Number Of Oligodendrocyte Precursor Cells Research Articles

Activation of Shh/Smo is sufficient to maintain oligodendrocyte precursor cells in an undifferentiated state and is not necessary for myelin formation and (re)myelination.

Myelination is the terminal step in a complex and precisely timed program that orchestrates the proliferation, migration and differentiation of oligodendroglial cells. It is thought that Sonic Hedgehog (Shh) acting on Smoothened (Smo) participates in regulating this process, but that these effects are highly context dependent. Here, we investigate oligodendroglial development and remyelination from three specific transgenic lines: NG2-CreERT2 (control), Smofl/fl/NG2-CreERT2 (loss of function), and SmoM2/NG2-CreERT2 (gain of function), as well as pharmacological manipulation that enhance or inhibit the Smo pathway (Smoothened Agonist (SAG) or cyclopamine treatment, respectively). To explore the effects of Shh/Smo on differentiation and myelination in vivo, we developed a highly quantifiable model by transplanting oligodendrocyte precursor cells (OPCs) in the retina. We find that myelination is greatly enhanced upon cyclopamine treatment and hypothesize that Shh/Smo could promote OPC proliferation to subsequently inhibit differentiation. Consistent with this hypothesis, we find that the genetic activation of Smo significantly increased numbers of OPCs and decreased oligodendrocyte differentiation when we examined the corpus callosum during development and after cuprizone demyelination and remyelination. However, upon loss of function with the conditional ablation of Smo, myelination in the same scenarios are unchanged. Taken together, our present findings suggest that the Shh pathway is sufficient to maintain OPCs in an undifferentiated state, but is not necessary for myelination and remyelination.

Reorganization of dopamine circuitry in the anterior corpus callosum between early adolescence and adulthood in the mouse.

The maturation of forebrain dopamine circuitry occurs over multiple developmental periods, extending from early postnatal life until adulthood, with the precise timing of maturation defined by the target region. We recently demonstrated in the adult mouse brain that axon terminals arising from midbrain dopamine neurons innervate the anterior corpus callosum and that oligodendrocyte lineage cells in this white matter tract express dopamine receptor transcripts. Whether corpus callosal dopamine circuitry undergoes maturational changes between early adolescence and adulthood is unknown but may be relevant to understanding the dramatic micro- and macro-anatomical changes that occur in the corpus callosum of multiple species during early adolescence, including in the degree of myelination. Using quantitative neuroanatomy, we show that dopamine innervation in the forceps minor, but not the rostral genu, of the corpus callosum, is greater during early adolescence (P21) compared to adulthood (>P90) in wild-type mice. We further demonstrate with RNAscope that, as in the adult, Drd1 and Drd2 transcripts are expressed at higher levels in oligodendrocyte precursor cells (OPCs) and decline as these cells differentiate into oligodendrocytes. In addition, the number of OPCs that express Drd1 transcripts during early adolescence is double the number of those expressing the transcript during early adulthood. These data further implicate dopamine in axon myelination and myelin regulation. Moreover, because developmental (activity-independent) myelination peaks during early adolescence, with experience-dependent (activity-dependent) myelination greatest during early adulthood, our data suggest that potential roles of dopamine on callosal myelination shift between early adolescence and adulthood, from a developmental role to an experience-dependent role.

Dynamic changes of oligodendrogenesis in neonatal rats with hypoxic-ischemic white matter injury

BackgroundWhite matter injury (WMI) is an important type of preterm brain injury, which may result in severe neurological sequelae and lack of effective treatments. It is ascertained that selective vulnerability of oligodendrocytes is closely related to the WMI in preterm infants. But the alteration of the endogenous oligodendrogenesis over long time after hypoxic-ischemic WMI is still not clearly elucidated. MethodsWe adopted an animal model of hypoxic-ischemic WMI in 3-day-old neonatal Sprague-Dawley rats. Immunofluorescence staining and western blotting were used to detect dynamic changes of oligodendrogenesis in the white matter region on postoperative day (POD) 1, 3, 7, 14, 28, 56 and 84. ResultsIn the sham group, the oligodendrocyte lineage in the white matter reached a developmental peak from POD 3 to 14. The proliferation and development of oligodendrocyte precursor cells (OPCs) occurred primarily within POD 14. The number of mature oligodendrocytes showed an upward trend and a dynamic change in proliferation over time. While in the WMI group, the oligodendrocyte lineage was upregulated on POD1 and 3 but downregulated on POD 7 and 14. The proliferation of OPCs increased on POD 1 and decreased on POD 3 and 7, with the total number of OPCs significantly reduced from POD 3 to 14. The number of mature oligodendrocytes decreased from POD 3 to 28, and return to the level of the sham group on POD 56 and 84, whereas the MBP expression was still significantly downregulated on POD 56 and 84. ConclusionsHypoxia-ischemia can have a long-term dynamic effect on the endogenous oligodendrogenesis of neonatal rat brain white matter. The proliferation of OPCs was promoted on POD 1 but inhibited from POD 3 to 14, which may be an early intervention target to improve oligodendrogenesis. The number of mature oligodendrocytes recover to the normal on POD 56 and 84 but the myelination is still blocked, which suggests it is essential to promote the maturation of oligodendrocyte and its function recovery at the same time within POD 28. Such efforts will provide the opportunity to test new interventions in pre-clinical studies for their promising clinical application.

Proper modulation of AHR signaling is necessary for establishing neural connectivity and oligodendrocyte precursor cell development in the embryonic zebrafish brain.

2,3,7,8-tetrachlorodibenzo-[p]-dioxin (TCDD) is a persistent global pollutant that exhibits a high affinity for the aryl hydrocarbon receptor (AHR), a ligand activated transcription factor. Epidemiological studies have associated AHR agonist exposure with multiple human neuropathologies. Consistent with the human data, research studies using laboratory models have linked pollutant-induced AHR activation to disruptions in learning and memory as well as motor impairments. Our understanding of endogenous AHR functions in brain development is limited and, correspondingly, scientists are still determining which cell types and brain regions are sensitive to AHR modulation. To identify novel phenotypes resulting from pollutant-induced AHR activation and ahr2 loss of function, we utilized the optically transparent zebrafish model. Early embryonic TCDD exposure impaired embryonic brain morphogenesis, resulted in ventriculomegaly, and disrupted neural connectivity in the optic tectum, habenula, cerebellum, and olfactory bulb. Altered neural network formation was accompanied by reduced expression of synaptic vesicle 2. Loss of ahr2 function also impaired nascent network development, but did not affect gross brain or ventricular morphology. To determine whether neural AHR activation was sufficient to disrupt connectivity, we used the Gal4/UAS system to express a constitutively active AHR specifically in differentiated neurons and observed disruptions only in the cerebellum; thus, suggesting that the phenotypes resulting from global AHR activation likely involve multiple cell types. Consistent with this hypothesis, we found that TCDD exposure reduced the number of oligodendrocyte precursor cells and their derivatives. Together, our findings indicate that proper modulation of AHR signaling is necessary for the growth and maturation of the embryonic zebrafish brain.

The orphan G protein-coupled receptor GPR149 is a negative regulator of myelination and remyelination.

Myelin sheath, formed by oligodendrocytes (OLs) in the central nervous system (CNS) and Schwann cells in periphery, plays a critical role in supporting neuronal functions. OLs, differentiated from oligodendrocyte precursor cells (OPCs), are important for myelination during development and myelin repair in CNS demyelinating disease. To identify mechanisms of myelin development and remyelination after myelin damage is of great clinical interest. Here we show that the orphan G protein-coupled receptor GPR149, enriched in OPCs, negatively regulate OPC to OL differentiation, myelination, as well as remyelination. The expression of GPR149 is downregulated during OPCs differentiation into OLs. GPR149 deficiency does not affect the number of OPCs, but promotes OPC to OL differentiation which results in earlier development of myelin. In cuprizone-induced demyelination model, GPR149 deficiency significantly enhances myelin regeneration. Further study indicates that GPR149 may regulate OL differentiation and myelin formation via MAPK/ERK pathway. Our study suggests that deleting or blocking GPR149 might be an intriguing way to promote myelin repair in demyelinating diseases.

The Extracellular Matrix Proteins Tenascin-C and Tenascin-R Retard Oligodendrocyte Precursor Maturation and Myelin Regeneration in a Cuprizone-Induced Long-Term Demyelination Animal Model.

Oligodendrocytes are the myelinating cells of the central nervous system. The physiological importance of oligodendrocytes is highlighted by diseases such as multiple sclerosis, in which the myelin sheaths are degraded and the axonal signal transmission is compromised. In a healthy brain, spontaneous remyelination is rare, and newly formed myelin sheaths are thinner and shorter than the former ones. The myelination process requires the migration, proliferation, and differentiation of oligodendrocyte precursor cells (OPCs) and is influenced by proteins of the extracellular matrix (ECM), which consists of a network of glycoproteins and proteoglycans. In particular, the glycoprotein tenascin-C (Tnc) has an inhibitory effect on the differentiation of OPCs and the remyelination efficiency of oligodendrocytes. The structurally similar tenascin-R (Tnr) exerts an inhibitory influence on the formation of myelin membranes in vitro. When Tnc knockout oligodendrocytes were applied to an in vitro myelination assay using artificial fibers, a higher number of sheaths per single cell were obtained compared to the wild-type control. This effect was enhanced by adding brain-derived neurotrophic factor (BDNF) to the culture system. Tnr−/− oligodendrocytes behaved differently in that the number of formed sheaths per single cell was decreased, indicating that Tnr supports the differentiation of OPCs. In order to study the functions of tenascin proteins in vivo Tnc−/− and Tnr−/− mice were exposed to Cuprizone-induced demyelination for a period of 10 weeks. Both Tnc−/− and Tnr−/− mouse knockout lines displayed a significant increase in the regenerating myelin sheath thickness after Cuprizone treatment. Furthermore, in the absence of either tenascin, the number of OPCs was increased. These results suggest that the fine-tuning of myelin regeneration is regulated by the major tenascin proteins of the CNS.

Diabetes Mellitus-Related Neurobehavioral Deficits in Mice Are Associated With Oligodendrocyte Precursor Cell Dysfunction.

Recent clinical studies demonstrated an increase of the incidence of neurobehavioral disorders in patients with diabetes mellitus. Studies also found an association between severity of diabetes mellitus and the progression of white matter hyperintensity on magnetic resonance imaging, which conferred risk for developing cognitive impairment. Since oligodendrocyte precursor cells participated in the white matter repair and remodeling after ischemic brain injury, we explored whether hyperglycemia induced neurobehavioral deficits were associated with dysfunction of oligodendrocyte precursor cells. Adult male C57BL/6 mice (n = 40) were randomly divided into 4-week diabetes, 8-week diabetes, and control groups. Experimental diabetic mice were induced by streptozotocin injection. Learning and cognitive function, exploratory, anxiety and depression behaviors were assessed by Morris water maze, open field test, elevated plus maze, and tail suspension test, respectively. Immunofluorescence staining of neuron-glial antigen 2 and myelin basic protein were performed. Oligodendrocyte precursor cells were cultured in different glucose level to explore possible mechanism in vitro. The learning and cognitive function of 4-week and 8-week diabetic mice were attenuated compared to the control group (p < 0.05). The diabetic mice had less exploratory behavior compared to the control (p < 0.05). However, the diabetic mice were more likely to show anxiety (p < 0.05) and depression (p < 0.01) compared to the control. Further study demonstrated the number of oligodendrocyte precursor cells and the level of myelin basic protein expression were decreased in diabetic mice and the migration and survival ability were suppressed in the hyperglycemic environment in vitro (p < 0.05). Our results demonstrated that diabetes mellitus induced neurological deficits were associated with the decreased number and dysfunction of oligodendrocyte precursor cells.

Postnatal myelination of the immature rat cingulum is regulated by GABAB receptor activity

Myelination of axons in the neonatal brain is a highly complex process primarily achieved by oligodendroglial cells (OLs). OLs express receptors for γ-aminobutyric acid (GABA) which is released from cortical interneurons on a basal level, while glial cells can be a source of GABA, too. We investigated GABA-induced oligodendroglial maturation, proliferation, apoptosis, and myelin production after pharmacological inhibition of GABAA and GABAB in the neonatal rat brain. Daily injections of the reverse GABAA receptor agonist (DMCM) and the GABAB receptor antagonist (CGP35348) were performed from postnatal day 6 (P6) to P11. MBP expression was examined by Western blots and immunohistochemistry. Furthermore, we determined the number of CC1+ OLIG2+ and CNP+ OLIG2+ cells to assess maturation, the number of PCNA+ OLIG2+ oligodendrocytes to assess proliferation, the number of oligodendrocyte precursor cells (PDGFRα+ OLIG2+ ), and apoptosis of OLs (CASP3A+ OLIG2+ ) as well as apoptotic cells in total (CASP3A+ DAPI+ ) at P11 and P15. In addition, we analyzed the expression Pdgfrα and CNP. MBP expression was significantly reduced after CGP treatment at P15. In the same animal group, CNP expression and CNP+ OLIG2+ cells decreased temporarily at P11. At P15, the proliferation of PCNA+ OLIG2+ cells and the number of PDGFRα+ OLIG2+ cells increased after GABAB receptor antagonization whereas no significant differences were visible in the Pdgfrα gene expression. No changes in apoptotic cell death were observed. CGP treatment induced a transient maturational delay at P11 and deficits in myelin expression at P15 with increased oligodendroglial proliferation. Our in vivo study indicates GABAB receptor activity as a potential modulator of oligodendroglial development.

Selective activation of cannabinoid receptor-2 reduces white matter injury via PERK signaling in a rat model of traumatic brain injury

Background and purposeTraumatic brain injury (TBI) destroys white matter, and this destruction is aggravated by secondary neuroinflammatory reactions. Although white matter injury (WMI) is strongly correlated with poor neurological function, understanding of white matter integrity maintenance is limited, and no available therapies can effectively protect white matter. One candidate approach that may fulfill this goal is cannabinoid receptor 2 (CB2) agonist treatment. Here, we confirmed that a selective CB2 agonist, JWH133, protected white matter after TBI. MethodsThe motor evoked potentials (MEPs), open field test, and Morris water maze test were used to assess neurobehavioral outcomes. Brain tissue loss, WM damage, Endoplasmic reticulum stress (ER stress), microglia responses were evaluated after TBI. The functional integrity of WM was measured by diffusion tensor imaging (DTI) and transmission electron microscopy (TEM). Primary microglia and oligodendrocyte cocultures were used for additional mechanistic studies. ResultsJWH133 increased myelin basic protein (MBP) and neurofilament heavy chain (NF200) levels and anatomic preservation of myelinated axons revealed by DTI and TEM. JWH133 also increased the numbers of oligodendrocyte precursor cells and mature oligodendrocytes. Furthermore, JWH133 drove microglial polarization toward the protective M2 phenotype and modulated the redistribution of microglia in the striatum. Further investigation of the underlying mechanism revealed that JWH133 downregulated phosphorylation of the protein kinase R (PKR)-like endoplasmic reticulum (ER) kinase (PERK) signaling pathway and its downstream signals eukaryotic translation initiation factor 2 α (eIF2α), activating transcription factor 4 (ATF4) and Growth arrest and DNA damage-inducible protein (GADD34); this downregulation was followed by p-Protein kinase B(p-Akt) upregulation. In primary cocultures of microglia and oligodendrocytes, JWH133 decreased phosphorylated PERK expression in microglia stimulated with tunicamycin and facilitated oligodendrocyte survival. These data reveal that JWH133 ultimately alleviates WMI and improves neurological behavior following TBI. However, these effects were prevented by SR144528, a selective CB2 antagonist. ConclusionsThis work illustrates the PERK-mediated interaction between microglia and oligodendrocytes. In addition, the results are consistent with recent findings that microglial polarization switching accelerates WMI, highlighting a previously unexplored role for CB2 agonists. Thus, CB2 agonists are potential therapeutic agents for TBI and other neurological conditions involving white matter destruction.

Characterisation of early ultrastructural changes in the cerebral white matter of CADASIL small vessel disease using high-pressure freezing/freeze-substitution.

The objective of this study was to elucidate the early white matter changes in CADASIL small vessel disease. We used high-pressure freezing and freeze substitution (HPF/FS) in combination with high-resolution electron microscopy (EM), immunohistochemistry and confocal microscopy of brain specimens from control and CADASIL (TgNotch3R169C ) mice aged 4-15months to study white matter lesions in the corpus callosum. We first optimised the HPF/FS protocol in which samples were chemically prefixed, frozen in a sample carrier filled with 20% polyvinylpyrrolidone and freeze-substituted in a cocktail of tannic acid, osmium tetroxide and uranyl acetate dissolved in acetone. EM analysis showed that CADASIL mice exhibit significant splitting of myelin layers and enlargement of the inner tongue of small calibre axons from the age of 6months, then vesiculation of the inner tongue and myelin sheath thinning at 15months of age. Immunohistochemistry revealed an increased number of oligodendrocyte precursor cells, although only in older mice, but no reduction in the number of mature oligodendrocytes at any age. The number of Iba1 positive microglial cells was increased in older but not in younger CADASIL mice, but the number of activated microglial cells (Iba1 and CD68 positive) was unchanged at any age. We conclude that early WM lesions in CADASIL affect first and foremost the myelin sheath and the inner tongue, suggestive of a primary myelin injury. We propose that those defects are consistent with a hypoxic/ischaemic mechanism.

Transient Receptor Potential Melastatin 3 Is Functionally Expressed in Oligodendrocyte Precursor Cells and Is Upregulated in Ischemic Demyelinated Lesions

Oligodendrocyte precursor cells (OPCs) are glial cells that differentiate into oligodendrocytes and myelinate axons. The number of OPCs is reportedly increased in brain lesions in some demyelinating diseases and during ischemia; however, these cells also secrete cytokines and elicit both protective and deleterious effects in response to brain injury. The mechanism regulating the behaviors of OPCs in physiological and pathological conditions must be elucidated to control these cells and to treat demyelinating diseases. Here, we focused on transient receptor potential melastatin 3 (TRPM3), a Ca2+-permeable channel that is activated by the neurosteroid pregnenolone sulfate (PS) and body temperature. Trpm3+/Pdgfra+ OPCs were detected in the cerebral cortex (CTX) and corpus callosum (CC) of P4 and adult rats by in situ hybridization. Trpm3 expression was detected in primary cultured rat OPCs and was increased by treatment with tumor necrosis factor α (TNFα). Application of PS (30-100 µM) increased the Ca2+ concentration in OPCs and this effect was inhibited by co-treatment with the TRP channel blocker Gd3+ (100 µM) or the TRPM3 inhibitor isosakuranetin (10 µM). Stimulation of TRPM3 with PS (50 µM) did not affect the differentiation or migration of OPCs. The number of Trpm3+ OPCs was markedly increased in demyelinated lesions in an endothelin-1 (ET-1)-induced ischemic rat model. In conclusion, TRPM3 is functionally expressed in OPCs in vivo and in vitro and is upregulated in inflammatory conditions such as ischemic insults and TNFα treatment, implying that TRPM3 is involved in the regulation of specific behaviors of OPCs in pathological conditions.

Roles of A-kinase Anchor Protein 12 in Astrocyte and Oligodendrocyte Precursor Cell in Postnatal Corpus Callosum.

The formation of the corpus callosum in the postnatal period is crucial for normal neurological function, and clinical genetic studies have identified an association of 6q24-25 microdeletion in this process. However, the mechanisms underlying corpus callosum formation and its critical gene(s) are not fully understood or identified. In this study, we examined the roles of AKAP12 in postnatal corpus callosum formation by focusing on the development of glial cells, because AKAP12 is coded on 6q25.1 and has recently been shown to play roles in the regulations of glial function. In mice, the levels of AKAP12 expression was confirmed to be larger in the corpus callosum compared to the cortex, and AKAP12 levels decreased with age both in the corpus callosum and cortex regions. In addition, astrocytes expressed AKAP12 in the corpus callosum after birth, but oligodendrocyte precursor cells (OPCs), another major type of glial cell in the developing corpus callosum, did not. Furthermore, compared to wild types, Akap12 knockout mice showed smaller numbers of both astrocytes and OPCs, along with slower development of corpus callosum after birth. These findings suggest that AKAP12 signaling may be required for postnatal glial formation in the corpus callosum through cell- and non-cell autonomous mechanisms.

Wnt-Dependent Oligodendroglial-Endothelial Interactions Regulate White Matter Vascularization and Attenuate Injury

Recent studies have indicated oligodendroglial-vascular crosstalk during brain development, but the underlying mechanisms are incompletely understood. We report that oligodendrocyte precursor cells (OPCs) contact sprouting endothelial tip cells in mouse, ferret, and human neonatal white matter. Using transgenic mice, we show that increased or decreased OPC density results in cognate changes in white matter vascular investment. Hypoxia induced increases in OPC numbers, vessel density and endothelial cell expression of the Wnt pathway targets Apcdd1 and Axin2 in white matter, suggesting paracrine OPC-endothelial signaling. Conditional knockout of OPC Wntless resulted in diminished white matter vascular growth in normoxia, whereas loss of Wnt7a/b function blunted the angiogenic response to hypoxia, resulting in severe white matter damage. These findings indicate that OPC-endothelial cell interactions regulate neonatal white matter vascular development in a Wnt-dependent manner and further suggest this mechanism is important in attenuating hypoxic injury.

GDE2-Dependent Activation of Canonical Wnt Signaling in Neurons Regulates Oligodendrocyte Maturation

SUMMARYNeurons and oligodendrocytes communicate to regulate oligodendrocyte development and ensure appropriate axonal myelination. Here, we show that Glycerophosphodiester phosphodiesterase 2 (GDE2) signaling underlies a neuronal pathway that promotes oligodendrocyte maturation through the release of soluble neuronally derived factors. Mice lacking global or neuronal GDE2 expression have reduced mature oligodendrocytes and myelin proteins but retain normal numbers of oligodendrocyte precursor cells (OPCs). Wild-type (WT) OPCs cultured in conditioned medium (CM) from Gde2-null (Gde2KO) neurons exhibit delayed maturation, recapitulating in vivo phenotypes. Gde2KO neurons show robust reduction in canonical Wnt signaling, and genetic activation of Wnt signaling in Gde2KO neurons rescues in vivo and in vitro oligodendrocyte maturation. Phosphacan, a known stimulant of oligodendrocyte maturation, is reduced in CM from Gde2KO neurons but is restored when Wnt signaling is activated. These studies identify GDE2 control of Wnt signaling as a neuronal pathway that signals to oligodendroglia to promote oligodendrocyte maturation.

The effects of A1/A2 astrocytes on oligodendrocyte linage cells against white matter injury under prolonged cerebral hypoperfusion.

As oligodendrocyte precursor cells (OPCs) are vulnerable to ischemia, their differentiation to oligodendrocytes (OLG) is impaired in chronic cerebral hypoperfusion. Astrocyte-OLG interaction is important for white matter homeostasis. Recently, reactive astrocytes were separated into two types, A1 (cytotoxic) and A2 (neurotrophic). However, their role in prolonged cerebral hypoperfusion remains unclear. We analyzed the effects of interaction between A1-A2 astrocytes and OPC-OLG under hypoperfusion, focusing on mitochondrial migration. As an in vivo model, chronic hypoperfusion model mice were created by bilateral common carotid artery stenosis (BCAS) using microcoils. As a matching in vitro study, rat primary cells were cocultured with a nonlethal concentration of CoCl2 . At 28 days after hypoperfusion, the number of OPC and astrocytes increased, whereas that of OLG decreased. Increased astrocytes were mainly A1-like astrocytes; however, the number of A2-like type decreased. In cell culture, OPC differentiation was interrupted under mimic chronic ischemia, but improved after astrocyte-conditioned medium (ACM) was added. However, injured-ACM was unable to improve OPC maturation. Incubation with CoCl2 changed astrocytes from A2-like to A1-like, and mitochondrial migration was also reduced. A Trkβ agonist was able to maintain astrocytes from A1-like to A2-like even under hyperperfused conditions, and aided in OPC maturation and memory impairment via mitochondrial migration and drug effects in cell culture study and BCAS model. The reduction of A1-like astrocytes protects against white matter injury. Trkβ agonists may play an important role in the impairment under chronic ischemic conditions. Mitochondrial migration may be a broad therapeutic strategy for cerebrovascular diseases. MAIN POINTS: Prolonged cerebral hypoperfusion leads to impaired oligodendrocyte (OLG) maturation and increased numbers of A1 astrocytes. Mitochondria migration maintained A2 astrocyte morphology, mature OLG, and myelinated white matter in vivo/vitro.

NEP1-40 alleviates behavioral phenotypes and promote oligodendrocyte progenitor cell differentiation in the hippocampus of cuprizone-induced demyelination mouse model

BackgroundStudies have demonstrated that the failure of oligodendrocyte precursor cells (OPCs) differentiation as a major cause of remyelination failure in demyelinating disease. The reasons for this failure are not completely understood. We hypothesized that the present of myelin debris in CNS play an important role in poor OPCs differentiation in the mouse model of demyelinating disease. MethodsMice were fed by the food mixed with normal or 0.2 % cuprizone (CPZ) for 6 weeks. Then the learning and memory impairment were tested by Morris water maze test. The spontaneous alternation behavior and depression-like symptoms were assessed by tail suspension test and open filed test. The number of OPCs and oligodendrocytes were counted by immunofluorescence. After exposed to CPZ for 6 weeks, the mice were then receiving stereotactic injection of NEP1-40 into the CA3 of hippocampus. The behavioral, learning and memory changes were assessed by tail suspension test and open field test. The differentiation of OPCs were detected by immunofluorescence and western blot. ResultsThe mice in CPZ group are more likely to show signs of depression and they showed impairment of long-term learning and memory function. The differentiation of OPCs were impaired in CPZ group. We found that mice treated with NEP1-40 showed less depression-like symptom in TST and higher locomotor activity in the OFT than the mice treated with PBS. ConclusionsOur study suggest that NEP1-40 can promote OPC differentiation and survival. Further study should focus on the effect of NEP1-40 on the differentiation and survival of OPCs in vitro.

Abstract WP148: The Effect of Mitochondrial Migration From Astrocyte to Glial Cells Under Prolonged Cerebral Hypoperfusion

Introduction: Astrocytes play broad roles in the Central nervous system, and are involved in the regulation of cerebral metabolism and blood flow. Normal astrocytes (A2) protect against oxidative stress and excitotoxicity, but unhealthy astrocytes (A1) may release deleterious factors. Oligodendrocytes (OLGs) differentiate from oligodendrocyte-precursor-cells (OPCs) for myelination in white matter, but OPC were vulnerable for ischemia. Therefore, differentiation is impaired when white matter injury occurs in a chronic cerebral hypoperfusion model. Thus, we examined the effects of the interaction between astrocyte and oligodendrocyte lineage cells on myelination focused on mitochondrial migration. Method: A microcoil was applied to the bilateral common carotid arteries in male C57BL/6 mice as an in vivo cerebral chronic hypoperfusion model (BCAS model). A nonlethal concentration of CoCl 2 was added to the primary cell culture from the postnatal rat cortex and incubated in vitro. Results: White matter injury progressed in the BCAS model as myelin decreased. The numbers of OPCs and astrocytes increased after the operation, whereas that of OLGs decreased at day 28. Increased astrocytes were mainly A1 type, and A2 type were decreased. OPC differentiation was disrupted under the stressed conditions in the cell culture, but improved after administration of astrocyte-conditioned medium (ACM), but injured ACM couldn’t improve maturation. Incubate with CoCl 2 change astrocyte A2 to A1, and mitochondrial migration also reduced. Trkβ agonist could change astrocyte A1 to A2 even in hyperperfused condition, and also help OPC maturation via mitochondrial migration and drug effect in vivo and in vitro. Conclusions: The reduction in incrementing A1 astrocytes protect white matter injury. and Trkβ agonist may play an important role in the impairment under chronic ischemic conditions. Mitochondrial migration could be a broad therapeutic strategy for cerebrovascular disorders.

Transplantation of iPS-derived vascular endothelial cells improves white matter ischemic damage.

White matter infarct induces demyelination and brain dysfunction. We previously reported that transplantation of brain microvascular endothelial cells improved the behavioral outcome and promoted remyelination by increasing the number of oligodendrocyte precursor cells in the rat model of white matter infarct. In this study, we investigated the effects of transplantation of vascular endothelial cells generated from human induced pluripotent stem cells (iPSCs) on the rat model of white matter infarct. Seven days after induction of ischemic demyelinating lesion by injection of endothelin‐1 into the internal capsule of a rat brain, iPSC‐derived vascular endothelial cells (iVECs) were transplanted into the site of demyelination. The majority of iVECs transplanted into the internal capsule survived for 14 days after transplantation when traced by immunohistochemistry for a human cytoplasmic protein. iVEC transplantation significantly recovered hind limb rotation angle as compared to human iPSC or rat meningeal cell transplantation when evaluated using footprint test. Fourteen days after iVEC transplantation, the infarct area remarkably decreased as compared to that just before the transplantation when evaluated using magnetic resonance imaging or luxol fast blue staining, and remyelination was promoted dramatically in the infarct when assessed using luxol fast blue staining. Transplantation of iVECs increased the number of oligodendrocyte lineage cells and suppressed the inflammatory response and reactive astrocytogenesis. These results suggest that iVEC transplantation may prove useful in treatment for white matter infarct.

Retinoic Acid Is Required for Oligodendrocyte Precursor Cell Production and Differentiation in the Postnatal Mouse Corpus Callosum.

Myelination of the CNS relies on the production and differentiation of oligodendrocyte (OL) precursor cells (OPCs) into mature OLs. During the first month of postnatal life, OPCs that populate the corpus callosum (CC) arise from neural stem cells (NSCs) in the subcallosal subventricular zone (SVZ), and then differentiate to generate myelinating OLs. However, the signals that regulate these processes are not fully understood. In this study, we show that endogenous expression of the retinoic acid (RA)-synthesizing enzyme retinaldehyde dehydrogenase 2 (RALDH2) is required for OPC generation and differentiation in the postnatal subcortical white matter. In male and female pups, conditional deletion of Raldh2 reduced OPC numbers and differentiation. Moreover, decreased OPC numbers coincided with reductions in NSC survival and expression of the sonic hedgehog (SHH) signaling effector protein Gli1 in the SVZ. Additionally, GFAP expression in the CC was decreased, and cortical neuron numbers were altered. Our work suggests a role for endogenous RALDH2-dependent RA synthesis in OPC production and differentiation in the CC, as well as in the development of other cell types derived from NSCs in the embryonic ventricular zone (VZ) and SVZ, as well as the postnatal subcallosal SVZ.

CNS myelin protein 36K regulates oligodendrocyte differentiation through Notch.

In contrast to humans and other mammals, zebrafish can successfully regenerate and remyelinate central nervous system (CNS) axons following injury. In addition to common myelin proteins found in mammalian myelin, 36K protein is a major component of teleost fish CNS myelin. Although 36K is one of the most abundant proteins in zebrafish brain, its function remains unknown. Here we investigate the function of 36K using translation-blocking Morpholinos. Morphant larvae showed fewer dorsally migrated oligodendrocyte precursor cells as well as upregulation of Notch ligand. A gamma secretase inhibitor, which prevents activation of Notch, could rescue oligodendrocyte precursor cell numbers in 36K morphants, suggesting that 36K regulates initial myelination through inhibition of Notch signaling. Since 36K like other short chain dehydrogenases might act on lipids, we performed thin layer chromatography and mass spectrometry of lipids and found changes in lipid composition in 36K morphant larvae. Altogether, we suggest that during early development 36K regulates membrane lipid composition, thereby altering the amount of transmembrane Notch ligands and the efficiency of intramembrane gamma secretase processing of Notch and thereby influencing oligodendrocyte precursor cell differentiation and further myelination. Further studies on the role of 36K short chain dehydrogenase in oligodendrocyte precursor cell differentiation during remyelination might open up new strategies for remyelination therapies in human patients.