, EAE animal models, mechanisms of neuronal injury and axonal transport, and therapeutics. In this article, we also focus on the mechanisms of mitochondrial dysfunction that are involved in MS, including mitochondrial DNA defects, and mitochondrial structural/functional changes.

In vitro and in vivo pharmacological models to assess demyelination and remyelination

In making a selection of cellular tools and animal models for generating screening assays in the search for new drugs, one needs to take into consideration the practicality of their use in the drug discovery process. Conducting high-throughput primary screens using libraries of small molecules, close to 1 million members in size, requires the generation of large numbers of cells which are easily acquired, reliably enriched, and reproducibly responsive to standard positive controls. These cells need to be similar in form and function to their counterparts in human disease. In vitro assays that can be mechanized by using robots can therefore save time and costs. In selecting in vivo models, consideration must be given to the species and strain of animal chosen, the appropriateness of the model to human disease, the extent of animal husbandry required during the in-life pharmacological assessment, the technical aspects of generating the model and harvesting the tissues for analyses, the cost of research tools in terms of time and money (demyelinating and remyelinating agents, amount of compound to be generated), and the length of time required for drug testing in the model. A consideration of the translational aspects of the in vivo model compared to those used in the clinic is also important. These themes will be developed with examples for drug discovery in the field of CNS demyelination and repair, specifically as it pertains to multiple sclerosis.

Remyelination protects axons from demyelination-associated axon degeneration

In multiple sclerosis, demyelination of the CNS axons is associated with axonal injury and degeneration, which is now accepted as the major cause of neurological disability in the disease. Although the kinetics and the extent of axonal damage have been described in detail, the mechanisms by which it occurs are as yet unclear; one suggestion is failure of remyelination. The goal of this study was to test the hypothesis that failure of prompt remyelination contributes to axonal degeneration following demyelination. Remyelination was inhibited by exposing the brain to 40 Gy of X-irradiation prior to cuprizone intoxication and this resulted in a significant increase in the extent of axonal degeneration and loss compared to non-irradiated cuprizone-fed mice. To exclude the possibility that this increase was a consequence of the X-irradiation and to highlight the significance of remyelination, we restored remyelinating capacity to the X-irradiated mouse brain by transplanting of GFP-expressing embryo-derived neural progenitors. Restoring the remyelinating capacity in these mice resulted in a significant increase in axon survival compared to non-transplanted, X-irradiated cuprizone-intoxicated mice. Our results support the concept that prompt remyelination protects axons from demyelination-associated axonal loss and that remyelination failure contributes to the axon loss that occurs in multiple sclerosis.

Up-regulation of platelet-derived growth factor by peripheral-blood leukocytes during experimental allergic encephalomyelitis

In multiple sclerosis (MS) and its animal model, experimental allergic encephalomyelitis (EAE), clinical disease is associated with infiltration of the central nervous system (CNS) by immune cells. Subsequent remission with remyelination has been linked to an increased occurrence of oligodendrocyte progenitor (O2A) cells. Platelet-derived growth factor (PDGF) and fibroblast growth factor-2 (FGF-2) are key growth factors for O2A cells, yet little is known about their relevance in EAE and MS. We analyzed the expression of PDGF, FGF-2, and their receptors by peripheral-blood leukocytes (PBLs) and lymphocyte subsets during MBP-induced EAE. Strong up-regulation of PDGF, but not FGF-2, was observed in PBLs, with the highest expression after the disease maximum. T, NK, and NKT cells expressed PDGF, which is a novel observation because thus far only monocytes/macrophages have been reported to express PDGF. These results extend the idea that growth factors may contribute to improved CNS tissue repair, including PDGF, which is secreted by lesion-homing immune cells. The production of PDGF by lymphocytes may have potential therapeutic value when activating or modulating T-cell responses in demyelinating diseases.

IGF-I-induced oligodendrocyte progenitor proliferation requires PI3K/Akt, MEK/ERK, and Src-like tyrosine kinases

Insulin-like growth factor-I (IGF-I) is required for the growth of oligodendrocytes, although the underlying mechanisms are not fully understood. Our aim was to investigate the role of phosphatidylinositol 3-kinase (PI3K), mitogen-activated protein kinase kinase (MEK1), and Src family tyrosine kinases in IGF-I-stimulated proliferation of oligodendrocyte progenitors. IGF-I treatment increased the proliferation of cultured oligodendrocyte progenitors as determined by measuring incorporation of [(3)H]-thymidine and bromodeoxy-uridine (BrdU). IGF-I stimulated a transient phosphorylation of 3-phosphoinositide-dependent kinase-1 (PDK1) and extracellular signal-regulated kinases (ERK1/2) (targets of MEK1), as well as a rapid and sustained activation of Akt (a target of PI3K). Furthermore, inhibitors of PI3K (LY294002 and Wortmannin), MEK1 (PD98059 and U0126), and Src family tyrosine kinases (PP2) decreased IGF-I-induced proliferation, and blocked ERK1/2 activation. LY294002, Wortmannin and PP2 also blocked Akt activation. To further determine whether Akt is required for IGF-I stimulated oligodendrocyte progenitor proliferation, cultures were infected with adenovirus vectors expressing dominant-negative mutants of Akt or treated with pharmacological inhibitors of Akt. All treatments reduced IGF-I-induced oligodendrocyte progenitor proliferation. Our data indicate that stimulation of oligodendrocyte progenitor proliferation by IGF-I requires Src-like tyrosine kinases as well as the PI3K/Akt and MEK1/ERK signaling pathways.

Functional recovery of chronic complete idiopathic transverse myelitis after administration of neurotrophic factors

STUDY DESIGN

Case report.

OBJECTIVE

To evaluate the functional recovery of chronic complete idiopathic transverse myelitis (ITM) after administration of acidic fibroblast growth factor (aFGF).

METHODS

A 28-year-old woman presented with a 4-year history of spastic paralysis, sensory level at T10, urinary retention and constipation due to ITM. In all, 20 microg aFGF bolus injection was applied via intradural lumbar puncture, which was repeated every 5 months for 15 months.

RESULTS

At 3 weeks after first injection, the patient experienced vague sensation at approximately T12-L1 dermatomes. At 2 months after the second injection, muscle activities and gait pattern were recorded in bilateral gluteus and hip abductors as she ambulated with long leg brace and axillary crutches. Increased walking speeds, reduced pelvic tilting and reduced compensatory trunk rotation during the swing phase were also demonstrated as compared to the initial gait analysis. At 18 months after injection, motor evoked potentials were obtained in hip abductors of both legs.

CONCLUSIONS

aFGF may increase the efficacy of spinal reactivation/regeneration and is a potential remedy for chronic transverse myelitis.

Neuroprotection in multiple sclerosis

In chronic inflammatory diseases like multiple sclerosis (MS), neuroprotection refers to strategies aimed at prevention of the irreversible damage of various neuronal and glial cell populations, and promoting regeneration. It is increasingly recognized that MS progression, in addition to demyelination, leads to substantial irreversible damage to, and loss of neurons, resulting in brain atrophy and cumulative disability. One of the most promising neuroprotective strategies involves the use of bone marrow derived stem cells. Both hematopoietic and non-hematopoietic (stromal) cells can, under certain circumstances, differentiate into cells of various neuronal and glial lineages. Neuronal stem cells have also been reported to suppress EAE by exerting direct in situ immunomodulating effects, in addition to their ability to provide a potential source for remyelination and neuroregeneration. Preliminary results from our laboratory indicate that intravenous or intracerebral/intraventricular injection of bone marrow derived stromal cells could differentiate in neuronal/glial cells and suppress the clinical signs of chronic EAE. Both bone marrow and neuronal stem cells may therefore have a therapeutic potential in MS. It seems that future treatment strategies for MS should combine immunomodulation with neuroprotective modalities to achieve maximal clinical benefit.

Autoantigen-pulsed dendritic cells constitute a beneficial cytokine and growth factor network in ameliorating experimental allergic encephalomyelitis

Injection of myelin basic protein (MBP)-pulsed dendritic cells (DC) into healthy rats, as we reported before and observed in this study, did not induce clinical experimental allergic encephalomyelitis (EAE), but effectively protected the rats from subsequent EAE induction. The mechanisms by which MBP-pulsed DC mediate immune protection are not completely understood. In the present study, we mainly explored the dynamic change of cytokine and growth factor mRNA expression in spinal cords after subcutaneous injection of MBP-pulsed and unpulsed DC. The expression of interleukin (IL)-1, interferon-gamma and tumour necrosis factor-alpha as well as programmed death ligand (PDL)-1, PDL-2, signal transducer and activator of transcription (STAT)4, STAT6, matrix metalloproteinase (MMP)-9 and tissue inhibitor of metalloproteinases (TIMP)-2 was increased on day 0 postimmunization (p.i.). The increase of IL-12 expression was observed on day 7 p.i., while the increase of IL-10 expression mainly occurred on day 14 p.i. Except downregulation of insulin-like growth factor-1, the expression of brain-derived neurotrophic factor, ciliary neurotrophic factor, fibroblast growth factor (FGF)-2 and platelet-derived growth factor (PDGF)-B/C as well as nerve growth factor receptor (NGF-R), FGF receptor, PDGF-R-alpha and beta was elevated on day 0 p.i., while the increase of TIMP and NGF was observed on days 0 and 7 p.i. There were no significant differences on MMP-2, spinal cord-derived growth factor and PDGF-A mRNA expression. In line with the suppression of EAE induced by MBP-pulsed DC, the dynamic change of cytokines and growth factors in spinal cords should constitute a beneficial microenvironment against EAE.

Markers for OLN-93 oligodendroglia differentiation

Oligodendrocytes are target cells in the pathogenesis of multiple sclerosis (MS), a chronic demyelinating disease of the central nervous system (CNS). During the course of the disease, inflammatory mediators may damage oligodendrocytes and their myelin sheaths. Differentiation of oligodendrocyte progenitors is an important step in the process of remyelination. In the present study, OLN-93 differentiation was studied in co-culture with C6 astrocytes as a natural source of growth and differentiation factors as well as after exposure to insulin-like growth factor-I (IGF-I). Morphological evaluation showed an increased degree of differentiation of OLN-93 cells after IGF-I administration, but not after co-culture with astrocytes. During early differentiation, 2', 3'-cyclic nucleotide 3'-phosphohydrolase (CNP) and zonula occludens-1 (ZO-1) tight junction protein expression were significantly increased. However, neither astrocyte co-culture nor exposure to IGF-I further increased the expression of these markers. Although reverse transcriptase-polymerase chain reaction revealed myelin basic protein (MBP) mRNA expression not to be affected during differentiation, we did find increased MBP protein expression by Western blotting. ZO-1 protein and DM20 mRNA levels were increased during the course of differentiation and after IGF-I administration. The present findings suggest that ZO-1 may be used as a marker for OLN-93 oligodendroglia differentiation.

Inhibition of Src-like kinases reveals Akt-dependent and -independent pathways in insulin-like growth factor I-mediated oligodendrocyte progenitor survival

Insulin-like growth factor I (IGF-I) has been previously shown to promote survival of oligodendrocyte progenitors; however, the underlying mechanisms are not fully understood. Our aim was to investigate the involvement of phosphatidylinositol 3-kinase (PI3K), MEK1, and Src family tyrosine kinases in IGF-I-mediated oligodendrocyte progenitor survival. In agreement with previous studies, IGF-I promoted cell survival. We show that IGF-I prevented apoptosis induced by growth factor deprivation in a PI3K-dependent and MEK/ERK-independent manner. In addition, IGF-I activated Akt while inhibiting caspase-3 activation, and these effects were reversed by the PI3K inhibitors LY 294002 and wortmannin, but not by the MEK1 inhibitor PD 98059. Interestingly, PP2, a specific Src-like kinase inhibitor, blocked the tyrosine phosphorylation of Src, Fyn, and Lyn and IGF-I-stimulated Akt activation, yet had no significant effects on caspase-3 activation or progenitor survival. To further determine whether Akt is required for IGF-I-mediated survival, oligodendrocyte progenitors were transduced with defective Akt mutants or treated with an Akt inhibitor. Although the Akt mutants and inhibitor decreased Akt activity and reduced basal cell survival, IGF-I could partially rescue oligodendrocyte progenitors by decreasing caspase-3 activation. These results suggest that 1) PI3K is essential for IGF-I-promoted cell survival, 2) downstream activation of Akt-dependent and -independent pathways is involved, and 3) Src-like tyrosine kinases participate in IGF-I-induced Akt activation. Therefore, an unidentified effector(s) of PI3K appears to be involved in conferring complete IGF-I-mediated protection of oligodendrocyte progenitors.

Presence of nerve growth factor and TrkA expression in the SVZ of EAE rats: evidence for a possible functional significance

Nerve growth factor (NGF) is a well-characterized neurotrophic factor that plays a crucial role during development in the growth, differentiation, and maintenance of brain neurons as well as in the reparative response of the adult brain to neuronal damage. Recent studies have shown that acute axonal loss occurs in multiple sclerosis (MS) and its animal model, experimental allergic encephalomyelitis (EAE), and that NGF suppresses clinical symptoms of EAE in nonhuman primates. Aim of the present study was to investigate the role of NGF in the regenerative response of the adult brain to neuronal damage occurring in EAE. Using EAE rats, we have found that exogenous NGF injection and NGF deprivation (NGF autoimmunization) can act on growth and differentiation of brain precursor cells in the subventricular zone (SVZ) of EAE rats. Moreover, NGF administration in brain of EAE rats stimulates the expression of early neuronal markers on proliferating precursor cells of the SVZ. The data obtained demonstrated that NGF and its antibody affect bromodeoxyuridine (BrdU) incorporation and NGF receptor expression by SVZ progenitor cells in the brain of EAE rats.

Role of nerve growth factor and other trophic factors in brain inflammation

Inflammation in the brain is a double-edged process that may be beneficial in promoting homeostasis and repair, but can also result in tissue injury through the damaging potential of inflammatory mediators. Thus, control mechanisms that minimize the extent of the inflammatory reaction are necessary in order to help preserve brain architecture and restore function. The expression of neurotrophic factors such as nerve growth factor (NGF) is increased after brain injury, in part mediated by effects on astrocytes of pro-inflammatory mediators and cytokines produced by immune cells. Conversely, cells of the immune system express NGF receptors, and NGF signaling modulates immune function. Multiple sclerosis (MS) and the disease model experimental autoimmune encephalomyelitis are neurodegenerative disorders whereby chronic destruction of the brain parenchyma results from an autoaggressive, immune-mediated inflammatory process and insufficient tissue regeneration. Here, we review evidence indicating that the increased production of NGF and other trophic factors in central nervous system (CNS) during these diseases can suppress inflammation by switching the immune response to an anti-inflammatory, suppressive mode in a brain-specific environment. Thus, trophic factors networks in the adult CNS not only protects axons and myelin but appear to also actively contribute to the maintenance of the brain immune privilege. These agents may represent good targets for therapeutic intervention in MS and other chronic CNS inflammatory diseases.

A pilot study of recombinant insulin-like growth factor-1 in seven multiple sderosis patients

The purpose of this open-label, crossover study was to determine the safety and efficacy of recombinant insulin-like growth factor-1 (rhIGF-1) using magnetic resonance imaging (MRI) and clinical measures of disease activity in seven multiple sderosis (MS) patients. Monthly clinical and MPI examinations were performed during a 24-week baseline and a 24-week treatment period with rhIGF-1. The primary outcome measure was contrast enhancing lesion (CEL) frequency on treatment compared to baseline. Secondary outcome measures included dinical and MRI measures of disease activity including: white matter lesion load (WMLL), magnetization transfer ratio (MTR), T1-Hypointensity volume, cervical spine cross-sectional area and proton magnetic resonance spectroscopic (MRS) imaging for determining regional metabolite ratios. rhIGF-1 (Cephalon) was administered at a dose of 50 mg subcutaneously twice a day for 6 months. rhIGF-1 was safe and well tolerated with no severe adverse reactions. There was no significant difference between baseline and treatment periods for any MRI or clinical measures of disease activity. Although rhIGF-1 did not alter the course of disease in this small cohort of MS patients, the drug was well tolerated. Further studies using rhIGF-1 alone or in combination with other therapies may be of value because of the proposed mechanism of action of this growth factor on the oligodendrocyte and remyelination.

Ciliary neurotrophic factor activates spinal cord astrocytes, stimulating their production and release of fibroblast growth factor-2, to increase motor neuron survival

At focal CNS injury sites, several cytokines accumulate, including ciliary neurotrophic factor (CNTF) and interleukin-1beta (IL-1beta). Additionally, the CNTF alpha receptor is induced on astrocytes, establishing an autocrine/paracrine loop. How astrocyte function is altered as a result of CNTF stimulation remains incompletely characterized. Here, we demonstrate that direct injection of CNTF into the spinal cord increases GFAP expression and astroglial size and that primary cultures of spinal cord astrocytes treated with CNTF, IL-1beta, or leukemia inhibitory factor exhibit nuclear hypertrophy comparable to that observed in vivo. Using a coculture bioassay, we further demonstrate that CNTF treatment of astrocytes increases their ability to support ChAT(+) ventral spinal cord neurons (presumably motor neurons) more than twofold compared with untreated astrocytes. Also, the complexity of neurites was significantly increased in neurons cultured with CNTF-treated astrocytes compared with untreated astrocytes. RT-PCR analysis demonstrated that CNTF increased levels of FGF-2 and nerve growth factor (NGF) mRNA and that IL-1beta increased NGF and hepatocyte growth factor mRNA levels. Furthermore, both CNTF and IL-1beta stimulated the release of FGF-2 from cultured spinal cord astrocytes. These findings demonstrate that cytokine-activated astrocytes better support CNS neuron survival via the production of neurotrophic molecules. We also show that CNTF synergizes with FGF-2, but not epidermal growth factor, to promote DNA synthesis in spinal cord astrocyte cultures. The significance of these findings is discussed by presenting a new model depicting the sequential activation of astrocytes by cytokines and growth factors in the context of CNS injury and repair.

IGF-I synergizes with FGF-2 to stimulate oligodendrocyte progenitor entry into the cell cycle

Secreted peptide growth factors are critical extracellular signals that interact to promote the proliferation, differentiation, and survival of progenitor cells in developing tissues. IGF-I signaling through the IGF type I receptor provides a mitogenic signal for numerous cell types, including stem and progenitor cells. We have utilized the O-2A oligodendrocyte progenitor to study the mechanism of IGF-I mitogenic actions since these progenitors respond to IGF-I in vitro, and gene targeting studies in mice have demonstrated that IGF-I is essential for normal oligodendrocyte development in vivo. The goal of this study was to elucidate the mechanism by which IGF-I promotes the proliferation of oligodendrocyte progenitors in the context of other mitogens critical for their proliferation. Results presented here show that IGF-I significantly amplified the actions of FGF-2 and PDGF to promote DNA synthesis in O-2A progenitors. Investigation of cell cycle kinetics revealed that IGF-I had no significant effect on the rate of cell cycle progression. Instead, IGF-I promoted increased recruitment of O-2A progenitors into the S phase of the cell cycle. These studies support a role for IGF-I as a cell cycle progression factor for progenitor cells.

Macrophage inflammatory protein-1alpha (MIP-1alpha), MIP-1beta, and RANTES mRNA semiquantification and protein expression in active demyelinating multiple sclerosis (MS) lesions

MS is a demyelinating disease characterized by infiltration of monocytes and lymphocytes into the brain parenchyma, destruction of oligodendrocytes and loss of myelin. Since chemokines play a major role in the migration of monocytes and T cells, we here investigated the expression of the CC chemokines MIP-1alpha, MIP-1beta, and RANTES in brain tissue from MS patients using reverse transcriptase-polymerase chain reaction techniques. Both MIP-1beta as well as RANTES were found to be significantly elevated in brain tissue of MS patients. In addition, MIP-1alpha was also increased, although not significantly. Immunohistochemistry revealed that, whereas RANTES was mainly localized in reactive astrocytes, MIP-1alpha and MIP-1beta immunoreactivity was predominantly found in perivascular and parenchymal macrophages, containing myelin degradation products. Thus, chemokines appear to be associated with MS and an increased chemokine expression may further enhance disease progression by attracting more leucocytes into the brain parenchyma and by activation of effector functions of astrocytes and microglial cells.

Akt-mediated survival of oligodendrocytes induced by neuregulins

Neuregulins have been implicated in a number of events in cells in the oligodendrocyte lineage, including enhanced survival, mitosis, migration, and differentiation. At least two signaling pathways have been shown to be involved in neuregulin signaling: the phosphatidylinositol (PI)-3 kinase and the mitogen-activated protein kinase pathways. In the present studies, we examined the signaling pathway involved in the survival function of heregulin, focusing on heregulin-induced changes in Akt activity in cultured glial cells, and the consequences of Akt activation in cells in the oligodendrocyte lineage. Heregulin binds erbB receptors, and in our studies, primary cultures of both oligodendrocyte progenitor cells and differentiating oligodendrocytes expressed erbB2, erbB3, and erbB4 receptors. In C6 glioma cells and primary cultures of oligodendrocytes, heregulin induced time- and dose-dependent Akt phosphorylation at Ser(473) in a wortmannin-sensitive manner. To investigate further the signaling pathway for heregulin in glial cells, BAD was overexpressed in C6 glioma cells. In these cells, heregulin induced phosphorylation of BAD at Ser(136). Apoptosis of oligodendrocyte progenitor cells induced by growth factor deprivation was effectively blocked by heregulin in a wortmannin-sensitive manner. Overexpression of dominant negative Akt but not of wild-type Akt by adenoviral gene transfer in primary cultures of both oligodendrocytes and their progenitors induced significant apoptosis through activation of the caspase cascade. The present data suggest that the survival function of heregulin is mediated through the PI-3 kinase/Akt pathway in cells in the oligodendrocyte lineage and that the Akt pathway may be quite important for survival of cells in this lineage.

Akt-mediated survival of oligodendrocytes induced by neuregulins

Neuregulins have been implicated in a number of events in cells in the oligodendrocyte lineage, including enhanced survival, mitosis, migration, and differentiation. At least two signaling pathways have been shown to be involved in neuregulin signaling: the phosphatidylinositol (PI)-3 kinase and the mitogen-activated protein kinase pathways. In the present studies, we examined the signaling pathway involved in the survival function of heregulin, focusing on heregulin-induced changes in Akt activity in cultured glial cells, and the consequences of Akt activation in cells in the oligodendrocyte lineage. Heregulin binds erbB receptors, and in our studies, primary cultures of both oligodendrocyte progenitor cells and differentiating oligodendrocytes expressed erbB2, erbB3, and erbB4 receptors. In C6 glioma cells and primary cultures of oligodendrocytes, heregulin induced time- and dose-dependent Akt phosphorylation at Ser(473) in a wortmannin-sensitive manner. To investigate further the signaling pathway for heregulin in glial cells, BAD was overexpressed in C6 glioma cells. In these cells, heregulin induced phosphorylation of BAD at Ser(136). Apoptosis of oligodendrocyte progenitor cells induced by growth factor deprivation was effectively blocked by heregulin in a wortmannin-sensitive manner. Overexpression of dominant negative Akt but not of wild-type Akt by adenoviral gene transfer in primary cultures of both oligodendrocytes and their progenitors induced significant apoptosis through activation of the caspase cascade. The present data suggest that the survival function of heregulin is mediated through the PI-3 kinase/Akt pathway in cells in the oligodendrocyte lineage and that the Akt pathway may be quite important for survival of cells in this lineage.

Insulin-like growth factor-I promotes myelination of peripheral sensory axons

Insulin-like growth factor-I (IGF-I) in vivo or in the presence of other permissive factors can promote myelination in the central nervous system. In the current study, we examine the role of IGF-I in the myelination of peripheral nerves. In rat cocultures of dorsal root ganglia (DRG) and Schwann cells (SC) grown in serum- and insulin-free defined medium, IGF-I induces a dose dependent upregulation in myelin proteins such as P0, corresponding to maximal SC ensheathment. Furthermore, IGF-I is essential in promoting a dose-dependent, long-term myelination of DRG sensory axons. In the absence of IGF-I, axons and SC survive, but fail to myelinate. In the presence of 10 nM IGF-I, 59% of axons are myelinated at 21 days, whereas in the absence of IGF-I myelination fails to occur. Maximum SC ensheathment occurs 48 hours after addition of IGF-I. If IGF-I is withdrawn at 48 hours, axon segregation by SC persists, however, most axons and SC do not exhibit a one-to-one relationship and little myelination is observed. IGF-I is important in myelination and is critical not only for initial SC ensheathment of the axon and upregulation of myelin proteins, but also for sustained myelination. Furthermore, IGF-I associated axonal size is not the sole determinant for myelination.

Temporal analysis of growth factor mRNA expression in myelinating rat brain aggregate cultures: increments in CNTF, FGF-2, IGF-I, and PDGF-AA mRNA are induced by antibody-mediated demyelination

Myelinogenesis in rat brain aggregate cultures is associated with a pattern of growth factor mRNA expression comparable to that of the developing brain. The rate of increase in platelet-derived growth factor-AA (PDGF-AA) expression was greatest just before the detection of myelin basic protein (MBP) mRNA in the cultures and remained high thereafter, consistent with in vivo observations. Levels of fibroblast growth factor-2 (FGF-2) and of ciliary neurotrophic factor (CNTF) mRNA increased continuously over the period of MBP accumulation. High rates of transforming growth factor beta1 (TGF-beta1), insulin-like growth factor-I (IGF-I), and neurotrophin-3 (NT-3) expression at early time points during the culture gradually decreased over time, indicative of a key regulatory role during oligodendrocyte development. The addition of demyelinative anti-myelin oligodendrocyte glycoprotein (anti-MOG) antibody resulted in a significant increase in MBP peptide fragments with a C-terminus at phenylalanine 89 indicating proteolytic breakdown of MBP after myelin phagocytosis. Immediately after antibody treatment the expression of CNTF mRNA was significantly increased, compared with controls, while that of FGF-2 and IGF-I, and of PDGF-AA peaked during the early and later stages of recovery respectively. Thus, specific growth factors combine to regulate myelination and remyelination in the aggregates; these data have implications for demyelinating disease in which protective growth factor secretion may be central to regeneration.

Multiple sclerosis, acute disseminated encephalomyelitis, and related conditions

Multiple sclerosis (MS) and acute disseminated encephalomyelitis (ADEM) are conditions whose closely related pathology suggests shared pathophysiological elements, but whose clinical courses are usually, but not always quite dissimilar. The former is largely a disease of adulthood, the latter of childhood. Optic neuritis, demyelinative transverse myelitis, and Devic's syndrome are neurological syndromes that may occur as manifestations of either MS or ADEM. Patients with Miller-Fisher syndrome and encephalomyelradiculoneuropathy usually have features suggesting ADEM in combination with acute demyelinative polyneuropathy. These various conditions and other forms of ADEM share an indistinct border with encephalitides, granulomatous, and vasculitic conditions. MS, ADEM, and the pertinent syndromic subtypes, their differential diagnosis, treatment, and prognosis are considered in this review. Acute cerebellar ataxia is a syndrome that is likely to be pathophysiologically distinct from ADEM, although its occurrence as a postinfectious illness suggests a distant kinship. It is also reviewed.

Human nerve growth factor protects common marmosets against autoimmune encephalomyelitis by switching the balance of T helper cell type 1 and 2 cytokines within the central nervous system

Multiple sclerosis is a demyelinating disorder of the central nervous system (CNS), in which an immune attack directed against myelin constituents causes myelin destruction and death of oligodendrocytes, the myelin-producing cells. Here, the efficacy of nerve growth factor (NGF), a growth factor for neurons and oligodendrocytes, in promoting myelin repair was evaluated using the demyelinating model of experimental allergic encephalomyelitis (EAE) in the common marmoset. Surprisingly, we found that NGF delayed the onset of clinical EAE and, pathologically, prevented the full development of EAE lesions. We demonstrate by immunocytochemistry that NGF exerts its antiinflammatory effect by downregulating the production of interferon gamma by T cells infiltrating the CNS, and upregulating the production of interleukin 10 by glial cells in both inflammatory lesions of EAE and normal-appearing CNS white matter. Thus, NGF, currently under investigation in human clinical trials as a neuronal trophic factor, may be an attractive candidate for therapy of autoimmune demyelinating disorders.

Radiation myelopathy: new perspective on an old problem

This article discusses recent advances in basic research that alter the view of the pathogenesis of radiation myelopathy and summarizes the available data from developmental neurobiology and preclinical studies on demyelinating diseases. These studies have produced interesting insights into oligodendrocyte development, intercellular signaling pathways, and myelination processes. Current findings suggest that administration of cytokines as platelet-derived growth factor and basic fibroblast growth factor could increase proliferation of oligodendrocyte progenitors, enhance their differentiation, up-regulate synthesis of myelin constituents, and promote myelin regeneration in the adult central nervous system (CNS). Other compounds might also be able to modulate the progression of pathogenic processes that lead to myelopathy. In addition, several possible biological prevention or treatment strategies, for example stimulation of endogenous cellular regeneration and glial cell transplantation, are discussed. Rationally designed animal experiments pursuing such strategies could further elucidate the pathogenesis of radiation-induced CNS damage.

Th2 T cells expressing transgene PDGF-A serve as vectors for gene therapy in autoimmune demyelinating disease

We hypothesized that T cells can be genetically modified to express growth factor transgene products capable of inducing oligodendrocyte progenitor proliferation. Autoreactive T cells isolated from SWXJ mice immunized with the p139-151 determinant of myelin proteolipid protein (PLP) were transfected with an antigen-inducible transgene for platelet-derived growth factor-A (PDGF), a growth factor important in regulating the development of oligodendrocytes. Isolated antigen-specific T cell clones expressed the PDGF transgene when stimulated with PLP 139-151 peptide and produced biologically active PDGF capable of inducing proliferation of oligodendrocyte progenitor cells. Furthermore, upon adoptive transfer, the PDGF transfected T cells migrated to the CNS and ameliorated ongoing disease. Our data indicate that autoreactive memory Th2 cells can be genetically modified so that upon engagement with self antigen they produce regenerative growth factors capable of mediating tissue repair during autoimmune disease.

Recent developments in drug therapy for multiple sclerosis

Symptomatic treatment of multiple sclerosis (MS) includes a diverse range of drugs intended to relieve the specific symptoms with which a patient may present at a particular point in the progression of the disease. These drugs, not specifically designed for the treatment of MS, may include antispastic agents (e.g. baclofen), drugs to reduce tremor (e.g. clonazepam), anticholinergics (e.g. oxybutynin) which relieve urinary symptoms, anti-epileptics (e.g. carbamazepine) to control neuralgia, stimulants to reduce fatigue (e.g. amantadine), and antidepressants (e.g. fluoxetine) to treat depression. The treatment of acute relapses or exacerbations is dominated by corticosteroids such as methylprednisolone. The most active area of current investigation is the development of drugs which will inhibit the progression of the disease process itself, and in this category the beta- and alpha-interferons are the most effective drugs currently available, although many new treatments are currently in trials, including immunoglobulin, copolymer-1. bovine myelin, T-cell receptor (TCR) peptide vaccines, platelet activating factor (PAF) antagonists, matrix metallo-proteinase inhibitors, campath-1, and insulin-like growth factor (IGF).

Basic FGF and FGF receptor 1 are expressed in microglia during experimental autoimmune encephalomyelitis: temporally distinct expression of midkine and pleiotrophin

Heparin-binding growth factors have been implicated in central nervous system development, regeneration and pathology. To assess the expression pattern and possible function in multiple sclerosis, the heparin-binding growth factors pleiotrophin (PTN), midkine (MK), basic fibroblast growth factor (FGF-2) and one of its receptors (FGFR1/flg) mRNA and protein levels were examined in an experimental autoimmune encephalomyelitis (EAE) model in the Lewis rat. We assessed the time course of expression of PTN, MK and FGF-2 during EAE and determined the cellular origin of FGF-2 and FGFR1 in normal spinal cord and during inflammatory demyelination. Basal expression of PTN and MK mRNAs in normal spinal cords was significantly upregulated after induction of EAE. MK expression was upregulated two to threefold correlating with disease progression, whereas PTN expression reached peak levels threefold above basal levels during the clinical recovery period. FGF-2 mRNA expression was low in normal spinal cord and dramatically increased in correlation with progressive demyelination. FGF-2 was confined to neurons in normal tissue and shifted dramatically to microglia, paralleling their activation during EAE. Double immunohistochemistry revealed colocalization of FGF-2 to activated microglia/macrophages with strongest expression in the macrophage-rich perivascular core area and microglial expression at the edges of white and gray matter perivascular regions. FGFR1, like its ligand, was induced in activated macrophages/microglia. Growth factor expression in demyelinating diseases could serve several functions, e.g., to modulate the activity of microglia/macrophage in an autocrine fashion, to induce the expression of other factors like insulin-like growth factor 1 or plasminogen activator, which can effect regeneration or degeneration, respectively, and finally to stimulate directly localized proliferation and/or regeneration of oligodendrocytes within the lesion area.

A new factor derived from 1321N1 human astrocytoma cells causes differentiation of PC-12 cells mediated through mitogen-activated protein kinase cascade

Glial cells play an important role in maintaining neural function. In the present study, we examined the effects of a factor derived from human astrocytoma cells (1321N1) on differentiation of rat pheochromocytoma cells (PC-12). The conditioned medium which had been used for culture of 1321N1 cells caused the differentiation of PC-12 cells, suggesting that 1321N1 cells release a neurotrophic factor. The factor was apparently distinct from well-known neurotrophic factors, such as nerve growth factor (NGF), since it was resistant to boiling and trypsin treatment. The molecular size of the factor was assumed to be below 1000 through dialysis and ultrafiltration experiments. Furthermore, PC-12 cells were differentiated synergistically by the combined addition of NGF and the conditioned medium of 1321N1 cells. Partially purified fraction of the factor by Sephadex G-15 gel filtration column caused the prolonged activation of mitogen-activated protein kinase (MAPK). The differentiation of PC-12 cells induced by the fraction or NGF disappeared after the treatment with PD98059, a specific inhibitor of MAPK kinase (MEK), suggesting the involvement of MAPK in the differentiation. These results suggest that the new low-molecular factor derived from glial cells causes differentiation of PC-12 cells mediated through an activation of MAPK.

Remyelination: cellular and gene therapy

Dysfunctional myelination or oligodendroglial abnormalities play a prominent role in a vast array of pediatric neurological diseases of genetic, inflammatory, immunological, traumatic, ischemic, developmental, metabolic, and infectious causes. Recent advances in glial cell biology have suggested that effective remyelination strategies may, indeed, be feasible. Evidence for myelin repair is accumulating in various experimental models of dysmyelinating and demyelinating disease. Attempts at remyelination have either been directed towards creating myelin de novo from exogenous sources of myelin-elaborating cells or promoting an intrinsic spontaneous remyelinating process. Ultimately, some disorders of myelin may require multiple repair strategies, not only the replacement of dysfunctional cells (oligodendroglia) but also the delivery or supplementation of gene products (i.e., growth factors, immune modulators, metabolic enzymes). Although primary oligodendrocytes or oligodendroglial precursors may be effective for glial cell replacement in certain discrete regions and circumstances and although various genetic vectors may be effective for the delivery of therapeutic molecules, multipotent neural stem cells may be most ideally suited for both gene transfer and cell replacement on transplantation into multiple regions of the central nervous system under a wide range of pathological conditions. We propose that, by virtue of their inherent biological properties, neural stem cells possess the multifaceted therapeutic capabilities that many diseases characterized by myelin dysfunction in the pediatric population may demand.

Identification of glial cell proliferation in early multiple sclerosis lesions

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system which leads to destruction of myelin sheaths. The patterns of cell proliferation in the early course of the disease are largely unknown. The present study used immunohistochemical identification of proliferating glial cells in stereotactic brain biopsy material of eight patients with early chronic MS. Double-labelling with the proliferation marker MIB-1 detected proliferating oligodendrocytes (MOG), astrocytes (GFAP) and microglia/macrophages (Ki-M1P). The majority of proliferating cells were macrophages/microglia when compared with oligodendrocytes (P > 0.005) or astrocytes (P > 0.0005); only a minor proportion of microglia/macrophages, however, proliferated in situ. Astrocytic and oligodendroglial proliferation was sparse to absent and showed significant variations between different patients. There were statistically significant differences when comparing the amount of proliferation between lesions of different demyelinating activity: highest numbers of proliferating cells were found in early active lesions compared with demyelinated and early remyelinated lesions (P > 0.05) or the periplaque white matter (P > 0.01). MOG-positive oligodendrocytes proliferated occasionally in the early stages of lesion formation; this proliferation occurred in four cases but was independent of the stage of the disease. Since MOG is expressed by mature oligodendrocytes, and not by immature precursors, this might suggest a potential role for the proliferation of mature surviving oligodendrocytes with subsequent remyelination.