Oligodendrocytes in central nervous system diseases:the effect of cytokine regulation

Cytokines including tumor necrosis factor, interleukins, interferons, and chemokines are abundantly produced in various diseases. As pleiotropic factors, cytokines are involved in nearly every aspect of cellular functions such as migration, survival, proliferation, and differentiation. Oligodendrocytes are the myelin-forming cells in the central nervous system and play critical roles in the conduction of action potentials, supply of metabolic components for axons, and other functions. Emerging evidence suggests that both oligodendrocytes and oligodendrocyte precursor cells are vulnerable to cytokines released under pathological conditions. This review mainly summarizes the effects of cytokines on oligodendrocyte lineage cells in central nervous system diseases. A comprehensive understanding of the effects of cytokines on oligodendrocyte lineage cells contributes to our understanding of central nervous system diseases and offers insights into treatment strategies.

The Protective Effects of Flavonoids from Scutellaria Baicalensis Georgi Stems and Leaves on Oligodendrocyte Damage Induced by Aβ1-42

Aim: This study aimed to investigate the protective effects of flavonoids from the stem and leaves of Scutellaria baicalensis Georgi (SSFs) against Aβ1-42-induced oligodendrocytes (OL) damage. Methods: Immunofluorescence was used for the detection of myelin-associated glycoprotein (MAG), a characteristic protein of rat oligodendrocytes (OLN-93 cells). To evaluate the potential protective effects of SSFs on OLN-93 cells injured by Aβ1-42, an injury model was established by subjecting OLN-93 cells to Aβ1-42 exposed. Cell morphology was examined using an inverted microscope, while cell viability was assessed using the colorimetric method of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). Additionally, lactate dehydrogenase (LDH) was measured using the pyruvic acid reduction assay. The Ginkgo biloba leaf extract (GBE) injection was used as a positive control. Results: A total of >95% of the MAG immunofluorescence-positive cells were identified as oligodendrocytes. Gradually increasing concentrations of SSFs impaired the cells, and the maximum nondetrimental dose for OLN-93 cells was 75 mg/L. This study assessed the effects of SSFs on OLN-93 cells damaged by Aβ1-42. The results indicated that SSFs significantly improved OLN-93 cell morphological abnormal changes, increased the OLN-93 cell survival rate, and reduced LDH release. Conclusion: SSFs can alleviate Aβ1-42-induced damage of OL.

Poly-L-ornithine blocks the inhibitory effects of fibronectin on oligodendrocyte differentiation and promotes myelin repair

The extracellular matrix surrounding oligodendrocytes plays an important role during myelination and remyelination in the brain.In many cases,the microenvironment surrounding demyelination lesions contains inhibitory molecules,which lead to repair failure.Accordingly,blocking the activity of these inhibitory factors in the extracellular matrix should lead to more successful remyelination.In the central nervous system,oligodendrocytes form the myelin sheath.We performed primary cell culture and found that a natural increase in fibronectin promoted the proliferation of oligodendrocyte progenitors during the initial stage of remyelination while inhibiting oligodendrocyte differentiation.Poly-L-ornithine blocked these inhibitory effects without compromising fibronectin’s pro-proliferation function.Experiments showed that poly-L-ornithine activated the Erk1/2 signaling pathway that is necessary in the early stages of differentiation,as well as PI3K signaling pathways that are needed in the mid-late stages.When poly-L-ornithine was tested in a lysolecithin-induced animal model of focal demyelination,it enhanced myelin regeneration and promoted motor function recovery.These findings suggest that poly-L-ornithine has the potential to be a treatment option for clinical myelin sheath injury.

The contribution of oligodendrocytes and oligodendrocyte progenitor cells to central nervous system repair in multiple sclerosis： perspectives for remyelination therapeutic strategies

Oligodencrocytes（OLs） are the main glial cells of the central nervous system involved in myelination of axons. In multiple sclerosis（MS）, there is an imbalance between demyelination and remyelination processes, the last one performed by oligodendrocyte progenitor cells（OPCs） and OLs, resulting into a permanent demyelination, axonal damage and neuronal loss. In MS lesions, astrocytes and microglias play an important part in permeabilization of blood-brain barrier and initiation of OPCs proliferation. Migration and differentiation of OPCs are influenced by various factors and the process is finalized by insufficient acummulation of OLs into the MS lesion. In relation to all these processes, the author will discuss the potential targets for remyelination strategies.

New insights into the immunologic role of oligodendrocyte lineage cells in demyelination diseases

Oligodendrocyte lineage cells(OL-lineage cells)are a cell population that are crucial for mammalian central nervous system(CNS)myelination.OL-lineage cells go through developmental stages,initially differentiating into oligodendrocyte precursor cells(OPCs),before becoming immature oligodendrocytes,then mature oligodendrocytes(OLs).While the main function of cell lineage is in myelin formation,and increasing number of studies have turned to explore the immunological characteristics of these cells.Initially,these studies focused on discovering how OPCs and OLs are affected by the immune system,and then,how these immunological changes influence the myelination process.However,recent studies have uncovered another feature of OL-lineage cells in our immune systems.It would appear that OL-lineage cells also express immunological factors such as cytokines and chemokines in response to immune activation,and the expression of these factors changes under various pathologic conditions.Evidence suggests that OL-lineage cells actually modulate immune functions.Indeed,OL-lineage cells appear to play both"victim"and"agent"in the CNS which raises a number of questions.Here,we summarize immunologic changes in OL-lineage cells and their effects,as well as consider OL-lineage cell changes which influence immune cells under pathological conditions.We also describe some of the underlying mechanisms of these changes and their effects.Finally,we describe several studies which use OL-lineage cells as immunotherapeutic targets for demyelination diseases.

Oligodendrocyte pathology in fetal alcohol spectrum disorders

The pathology of fetal alcohol syndrome and the less severe fetal alcohol spectrum disorders includes brain dysmyelination.Recent studies have shed light on the molecular mechanisms underlying these white matter abnormalities.Rodent models of fetal alcohol syndrome and human studies have shown suppressed oligodendrocyte differentiation and apoptosis of oligodendrocyte precursor cells.Ethanol exposure led to reduced expression of myelin basic protein and delayed myelin basic protein expression in rat and mouse models of fetal alcohol syndrome and in human histopathological specimens.Several studies have reported increased expression of many chemokines in dysmyelinating disorders in central nervous system,including multiple sclerosis and fetal alcohol syndrome.Acute ethanol exposure reduced levels of the neuroprotective insulin-like growth factor-1 in fetal and maternal sheep and in human fetal brain tissues,while ethanol increased the expression of tumor necrosis factor α in mouse and human neurons.White matter lesions have been induced in the developing sheep brain by alcohol exposure in early gestation.Rat fetal alcohol syndrome models have shown reduced axon diameters,with thinner myelin sheaths,as well as reduced numbers of oligodendrocytes,which were also morphologically aberrant oligodendrocytes.Expressions of markers for mature myelination,including myelin basic protein,also were reduced.The accumulating knowledge concerning the mechanisms of ethanol-induced dysmyelination could lead to the development of strategies to prevent dysmyelination in children exposed to ethanol during fetal development.Future studies using fetal oligodendrocyte-and oligodendrocyte precursor cell-derived exosomes isolated from the mother's blood may identify biomarkers for fetal alcohol syndrome and even implicate epigenetic changes in early development that affect oligodendrocyte precursor cell and oligodendrocyte function in adulthood.By combining various imaging modalities with molecular studies,it may be possible to determine which fetuses are at risk and to intervene therapeutically early in the pregnancy.

Oligodendrocyte transcription factor 1 overexpression promotes oligodendrocyte transcription factor 2 expression in the brains of neonatal rats exposed to hypoxia

To examine the expression profiles of oligodendrocyte transcription factors 1 and 2 （Oligl and Olig2） and the interaction between these two proteins, Oligl was transfected into the lateral ventricles of neonatal rats subjected to hypoxia. Immunohistochemistry demonstrated that Olig2 was expressed throughout the nuclei in the brain, and expression increased at 3 days following hypoxia and was higher than levels at 7 days following Ad5-Oligl transfection. Western blot revealed that Oligl and Olig2 expression increased in Oligl-transfected brain cells 3 days after hypoxia, but Oligl and Olig2 expression decreased at 7 days. These results indicate that Oligl overexpression enhances Olig2 expression in brain tissues of hypoxia rats.

Oligodendrocyte precursor cell maturation: role of adenosine receptors

Oligodendrocyte-formed myelin sheaths allow fast synaptic transmission in the brain and their degeneration leads to demyelinating diseases such as multiple sclerosis. Remyelination requires the differentiation of oligodendrocyte progenitor cells into mature oligodendrocytes but, in chronic neurodegenerative disorders, remyelination fails due to adverse environment. Therefore, a strategy to prompt oligodendrocyte progenitor cell differentiation towards myelinating oligodendrocytes is required. The neuromodulator adenosine, and its receptors(A1, A(2A), A(2B) and A3 receptors: A1R, A(2A)R, A(2B)R and A3R), are crucial mediators in remyelination processes. It is known that A1Rs facilitate oligodendrocyte progenitor cell maturation and migration whereas the A3Rs initiates apoptosis in oligodendrocyte progenitor cells. Our group of research contributed to the field by demonstrating that A(2A)R and A(2B)R inhibit oligodendrocyte progenitor cell maturation by reducing voltage-dependent K^+ currents necessary for cell differentiation. The present review summarizes the possible role of adenosine receptor ligands as potential therapeutic targets in demyelinating pathologies such as multiple sclerosis.

Expression of hypoxia-inducible factor 1 alpha and oligodendrocyte lineage gene-1 in cultured brain slices after oxygen-glucose deprivation

Oligodendrocyte lineage gene-1 expressed in oligodendrocytes may trigger the repair of neuronal myelin impairment, and play a crucial role in myelin repair. Hypoxia-inducible factor la, a transcription factor, is of great significance in premature infants with hypoxic-ischemic brain damage There is little evidence of direct regulatory effects of hypoxia-inducible factor le on oligodendrocyte lineage gene-l. In this study, brain slices of Sprague-Dawley rats were cultured and subjected to oxygen-glucose deprivation. Then, slices were transfected with hypoxia-inducible factor la or oligodendrocyte lineage gene-1. The expression levels of hypoxia-inducible factor la and oligodendrocyte lineage gene-1 were significantly up-regulated in rat brains prior to transfection, as detected by immunohistochemical staining. Eight hours after transfection of slices with hypoxia-inducible factor la, oligodendrocyte lineage gene-1 expression was upregulated, and reached a peak 24 hours after transfection. Oligodendrocyte lineage gene-1 transfection induced no significant differences in hypoxia-inducible factor la levels in rat brain tissues with oxygen-glucose deprivation. These experimental findings indicate that hypoxia-inducible factor la can regulate oligodendrocyte lineage gene-1 expression in hypoxic brain tissue, thus repairing the neural impairment.

Liproxstatin-1 is an effective inhibitor of oligodendrocyte ferroptosis induced by inhibition of glutathione peroxidase 4

Our previous studies showed that ferroptosis plays an important role in the acute and subacute stages of spinal cord injury.High intracellular iron levels and low glutathione levels make oligodendrocytes vulnerable to cell death after central nervous system trauma.In this study,we established an oligodendrocyte(OLN-93 cell line)model of ferroptosis induced by RSL-3,an inhibitor of glutathione peroxidase 4(GPX4).RSL-3 significantly increased intracellular concentrations of reactive oxygen species and malondialdehyde.RSL-3 also inhibited the main antiferroptosis pathway,i.e.,SLC7A11/glutathione/glutathione peroxidase 4(xCT/GSH/GPX4),and downregulated acyl-coenzyme A synthetase long chain family member 4.Furthermore,we evaluated the ability of several compounds to rescue oligodendrocytes from ferroptosis.Liproxstatin-1 was more potent than edaravone or deferoxamine.Liproxstatin-1 not only inhibited mitochondrial lipid peroxidation,but also restored the expression of GSH,GPX4 and ferroptosis suppressor protein 1.These findings suggest that GPX4 inhibition induces ferroptosis in oligodendrocytes,and that liproxstatin-1 is a potent inhibitor of ferroptosis.Therefore,liproxstatin-1 may be a promising drug for the treatment of central nervous system diseases.

Transferrin receptor and ferritin-H are developmentally regulated in oligodendrocyte lineage cells

Iron is an essential trophic element that is required for cell viability and differentiation, especially in oligodendrocytes, which consume relatively high rates of energy to produce myelin. Multiple iron metabolism proteins are expressed in the brain including transferrin receptor and ferritin-H. However, it is still unknown whether they are developmentally regulated in oligodendrocyte lineage cells for myelination. Here, using an in vitro cultured differentiation model of oligodendrocytes, we found that both transferrin receptor and ferritin-H are significantly upregulated during oligodendrocyte maturation, implying the essential role of iron in the development of oligodendrocytes. Additional different doses of Fe3＋ in the cultured medium did not affect oligodendrocyte precursor cell maturation or ferritin-H expression but decreased the expression of the transferrin receptor. These results indicate that upregulation of both transferrin receptor and ferritin-H contributes to maturation and myelination of oligodendrocyte precursor cells.

Human umbilical cord Wharton's jelly-derived oligodendrocyte precursor-like cells for axon and myelin sheath regeneration

Human umbilical mesenchymal stem cells from Wharton＇s jelly of the umbilical cord were induced to differentiate into oligodendrocyte precursor-like cells in vitro. Oligodendrocyte precursor cells were transplanted into contused rat spinal cords. Immunofluorescence double staining indicated that transplanted cells survived in injured spinal cord, and differentiated into mature and immature oligodendrocyte precursor cells. Biotinylated dextran amine tracing results showed that cell transplantation promoted a higher density of the corticospinal tract in the central and caudal parts of the injured spinal cord. Luxol fast blue and toluidine blue staining showed that the volume of residual myelin was significantly increased at 1 and 2 mm rostral and caudal to the lesion epicenter after cell transplantation. Furthermore, immunofluorescence staining verified that the newly regenerated myelin sheath was derived from the central nervous system. Basso, Beattie and Bresnahan testing showed an evident behavioral recovery. These results suggest that human umbilical mesenchymal stem cell-derived oligodendrocyte precursor cells promote the regeneration of spinal axons and myelin sheaths.

Negative regulation of miRNA-9 on oligodendrocyte lineage gene 1 during hypoxic-ischemic brain damage

Oligodendrocyte lineage gene 1 plays a key role in hypoxic-ischemic brain damage and myelin repair, miRNA-9 is involved in the occurrence of many related neurological disorders. Bioin- formatics analysis demonstrated that miRNA-9 complementarily, but incompletely, bound oligodendrocyte lineage gene 1, but whether miRNA-9 regulates oligodendrocyte lineage gene 1 remains poorly understood. Whole brain slices of 3-day-old Sprague-Dawley rats were cultured and divided into four groups： control group; oxygen-glucose deprivation group （treatment with 8% O2 ＋ 92% N2 and sugar-free medium for 60 minutes）; transfection control group （after oxygen and glucose deprivation for 60 minutes, transfected with control plasmid） and miRNA-9 transfection group （after oxygen and glucose deprivation for 60 minutes, transfected with miRNA-9 plasmid）. From the third day of transfection, and with increasing culture days, oligodendrocyte lineage gene 1 expression increased in each group, peaked at 14 days, and then decreased at 21 days. Real-time quantitative PCR results, however, demonstrated that oligoden- drocyte lineage gene 1 expression was lower in the miRNA-9 transfection group than that in the transfection control group at 1, 3, 7, 14, 21 and 28 days after transfection. Results suggested that miRNA-9 possibly negatively regulated oligodendrocyte lineage gene 1 in brain tissues during hypoxic-ischemic brain damage.

Electroacupuncture promotes the proliferation of endogenous neural stem cells and oligodendrocytes in the injured spinal cord of adult rats

A contusive model of spinal cord injury at spinal segment T8-9 was established in rats. Huantiao （GB30） and Huatuojiaji （Ex-B05） were punctured with needles, and endogenous neural stem cells were labeled with 5-bromo-2＇-deoxyuridine （BrdU） and NG2. Double immunofluorescence staining showed that electroacupuncture markedly increased the numbers of BrdU＋/NG2＋cells at spinal cord tissue 15 mm away from the injury center in the rostral and caudal directions. The results suggest that electroacupuncture promotes the proliferation of endogenous neural stem cells and oligodendrocytes in rats with spinal cord injury.

Inhibitory Effect of LPS on the Proliferation of Oligodendrocyte Precursor Cells through the Notch Signaling Pathway inIntrauterine Infection-induced Rats

Periventricular white matter injury (PWMI)is very common in survivors of premature birth,and the final outcomes are a reduction in myelinated neurons leading to white matter hypomyelination.How and (or) why the oligodendrocyte lineage develops abnormally and myelination is reduced is a hot topic in the field.This study focuses on the effect of intrauterine inflammation on the proliferation of oligodendrocyte lineage cells and the underlying mechanisms.Lipopolysaccharide (LPS)(300μg/kg)was intraperitoneally injected into pregnant Sprague-Dawley rats at embryonic days 19 and 20 to establish a rat model of intrauterine infection-induced white matter injury.Corpus callosum tissues were collected at postnatal day 14(P14)to quantify the number of oligodendrocytes,the number and proliferation of oligodendrocyte precursor cells (OPCs), and the expression of myelin proteins (MBP and PLP).Furthermore,the expression of Writ and Notch signaling-related proteins was analyzed.The results showed that the number of oligodendrocytes in the corpus callosum tissues of LPS-treated rats was reduced,and the expression levels of myelinating proteins were down-regulated.Further analysis showed that the Notch signaling pathway was down-regulated in the LPS-treated group.These results indicate that intrauterine LPS may inhibit the proliferation of OPCs by down-regulating the Notch rather than the Writ signaling pathway,leading to hypomyelination of white matter.

Trophic factors are essential for the survival of grafted oligodendrocyte progenitors and for neuroprotection after perinatal excitotoxicity

The consequences of neonatal white matter injury are devastating and represent a major societal problem as currently there is no cure.Prematurity,low weight birth and maternal pre-natal infection are the most frequent causes of acquired myelin deficiency in the human neonate leading to cerebral palsy and cognitive impairment.In the developing brain,oligodendrocyte(OL)maturation occurs perinatally,and immature OLs are particularly vulnerable.Cell replacement therapy is often considered a viable option to replace progenitors that die due to glutamate excitotoxicity.We previously reported directed specification and mobilization of endogenous committed and uncommitted neural progenitors by the combination of transferrin and insulin growth factor 1(TSC1).Here,considering cell replacement and integration as therapeutic goals,we examined if OL progenitors(OLPs)grafted into the brain parenchyma of mice that were subjected to an excitotoxic insult could rescue white matter injury.For that purpose,we used a well-established model of glutamate excitotoxic injury.Four-day-old mice received a single intraparenchymal injection of the glutamate receptor agonist N-methyl-D-aspartate alone or in conjunction with TSC1 in the presence or absence of OLPs grafted into the brain parenchyma.Energetics and expression of stress proteins and OL developmental specific markers were examined.A comparison of the proteomic profile per treatment was also ascertained.We found that OLPs did not survive in the excitotoxic environment when grafted alone.In contrast,when combined with TSC1,survival and integration of grafted OLPs was observed.Further,energy metabolism in OLPs was significantly increased by N-methyl-D-aspartate and modulated by TSC1.The proteomic profile after the various treatments showed elevated ubiquitination and stress/heat shock protein 90 in response to N-methyl-D-aspartate.These changes were reversed in the presence of TSC1 and ubiquitination was decreased.The results obtained in this pre-clinical study indicate that the use of a combinatorial intervention including both trophic support and healthy OLPs constitutes a promising approach for long-term survival and successful graft integration.We established optimal conditioning of the host brain environment to promote long-term survival and integration of grafted OLPs into an inflamed neonate host brain.Experimental procedures were performed under the United States Public Health Service Guide for the Care and Use of Laboratory Animals and were approved by the Institutional Animal Care Committee at(UCLA)(ARC#1992-034-61)on July 1,2010.

Nogo-A aggravates oxidative damage in oligodendrocytes

Nogo-A is considered one of the most important inhibitors of myelin-associated axonal regeneration in the central nervous system.It is mainly expressed by oligodendrocytes.Although previous studies have found regulatory roles for Nogo-A in neurite outgrowth inhibition,neuronal homeostasis,precursor migration,plasticity,and neurodegeneration,its functions in the process of oxidative injury are largely uncharacterized.In this study,oligodendrocytes were extracted from the cerebral cortex of newborn Sprague-Dawley rats.We used hydrogen peroxide(H2O2)to induce an in vitro oligodendrocyte oxidative damage model and found that endogenously expressed Nogo-A is significantly upregulated in oligodendrocytes.After recombinant virus Ad-ZsGreen-rat Nogo-A infection of oligodendrocytes,Nogo-A expression was increased,and the infected oligodendrocytes were more susceptible to acute oxidative insults and exhibited a markedly elevated rate of cell death.Furthermore,knockdown of Nogo-A expression in oligodendrocytes by Ad-ZsGreen-shRNA-Nogo-A almost completely protected against oxidative stress induced by exogenous H2O2.Intervention with a Nogo-66 antibody,a LINGO1 blocker,or Y27632,an inhibitor in the Nogo-66-NgR/p75/LINGO-1-RhoA-ROCK pathway,did not affect the death of oligodendrocytes.Ad-ZsGreen-shRNA-Nogo-A also increased the levels of phosphorylated extracellular signal-regulated kinase 1/2 and inhibited BCL2 expression in oligodendrocytes.In conclusion,Nogo-A aggravated reactive oxygen species damage in oligodendrocytes,and phosphorylated extracellular signal-regulated kinase 1/2 and BCL2 might be involved in this process.This study was approved by the Ethics Committee of Peking University People’s Hospital,China(approval No.2018PHC081)on December 18,2018.

Association between Alzheimer's disease pathogenesis and early demyelination and oligodendrocyte dysfunction

The APPSwe/PSEN1 dE9（APP/PS1） transgenic mouse model is an Alzheimer＇s disease mouse model exhibiting symptoms of dementia, and is commonly used to explore pathological changes in the development of Alzheimer＇s disease. Previous clinical autopsy and imaging studies suggest that Alzheimer＇s disease patients have white matter and oligodendrocyte damage, but the underlying mechanisms of these have not been revealed. Therefore, the present study used APP/PS1 mice to assess cognitive change, myelin loss, and corresponding changes in oligodendrocytes, and to explore the underlying mechanisms. Morris water maze tests were performed to evaluate cognitive change in APP/PS1 mice and normal C57 BL/6 mice aged 3 and 6 months. Luxol fast blue staining of the corpus callosum and quantitative reverse transcription-polymerase chain reaction（q RT-PCR） for myelin basic protein（MBP） mRNA were carried out to quantify myelin damage. Immunohistochemistry staining for NG2 and qRT-PCR for monocarboxylic acid transporter 1（MCT1） mRNA were conducted to assess corresponding changes in oligodendrocytes. Our results demonstrate that compared with C57 BL/6 mice, there was a downregulation of MBP mRNA in APP/PS1 mice aged 3 months. This became more obvious in APP/PS1 mice aged 6 months accompanied by other abnormalities such as prolonged escape latency in the Morris water maze test, shrinkage of the corpus callosum, upregulation of NG2-immunoreactive cells, and downregulation of MCT1 mRNA. These findings indicate that the involvement of early demyelination at 3 months and the oligodendrocyte dysfunction at 6 months in APP/PS1 mice are in association with Alzheimer＇s disease pathogenesis.

Progesterone effects on the oligodendrocyte linage: all roads lead to the progesterone receptor

A new role has emerged for progesterone after discovering its potent actions away from reproduction in both the central and the peripheral nervous system. The aim of the present report is to discuss progesterone’s mechanisms of action involved in myelination, remyelination and neuroinflammation. The pivotal role of the classic progesterone receptor is described and evidence is compiled about progesterone’s direct effects on oligodendrocyte linage and its indirect effects on oligodendrocyte precursor cell differentiation by decreasing the neuroinflammatory environment.

Axonal damage in myelin oligodendrocyte glycoprotein peptide-induced experimental autoimmune encephalomyelitis in a C57BL/6 mouse model may be not secondary to inflammatory demyelination

The present study established a chronic experimental autoimmune encephalomyelitis model in C57BL/6 mice induced by myelin oligodendrocyte glycoprotein peptides and complete Freund＇s adjuvant. Onset latency was 12 days, with an incidence rate of 100%. Neuropathological characteristics included perivascular inflammatory cell infiltration, demyelination, neuronal degeneration, and axonal damage within cerebral and myelic white matter. Electron microscopy revealed swollen mitochondria, complete organ disappearance, and fused or broken myelin sheath structure, which were accompanied by myelin sheath reconstruction. Moreover, axonal damage was not consistent with demyelination distribution, and severity of axonal damage did not correlate with demyelination. Results suggested that axonal damage in an experimental autoimmune encephalomyelitis model is not secondary to inflammatory demyelination.