Remyelinating strategies for the treatment of multiple sclerosis

Enhancing nerve regeneration in infraorbital nerve injury rat model: effects of vitamin B complex and photobiomodulation

Orofacial nerve injuries may result in temporary or long-term loss of sensory function and decreased quality of life in patients. B vitamins are required for DNA synthesis and the repair and maintenance of phospholipids. In particular, vitamins B1, B6, and B12 are essential for neuronal function. Deficiency in vitamin B complex (VBC) has been linked to increased oxidative stress, inflammation and demyelination. Photobiomodulation (PBM) has antioxidant activity and is neuroprotective. In addition, a growing literature attests to the positive effects of PBM on nerve repair. To assess the effect of PBM and VBC on regenerative process we evaluated the expression of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), myelin basic protein (MBP), laminin and neurofilaments (NFs) using Western blotting to identify regenerative pattern after chronic constriction injury of the infraorbital nerve (CCI IoN) treated by PBM, VBC or its combination. After CCI IoN, the rats were divided into six groups naive, sham, injured (CCI IoN), treated with photobiomodulation (904 nm, 6.23 J/cm2, CCI IoN + PBM), treated with VBC (containing B1, B6 and B12) 5 times, CCI IoN + VBC) and treated with PBM and VBC (CCI IoN + VBC + PBM). The treatments could revert low expression of BDNF, MBP and laminin. Also reverted the higher expression of neurofilaments and enhanced expression of NGF. PBM and VBC could accelerate injured infraorbital nerve repair in rats through reducing the expression of neurofilaments, increasing the expression of BDNF, laminin and MBP and overexpressing NGF. These data support the notion that the use of PBM and VBC may help in the treatment of nerve injuries. This finding has potential clinical applications.

Exercise induced myelin protein zero improvement in neuropathic pain rats

PURPOSE

Aerobic exercise including swimming plays a suitable role in improving somatosensory injuries. Neuropathic pain is a debilitating condition that occurs following injury or diseases of somatosensory system. In the present study, we tried to investigate the effect of exercise on myelin protein zero of sciatic nerve injured rats.

MATERIALS AND METHODS

Forty male rats (180-220 g) were divided into five groups (intact, sham, sham + exercise, neuropathy, and neuropathy + exercise). Right Sciatic nerve of anesthetized rats was exposed and loosely ligated (four ligations with 1 mm apart) using catgut chromic sutures to induce neuropathy. After 3 days of recovery, swimming exercise began (20 min/day/5 days a week/4 weeks). Mechanical allodynia and thermal hyperalgesia were detected using Von Frey filaments and plantar test, respectively. Sciatic nerve at the place of injury was dissected out to measure the myelin protein zero by western blot analysis. In the intact and sham groups, sciatic nerve removed at the place similar to injured group.

RESULTS

We found that neuropathy significantly (p < 0.05) reduced paw withdrawal mechanical and thermal thresholds and swimming exercise significantly (p < 0.05) increased paw withdrawal mechanical and thermal thresholds compared to the neuropathy group. Moreover, we found that MPZ level significantly (p < 0.01) decreased in neuropathy group against that in sham group, and exercise prominently (p < 0.05) reversed MPZ level towards control level.

CONCLUSIONS

Swimming exercise improves myelin protein zero level in neuropathic rats along with attenuating neuropathic pain. This is a promising approach in improving neuropathological disorders including Charcot-Marie-Tooth and Dejerine-Sottas disease.

Dynamics of reactive astrocytes fosters tissue regeneration after cuprizone-induced demyelination

Demyelination in the central nervous system (CNS) is a hallmark of many neurodegenerative diseases such as multiple sclerosis (MS) and others. Here, we studied astrocytes during de- and remyelination in the cuprizone mouse model. To this end, we exploited the ribosomal tagging (RiboTag) technology that is based on Cre-mediated cell type-selective HA-tagging of ribosomes. Analyses were performed in the corpus callosum of GFAP-Cre+/- Rpl22HA/wt mice 5 weeks after cuprizone feeding, at the peak of demyelination, and 0.5 and 2 weeks after cuprizone withdrawal, when remyelination and tissue repair is initiated. After 5 weeks of cuprizone feeding, reactive astrocytes showed inflammatory signatures with enhanced expression of genes that modulate leukocyte migration (Tlr2, Cd86, Parp14) and they produced the chemokine CXCL10, as verified by histology. Furthermore, demyelination-induced reactive astrocytes expressed numerous ligands including Cx3cl1, Csf1, Il34, and Gas6 that act on homeostatic as well as activated microglia and thus potentially mediate activation and recruitment of microglia and enhancement of their phagocytotic activity. During early remyelination, HA-tagged cells displayed reduced inflammatory response signatures, as indicated by shutdown of CXCL10 production, and enhanced expression of osteopontin (SPP1) as well as of factors that are relevant for tissue remodeling (Timp1), regeneration and axonal repair. During late remyelination, the signatures shifted towards resolving inflammation by active suppression of lymphocyte activation and differentiation and support of glia cell differentiation. In conclusion, we detected highly dynamic astroglial transcriptomic signatures in the cuprizone model, which reflects excessive communication among glia cells and highlights different astrocyte functions during neurodegeneration and regeneration.

Analyzing global features of magnetic resonance images in widespread neurodegenerative diseases: new hope to understand brain mechanism and robust neurodegenerative disease diagnosis

Neurodegenerative diseases are caused by progressive degeneration of the central nervous system (CNS)'s neuronal structure. Well-known diseases in this category include Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS), which are also addressed in this study. The CNS appears to be a complex dynamic system, whose parameters change during the disease due to neuronal damage, resulting in various symptoms. Since the change in dynamic behavior is due to the neurons' death and change in neurons' connectivity, brain images of the affected areas appear to provide a good understanding of this change. This work attempts to focus on brain magnetic resonance images (MRI) and examine the effect of neuronal loss on the images. To this end, the complex features of these images, including 2D and Higuchi's fractal dimensions (HFD), correlation dimension (CD), largest Lyapunov exponent (LLE), and approximate entropy (ApEn) were calculated. Despite small differences in numerical values (0.01-0.35), these values differ significantly. This shows that the brain dynamic system behaves and functions differently in the disease state, which is clear in the behavior of global features. These three diseases have the same functional pattern, and this study seems to have captured the roots of these seemingly variant diseases.

Novel Treatment Strategies Targeting Myelin and Oligodendrocyte Dysfunction in Schizophrenia

Oligodendrocytes are the glial cells responsible for the formation of the myelin sheath around axons. During neurodevelopment, oligodendrocytes undergo maturation and differentiation, and later remyelination in adulthood. Abnormalities in these processes have been associated with behavioral and cognitive dysfunctions and the development of various mental illnesses like schizophrenia. Several studies have implicated oligodendrocyte dysfunction and myelin abnormalities in the disorder, together with altered expression of myelin-related genes such as Olig2, CNP, and NRG1. However, the molecular mechanisms subjacent of these alterations remain elusive. Schizophrenia is a severe, chronic psychiatric disorder affecting more than 23 million individuals worldwide and its symptoms usually appear at the beginning of adulthood. Currently, the major therapeutic strategy for schizophrenia relies on the use of antipsychotics. Despite their widespread use, the effects of antipsychotics on glial cells, especially oligodendrocytes, remain unclear. Thus, in this review we highlight the current knowledge regarding oligodendrocyte dysfunction in schizophrenia, compiling data from (epi)genetic studies and up-to-date models to investigate the role of oligodendrocytes in the disorder. In addition, we examined potential targets currently investigated for the improvement of schizophrenia symptoms. Research in this area has been investigating potential beneficial compounds, including the D-amino acids D-aspartate and D-serine, that act as NMDA receptor agonists, modulating the glutamatergic signaling; the antioxidant N-acetylcysteine, a precursor in the synthesis of glutathione, protecting against the redox imbalance; as well as lithium, an inhibitor of glycogen synthase kinase 3β (GSK3β) signaling, contributing to oligodendrocyte survival and functioning. In conclusion, there is strong evidence linking oligodendrocyte dysfunction to the development of schizophrenia. Hence, a better understanding of oligodendrocyte differentiation, as well as the effects of antipsychotic medication in these cells, could have potential implications for understanding the development of schizophrenia and finding new targets for drug development.

The Notch pathway in CNS homeostasis and neurodegeneration

The role of the Notch signaling pathway in neural development has been well established over many years. More recent studies, however, have demonstrated that Notch continues to be expressed and active throughout adulthood in many areas of the central nervous system. Notch signals have been implicated in adult neurogenesis, memory formation, and synaptic plasticity in the adult organism, as well as linked to acute brain trauma and chronic neurodegenerative conditions. NOTCH3 mutations are responsible for the most common form of hereditary stroke, the progressive disorder cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy. Notch has also been associated with several progressive neurodegenerative diseases, including Alzheimer's disease, multiple sclerosis, and amyotrophic lateral sclerosis. Although numerous studies link Notch activity with CNS homeostasis and neurodegenerative diseases, the data thus far are primarily correlative, rather than functional. Nevertheless, the evidence for Notch pathway activity in specific neural cellular contexts is strong, and certainly intriguing, and points to the possibility that the pathway carries therapeutic promise. This article is categorized under: Nervous System Development > Flies Signaling Pathways > Cell Fate Signaling Nervous System Development > Vertebrates: General Principles.

Maturation of a Human Oligodendrocyte Cell Line

Techniques such as the maturation and differentiation of cell lines and progenitor cells are important for the improvement and development of representative and relevant in vitro models. In this context, the following chapter proposes a maturation model of the MO3.13 cell line, aiming to contribute to a more robust and credible in vitro model of human oligodendrocytes. This may prove to be an important tool in the study of diseases related to dysfunctions in oligodendrocytes and demyelination, including schizophrenia and multiple sclerosis.

Peripheral Demyelinating Diseases: From Biology to Translational Medicine

Demyelinating diseases represent a spectrum of disorders that impose significant burden on global economy and society. Generally, the prognosis of these diseases is poor and there is no available cure. In recent decades, research has shed some light on the biology and physiology of Schwann cells and its neuroprotective effects in the peripheral nervous system (PNS). Insults to the PNS by various infectious agents, genetic predisposition and immune-related mechanisms jeopardize Schwann cell functions and cause demyelination. To date, there are no effective and reliable biomarkers for PNS-related diseases. Here, we aim to review the following: pathogenesis of various types of peripheral demyelinating diseases such as Guillain-Barre syndrome, Chronic Inflammatory Demyelinating Polyradiculoneuropathy, Anti-Myelin Associated Glycoprotein Neuropathy, POEMS syndrome, and Charcot-Marie-Tooth disease; emerging novel biomarkers for peripheral demyelinating diseases, and Schwann cell associated markers for demyelination.

Dynamic Calcium Release From Endoplasmic Reticulum Mediated by Ryanodine Receptor 3 Is Crucial for Oligodendroglial Differentiation

Increased intracellular Ca²⁺ in oligodendrocyte progenitor cells (OPCs) is important to initiate their differentiation, but the intracellular Ca²⁺ channel involved in this process remains unclear. As a Ca²⁺-induced Ca²⁺ release (CICR) channel that mediates endoplasmic reticulum (ER) Ca²⁺ release, the role of ryanodine receptors (RyRs) in oligodendroglial development is unexplored. In the present study, we observed that among the three mammalian isoforms, oligodendroglial lineage cells selectively expressed RyR3. Strong RyR3-positive signal was distributed all over the cytoplasm and processes in OPCs and/or immature OLs (imOLs), whereas it gradually decreased and was located mainly around the perinuclear region in mature oligodendrocytes (OLs). In addition, RyR3-mediated intracellular Ca²⁺ waves following caffeine stimulation were correlated with the expression pattern of RyR3, in which high flat Ca²⁺ fluctuations and oscillatory Ca²⁺ waves were more frequently recorded in OPCs and/or imOLs than in OLs. Through further functional exploration, we demonstrated that pretreatment with the RyR antagonist ryanodine could neutralize the increase in intracellular Ca²⁺ induced by OPC differentiation and reduce the number of mature OLs. Moreover, gene-level knockdown of RyR3 by lentivirus in OPCs resulted in inhibition of OPC differentiation. Taken together, our results provide new insight into the crucial role of RyR3-mediated ER Ca²⁺ release in the regulation of OPC differentiation and/or myelination.

Achievements and obstacles of remyelinating therapies in multiple sclerosis

Remyelination in the CNS is the natural process of damage repair in demyelinating diseases such as multiple sclerosis (MS). However, remyelination becomes inadequate in many people with MS, which results in axonal degeneration and clinical disability. Enhancement of remyelination is a logical therapeutic goal; nevertheless, all currently licensed therapies for MS are immunomodulatory and do not support remyelination directly. Several molecular pathways have been identified as potential therapeutic targets to induce remyelination, and some of these have now been assessed in proof-of-concept clinical trials. However, trial design faces several obstacles: optimal clinical or paraclinical outcome measures to assess remyelination remain ill-defined, and identification of the ideal timing of therapy is also a crucial issue. In addition, realistic expectations are needed concerning the probable benefits of such therapies. Nevertheless, approaches that enhance remyelination are likely to be protective for axons and so could prevent long-term neurodegeneration. Future MS treatment paradigms, therefore, are likely to comprise a combinatorial approach that involves both immunomodulatory and regenerative treatments.

Ameliorating Effect of Osteopontin on H2O2-Induced Apoptosis of Human Oligodendrocyte Progenitor Cells

Recently our group used oligodendrocyte progenitor cells (OPCs) as appropriate model cells to pinpoint the mechanism of the progress of neurodegenerative disorders. In the present study, we focused on the therapeutic role of osteopontin (OPN), a secreted glycosylated phosphoprotein, involved in a number of physiological events including bone formation and remodeling, immune responses, and tumor progression. Protective role of OPN, as a negative regulator of tumorigenesis, has already been clarified. Human embryonic stem cell-derived OPCs were pretreated with OPN before induction of apoptosis by H₂O₂. Data indicated that OPN prohibited cell death and enhanced OPC viability. This effect is achieved through reduction of apoptosis and induction of anti-apoptosis markers. In addition OPN induces expression of several integrin subunits, responsible for OPN interaction. Notably, our findings showed that expression of αV β1/β3/β5 and β8 integrins increased in response to OPN, while treatment with H₂O₂ down-regulated αV β1/β5 and β8 integrins expression significantly. In conclusion, OPN may act via αV integrin signaling and trigger suppression of P53-dependent apoptotic cascades. Therefore OPN therapy may be considered as a feasible process to prevent progress of neurodegenerative diseases in human.

The Effect of Levothyroxine on Serum Levels of Interleukin 10 and Interferon-gamma in Rat Model of Multiple Sclerosis

Background:

There is an increase in inflammatory and a reduction in anti-inflammatory cytokines in multiple sclerosis (MS). Considering the role of thyroid hormones in the development and regulation of both neural and immune systems, the aim of this study was to evaluate the effects of levothyroxine on serum concentrations of interleukin-10 (IL-10) and interferon gamma (IFN-γ) in animal models of MS.

Materials and Methods:

To induce demyelination in male Wistar rats, lysolecithin was injected into the optic chiasm. Then levothyroxine was injected intraperitoneally (20, 50, and 100 μg/kg) for 21 days. Serum levels of cytokines were measured by enzyme-linked immunosorbent assay at 7, 14, and 21 days after that.

Results:

The results showed that injection of lysolecithin to the optic chiasm only increased serum concentrations of IL-10 compared to the sham group (P < 0.05) at 7^th day, but this increase was prevented by all doses of levothyroxine. IFN-γ was decreased significantly (P < 0.001) 21 days after. Comparing to the sham group at all sampling time and with respect to the MS group at the days 7 and 21, levothyroxine decreased serum concentrations of IFN-γ significantly.

Conclusion:

The results showed that thyroid hormones probably could produce protective effects against induced demyelination through affecting immune responses.

Mice lacking Gpr37 exhibit decreased expression of the myelin-associated glycoprotein MAG and increased susceptibility to demyelination

GPR37 is an orphan G protein-coupled receptor that is predominantly expressed in the brain and found at particularly high levels in oligodendrocytes. GPR37 has been shown to exert effects on oligodendrocyte differentiation and myelination during development, but the molecular basis of these actions is incompletely understood and moreover nothing is known about the potential role(s) of this receptor under demyelinating conditions. To shed light on the fundamental biology of GPR37, we performed proteomic studies comparing protein expression levels in the brains of mice lacking GPR37 and its close relative GPR37-like 1 (GPR37L1). These studies revealed that one of the proteins most sharply decreased in the brains of Gpr37/Gpr37L1 double knockout mice is the myelin-associated glycoprotein MAG. Follow-up Western blot studies confirmed this finding and demonstrated that genetic deletion of Gpr37, but not Gpr37L1, results in strikingly decreased brain expression of MAG. Further in vitro studies demonstrated that GPR37 and MAG form a complex when expressed together in cells. As loss of MAG has previously been shown to result in increased susceptibility to brain insults, we additionally assessed Gpr37-knockout (Gpr37^-/-) vs. wild-type mice in the cuprizone model of demyelination. These studies revealed that Gpr37^-/- mice exhibit dramatically increased loss of myelin in response to cuprizone, yet do not show any increased loss of oligodendrocyte precursor cells or mature oligodendrocytes. These findings reveal that loss of GPR37 alters oligodendrocyte physiology and increases susceptibility to demyelination, indicating that GPR37 could be a potential drug target for the treatment of demyelinating diseases such as multiple sclerosis.

Effects of chlorogenic acid on adenine nucleotides hydrolyzing enzyme activities and expression in platelets of rats experimentally demyelinated with ethidium bromide

BACKGROUND

The effects of chlorogenic acid (one of the major phenolic acid found in human diets) were investigated on the adenine nucleotides hydrolyzing enzymes; ecto-nucleotide pyrophosphatase/phophodiesterase (E-NPP), ecto-nucleoside triphosphate diphosphohydrolase (E-NTPDase), E-5'- nucleotidase and ecto-adenosine deaminase (E-ADA) activities and expression in platelets of rats experimentally demyelinated with ethidium bromide.

METHODS

Rats were divided into four groups of eight animals each. Group I rats were control rats; injected with saline (CT), group II rats were injected with saline and treated with chlorogenic acid (AC), group III rats were injected with 0.1% ethidium bromide (EB) and group IV rats were injected with 0.1% EB and treated with chlorogenic acid (EB+AC). The activities of the enzymes were analyzed using colorimetric methods, and the gene expression of NTPDase 1, 2 and 3 were analyzed using the polymerase chain reaction (PCR).

RESULTS

The results revealed that there was a significant (P<0.01) reduction in E-NPP activity in EB group (1.63±0.10nmol p-nitrophenol released/min/mg protein) when compared to CT group (2.33±0.14nmol p-nitrophenol released/min/mg protein). However, treatment with chlorogenic acid significantly (P<0.05) increased E-NPP activity in EB group. Furthermore, no significant (P>0.05) change was observed in the E-NPP activity of EB+AC group (2.19±0.08nmol p-nitrophenol released/min/mg protein) when compared to CT group (2.33±0.14nmol p-nitrophenol released/min/mg protein). In addition, there was a significant (P<0.05) increase in AMP hydrolysis in EB rat group when compared to CT group. No significant (P>0.05) difference was observed in AMP hydrolysis between AC, AC+EB and CT groups. Conversely, there were no significant (P>0.05) differences in ATP and ADP hydrolyses between all the groups (AC, EB, AC+EB and CT groups). Likewise, there were no significant (P>0.05) changes in E-ADA activity and percentage platelet aggregation among all groups studied. Similarly, no significant (P>0.05) change was observed in the expression of E-NTPDase 1, 2 and 3 in all the groups tested.

CONCLUSIONS

Our study revealed that chlorogenic acid may modulate the hydrolysis of adenine nucleotides in platelets of rats demyelinated and treated with chlorogenic acid via alteration of E-NPP and ecto-5'-nucleotidase activities.

Transplantation of mouse embryonic stem cell-derived oligodendrocytes in the murine model of globoid cell leukodystrophy

Introduction

Globoid cell leukodystrophy (GLD) is a severe disorder of the central and peripheral nervous system caused by the absence of galactocerebrosidase (GALC) activity. Cell-based therapies are highly promising strategies for GLD. In this study, G-Olig2 mouse embryonic stem cells (ESCs) were induced into oligodendrocyte progenitor cells (OPCs) and were implanted into the brains of twitcher mice, an animal model of GLD, to explore the therapeutic potential of the cells.

Methods

The G-Olig2 ESCs were induced into OPCs by using cytokines and a multi-step differentiation procedure. Oligodendrocyte markers were detected by reverse transcription-polymerase chain reaction (RT-PCR) and immunocytochemistry. The toxicity of psychosine to OPCs was determined by a cell proliferation assay kit. The GALC level of OPCs was also examined. OPCs were labeled with Dir and transplanted into the brains of twitcher mice. The transplanted cells were detected by in-Vivo Multispectral Imaging System and real-time PCR. The physiological effects of twitcher mice were assessed.

Results

Oligodendrocyte markers were expressed in OPCs, and 76% ± 5.76% of the OPCs were enhanced green fluorescent protein (eGFP)-positive, eGFP was driven by the Olig2 promoter. The effect of psychosine on cell viability indicated that OPCs were more resistant to psychosine toxicity. The GALC level of OPCs was 10.0 ± 1.23 nmol/hour per mg protein, which was significantly higher than other cells. Dir-labeled OPCs were injected into the forebrain of post-natal day 10 twitcher mice. The transplanted OPCs were myelin basic protein (MBP)-positive and remained along the injection tract as observed by fluorescent microscopy. The level of the Dir fluorescent signal and eGFP mRNA significantly decreased at days 10 and 20 after injection, as indicated by in-Vivo Multispectral Imaging System and real-time PCR. Because of poor cell survival and limited migration ability, there was no significant improvement in brain GALC activity, MBP level, life span, body weight, and behavioral deficits of twitcher mice.

Conclusions

ESC-derived OPC transplantation was not sufficient to reverse the clinical course of GLD in twitcher mice.

Glial response during cuprizone-induced de- and remyelination in the CNS: lessons learned

Although astrogliosis and microglia activation are characteristic features of multiple sclerosis (MS) and other central nervous system (CNS) lesions the exact functions of these events are not fully understood. Animal models help to understand the complex interplay between the different cell types of the CNS and uncover general mechanisms of damage and repair of myelin sheaths. The so called cuprizone model is a toxic model of demyelination in the CNS white and gray matter, which lacks an autoimmune component. Cuprizone induces apoptosis of mature oligodendrocytes that leads to a robust demyelination and profound activation of both astrocytes and microglia with regional heterogeneity between different white and gray matter regions. Although not suitable to study autoimmune mediated demyelination, this model is extremely helpful to elucidate basic cellular and molecular mechanisms during de- and particularly remyelination independently of interactions with peripheral immune cells. Phagocytosis and removal of damaged myelin seems to be one of the major roles of microglia in this model and it is well known that removal of myelin debris is a prerequisite of successful remyelination. Furthermore, microglia provide several signals that support remyelination. The role of astrocytes during de- and remyelination is not well defined. Both supportive and destructive functions have been suggested. Using the cuprizone model we could demonstrate that there is an important crosstalk between astrocytes and microglia. In this review we focus on the role of glial reactions and interaction in the cuprizone model. Advantages and limitations of as well as its potential therapeutic relevance for the human disease MS are critically discussed in comparison to other animal models.

Oligodendrocytes engineered with migratory proteins as effective graft source for cell transplantation in multiple sclerosis

Multiple sclerosis (MS) is characterized by widespread immunomodulatory demyelination of the CNS resulting in nerve cell dysfunction. Accordingly, treatment strategies have been centered on immunodulation and remyelination, with the former primarily focused on reducing the pathology rather than enhancing myelin repair which the latter targets. While conceding to the emerging view of heterogeneity in the pathology of MS, which precludes variations in degree of immune response (i.e., inflammation) and demyelination, the concept of enhancing myelin repair is appealing since it is likely to provide both disease-reducing and disease-inhibiting therapeutic approach to MS. In this regard, we and several others, have proposed that cell replacement therapy is an effective strategy to repair the myelin in MS. Here, we hypothesize that transplantation of mouse bone marrow-derived oligodendrocytes (BMDOs) and BMDOs transfected with Ephrin proteins (BMDO+Ephrin), which are known to enhance cell and axonal migratory capacity, may produce therapeutic benefits in animal models of MS.

Protocol to isolate a large amount of functional oligodendrocyte precursor cells from the cerebral cortex of adult mice and humans

During development, oligodendrocytes are generated from oligodendrocyte precursor cells (OPCs), a cell type that is a significant proportion of the total cells (3-8%) in the adult central nervous system (CNS) of both rodents and humans. Adult OPCs are responsible for the spontaneous remyelination that occurs in demyelinating diseases like Multiple Sclerosis (MS) and they constitute an interesting source of cells for regenerative therapy in such conditions. However, there is little data regarding the neurobiology of adult OPCs isolated from mice since an efficient method to isolate them has yet to be established. We have designed a protocol to obtain viable adult OPCs from the cerebral cortex of different mouse strains and we have compared its efficiency with other well-known methods. In addition, we show that this protocol is also useful to isolate functional OPCs from human brain biopsies. Using this method we can isolate primary cortical OPCs in sufficient quantities so as to be able to study their survival, maturation and function, and to facilitate an evaluation of their utility in myelin repair.

Induction of human umbilical Wharton's jelly-derived stem cells toward oligodendrocyte phenotype

In this study, we examined phenotypic features of human Wharton's jelly mesenchymal stem cells-derived oligodendrocytes. We induced human WJMSCs to form OLs by signaling molecules including basic fibroblastic growth factor, platelet-derived growth factor-AA, and triiodothyronine hormone. Differentiated WJMSCs showed morphologic characteristics of an OL phenotype. Expression of surface markers and genes in oligodendrocyte precursor cells or OLs were analyzed by immunocytochemistry staining and real-time polymerase chain reaction, respectively. These results suggest that WJMSCs could be programmed to OLs and might provide a potential source for cell therapy in neurodegenerative disease.

Field potential recording from rat hippocampus provides a functional evaluation method for assessing demyelination and myelin repair

OBJECTIVES

In multiple sclerosis (MS) demyelination occurs in both white and gray matter. Here we introduce an electrophysiological approach for studying functional demyelination and myelin repair in rat hippocampus, a gray matter structure, which is frequently affected in patients suffering from MS.

METHODS

Using a stereotaxic approach, bipolar stimulating and monopolar recording electrodes were respectively implanted into the perforant path and the dentate gyrus of the hippocampus of the adult male Sprague-Dawley rats weighing 280-320 g. Animals received intra-hippocampal injections of saline or lysolecithin (LPC) and afterward, changes in the parameters of field potentials recorded from the dentate gyrus granular cells in response to electrical stimulation of perforant path were investigated on days 7, 14, and 28, post-lesion. Changes in the electrophysiological parameters were compared with changes in the molecular markers of myelination (myelin basic protein, MBP) and repairing cells (Olig2).

RESULTS

On day 2, a significant decrease in the slope of the population excitatory postsynaptic potential (pEPSP) and the amplitude of population spike (PS) was observed. However, during days 7-28, these parameters were increased toward control. Decreased expression of MBP and increased expression of Olig2 were observed on days 2 and 7 while the expression levels were partially reversed toward control on day 28.

DISCUSSION

Our data showed the efficacy of field potential recording for studying demyelination and endogenous myelin repair in hippocampus. Changes in electrophysiological parameters were concomitant with the level of molecular markers. This recording method provides an opportunity for functional evaluation of myelin loss and repair and the effect of potential therapies.

Peripheral axons of the adult zebrafish maxillary barbel extensively remyelinate during sensory appendage regeneration

Myelination is a cellular adaptation allowing rapid conduction along axons. We have investigated peripheral axons of the zebrafish maxillary barbel (ZMB), an optically clear sensory appendage. Each barbel carries taste buds, solitary chemosensory cells, and epithelial nerve endings, all of which regenerate after amputation (LeClair and Topczewski [2010] PLoS One 5:e8737). The ZMB contains axons from the facial nerve; however, myelination within the barbel itself has not been established. Transcripts of myelin basic protein (mbp) are expressed in normal and regenerating adult barbels, indicating activity in both maintenance and repair. Myelin was confirmed in situ by using toluidine blue, an anti-MBP antibody, and transmission electron microscopy (TEM). The adult ZMB contains ∼180 small-diameter axons (<2 μm), approximately 60% of which are myelinated. Developmental myelination was observed via whole-mount immunohistochemistry 4-6 weeks postfertilization, showing myelin sheaths lagging behind growing axons. Early-regenerating axons (10 days postsurgery), having no or few myelin layers, were disorganized within a fibroblast-rich collagenous scar. Twenty-eight days postsurgery, barbel axons had grown out several millimeters and were organized with compact myelin sheaths. Fiber types and axon areas were similar between normal and regenerated tissue; within 4 weeks, regenerating axons restored ∼85% of normal myelin thickness. Regenerating barbels express multiple promyelinating transcription factors (sox10, oct6 = pou3f1; krox20a/b = egr2a/b) typical of Schwann cells. These observations extend our understanding of the zebrafish peripheral nervous system within a little-studied sensory appendage. The accessible ZMB provides a novel context for studying axon regeneration, Schwann cell migration, and remyelination in a model vertebrate.

Improving myelin/oligodendrocyte-related dysfunction: a new mechanism of antipsychotics in the treatment of schizophrenia?

Schizophrenia is a severe psychiatric disorder with complex clinical manifestations and its aetiological factors remain unclear. During the past decade, the oligodendrocyte-related myelin dysfunction was proposed as a hypothesis for schizophrenia, supported initially by a series of neuroimaging studies and genetic evidence. Recently, the effects of antipsychotics on myelination and oligodendroglial lineage development and their underlying molecular mechanisms were evaluated. Data from those studies suggest that the antipsychotics-resulting improvement in myelin/oligodendrocyte-related dysfunction may contribute, at least in part, to their therapeutic effect on schizophrenia. Importantly, these findings may provide the basis for a new insight into the therapeutic strategy by targeting the oligodendroglia lineage cells against schizophrenia.

An update on spinal cord injury research

Spinal cord injury (SCI) can have a range of debilitating effects and permanently alter the capabilities and quality of life of survivors. The first specialized centers of care for SCI were established in 1944 and since then an increasing amount of research has been carried out in this area. Despite this, the present treatment and care levels for SCI are not comparable to those in other areas of medicine. In the clinic, the aim of SCI treatment is primarily to limit secondary damage by reducing compression in trauma spots and stabilizing the spinal column. Currently, no effective strategy for functional recovery is offered. In this review, we focus on research progress on the molecular mechanisms underlying SCI, and assess the treatment outcomes of SCI in animal models, i.e., neurotrophins and stem cells are discussed as pre-clinical therapies in animal models. We also assess the resources available and national research projects carried out on SCI in China in recent years, as well as making recommendations for the future allocation of funds in this area.

An efficient and economical culture approach for the enrichment of purified oligodendrocyte progenitor cells

Oligodendrocyte progenitor cell (OPC) culture has provided a powerful approach to mechanistically investigate the proliferation and differentiation of oligodendroglia. However, existing culture methods (including the traditional shake-off method) have limitations, particularly their low productivities. Therefore, we developed a simplified and highly efficient method to produce a large yield of OPCs with low expense by using specialised modified media, in which B104-conditioned medium (B104-CM) instead of growth factors was used as a mitogenic source for OPC propagation, while a modified OPC isolation-medium was applied to improve the isolation of OPCs. First, we withdrew foetal bovine serum when primary mixed glial cultures were 65-75% confluent and substituted with modified oligodendrocyte growth medium to enrich OPCs. Second, we employed a chemical-based method to isolate and purify OPCs from mixed glial cultures using a modified oligodendrocyte isolation medium. As a result, our approach produced a high yield of purified OPCs, approximately 90-fold higher than that produced via the traditional shake-off method. Importantly, the purified OPCs produced via our modified approach maintained typical capacities of proliferation and differentiation observed in oligodendrocyte lineage cells. Together, our modified method provides a highly efficient approach to OPC culture for oligodendrocyte research.

Phosphorylated olig1 localizes to the cytosol of oligodendrocytes and promotes membrane expansion and maturation

Oligodendroglial cells undergo rapid transcriptional and dynamic morphological transformation in order to effectively myelinate neuronal axons. Olig1, a basic helix-loop-helix transcription factor, functions to promote the transcription of myelin-specific genes and promotes differentiation and (re)myelination. While the role for nuclear Olig1 is well established, the function for cytoplasmic Olig1 remains uncertain. We observe that translocation of Olig1 into the cytosol highly correlates with differentiation of oligodendrocytes both invivo and invitro. By enforcing expression of a nuclear-specific form of Olig1 into OPCs in a null-Olig1 background, we demonstrate that nuclear Olig1 is sufficient to facilitate MBP expression, but with greatly diminished membrane volume and area. We demonstrate that serine 138 in the helix-loop-helix domain of Olig1 is phosphorylated and that this form resides in the cytosol. Mutating serine 138 to alanine restricts Olig1 to the nucleus, facilitating MBP expression but limiting membrane expansion. However, a serine to aspartic acid mutation results in the cytoplasmic localization of Olig1 enhancing membrane expansion. Our results suggest a novel role for a phosphorylated cytosolic Olig1 in membrane expansion and maturation of oligodendrocytes.

Nonmuscle myosin-2: mix and match

Members of the nonmuscle myosin-2 (NM-2) family of actin-based molecular motors catalyze the conversion of chemical energy into directed movement and force thereby acting as central regulatory components of the eukaryotic cytoskeleton. By cyclically interacting with adenosine triphosphate and F-actin, NM-2 isoforms promote cytoskeletal force generation in established cellular processes like cell migration, shape changes, adhesion dynamics, endo- and exo-cytosis, and cytokinesis. Novel functions of the NM-2 family members in autophagy and viral infection are emerging, making NM-2 isoforms regulators of nearly all cellular processes that require the spatiotemporal organization of cytoskeletal scaffolding. Here, we assess current views about the role of NM-2 isoforms in these activities including the tight regulation of NM-2 assembly and activation through phosphorylation and how NM-2-mediated changes in cytoskeletal dynamics and mechanics affect cell physiological functions in health and disease.

Basic fibroblast growth factor potentiates myelin repair following induction of experimental demyelination in adult mouse optic chiasm and nerves

Induction of demyelination in the central nervous system induce the oligodendrocyte progenitors to proliferate, migrate, and differentiate for restoring new myelin sheathes around demyelinated axons. Factors which increase the response of endogenous progenitor cells could be used to improve remyelination. In the current study, the effect of bFGF on lysolecithin-induced demyelination and remyelination processes in mouse optic chiasm and nerves was investigated. Lysolecithin was injected into the optic chiasm of Balb/C mice. Two groups of animals received doses of bFGF (1 or 5 ng/kg i.p.) just before and every 3 days after lysolecithin injection. Delay and amplitude of visual evoked potential (VEP) waves were recorded as indices of axonal demyelination at 7th, 13th, and 28th days post-lesion. Myelin basic protein (MBP) and Olig2 gene expressions were studied as indices of myelination and oligodendrocyte precursors' recruitment into the lesion. Lysolecithin elongated delay of P1 wave and declined the amplitude of P1-N1 wave. Lysolecithin decreased MBP and increased Olig2 expression in different days post-lesion. Lysolecithin-induced changes in VEPs were partially ameliorated by endogenous repair. bFGF reduced the increased delay, increased the reduced amplitude of P1-N1 wave, increased MBP gene expression, and accelerated the increasing pattern of Olig2. bFGF seems to be able to potentiate the endogenous repair mechanisms of myelin. Its effect on demyelination and remyelination processes seems to be mediated by oligodendrocyte progenitor cells and their differentiation to myelinating cells.

Longitudinal in vivo coherent anti-Stokes Raman scattering imaging of demyelination and remyelination in injured spinal cord

In vivo imaging of white matter is important for the mechanistic understanding of demyelination and evaluation of remyelination therapies. Although white matter can be visualized by a strong coherent anti-Stokes Raman scattering (CARS) signal from axonal myelin, in vivo repetitive CARS imaging of the spinal cord remains a challenge due to complexities induced by the laminectomy surgery. We present a careful experimental design that enabled longitudinal CARS imaging of de- and remyelination at single axon level in live rats. In vivo CARS imaging of secretory phospholipase A(2) induced myelin vesiculation, macrophage uptake of myelin debris, and spontaneous remyelination by Schwann cells are sequentially monitored over a 3 week period. Longitudinal visualization of de- and remyelination at a single axon level provides a novel platform for rational design of therapies aimed at promoting myelin plasticity and repair.

Enhancing remyelination in disease--can we wrap it up?

Demyelinating disorders of the central nervous system are among the most crippling neurological diseases affecting patients at various stages of life. In the most prominent demyelinating disease, multiple sclerosis, the regeneration of myelin sheaths often fails due to a default of the resident stem/precursor cells (oligodendrocyte precursor cells) to differentiate into mature myelin forming cells. Significant advances have been made in our understanding of the molecular and cellular processes involved in remyelination. Furthermore, important insight has been gained from studies investigating the interaction of stem/precursor cells with the distinct environment of demyelinating lesions. These suggest that successful regeneration depends on a signalling environment conducive to remyelination, which is provided in the context of acute inflammation. However, multiple sclerosis lesions also contain factors that inhibit the differentiation of oligodendrocyte precursor cells into myelinating oligodendrocytes. The pattern by which remyelination inducers and inhibitors are expressed in multiple sclerosis lesions may determine a window of opportunity during which oligodendrocyte precursor cells can successfully differentiate. As the first molecules aiming at promoting remyelination are about to enter clinical trials, this review critically evaluates recent advances in our understanding of the biology of oligodendrocyte precursor cells and of the stage-dependent molecular pathology of multiple sclerosis lesions relevant to the regeneration of myelin sheaths. We propose a model that may help to provide cues for how remyelination can be therapeutically enhanced in clinical disease.

Design, synthesis, and evaluation of coumarin-based molecular probes for imaging of myelination

Myelination represents one of the most fundamental biological processes in the vertebrate nervous system. Abnormalities and changes in myelination in the central nervous system (CNS) are seen in many neurodegenerative disorders, such as multiple sclerosis (MS). A long-standing goal has been to directly detect and quantify myelin content in order to facilitate diagnosis and therapeutic treatments of myelin-related diseases. In the course of our studies, we have developed a series of small-molecule probes (SMP) as myelin-imaging agents. Among them are coumarin derivatives, which exhibit promising brain permeability and myelin-binding properties. Herein we report a full account of the design and synthesis of coumarin-based SMPs as myelin-imaging agents. Systematic evaluation of these SMPs in both the CNS and peripheral nervous system (PNS) allowed us to identify some lead agents for potential use as fluorescent dyes for intraoperative nerve mapping in surgical operations or as radiotracers for positron emission tomography (PET) imaging of myelination.

TSC1/TSC2 signaling in the CNS

Over the past several years, the study of a hereditary tumor syndrome, tuberous sclerosis complex (TSC), has shed light on the regulation of cellular proliferation and growth. TSC is an autosomal dominant disorder that is due to inactivating mutations in TSC1 or TSC2 and characterized by benign tumors (hamartomas) involving multiple organ systems. The TSC1/2 complex has been found to play a crucial role in an evolutionarily-conserved signaling pathway that regulates cell growth: the mTORC1 pathway. This pathway promotes anabolic processes and inhibits catabolic processes in response to extracellular and intracellular factors. Findings in cancer biology have reinforced the critical role for TSC1/2 in cell growth and proliferation. In contrast to cancer cells, in the CNS, the TSC1/2 complex not only regulates cell growth/proliferation, but also orchestrates an intricate and finely tuned system that has distinctive roles under different conditions, depending on cell type, stage of development, and subcellular localization. Overall, TSC1/2 signaling in the CNS, via its multi-faceted roles, contributes to proper neural connectivity. Here, we will review the TSC signaling in the CNS.

Quadriplegia recovery after hemi-section and transplant model of spinal cord at the level of C5 and C6

A spinal cord hemi-section with a homologous transplant of medullar tissue at the level of C5-C6 and preservation of the anterior spinal artery was used to evaluate the histological characteristics such as quantity and quality of axons, myelin index and blood vessels after quadriplegia recovery. Vascular changes after spinal injury results in severe endothelial damage, axonal edema, neuronal necrosis and demyelinization as well as cysts and infarction. Preservation of the anterior spinal artery has demonstrated clinical recuperation; therefore, in addition to the lesion we included a homologous transplant to visualize changes at a cellular level. Two groups of dogs (hemi-section and transplant) went through a traumatic spinal cord hemi-section of 50% at the level of C5-C6. The transplant group formed by animals which simultaneously had 4 mm of spinal cord removed and the equal amount substituted from a donor animal at the level of C5-C6 corresponding to the half right side; both preserving the anterior spinal artery. Histological evaluation of all groups took place at days 3 (acute) and 28 (chronic) post-operation. Changes of degeneration and axonal regeneration were found in the hemi-section and transplant groups at acute and chronic time, as well as same quadriplegia recovery at chronic time in the hemi-section and transplant groups which closely related to mechanisms which participate in regeneration and functional recuperation due to the preservation of the anterior spinal artery and presence of new blood vessels.

Chapter 55: neural transplantation

The history of cell transplantation in the nervous system is reviewed in four main sections. The "early era" spans the period from 1890 to 1940, during which the first attempts at cell transplantation in the brain were undertaken. Many contemporary themes were first addressed such as surgical factors to achieve survival of grafted cells and how that should be assessed, immunological factors, use of tumors as a readily viable cell source; and use of the anterior eye chamber as a model transplantation site. However, such studies generally exhibited only low levels of viability or successful implantation. The "middle era" from 1940 to 1970 spans the period when the techniques for viable and reliable cell transplantation using embryonic donor tissues implanted into sites with effective vascularization were first established in brain and neuroendocrine systems in a limited number of specialist centers. However, although sometimes impressive, these results were at variance with the prevailing view that the adult mammalian brain is immutable and resistant to plasticity, growth or regeneration, and were largely ignored. The "modern era," since 1970, began with the pioneering studies that combined cell transplantation with the use of improved histochemical and ultrastructural anatomical techniques to demonstrate selectivity, specificity and regenerative capacity of implanted cells, and the slow acceptance that the adult brain does exhibit considerable potential for plasticity and repair. The last three decades have witnessed the identification of reliable and efficient transplantation technologies combined with progressively refined methods of molecular, cellular, biochemical, physiological and functional analysis. This now enables the ready use of cell transplantation as a powerful novel method within the neuroscience tool-kit, which is being used: to analyze normal organization and function of the nervous system; to reveal the biological mechanisms and principles of neuronal development, regeneration and plasticity; and to study the principles of surgically directed cell therapies for promoting plasticity, replacement and repair in response to injury and disease. The final section reviews recent progress in translating cell transplantation to the clinic for application in Parkinson's and other central nervous system diseases.

Haloperidol promotes proliferation but inhibits differentiation in rat oligodendrocyte progenitor cell culturesThis paper is one of a selection of papers published in this special issue entitled “Second International Symposium on Recent Advances in Basic, Clinical, and Social Medicine” and has undergone the Journal's usual peer review process

Haloperidol is a commonly used, typical, antipsychotic drug (APD) that acts strongly against positive symptoms, but has fewer therapeutic effects on, or may even aggravate, negative symptoms and cognitive deficits in patients with schizophrenia. Loss of oligodendrocytes has been suggested as a factor associated with the negative symptoms of schizophrenia. Recent study shows that chronic haloperidol treatment induced down-regulation of oligodendrocyte-related genes in certain brain regions of mouse. In this study, we used primary oligodendrocyte progenitor cell cultures from 1- to 3-day-postnatal rats to investigate the direct effects of haloperidol on the proliferation and differentiation of oligodendrocyte progenitor cells. Our results showed that (i) haloperidol (0–10.0 µmol·L–1) facilitated the proliferation of oligodendrocyte progenitor cells, (ii) chronic haloperidol (0.5 µmol·L–1) treatment decreased the number of myelin basic protein positive oligodendrocytes and reduced the oligodendrocytes cells possessing myelin-like membranes, resulting in inhibition of the terminal differentiation of oligodendrocytes, and (iii) D3 receptor mRNA was detected in oligodendrocyte progenitor cells, and haloperidol treatment induced a down-regulation of D3 receptor mRNA. These results suggest that the typical antipsychotic drug haloperidol affects the development of oligodendrocyte progenitor cells, and that D3 receptor down regulation may be involved. Our observations provide new insight into possible cellular mechanisms responsible for the side effects of typical antipsychotic drugs and support the concept that abnormality of oligodendrocytes may be involved in the pathogenesis of schizophrenia.

Visual evoked potentials and MBP gene expression imply endogenous myelin repair in adult rat optic nerve and chiasm following local lysolecithin induced demyelination

Multiple sclerosis (MS) patients may suffer from optic disturbances. Toxin-induced demyelinations have frequently been developed to investigate the cellular and structural aspects of demyelination and remyelination processes, separately. The present study describes functional consequence of lysolecithin (LPC)-induced lesion in the adult rat optic nerves and chiasm by recording the visual evoked potentials (VEPs) from the visual cortex and its correlation with myelin basic protein (MBP) expression in lesion site. Records of VEP were obtained at 2, 7, 14 and 28 days post-injection. We observed that the VEPs generated by light stimuli progressively changed in both amplitude and latency after the lesion as well as in comparison with those generated in control animals. These observations were confirmed through measurement of mRNA expression level for MBP which is one of the important genes expressed in mature oligodendrocytes and Schwann cells. The level of MBP mRNAs in demyelinated chiasm and optic nerves decreased following lysolecithin injection with its least value on day 7, and then it increased to the control level 14 days post-lesion. However, it continued to increase even after that and reached a maximum level 28 days post lesion. Results of the present paper show that, LPC injection in the chiasm share functional and molecular alterations which are found in demyelinating disorders in both the optic nerves and chiasm and also these alterations were coming back to level of control animal on 28 days post lesion, which is typically seen in myelin repair process. The present paper provides new insights into the experimental toxin-induced models that may be useful for evaluating the functional recovery of demyelinated optic nerves and chiasm following various repairing strategies. It also seems to be useful for studying the protective or remyelinating effects of different therapies in e.g. optic apparatus which is more affected by MS.

Gliopathic pain: when satellite glial cells go bad

Neurons in sensory ganglia are surrounded by satellite glial cells (SGCs) that perform similar functions to the glia found in the CNS. When primary sensory neurons are injured, the surrounding SGCs undergo characteristic changes. There is good evidence that the SGCs are not just bystanders to the injury but play an active role in the initiation and maintenance of neuronal changes that underlie neuropathic pain. In this article the authors review the literature on the relationship between SGCs and nociception and present evidence that changes in SGC potassium ion buffering capacity and glutamate recycling can lead to neuropathic pain-like behavior in animal models. The role that SGCs play in the immune responses to injury is also considered. We propose the term gliopathic pain to describe those conditions in which central or peripheral glia are thought to be the principal generators of principal pain generators.

Are induced pluripotent stem cells the future of cell-based regenerative therapies for spinal cord injury?

Despite advances in medical and surgical care, current clinical therapies for spinal cord injury (SCI) are limited. During the last two decades, the search for new therapies has been revolutionized by the discovery of stem cells, inspiring scientists and clinicians to search for stem cell-based reparative approaches for many disorders, including neurotrauma. Cell-based therapies using embryonic and adult stem cells in animal models of these disorders have provided positive outcome results. However, the availability of clinically suitable cell sources for human application has been hindered by both technical and ethical issues. The recent discovery of induced pluripotent stem (iPS) cells holds the potential to revolutionize the field of regenerative medicine by offering the option of autologous transplantation, thus eliminating the issue of host rejection. Herein, we will provide the rationale for the use of iPS cells in SCI therapies. In this review, we will evaluate the recent advancements in the field of iPS cells including their capacity for differentiation toward neural lineages that may allow iPS cells transplantation in cell-based therapy for spinal cord repair.

In vivo quantification of myelin changes in the vertebrate nervous system

Destruction or changes associated with myelin membranes in the CNS play a key role in the pathogenesis of multiple sclerosis and other related neurodegenerative disorders. A long-standing goal has been to detect and quantify myelin content in vivo. For this reason, we have developed a myelin-imaging technique based on positron emission tomography (PET). PET is a quantitative imaging modality that has been widely used in clinical settings for direct assessment of biological processes at the molecular level. However, lack of myelin-imaging probes has hampered the use of PET for imaging of myelination in the CNS. Here, we report a myelin-imaging agent, termed Case Imaging Compound (CIC) that readily penetrates the blood-brain barrier and preferentially localizes to myelinated regions of the brain. After radiolabeling with positron-emitting carbon-11, [(11)C]CIC-PET was conducted in longitudinal studies using a lysolethicin-induced rat model of focal demyelination and subsequent remyelination. Quantitative analysis showed that the retention of [(11)C]CIC correlates with the level of demyelination/remyelination. These studies indicate that, for the first time, [(11)C]CIC-PET can be used as an imaging marker of myelination, which has the potential to be translated into clinical studies in multiple sclerosis and other myelin-related diseases for early diagnosis, subtyping, and efficacy evaluation of therapeutic treatments aimed at myelin repair.

Neurological functional recovery after thymosin beta4 treatment in mice with experimental auto encephalomyelitis

In the present study, we hypothesized that thymosin beta 4 (Tbeta4) is a potential therapy of multiple sclerosis (MS). To test this hypothesis, SJL/J mice (n=21) were subjected to experimental autoimmune encephalomyelitis (EAE), an animal model of MS. EAE mice were treated with saline or Tbeta4 (6 mg/kg, n=10) every 3 days starting on the day of myelin proteolipid protein (PLP) immunization for total five doses. Neurological function, inflammatory infiltration, oligodendrocyte progenitor cells (OPCs) and mature oligodendrocytes were measured in the brain of EAE mice. Double immunohistochemical staining was used to detect proliferation and differentiation of OPCs. Tbeta4 was used to treat N20.1 cells (premature oligodendrocyte cell line) in vitro, and proliferation of N20.1 cells was measured by bromodeoxyuridine (BrdU) immunostaining. Tbeta4 treatment improved functional recovery after EAE. Inflammatory infiltrates were significantly reduced in the Tbeta4 treatment group compared to the saline groups (3.6+/-0.3/slide vs 5+/-0.5/slide, P<0.05). NG2(+) OPCs (447.7+/-41.9 vs 195.2+/-31/mm(2) in subventricular zone (SVZ), 75.1+/-4.7 vs 41.7+/-3.2/mm(2) in white matter), CNPase(+) mature oligodendrocytes (267.5+/-10.3 vs 141.4+/-22.9/mm(2)), BrdU(+) with NG2(+) OPCs (32.9+/-3.7 vs 17.9+/-3.6/mm(2)), BrdU(+) with CNPase(+) mature oligodendrocytes (18.2+/-1.7 vs 10.7+/-2.2/mm(2)) were significantly increased in the Tbeta4 treated mice compared to those of saline controls (P<0.05). These data indicate that Tbeta4 treatment improved functional recovery after EAE, possibly, via reducing inflammatory infiltrates, and stimulating oligodendrogenesis.

IGF-1-stimulated protein synthesis in oligodendrocyte progenitors requires PI3K/mTOR/Akt and MEK/ERK pathways

Insulin-like growth factor-1 (IGF-1) interacts with the Type I receptor to activate two main signaling pathways, the mitogen-activated protein kinase kinase (MEK)-extracellular signal-regulated kinase (ERK) and the phosphatidylinositol 3-kinase (PI3K)-Akt cascades, which mediate proliferation or survival of oligodendrocyte (OL) progenitors (OLPs). In other cellular systems, mammalian target of rapamycin (mTOR) and the p70 S6 kinase are downstream effectors that phosphorylate translation initiation factors (e.g. eIF-4E), their regulators (e.g. 4E-binding protein 1, 4E-BP1) and ribosomal protein S6 (S6). The aim of this study was to determine whether these pathways are involved in IGF-1-stimulated protein synthesis, important for growth and differentiation of OLs. Rat cultured OLPs were treated with IGF-1 with or without inhibitors of PI3K (LY294002 or Wortmannin), mTOR (rapamycin), MEK (PD98059), and Akt (III or IV), as well as an adenovirus encoding a dominant negative form of Akt. Protein synthesis, as assessed by [(35)S]-methionine incorporation, was stimulated by IGF-1 and required the upstream activation of PI3K, Akt, mTOR and MEK/ERK. Concordant with the experiments using protein kinase inhibitors, western blotting revealed that IGF-1 stimulates phosphorylation of Akt, mTOR, ERK, S6 and 4E-BP1. Activation of S6 and inactivation of 4E-BP1, necessary for protein synthesis to take place, were dependent on the upstream activation of PI3K and mTOR. Finally, IGF-1 consistently stimulated protein synthesis through mTOR in differentiating OLPs but mRNA transcription was not required at day 4, indicating a differential role of IGF-1 throughout OL development.