Number Of Oligodendrocyte Precursor Cells Research Articles

Abstract PR01: H-RasG12V overexpression in the central nervous system leads to expansion of oligodendrocyte precursor cells and neural crest cells

Abstract Somatic mutations in Ras proto-oncogenes have been found in a large number of different cancers. In addition, germline mutations in the H-Ras gene have been shown to be the causative genetic alteration underlying Costello Syndrome (CS). Costello Syndrome belongs to the large group of Ras/MAPK pathway diseases commonly termed Rasopathies. CS patients exhibit craniofacial and cardiac abnormalities, mental retardation and are prone to develop cancers including neural crest derived neoplasias. Since Costello Syndrome is a rare disease, the effects of H-RasG12V expression on the development of the central nervous system remain largely uncharacterized. Towards this goal, we have established a zebrafish model suitable for live imaging and cost-effective drug screening. Using the Gal4/UAS system we have enforced expression of H-RasG12V in the central nervous system starting at early neurulation stages. H-RasG12V expressing embryos develop hyperplasia of the forebrain and the spinal cord and show an outgrowth in the dorsal tail region around 3 days post fertilization (dpf). In situ hybridisation revealed an increase in oligodendrocyte precursor cells, similar to what has been reported for zebrafish neurofibromin 1 mutants. In addition, cells expressing the neural crest markers Sox10 and FoxD3 accumulate lateral to the neural tube and notochord. Time-lapse imaging revealed that H-RasG12V expressing cells indeed migrate out of the spinal cord. This migration was ectopic, occuring several hours after normal neural crest migration. Furthermore, coinciding with the accumulation of neural crest like cells around the neural tube, the intersomitic vasculature hyperbranches to form new blood vessels towards domains of H-RasG12V expressing cells. Taking advantage of the early onset and obvious phenotypes in our H-RasG12V overexpression model we performed a pilot drug screen to identify potential therapeutic compounds for Costello Syndrome. We found the Mek1/Mek2 inhibitor PD98059 successfully inhibited hyperplasia of the forebrain and the spinal cord, with normal numbers of oligodendrocyte precursor cells and neural crest cells. Thus, this zebrafish model will be a valuable tool to further investigate the mechanisms underlying CNS- abnormalities of Costello Syndrome patients, including the formation of neural crest derived neoplasias and will be useful to identify therapies against this disease. This abstract is also presented as Poster A3. Citation Format: Martin Distel, David Traver. H-RasG12V overexpression in the central nervous system leads to expansion of oligodendrocyte precursor cells and neural crest cells. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr PR01.

Age-related differences in oligodendrogenesis across the dorsal-ventral axis of the mouse hippocampus.

Oligodendrocyte precursor cells (OPCs) continue to divide and generate new oligodendrocytes (OLs) in the healthy adult brain. Although recent studies have indicated that adult oligodendrogenesis may be vital for the maintenance of normal brain function, the significance of adult oligodendrogenesis in brain aging remains unclear. In this study, we report a stereological estimation of age-related oligodendrogenesis changes in the mouse hippocampus: the dorsal subdivision is related to learning and memory, while the ventral subdivision is involved in emotional behaviors. To identify OPCs and OLs, we used a set of molecular markers, OL lineage transcription factor (Olig2) and platelet-derived growth factor receptor-alpha (PDGFαR). Intracellular dye injection shows that PDGFαR+/Olig2+ cells and PDGFαR-/Olig2+ cells can be defined as OPCs and OLs, respectively. In the dorsal Ammon's horn, the numbers of OPCs decreased with age, while those of OLs remained unchanged during aging. In the ventral Ammon's horn, the numbers of OPCs and OLs generally decreased with age. Bromodeoxyuridine (BrdU) fate-tracing analysis revealed that the numbers of BrdU+ mitotic OPCs in the Ammon's horn remained unchanged during aging in both the dorsal and ventral subdivisions. Unexpectedly, the numbers of BrdU+ newly generated OLs increased with age in the dorsal Ammon's horn, but remained unchanged in the ventral Ammon's horn. Together, the numbers of OLs in the dorsal Ammon's horn may be maintained during aging by increased survival of adult born OLs, while the numbers of OLs in the ventral Ammon's horn may be reduced with age due to the lack of such compensatory mechanisms. These observations provide new insight into the involvement of adult oligodendrogenesis in age-related changes in the structure and function of the hippocampus.

Oscillating field stimulation promotes spinal cord remyelination by inducing differentiation of oligodendrocyte precursor cells after spinal cord injury.

Demyelination is part of the cascading secondary injury after the primary insult and contributes to the loss of function after spinal cord injury (SCI). Oligodendrocyte precursor cells (OPCs) are the main remyelinating cells in the central nervous system (CNS). We explored whether oscillating field stimulation (OFS) could efficiently promote OPC differentiation and improve remyelination after SCI. SD rats with SCI induced by the Allen method were randomly divided into two groups, the SCI+OFS group and SCI group. The former group received active stimulator units and the latter group received sham (inoperative) stimulator units. Additionally, rats that only received laminectomy were referred as the sham group. The electric field intensity was 600 μV/mm, and the polarity was alternated every 15 minutes. The results showed that the SCI+OFS rats had significantly less demyelination and better locomotor function recovery after 12-weeks treatment. The OFS treatment significantly increased the number of Gal C-positive OPCs after 2-weeks treatment. Furthermore, these rats had higher protein expression of oligodendroglial transcription factors Olig2 and NKx2.2. These findings suggest OFS can promote locomotor recovery and remyelination in SCI rats and this effect may be related to the improved differentiation of OPCs in the spinal cord.

Organelle and Cellular Abnormalities Associated with Hippocampal Heterotopia in Neonatal Doublecortin Knockout Mice

Heterotopic or aberrantly positioned cortical neurons are associated with epilepsy and intellectual disability. Various mouse models exist with forms of heterotopia, but the composition and state of cells developing in heterotopic bands has been little studied. Dcx knockout (KO) mice show hippocampal CA3 pyramidal cell lamination abnormalities, appearing from the age of E17.5, and mice suffer from spontaneous epilepsy. The Dcx KO CA3 region is organized in two distinct pyramidal cell layers, resembling a heterotopic situation, and exhibits hyperexcitability. Here, we characterized the abnormally organized cells in postnatal mouse brains. Electron microscopy confirmed that the Dcx KO CA3 layers at postnatal day (P) 0 are distinct and separated by an intermediate layer devoid of neuronal somata. We found that organization and cytoplasm content of pyramidal neurons in each layer were altered compared to wild type (WT) cells. Less regular nuclei and differences in mitochondria and Golgi apparatuses were identified. Each Dcx KO CA3 layer at P0 contained pyramidal neurons but also other closely apposed cells, displaying different morphologies. Quantitative PCR and immunodetections revealed increased numbers of oligodendrocyte precursor cells (OPCs) and interneurons in close proximity to Dcx KO pyramidal cells. Immunohistochemistry experiments also showed that caspase-3 dependent cell death was increased in the CA1 and CA3 regions of Dcx KO hippocampi at P2. Thus, unsuspected ultrastructural abnormalities and cellular heterogeneity may lead to abnormal neuronal function and survival in this model, which together may contribute to the development of hyperexcitability.

Regulation of oligodendrocyte precursor migration during development, in adulthood and in pathology.

Oligodendrocytes are the myelin-forming cells in the central nervous system (CNS). These cells originate from oligodendrocyte precursor cells (OPCs) during development, and they migrate extensively from oligodendrogliogenic niches along the neural tube to colonise the entire CNS. Like many other such events, this migratory process is precisely regulated by a battery of positional and signalling cues that act via their corresponding receptors and that are expressed dynamically by OPCs. Here, we will review the cellular and molecular basis of this important event during embryonic and postnatal development, and we will discuss the relevance of the substantial number of OPCs existing in the adult CNS. Similarly, we will consider the behaviour of OPCs in normal and pathological conditions, especially in animal models of demyelination and of the demyelinating disease, multiple sclerosis. The spontaneous remyelination observed after damage in demyelinating pathologies has a limited effect. Understanding the cellular and molecular mechanisms underlying the biology of OPCs, particularly adult OPCs, should help in the design of neuroregenerative strategies to combat multiple sclerosis and other demyelinating diseases.

The homeobox gene Gsx2 controls the timing of oligodendroglial fate specification in mouse lateral ganglionic eminence progenitors

The homeobox gene Gsx2 has previously been shown to be required for the specification of distinct neuronal subtypes derived from lateral ganglionic eminence (LGE) progenitors at specific embryonic time points. However, its role in the subsequent generation of oligodendrocytes from these progenitors remains unclear. We have utilized conditional gain-of-function and loss-of-function approaches in order to elucidate the role of Gsx2 in the switch between neurogenesis and oligodendrogenesis within the embryonic ventral telencephalon. In the absence of Gsx2 expression, an increase in oligodendrocyte precursor cells (OPCs) with a concomitant decrease in neurogenesis is observed in the subventricular zone of the LGE at mid-stages of embryogenesis (i.e. E12.5-15.5), which subsequently leads to an increased number of Gsx2-derived OPCs within the adjacent mantle regions of the cortex before birth at E18.5. Moreover, using Olig2(cre) to conditionally inactivate Gsx2 throughout the ventral telencephalon with the exception of the dorsal (d)LGE, we found that the increase in cortical OPCs in Gsx2 germline mutants are derived from dLGE progenitors. We also show that Ascl1 is required for the expansion of these dLGE-derived OPCs in the cortex of Gsx2 mutants. Complementing these results, gain-of-function experiments in which Gsx2 was expressed throughout most of the late-stage embryonic telencephalon (i.e. E15.5-18.5) result in a significant decrease in the number of cortical OPCs. These results support the notion that high levels of Gsx2 suppress OPC specification in dLGE progenitors and that its downregulation is required for the transition from neurogenesis to oligodendrogenesis.

Inhibitory effect of IL-17 on neural stem cell proliferation and neural cell differentiation

BackgroundIL-17, a Th17 cell-derived proinflammatory molecule, has been found to play an important role in the pathogenesis of autoimmune diseases, including multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). While IL-17 receptor (IL-17R) is expressed in many immune-related cells, microglia, and astrocytes, it is not known whether IL-17 exerts a direct effect on neural stem cells (NSCs) and oligodendrocytes, thus inducing inflammatory demyelination in the central nervous system.MethodsWe first detected IL-17 receptor expression in NSCs with immunostaining and real time PCR. We then cultured NSCs with IL-17 and determined NSC proliferation by neurosphere formation capability and cell number count, differentiation by immunostaining neural specific markers, and apoptosis of NSCs by flow cytometry.ResultsNSCs constitutively express IL-17R, and when the IL-17R signal pathway was activated by adding IL-17 to NSC culture medium, the number of NSCs was significantly reduced and their ability to form neurospheres was greatly diminished. IL-17 inhibited NSC proliferation, but did not induce cytotoxicity or apoptosis. IL-17 hampered the differentiation of NSCs into astrocytes and oligodendrocyte precursor cells (OPCs). The effects of IL-17 on NSCs can be partially blocked by p38 MAPK inhibitor.ConclusionsIL-17 blocks proliferation of NSCs, resulting in significantly reduced numbers of astrocytes and OPCs. Thus, in addition to its proinflammatory role in the immune system, IL-17 may also play a direct role in blocking remyelination and neural repair in the CNS.

Insufficient OPC migration into demyelinated lesions is a cause of poor remyelination in MS and mouse models

Failure of remyelination of multiple sclerosis (MS) lesions contributes to neurodegeneration that correlates with chronic disability in patients. Currently, there are no available treatments to reduce neurodegeneration, but one therapeutic approach to fill this unmet need is to promote remyelination. As many demyelinated MS lesions contain plentiful oligodendrocyte precursor cells (OPCs), but no mature myelinating oligodendrocytes, research has previously concentrated on promoting OPC maturation. However, some MS lesions contain few OPCs, and therefore, remyelination failure may also be secondary to OPC recruitment failure. Here, in a series of MS samples, we determined how many lesions contained few OPCs, and correlated this to pathological subtype and expression of the chemotactic molecules Semaphorin (Sema) 3A and 3F. 37 % of MS lesions contained low numbers of OPCs, and these were mostly chronic active lesions, in which cells expressed Sema3A (chemorepellent). To test the hypothesis that differential Sema3 expression in demyelinated lesions alters OPC recruitment and the efficiency of subsequent remyelination, we used a focal myelinotoxic mouse model of demyelination. Adding recombinant (r)Sema3A (chemorepellent) to demyelinated lesions reduced OPC recruitment and remyelination, whereas the addition of rSema3F (chemoattractant), or use of transgenic mice with reduced Sema3A expression increased OPC recruitment and remyelination. We conclude that some MS lesions fail to remyelinate secondary to reduced OPC recruitment, and that chemotactic molecules are involved in the mechanism, providing a new group of drug targets to improve remyelination, with a specific target in the Sema3A receptor neuropilin-1.Electronic supplementary materialThe online version of this article (doi:10.1007/s00401-013-1112-y) contains supplementary material, which is available to authorized users.

Abstract 351: Gliomagenesis via the reactivation of quiescent adult oligodendrocyte precursor cells.

Abstract Malignant gliomas are devastating, incurable brain tumors. Surprisingly, though the proliferative activity of brain cells decreases precipitously with age, glioma occurs most frequently in the elderly. Our lab recently showed that introducing p53 and NF1 mutations into perinatal oligodendrocyte precursor cells (OPCs) can lead to gliomagenesis. However, perinatal OPCs are highly migratory and proliferative, whereas adult OPCs are much more quiescent. Therefore, to better understand the impact of age on gliomagenesis, we asked if adult OPCs can be transformed into gliomas, and if so, what would be the reactivating mechanisms. Using NG2-CreER, a temporally controllable Cre, we introduced p53/NF1 mutations specifically into adult OPCs by giving Tamoxifen (Tmx) to young adult (P45) and aging mice (P180). We found that gliomas formed with high penetrance in both groups. Notably, tumor latency of both groups was very similar (120-180 days post-Tmx), suggesting that OPC transforming potential does not decrease as the brain ages. Adult OPC-derived tumors have pathological features of malignant anaplastic (grade III) glioma and a transcriptional profile similar to human proneural glioma. Interestingly, these features are comparable to gliomas derived from embryonic neural stem cells and perinatal OPCs, indicating that the age at which mutations arise does not influence tumor type. The transcriptional profile of adult OPC-derived tumor cells closely matched that of wild type perinatal OPCs, suggesting that tumor OPCs have been rejuvenated. To identify when mutant OPCs first become reactivated, we analyzed brain regions where these tumors tend to occur (olfactory bulb, thalamus, pyriform cortex, amygdala) at various time points after mutation. At both 50 and 90 days post-Tmx, the number of mutant OPCs was 6-fold higher than that of WT OPCs, indicating pre-malignant over-expansion of these cells. Surprisingly, mutant OPC proliferation was not increased at either time point. Further analysis showed that mutant OPCs have defects in differentiation into mature oligodendrocytes. These results suggest that mutant OPCs become reactivated soon after mutagenesis, and that their inability to differentiate might play a role in malignant transformation. To understand the molecular mechanisms of adult OPC reactivation, we are currently investigating the involvement of signal transduction pathways known to play important roles in early OPC development. In summary, our results show that, despite being mostly quiescent, adult OPCs have the potential to become reactivated by the loss of tumor suppressor genes and can give rise to malignant gliomas. Signaling pathways with known roles in early OPC development might once again play a role in malignant transformation of these cells in the adult brain. Therefore, studying gliomagenesis and OPC development in parallel could lead to novel strategies for treating these deadly tumors. Citation Format: Rui P. Galvao, Roeland G. W. Verhaak, Oded Foreman, Hui Zong. Gliomagenesis via the reactivation of quiescent adult oligodendrocyte precursor cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 351. doi:10.1158/1538-7445.AM2013-351

Abstract WP96: Age Related Decline Of Oligodendrogenesis After White Matter Injury

Background and Purpose: Adult white mater retains endogenous repair mechanisms. But how aging affects this ability for self-repair remains to be fully understood. Here, we assessed the hypothesis that aged white matter loses the capacity for oligodendrogenesis, and hence is more vulnerable to external stress. Methods: A mouse model of chronic cerebral hypoperfusion was prepared by bilateral common carotid artery stenosis in young (2-month old) and middle-aged (8-month old) mice (n=30 each). White matter integrity and injury were assessed with myelin staining, myelin-basic-protein staining, and optical coherence tomography. Cognitive function was assessed by spontaneous Y-maze test. Proliferation and differentiation of oligodendrocyte precursor cells (OPCs) were evaluated using a bromodeoxyuridine assay. Results: While there was no clear difference in myelin density of the corpus callosum between young and middle-aged mice under normal conditions, the latter showed larger white matter injury and working memory deficits after chronic cerebral hypoperfusion insults (P<0.05). The numbers of newly-born oligodendrocytes and OPCs in young mice were both increased by the hypoxic stress, but these responses in middle-aged mice were lower with less activation of cAMP response element binding protein (CREB) (P<0.05). Notably, activating CREB by a type-III phosphodiesterase inhibitor cilostazol in middle-aged mice enhanced the differentiation of OPCs, which alleviated myelin loss and cognitive dysfunction (P<0.05). Conclusions: An age-related decline in oligodendrogenesis may compromise endogenous repair mechanisms, and CREB-activating therapies may rescue white matter after chronic cerebral hypoperfusion. Approaches that promote OPC function and repair may be useful for treating white matter rendered vulnerable by age in stroke or vascular dementia.

In vivo analysis of kallikrein-related peptidase 6 (KLK6) function in oligodendrocyte development and the expression of myelin proteins

Oligodendrocytes are important for not only nerve conduction but also central nervous system (CNS) development and neuronal survival in a variety of conditions. Kallikrein-related peptidase 6 (KLK6) is expressed in oligodendrocytes in the CNS and its expression is changed in several physiological and pathological conditions, especially following spinal cord injury (SCI) and experimental autoimmune encephalomyelitis. In this study, we investigated the functions of KLK6 in oligodendrocyte lineage cell development and the production of myelin proteins using KLK6-deficient (KLK6−/−) mice. KLK6−/− mice were born without apparent defects and lived as long as wild-type (WT) mice. There was no significant difference in the numbers of oligodendrocyte precursor cells and mature oligodendrocytes in the adult naive spinal cord between WT and KLK6−/− mice. However, there were fewer mature oligodendrocytes in the KLK6−/− spinal cord than in the WT spinal cord at postnatal day 7 (P7). Expression of myelin basic protein (MBP) and oligodendrocyte-specific protein/claudin-11, major myelin proteins, was also decreased in the KLK6−/− spinal cord compared with the WT spinal cord at P7–21. Moreover, after SCI, the amount of MBP in the damaged spinal cords of KLK6−/− mice was significantly less than that in the damaged spinal cords of WT mice. These results indicate that KLK6 plays a functional role in oligodendrocyte development and the expression of myelin proteins.

Effect of leptin administration on myelination in ob/ob mouse cerebrum after birth

Brain weight and size are known to be reduced in adult leptin-deficient Lep/Lep (OB) mice when compared with the wild-type (+/+) mice (C57BL/6: B6). We here analyzed leptin's effects on myelination by examining morphometrically the myelin sheath (MS) in the cerebrum of postnatal day (P) 14 and P28 OB that had received leptin 1 nmol/capita/day from P7 to P14 or P28 (OB+lep), in comparison with OB and B6. We examined myelin basic protein (MBP) mRNA levels and the differentiation of oligodendrocytes by comparing the number of oligodendrocyte precursor cells (OPCs) and the mature oligodendrocytes in the cerebrum between OB, OB+lep, and B6 on P14 and P28. MBP-mRNA expression was lower in OB than in B6 on P14 and P28. On P14, it was higher in OB+lep than in OB but was still lower than in B6, whereas on P28 it was even higher in OB+lep than in B6. On P28, the radii of myelinated axons were larger in OB than in B6 and OB+lep. The MS on P28 was significantly thinner in OB than in B6, but there was no significant difference between OB and OB+lep. There were significantly fewer mature oligodendrocytes in OB and OB+lep than in B6 on P28, whereas on P14 there were significantly fewer OPCs in OB and OB+lep than in B6. Our results suggested that leptin regulates the myelination of oligodendrocytes and that the replenishment of leptin in OB recovered myelination but did not affect the differentiation of OPCs from P7 to P28.

NG2+ Oligodendrocyte Precursor Cells (OPCs) take part in neurovascular unit remodelling during EAE

NG2+ Oligodendrocyte Precursor Cells (OPCs) are an abundant glial population in mammalian adult Central Nervous System (CNS) committed to oligodendrocyte differentiation and myelin repair (1). Our previous studies in a model of murine Experimental Autoimmune Encephalomyelitis (EAE) revealed demyelination of cerebral cortex subpial areas together with an increased number of OPCs and Blood-Brain Barrier (BBB) breakdown (2,3). The observation of several EAE activated OPCs in tight contact with EAE cortex microvessels prompt us to further analyse the nature of this association and ascertain if during EAE, OPCs establish a privileged relationship with BBB microvessels. Laser confocal microscopy and morphometric analyses were applied to immunohistochemically revealed cell- (OPCs, endothelial cells, pericytes, astrocytes) and vascular basement membrane- (collagen type IV and VI) specific antigens. The main vessel/OPC assessed parameters were OPC vascular coverage (OPC number/vessel length) and raw integrated density (OPC area x mean gray value)/vessel density which were calculated in brains from both healthy control and EAE affected mice. The results confirmed the increased number of EAE OPCs, their enhanced branching and frequent perivascular location. Compared with healthy mice, in EAE the OPC coverage and the integrated density, as well as the evaluated minimal vascular OPC distance were significantly increased. These data suggest that in EAE, OPCs assume a critical position with respect to the vessel wall, remaining distinct from GFAP+ astrocytes, as an additional cell component of the neurovascular unit. In this position, the increased vascular subset of EAE NG2+ OPCs may interfere with neurovascular unit cell-cell signalling in turn affecting BBB regulation and maintenance.

Strategies for repair of white matter: influence of osmolarity and microglia on proliferation and apoptosis of oligodendrocyte precursor cells in different basal culture media

The aim of the present study has been to obtain high yields of oligodendrocyte precursor cells (OPCs) in culture. This is a first step in facilitation of myelin repair. We show that, in addition to factors, known to promote proliferation, such as basic fibroblast growth factor (FGF-2) and platelet derived growth factor (PDGF) the choice of the basal medium exerts a significant influence on the yield of OPCs in cultures from newborn rats. During a culture period of up to 9 days we observed larger numbers of surviving cells in Dulbecco's Modified Eagle Medium (DMEM), and Roswell Park Memorial Institute Medium (RPMI) compared with Neurobasal Medium (NB). A larger number of A2B5-positive OPCs was found after 6 days in RPMI based media compared with NB. The percentage of bromodeoxyuridine (BrdU)-positive cells was largest in cultures maintained in DMEM and RPMI. The percentage of caspase-3 positive cells was largest in NB, suggesting that this medium inhibits OPC proliferation and favors apoptosis. A difference between NB and DMEM as well as RPMI is the reduced Na+-content. The addition of equiosmolar supplements of mannitol or NaCl to NB medium rescued the BrdU-incorporation rate. This suggested that the osmolarity influences the proliferation of OPCs. Plating density as well as residual microglia influence OPC survival, BrdU incorporation, and caspase-3 expression. We found, that high density cultures secrete factors that inhibit BrdU incorporation whereas the presence of additional microglia induces an increase in caspase-3 positive cells, indicative of enhanced apoptosis. An enhanced number of microglia could thus also explain the stronger inhibition of OPC differentiation observed in high density cultures in response to treatment with the cytokines TNF-α and IFN-γ. We conclude that a maximal yield of OPCs is obtained in a medium of an osmolarity higher than 280 mOsm plated at a relatively low density in the presence of as little microglia as technically achievable.

Possible roles of Plexin-A4 in positioning of oligodendrocyte precursor cells in developing cerebral cortex

Molecular mechanisms regulating positions of oligodendrocyte precursor cells (OPCs) remain unclear in developing cerebral cortex. To explore the mechanisms, we investigated how Plexin-A4, receptor of Semaphorin in OPCs, is involved in the positioning. We found that Plexin-A4 knockout mice exhibited (1) an increased number of OPCs in both the upper- and middle-regions of the cortical plate, where both indirect- and direct-ligands of Plexin-A4, Sema3A and Sema6A, respectively, were continuously expressed, and (2) aberrant distributions of OPCs in both the intermediate zone and corpus callosum, where Plexin-A4 was richly expressed in wild-type mice. These results suggest that Plexin-A4 is involved in the precise positioning of OPCs in developing cerebral cortex.

Silencing or knocking out the Na+/Ca2+ exchanger-3 (NCX3) impairs oligodendrocyte differentiation

Changes in intracellular [Ca(2+)](i) levels have been shown to influence developmental processes that accompany the transition of human oligodendrocyte precursor cells (OPCs) into mature myelinating oligodendrocytes and are required for the initiation of the myelination and re-myelination processes. In the present study, we explored whether calcium signals mediated by the selective sodium calcium exchanger (NCX) family members NCX1, NCX2, and NCX3, play a role in oligodendrocyte maturation. Functional studies, as well as mRNA and protein expression analyses, revealed that NCX1 and NCX3, but not NCX2, were divergently modulated during OPC differentiation into oligodendrocyte phenotype. In fact, whereas NCX1 was downregulated, NCX3 was strongly upregulated during oligodendrocyte development. The importance of calcium signaling mediated by NCX3 during oligodendrocyte maturation was supported by several findings. Indeed, whereas knocking down the NCX3 isoform in OPCs prevented the upregulation of the myelin protein markers 2',3'-cyclic nucleotide-3'-phosphodiesterase (CNPase) and myelin basic protein (MBP), its overexpression induced an upregulation of CNPase and MBP. Furthermore, NCX3-knockout mice showed not only a reduced size of spinal cord but also marked hypo-myelination, as revealed by decrease in MBP expression and by an accompanying increase in OPC number. Collectively, our findings indicate that calcium signaling mediated by NCX3 has a crucial role in oligodendrocyte maturation and myelin formation.

Dorsally‐derived oligodendrocytes in the spinal cord contribute to axonal myelination during development and remyelination following focal demyelination

In the developing spinal cord, the majority of oligodendrocytes are derived from the ventral ventricular zone. Several recent studies suggested that a small number of oligodendrocyte precursor cells (OPCs) can also be generated in the dorsal spinal cord. However, it is not clear whether these dorsal oligodendrocyte precursor cells participate in myelination and remyelination. To investigate the fate and potential function of these dorsally-derived oligodendrocytes (dOLs) in the adult spinal cord, Cre-lox genetic fate mapping in transgenic mice was employed. We used the Pax3(Cre) knock-in mouse to drive Cre expression in the entire dorsal epithelium and the Rosa26-lacZ or Z/EG reporter line to trace their spatial distribution and population dynamics in the spinal cord. The dorsal OPCs generated from the Pax3-expressing domains migrate into all regions of spinal cord and subsequently undergo terminal differentiation and axonal myelination. In response to a focal demyelination injury, a large number of newly differentiated oligodendrocytes originated from dOLs, suggesting that dOLs may provide an important source of OPCs for axonal remyelination in multiple sclerosis or spinal cord injury.

An experimental electro-acupuncture study in treatment of the rat demyelinated spinal cord injury induced by ethidium bromide

Oligodendrocyte precursor cells (OPCs) are one of the potential treating tools for multiple sclerosis (MS). Therefore, the cell number and differentiation of OPCs in a demyelinated spinal cord are crucial for improvement of reparative process. In the present study, we investigated whether “Governor Vessel (GV)” electro-acupuncture (EA) could efficiently promote increase in cell number and differentiation of OPCs into oligodendrocytes, remyelination and functional recovery in the demyelinated spinal cord. The spinal cord of adult Sprague–Dawley rats was microinjected with ethidium bromide (EB) at T10, to establish a demyelinated model. Six groups of animals were performed for the experiment. After 15 days EA treatment, neurotrophin-3 (NT-3) level and number of NG2-positive OPCs were significantly increased. Compared with the sham group, more NG2-positive OPCs were distributed between neurofilament (NF)-positive nerve fibres or closely associated with them in the lesion site and nearby tissue. In rats given longer EA treatment for 30 days, the number of adenomatous polyposis coli (APC)-positive oligodendrocytes was increased. Concomitantly, the number of newly formed myelins was increased. This was coupled by increase in endogenous oligodendrocyte involved in myelin formation. Furthermore, behavioural test and spinal cord evoked potential detection demonstrated a significant functional recovery in the EA + EB day 30 group. Our results suggest EA treatment can promote NT-3 expression, increase the cell number and differentiation of endogenous OPCs, and remyelination in the demyelinated spinal cord as well as the functional improvement of demyelinated spinal cord.

Maternal Undernutrition with Vaginal Inflammation Impairs the Neonatal Oligodendrogenesis in Mice

Maternal undernutrition and infection during pregnancy may impair development of oligodendrocytes, thereby increasing risks of neuropsychiatric disorders of their children. We analyzed the effects of those risk factors on oligodendrogenesis in fetal and neonatal brains. Female mice were given low-protein or regular food for 2 weeks before their pregnancy. On the 14th day of pregnancy, they received a transvaginal injection of lipopolysaccharide to induce inflammation or control solution, consisting of four groups, depending on nutritional conditions with or without vaginal inflammation. We collected fetal brains on embryonic day (E) 17 for evaluating oligodendrocyte precursor cells (OPCs) and neonatal brains on postnatal day (P) 7 for evaluating mature oligodendrocytes. OPCs and mature oligodendrocytes were identified as positive immunostaining for oligodendrocyte-lineage transcription factor 2 and myelin basic protein, respectively. There was no difference in the number of OPCs in E17 brains among the four groups, suggesting that nutritional restriction with or without inflammation exerts no noticeable influence on the differentiation of OPCs. However, the number of mature oligodendrocytes was decreased in P7 brains obtained from nutrient-restricted mice with inflammation, suggesting that their combination impairs oligodendrogenesis in the neonatal brain. We also analyzed reactive astrocytes that express both glial fibrillary acidic protein and nestin for evaluating brain inflammation. The population of reactive astrocytes was increased in P7 brains derived from mice with LPS injection, irrespective of nutritional restriction, indicating that maternal vaginal inflammation induces neonatal brain inflammation. The maternal management of both nutrition and infection is crucial to prevent neuropsychiatric disorders of the children.

Sox10 directs neural stem cells toward the oligodendrocyte lineage by decreasing Suppressor of Fused expression

Oligodendrocyte precursor cells (OPCs) are lineage-restricted progenitors generally limited in vivo to producing oligodendrocytes. Mechanisms controlling genesis of OPCs are of interest because of their importance in myelin development and their potential for regenerative therapies in multiple sclerosis and dysmyelinating syndromes. We show here that the SoxE transcription factors (comprising Sox8, 9, and 10) induce multipotent neural precursor cells (NPCs) from the early postnatal subventricular zone (SVZ) to become OPCs in an autonomous manner. We performed a chromatin immunoprecipitation-based bioinformatic screen and identified Suppressor of Fused (Sufu) as a direct target of repression by Sox10. In vitro, overexpression of Sufu blocked OPC production, whereas RNAi-mediated inhibition augmented OPC production. Furthermore, mice heterozygous for Sufu have increased numbers of OPCs in the telencephalon during development. We conclude that Sox10 acts to restrict the potential of NPCs toward the oligodendrocyte lineage in part by regulating the expression of Sufu.