Myelin Production Research Articles

Generation of oligodendrocytes and establishment of an all-human myelinating platform from human pluripotent stem cells.

Oligodendrocytes (OLs) are responsible for myelin production and metabolic support of neurons. Defects in OLs are crucial in several neurodegenerative diseases including multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS). This protocol describes a method to generate oligodendrocyte precursor cells (OPCs) from human pluripotent stem cells (hPSCs) in only ~20 d, which can subsequently myelinate neurons, both in vitro and in vivo. To date, OPCs have been derived from eight different hPSC lines including those derived from patients with spontaneous and familial forms of MS and ALS, respectively. hPSCs, fated for 8 d toward neural progenitors, are transduced with an inducible lentiviral vector encoding for SOX10. The addition of doxycycline for 10 d results in >60% of cells being O4-expressing OPCs, of which 20% co-express the mature OL marker myelin basic protein (MBP). The protocol also describes an alternative for viral transduction, by incorporating an inducible SOX10 in the safe harbor locus AAVS1, yielding ~100% pure OPCs. O4+ OPCs can be purified and either cryopreserved or used for functional studies. As an example of the type of functional study for which the derived cells could be used, O4+ cells can be co-cultured with maturing hPSC-derived neurons in 96/384-well-format plates, allowing the screening of pro-myelinating compounds.

Clobetasol Attenuates White Matter Injury by Promoting Oligodendrocyte Precursor Cell Differentiation

Introduction: White matter injury (WMI) is the most common brain injury in preterm infants and can result in life-long neurological deficits. The main cause of WMI is damage to the oligodendrocyte precursor cells (OPC) in the brain that results in delayed myelin sheath formation, or the destruction of existing myelin sheaths. OPC undergo highly regulated and strictly timed developmental changes that result in their transformation to mature oligodendrocytes capable of myelin production. Objective: Studies have shown that clobetasol strongly promotes differentiation of OPC into myelin sheaths. Therefore, we hypothesized that clobetasol may be a therapeutic option for the treatment of preterm WMI. Methods: We induced a WMI rat model and observed white matter damage under an optical microscope. Rats subjected to WMI were injected intraperitoneally with clobetasol (2 or 5 mg/kg daily) from day 1 to day 5 in the early treatment groups, or from day 6 to day 10 in the late treatment groups. After 17 days, the rats were sacrificed and the expression of myelin basic protein (MBP) was visualized using immunofluorescence. In addition, we evaluated myelin sheath formation using electron microscopy. The rats were also subjected to the suspension test, ramp test, and open field test to evaluate neurobehavioral functions. Results: A rat model of WMI was successfully induced. It was found that clobetasol significantly induced MBP expression and myelin sheath formation and improved neurobehavioral function in the rats subjected to WMI. Conclusions: Our results indicate that clobetasol attenuates WMI by promoting OPC differentiation, and it may be an effective therapeutic agent for the treatment of preterm WMI.

Impaired Postnatal Myelination in a Conditional Knockout Mouse for the Ferritin Heavy Chain in Oligodendroglial Cells.

To define the importance of iron storage in oligodendrocyte development and function, the ferritin heavy subunit (Fth) was specifically deleted in oligodendroglial cells. Blocking Fth synthesis in Sox10 or NG2-positive oligodendrocytes during the first or the third postnatal week significantly reduces oligodendrocyte iron storage and maturation. The brain of Fth KO animals presented an important decrease in the expression of myelin proteins and a substantial reduction in the percentage of myelinated axons. This hypomyelination was accompanied by a decline in the number of myelinating oligodendrocytes and with a reduction in proliferating oligodendrocyte progenitor cells (OPCs). Importantly, deleting Fth in Sox10-positive oligodendroglial cells after postnatal day 60 has no effect on myelin production and/or oligodendrocyte quantities. We also tested the capacity of Fth-deficient OPCs to remyelinate the adult brain in the cuprizone model of myelin injury and repair. Fth deletion in NG2-positive OPCs significantly reduces the number of mature oligodendrocytes and myelin production throughout the remyelination process. Furthermore, the corpus callosum of Fth KO animals presented a significant decrease in the percentage of remyelinated axons and a substantial reduction in the average myelin thickness. These results indicate that Fth synthesis during the first three postnatal weeks is important for an appropriate oligodendrocyte development, and suggest that Fth iron storage in adult OPCs is also essential for an effective remyelination of the mouse brain.SIGNIFICANCE STATEMENT To define the importance of iron storage in oligodendrocyte function, we have deleted the ferritin heavy chain (Fth) specifically in the oligodendrocyte lineage. Fth ablation in oligodendroglial cells throughout early postnatal development significantly reduces oligodendrocyte maturation and myelination. In contrast, deletion of Fth in oligodendroglial cells after postnatal day 60 has no effect on myelin production and/or oligodendrocyte numbers. We have also tested the consequences of disrupting Fth iron storage in oligodendrocyte progenitor cells (OPCs) after demyelination. We have found that Fth deletion in NG2-positive OPCs significantly delays the remyelination process in the adult brain. Therefore, Fth iron storage is essential for early oligodendrocyte development as well as for OPC maturation in the demyelinated adult brain.

Guiding Oligodendrocyte Precursor Cell Maturation With Urokinase Plasminogen Activator-Degradable Elastin-like Protein Hydrogels.

Demyelinating injuries and diseases, like multiple sclerosis, affect millions of people worldwide. Oligodendrocyte precursor cells (OPCs) have the potential to repair demyelinated tissues because they can both self-renew and differentiate into oligodendrocytes (OLs), the myelin producing cells of the central nervous system (CNS). Cell-matrix interactions impact OPC differentiation into OLs, but the process is not fully understood. Biomaterial hydrogel systems help to elucidate cell-matrix interactions because they can mimic specific properties of native CNS tissues in an in vitro setting. We investigated whether OPC maturation into OLs is influenced by interacting with a urokinase plasminogen activator (uPA) degradable extracellular matrix (ECM). uPA is a proteolytic enzyme that is transiently upregulated in the developing rat brain, with peak uPA expression correlating with an increase in myelin production in vivo. OPC-like cells isolated through the Mosaic Analysis with Double Marker technique (MADM OPCs) produced low-molecular-weight uPA in culture. MADM OPCs were encapsulated into two otherwise similar elastin-like protein (ELP) hydrogel systems: one that was uPA degradable and one that was nondegradable. Encapsulated MADM OPCs had similar viability, proliferation, and metabolic activity in uPA degradable and nondegradable ELP hydrogels. Expression of OPC maturation-associated genes, however, indicated that uPA degradable ELP hydrogels promoted MADM OPC maturation although not sufficiently for these cells to differentiate into OLs.

Brain booster foods for children

About 95% of brain volume development takes place by 6 years. As growth occurs, volume of the grey matter decreases and white matter increases with the 100-fold increase for the signal transmissions. Human brain is composed of 60% fat mainly as docosahexaenoic acid (DHA) for the normal functioning. Brain cells rich in phospholipids facilitate the transport of neurotransmitters which improves processing speed, visual-motor coordination, attention, and executive function up to 70%. The intake of ω – 3/6 fatty acids should be in the ratio of 9:3:1 with eicosapentaenoic, docosahexaenoic and γ – linolenic acid improved erythrocyte fatty acid ω – 3 profile thereby enhancing the neuro cognitive functions. The vulnerable early years of growth affected by malnutrition decreases the number of brain cells, myelin production and alters the functioning of neurotransmitters leading to cognitive impairments, learning disorders and schizophrenia. So the supplementation of brain booster foods helps to improve the normal functioning of the brain in individuals.

4492 The role of creatine in developmental myelination and remyelination

OBJECTIVES/GOALS: Oligodendrocytes (OL) are glial cells of the central nervous system (CNS) responsible for the energy demanding task of generating myelin sheaths during development and remyelination after demyelinating injury. One metabolite shown to significantly increase ATP production in OL is the nitrogenous organic acid, creatine. Creatine plays an essential role in ATP buffering within tissues with highly fluctuating energy demands such as brain and muscle. Interestingly, mature OL, which are the cells capable of myelin production, are the main cells in the CNS expressing the rate-limiting enzyme for creatine synthesis, guanidinoacetate methyltransferase (Gamt). Patients with mutations in Gamt display intellectual disabilities, impaired myelination and seizures. Therefore, we hypothesize that creatine may be essential for developmental myelination and improve remyelination. METHODS/STUDY POPULATION: To investigate these hypotheses, we developed a new transgenic mouse model with LoxP sites flanking exons 2-6 of the Gamt gene where excision leads to expression of a green fluorescent tag allowing us to track the cells normally expressing Gamt. RESULTS/ANTICIPATED RESULTS: In this mouse model, we show a 95% (±0.47%, n = 3) co-localization of Gamt within mature OL during postnatal (P) day P14. Next, we show that knocking out Gamt leads to a significant reduction in OL in the major CNS white matter tract, the corpus callosum, at P14 and P21 (P14: 0.007, n = 3; P21: 0.04, n = 3). Here, we also investigate whether dietary creatine can enhance remyelination in the cuprizone model of toxic demyelination. DISCUSSION/SIGNIFICANCE OF IMPACT: These studies highlight the important role creatine plays in developmental myelination and investigate whether creatine can provide a therapeutic value during a CNS demyelinating insult.

Effects of Biotin on survival, ensheathment, and ATP production by oligodendrocyte lineage cells in vitro.

Mechanisms implicated in disease progression in multiple sclerosis include continued oligodendrocyte (OL)/myelin injury and failure of myelin repair. Underlying causes include metabolic stress with resultant energy deficiency. Biotin is a cofactor for carboxylases involved in ATP production that impact myelin production by promoting fatty acid synthesis. Here, we investigate the effects of high dose Biotin (MD1003) on the functional properties of post-natal rat derived oligodendrocyte progenitor cells (OPCs). A2B5 positive OPCs were assessed using an in vitro injury assay, culturing cells in either DFM (DMEM/F12+N1) or "stress media" (no glucose (NG)-DMEM), with Biotin added over a range from 2.5 to 250 μg/ml, and cell viability determined after 24 hrs. Biotin reduced the increase in OPC cell death in the NG condition. In nanofiber myelination assays, biotin increased the percentage of ensheathing cells, the number of ensheathed segments per cell, and length of ensheathed segments. In dispersed cell culture, Biotin also significantly increased ATP production, assessed using a Seahorse bio-analyzer. For most assays, the positive effects of Biotin were observed at the higher end of the dose-response analysis. We conclude that Biotin, in vitro, protects OL lineage cells from metabolic injury, enhances myelin-like ensheathment, and is associated with increased ATP production.

Astrocytes and Microglia as Major Players of Myelin Production in Normal and Pathological Conditions.

Myelination is an essential process that consists of the ensheathment of axons by myelin. In the central nervous system (CNS), myelin is synthesized by oligodendrocytes. The proliferation, migration, and differentiation of oligodendrocyte precursor cells constitute a prerequisite before mature oligodendrocytes extend their processes around the axons and progressively generate a multilamellar lipidic sheath. Although myelination is predominately driven by oligodendrocytes, the other glial cells including astrocytes and microglia, also contribute to this process. The present review is an update of the most recent emerging mechanisms involving astrocyte and microglia in myelin production. The contribution of these cells will be first described during developmental myelination that occurs in the early postnatal period and is critical for the proper development of cognition and behavior. Then, we will report the novel findings regarding the beneficial or deleterious effects of astroglia and microglia, which respectively promote or impair the endogenous capacity of oligodendrocyte progenitor cells (OPCs) to induce spontaneous remyelination after myelin loss. Acute delineation of astrocyte and microglia activities and cross-talk should uncover the way towards novel therapeutic perspectives aimed at recovering proper myelination during development or at breaking down the barriers impeding the regeneration of the damaged myelin that occurs in CNS demyelinating diseases.

Dynamics of sphingolipids and the serine palmitoyltransferase complex in rat oligodendrocytes during myelination

Myelin is a unique lipid-rich membrane structure that accelerates neurotransmission and supports neuronal function. Sphingolipids are critical myelin components. Yet sphingolipid content and synthesis have not been well characterized in oligodendrocytes, the myelin-producing cells of the CNS. Here, using quantitative real-time PCR, LC-MS/MS-based lipid analysis, and biochemical assays, we examined sphingolipid synthesis during the peak period of myelination in the postnatal rat brain. Importantly, we characterized sphingolipid production in isolated oligodendrocytes. We analyzed sphingolipid distribution and levels of critical enzymes and regulators in the sphingolipid biosynthetic pathway, with focus on the serine palmitoyltransferase (SPT) complex, the rate-limiting step in this pathway. During myelination, levels of the major SPT subunits increased and oligodendrocyte maturation was accompanied by extensive alterations in the composition of the SPT complex. These included changes in the relative levels of two alternative catalytic subunits, SPTLC2 and -3, in the relative levels of isoforms of the small subunits, ssSPTa and -b, and in the isoform distribution of the SPT regulators, the ORMDLs. Myelination progression was accompanied by distinct changes in both the nature of the sphingoid backbone and the N-acyl chains incorporated into sphingolipids. We conclude that the distribution of these changes among sphingolipid family members is indicative of a selective channeling of the ceramide backbone toward specific downstream metabolic pathways during myelination. Our findings provide insights into myelin production in oligodendrocytes and suggest how dysregulation of the biosynthesis of this highly specialized membrane could contribute to demyelinating diseases.

Response of neuroglia to hypoxia-induced oxidative stress using enzymatically crosslinked hydrogels.

Three-dimensional cultures have exciting potential to mimic aspects of healthy and diseased brain tissue to examine the role of physiological conditions on neural biomarkers, as well as disease onset and progression. Hypoxia is associated with oxidative stress, mitochondrial damage, and inflammation, key processes potentially involved in Alzheimer's and multiple sclerosis. We describe the use of an enzymatically-crosslinkable gelatin hydrogel system within a microfluidic device to explore the effects of hypoxia-induced oxidative stress on rat neuroglia, human astrocyte reactivity, and myelin production. This versatile platform offers new possibilities for drug discovery and modeling disease progression.

Blocking the Thrombin Receptor Promotes Repair of Demyelinated Lesions in the Adult Brain.

Myelin loss limits neurological recovery and myelin regeneration and is critical for restoration of function. We recently discovered that global knock-out of the thrombin receptor, also known as Protease Activated Receptor 1 (PAR1), accelerates myelin development. Here we demonstrate that knocking out PAR1 also promotes myelin regeneration. Outcomes in two unique models of myelin injury and repair, that is lysolecithin or cuprizone-mediated demyelination, showed that PAR1 knock-out in male mice improves replenishment of myelinating cells and remyelinated nerve fibers and slows early axon damage. Improvements in myelin regeneration in PAR1 knock-out mice occurred in tandem with a skewing of reactive astrocyte signatures toward a prorepair phenotype. In cell culture, the promyelinating effects of PAR1 loss of function are consistent with possible direct effects on the myelinating potential of oligodendrocyte progenitor cells (OPCs), in addition to OPC-indirect effects involving enhanced astrocyte expression of promyelinating factors, such as BDNF. These findings highlight previously unrecognized roles of PAR1 in myelin regeneration, including integrated actions across the oligodendrocyte and astroglial compartments that are at least partially mechanistically linked to the powerful BDNF-TrkB neurotrophic signaling system. Altogether, findings suggest PAR1 may be a therapeutically tractable target for demyelinating disorders of the CNS.SIGNIFICANCE STATEMENT Replacement of oligodendroglia and myelin regeneration holds tremendous potential to improve function across neurological conditions. Here we demonstrate Protease Activated Receptor 1 (PAR1) is an important regulator of the capacity for myelin regeneration across two experimental murine models of myelin injury. PAR1 is a G-protein-coupled receptor densely expressed in the CNS, however there is limited information regarding its physiological roles in health and disease. Using a combination of PAR1 knock-out mice, oligodendrocyte monocultures and oligodendrocyte-astrocyte cocultures, we demonstrate blocking PAR1 improves myelin production by a mechanism related to effects across glial compartments and linked in part to regulatory actions toward growth factors such as BDNF. These findings set the stage for development of new clinically relevant myelin regeneration strategies.

Iron Metabolism in Oligodendrocytes and Astrocytes, Implications for Myelination and Remyelination.

Iron is a key nutrient for normal central nervous system (CNS) development and function; thus, iron deficiency as well as iron excess may result in harmful effects in the CNS. Oligodendrocytes and astrocytes are crucial players in brain iron equilibrium. However, the mechanisms of iron uptake, storage, and efflux in oligodendrocytes and astrocytes during CNS development or under pathological situations such as demyelination are not completely understood. In the CNS, iron is directly required for myelin production as a cofactor for enzymes involved in ATP, cholesterol and lipid synthesis, and oligodendrocytes are the cells with the highest iron levels in the brain which is linked to their elevated metabolic needs associated with the process of myelination. Unlike oligodendrocytes, astrocytes do not have a high metabolic requirement for iron. However, these cells are in close contact with blood vessel and have a strong iron transport capacity. In several pathological situations, changes in iron homoeostasis result in altered cellular iron distribution and accumulation and oxidative stress. In inflammatory demyelinating diseases such as multiple sclerosis, reactive astrocytes accumulate iron and upregulate iron efflux and influx molecules, which suggest that they are outfitted to take up and safely recycle iron. In this review, we will discuss the participation of oligodendrocytes and astrocytes in CNS iron homeostasis. Understanding the molecular mechanisms of iron uptake, storage, and efflux in oligodendrocytes and astrocytes is necessary for planning effective strategies for iron management during CNS development as well as for the treatment of demyelinating diseases.

Staining and Quantitative Analysis of Myelinating Oligodendrocytes in the Mouse Grey Matter.

Oligodendrocytes generate distinct patterns of myelination throughout the CNS. Variations in myelination along axons may enable neurons to fine-tune conduction velocities and alter signal synchronisation. Here we outline a staining protocol permitting the assessment of the number and length of myelin sheaths formed by oligodendrocyte in the mouse grey matter. This protocol enables the investigation of myelination without the need for reporter mice or technically challenging protocols, aiding the investigation of factors influencing myelin production in the brain.

Oligogenesis in the "oligovascular unit" involves PI3K/AKT/mTOR signaling in hypoxic-ischemic neonatal mice

The "oligovascular unit" is a dynamic structural complex composed of endothelial cells (ECs) and oligodendrocyte progenitor cells (OPCs)/oligodendrocytes. By improving the microenvironment of OPCs in the "oligovascular unit" and promoting the proliferation and differentiation of OPCs, both myelination and white matter injury can be repaired. However, it is unclear what characteristic changes occur in the microenvironment of the "oligovascular unit" after preterm white matter injury (PWMI). Here, we demonstrate the changes in the "oligovascular unit" induced by hypoxia-ischemia (HI) and its underlying mechanism in PWMI mice. White matter injury and inhibited production of myelin from OPCs were observed by histopathological staining in HI neonatal mice. We further observed that the proliferation of OPCs and angiogenesis were increased after HI, which is considered the response of the body and cells to HI. HI-induced oligogenesis occurs around the vessels, indicating that "oligovascular units" exist and promote the proliferation and differentiation of OPCs after HI in the short term. We also determined that angiogenesis and oligogenesis induced by HI in the white matter are related to the PI3K/AKT/mTOR pathway. Furthermore, the myelin sheaths were shown to be disordered on the side of the surgery, and the myelin-dense layer was poorly developed at P14 and P28. Different degrees of damage to the vascular ECs and basement membrane on the surgical side were detected beginning at P4, indicating that EC injury is an early phenomenon that subsequently affects oligogenesis. Taken together, our findings indicate that the proliferation of OPCs and angiogenesis in white matter are increased in the early stage of HI involving PI3K/AKT/mTOR pathway activation. Promoting vascular endothelial function and angiogenesis may increase the proliferation and survival of OPCs via the "oligovascular unit," which suggests a potential method to repair injured white matter in the early stage of PWMI.

Neuropathie optique dans le syndrome des anticorps anti MOG positif

The diagnosis of optic neuritis (ON), or inflammation of the optic nerve, is based on clinical findings: first marked by rapidly progressive visual decline associated with eye pain accentuated by eye movements; abnormalities of color perception and/or contrast sensitivity may also be reported. In this case, inflammatory neuropathies are associated with anti-MOG antibodies. MOGs, oligodendrocytic glycoproteins involved in the production of myelin, were identified nearly three decades ago in association with demyelinating ON. The first series were reported in children following demyelinating neurological manifestations, particularly in ADEM (acute demyelinating encephalomyelitis) or multiple sclerosis (MS) [1]. Anti-MOGs are associated with neuropathies in the phenotypic setting of the neuromyelitis optica (NO) spectrum, and anti-Aquaporin 4antibodies (AQP4) are negative by definition. Thus, anti-MOG could explain up to 30% of cases of seronegative optic neuritis; their presence thus represents a significant diagnostic aid for the clinician, especially during a first neurological episode [1]. The first short published series in AQP4-/MOG+populations revealed primarily ophthalmological involvement with a good prognosis for recovery [1]. Knowledge of these antigens is important; it may permit not only an understanding of the physiopathology but also the stratification of patients in terms of prognosis and response to treatment [2]. Thus, the early diagnosis of anti-MOG positive ON must prompt aggressive initial treatment and a more or less maintenance therapy to prevent recurrence. The role of the ophthalmologist remains paramount, since most cases present with purely ocular involvement. We report herein the clinical, ophthalmological, laboratory and radiological data for 25patients (45eyes) managed between February 2011and January 2017. All of our patients had optic neuritis associated with anti-MOG antibodies. All patients underwent the following testing: -Visual acuity; -Humphrey and/or Goldmann visual field; -Non-mydriatic fundus photography; -Optic disc OCT; -3Tesla orbital-cerebral MRI with and without contrast; -Standard and immunological laboratory testing for anti-MOG and anti AQP4antibodies by Western Blot and ELISA. The male: female ratio of the population was 0.92 (13women and 12men). The average age at onset was 35.68years (15to 60years); 40% of the subjects were between 31and 40years old. The initial symptoms leading to consultation were mostly visual acuity (80%) and pain (88%). Involvement was bilateral in 80% of cases (5unilateral). Initial visual acuity was poor; 52% of eyes were less than or equal to count fingers. The course was favorable however, with visual acuity returning to 10-12/10after 6months of follow-up (84% of eyes). Orbital/cerebral MRI with attention to the visual pathways revealed involvement of the anterior visual pathways with gadolinium uptake in 92% of cases. Of the 35eyes initially considered affected, the main initial diagnoses were: -36% retro-bulbar optic neuritis (RBON); -40% anterior optic neuritis (AON); -24% other; of which 16% were initially diagnosed as acute anterior ischemic optic neuropathy (AAION). 96% of patients received corticosteroid treatment in the acute phase. 16% required plasma exchange sessions. Maintenance therapy was proposed for only 36% of the population. Optic neuritis is a pathology frequently encountered in ophthalmology; a good knowledge of symptoms and clinical signs is essential for early diagnosis and optimal management. The identification of autoantibodies, including anti-MOG antibodies, is important for patient management and is part of the required testing for all cases of optic neuritis, in order to adapt the treatment of the acute episode and to provide maintenance therapy to avoid recurrence.

White Matter Abnormalities Linked to Interferon, Stress Response, and Energy Metabolism Gene Expression Changes in Older HIV-Positive Patients on Antiretroviral Therapy.

Neurocognitive impairment (NCI) remains a significant cause of morbidity in human immunodeficiency virus (HIV)-positive individuals despite highly active antiretroviral therapy (HAART). White matter abnormalities have emerged as a key component of age-related neurodegeneration, and accumulating evidence suggests they play a role in HIV-associated neurocognitive disorders. Viral persistence in the brain induces chronic inflammation associated with lymphocytic infiltration, microglial proliferation, myelin loss, and cerebrovascular lesions. In this study, gene expression profiling was performed on frontal white matter from 34 older HIV+ individuals on HAART (18 with NCI) and 24 HIV-negative controls. We used the NanoString nCounter platform to evaluate 933 probes targeting inflammation, interferon and stress responses, energy metabolism, and central nervous system-related genes. Viral loads were measured using single-copy assays. Compared to HIV- controls, HIV+ individuals exhibited increased expression of genes related to interferon, MHC-1, and stress responses, myeloid cells, and T cells and decreased expression of genes associated with oligodendrocytes and energy metabolism in white matter. These findings correlated with increased white matter inflammation and myelin pallor, suggesting interferon (IRFs, IFITM1, ISG15, MX1, OAS3) and stress response (ATF4, XBP1, CHOP, CASP1, WARS) gene expression changes are associated with decreased energy metabolism (SREBF1, SREBF2, PARK2, TXNIP) and oligodendrocyte myelin production (MAG, MOG), leading to white matter dysfunction. Machine learning identified a 15-gene signature predictive of HIV status that was validated in an independent cohort. No specific gene expression patterns were associated with NCI. These findings suggest therapies that decrease chronic inflammation while protecting mitochondrial function may help to preserve white matter integrity in older HIV+ individuals.

Myelin Disturbances Produced by Sub-Toxic Concentration of Heavy Metals: The Role of Oligodendrocyte Dysfunction

Evidence has been accumulated demonstrating that heavy metals may accumulate in various organs, leading to tissue damage and toxic effects in mammals. In particular, the Central Nervous System (CNS) seems to be particularly vulnerable to cumulative concentrations of heavy metals, though the pathophysiological mechanisms is still to be clarified. In particular, the potential role of oligodendrocyte dysfunction and myelin production after exposure to subtoxic concentration I confirmed. It is ok of heavy metals is to be better assessed. Here we investigated on the effect of sub-toxic concentration of several essential (Cu2 +, Cr3 +, Ni2 +, Co2+) and non-essential (Pb2 +, Cd2+, Al3+) heavy metals on human oligodendrocyte MO3.13 and human neuronal SHSY5Y cell lines (grown individually or in co-culture). MO3.13 cells are an immortal human–human hybrid cell line with the phenotypic characteristics of primary oligodendrocytes but following the differentiation assume the morphological and biochemical features of mature oligodendrocytes. For this reason, we decided to use differentiated MO3.13 cell line. In particular, exposure of both cell lines to heavy metals produced a reduced cell viability of co-cultured cell lines compared to cells grown separately. This effect was more pronounced in neurons that were more sensitive to metals than oligodendrocytes when the cells were grown in co-culture. On the other hand, a significant reduction of lipid component in cells occurred after their exposure to heavy metals, an effect accompanied by substantial reduction of the main protein that makes up myelin (MBP) in co-cultured cells. Finally, the effect of heavy metals in oligodendrocytes were associated to imbalanced intracellular calcium ion concentration as measured through the fluorescent Rhod-2 probe, thus confirming that heavy metals, even used at subtoxic concentrations, lead to dysfunctional oligodendrocytes. In conclusion, our data show, for the first time, that sub-toxic concentrations of several heavy metals lead to dysfunctional oligodendrocytes, an effect highlighted when these cells are co-cultured with neurons. The pathophysiological mechanism(s) underlying this effect is to be better clarified. However, imbalanced intracellular calcium ion regulation, altered lipid formation and, finally, imbalanced myelin formation seem to play a major role in early stages of heavy metal-related oligodendrocyte dysfunction.

Quetiapine has an additive effect to triiodothyronine in inducing differentiation of oligodendrocyte precursor cells through induction of cholesterol biosynthesis.

Multiple sclerosis (MS) is characterized by demyelinated lesions in the central nervous system. Destruction of myelin and secondary damage to axons and neurons leads to significant disability, particularly in people with progressive MS. Accumulating evidence suggests that the potential for myelin repair exists in MS, although for unclear reasons this process fails. The cells responsible for producing myelin, the oligodendrocytes, and their progenitors, oligodendrocyte precursor cells (OPCs), have been identified at the site of lesions, even in adults. Their presence suggests the possibility that endogenous remyelination without transplantation of donor stem cells may be a mechanism for myelin repair in MS. Strategies to develop novel therapies have focused on induction of signaling pathways that stimulate OPCs to mature into myelin-producing oligodendrocytes that could then possibly remyelinate lesions. We have been investigating pharmacological approaches to enhance OPC differentiation, and have identified that the combination of two agents, triiodothyronine (T3) and quetiapine, leads to an additive effect on OPC differentiation and consequent myelin production via both overlapping and distinct signaling pathways. While the ultimate production of myelin requires cholesterol biosynthesis, we identified that quetiapine enhances gene expression in this pathway more potently than T3. Two blockers of cholesterol production, betulin and simvastatin, reduced OPC differentiation into myelin producing oligodendrocytes. Elucidating the nature of agents that lead to complementary and additive effects on oligodendrocyte differentiation and myelin production may pave the way for more efficient induction of remyelination in people with MS.

Disrupted CXCR2 Signaling in Oligodendroglia Lineage Cells Enhances Myelin Repair in a Viral Model of Multiple Sclerosis.

CXCR2 is a chemokine receptor expressed on oligodendroglia that has been implicated in the pathogenesis of neuroinflammatory demyelinating diseases as well as enhancement of the migration, proliferation, and myelin production by oligodendroglia. Using an inducible proteolipid protein (Plp) promoter-driven Cre-loxP recombination system, we were able to assess how timed ablation of Cxcr2 in oligodendroglia affected disease following intracranial infection with the neurotropic JHM strain of mouse hepatitis virus (JHMV). Generation of Plp-Cre-ER(T)::Cxcr2flox/flox transgenic mice (termed Cxcr2-CKO mice) allows for Cxcr2 to be silenced in oligodendrocytes in adult mice following treatment with tamoxifen. Ablation of oligodendroglia Cxcr2 did not influence clinical severity in response to intracranial infection with JHMV. Infiltration of activated T cells or myeloid cells into the central nervous system (CNS) was not affected, nor was the ability to control viral infection. In addition, the severity of demyelination was similar between tamoxifen-treated mice and vehicle-treated controls. Notably, deletion of Cxcr2 resulted in increased remyelination, as assessed by g-ratio (the ratio of the inner axonal diameter to the total outer fiber diameter) calculation, compared to that in vehicle-treated control mice. Collectively, our findings argue that CXCR2 signaling in oligodendroglia is dispensable with regard to contributing to neuroinflammation, but its deletion enhances remyelination in a preclinical model of the human demyelinating disease multiple sclerosis (MS).IMPORTANCE Signaling through the chemokine receptor CXCR2 in oligodendroglia is important for developmental myelination in rodents, while chemical inhibition or nonspecific genetic deletion of CXCR2 appears to augment myelin repair in animal models of the human demyelinating disease multiple sclerosis (MS). To better understand the biology of CXCR2 signaling on oligodendroglia, we generated transgenic mice in which Cxcr2 is selectively ablated in oligodendroglia upon treatment with tamoxifen. Using a viral model of neuroinflammation and demyelination, we demonstrate that genetic silencing of CXCR2 on oligodendroglia did not affect clinical disease, neuroinflammation, or demyelination, yet there was increased remyelination. These findings support and extend previous findings suggesting that targeting CXCR2 may offer a therapeutic avenue for enhancing remyelination in patients with demyelinating diseases.

Therapeutic Effect of the Mitochondria-Targeted Antioxidant SkQ1 on the Culture Model of Multiple Sclerosis.

Multiple sclerosis (MS) is a heterogeneous autoimmune disease of unknown etiology characterized by inflammation, demyelination, and axonal degeneration that affects both the white and gray matter of CNS. Recent large-scale epidemiological and genomic studies identified several genetic and environmental risk factors for the disease. Among them are environmental factors of infectious origin, possibly causing MS, which include Epstein-Barr virus infection, reactivation of some endogenous retrovirus groups, and infection by pathogenic bacteria (mycobacteria, Chlamydia pneumoniae, and Helicobacter pylori). However, the nature of the events leading to the activation of immune cells in MS is mostly unknown and there is no effective therapy against the disease. Amazingly, whatever the cause of the disease, signs of damage to the nerve tissue with MS lesions were the same as with infectious leprosy, while in the latter case nitrozooxidative stress was suggested as the main cause of the nerve damage. With this in mind and following the hypothesis that excessive production of mitochondrial reactive oxygen species critically contributes to MS pathogenesis, we studied the effect of mitochondria-targeted antioxidant SkQ1 in an in vitro MS model of the primary oligodendrocyte culture of the cerebellum, challenged with lipopolysaccharide (LPS). SkQ1 was found to accumulate in the mitochondria of oligodendrocytes and microglial cells, and it was also found to prevent LPS-induced inhibition of myelin production in oligodendrocytes. The results implicate that mitochondria-targeted antioxidants could be promising candidates as components of a combined therapy for MS and related neurological disorders.