OBJECTIVE: To investigate the effects of gestational age (GA) and phototherapy on the plasma metabolite profile of preterm infants with neonatal hyperbilirubinemia (NHB).
METHODS: From a cohort of prospectively enrolled infants born preterm (N=92), plasma samples of very preterm (VPT; GA, 28+0 to 31+6 weeks, N =27) and moderate/late preterm (M/LPT; GA, 32+0 to 35+6 weeks, N =33) infants requiring phototherapy for NHB were collected prior to the initiation of phototherapy and 24 hours after starting phototherapy. An additional sample was collected 48 hours after starting phototherapy in a randomly selected subset (N=30; VPT N=15; M/LPT N=15). Metabolite profiles were determined using ultraperformance liquid chromatography tandem mass spectroscopy. Two-way ANCOVA was used to identify metabolites that differed between GA groups and timepoints after adjusting for total serum bilirubin (TSB) levels (FDR q-value<0.05). Top impacted pathways were identified using pathway over-representation analysis.
RESULTS: Phototherapy was initiated at lower TSB (mean ± SD mg/dL) levels in VPT compared with M/LPT infants (7.3 ± 1.4 vs. 9.9 ± 1.9, p<0.01). We identified 664 metabolites that were significant for a phototherapy effect, 191 metabolites significant for GA, and 46 metabolites significant for GA x phototherapy interaction (FDR q-value<0.05). Longer duration phototherapy had a larger mean effect size (24 hours post-phototherapy: d=0.36; 48 hours post-phototherapy: d=0.43). Top pathways affected by phototherapy included membrane lipid metabolism, one-carbon metabolism, creatine biosynthesis, and oligodendrocyte differentiation.
CONCLUSIONS: Phototherapy alters the plasma metabolite profile more than GA in preterm infants with NHB, affecting pathways related to lipid and one-carbon metabolism, energy biosynthesis, and oligodendrocyte differentiation.

Oligodendrocytes (OLs) are differentiated from oligodendrocyte precursor cells (OPCs) in the central nervous system (CNS). Demyelination is a common feature of many neurological diseases such as multiple sclerosis (MS) and leukodystrophies. Although spontaneous remyelination can happen after myelin injury, nevertheless, it is often insufficient and may lead to aggravated neurodegeneration and neurological disabilities. Our previous study has discovered that MEK/ERK pathway negatively regulates OPC-to-OL differentiation and remyelination in mouse models. To facilitate possible clinical evaluation, here we investigate several MEK inhibitors which have been approved by FDA for cancer therapies in both mouse and human OPC-to-OL differentiation systems. Trametinib, the first FDA approved MEK inhibitor, displays the best effect in stimulating OL generation in vitro among the four MEK inhibitors examined. Trametinib also significantly enhances remyelination in both MOG-induced EAE model and LPC-induced focal demyelination model. More exciting, trametinib facilitates the generation of MBP+ OLs from human embryonic stem cells (ESCs)-derived OPCs. Mechanism study indicates that trametinib promotes OL generation by reducing E2F1 nuclear translocation and subsequent transcriptional activity. In summary, our studies indicate a similar inhibitory role of MEK/ERK in human and mouse OL generation. Targeting the MEK/ERK pathway might help to develop new therapies or repurpose existing drugs for demyelinating diseases.

Oligodendrocyte-lineage cells are central nervous system (CNS) glia that perform multiple functions including the selective myelination of some but not all axons. During myelination, synaptic vesicle release from axons promotes sheath stabilization and growth on a subset of neuron subtypes. In comparison, it is unknown if pre-myelinating oligodendrocyte process extensions selectively interact with specific neural circuits or axon subtypes, and whether the formation and stabilization of these neuron-glia interactions involves synaptic vesicle release. In this study, we used fluorescent reporters in the larval zebrafish model to track pre-myelinating oligodendrocyte process extensions interacting with spinal axons utilizing in vivo imaging. Monitoring motile oligodendrocyte processes and their interactions with individually labeled axons revealed that synaptic vesicle release regulates the behavior of subsets of process extensions. Specifically, blocking synaptic vesicle release decreased the longevity of oligodendrocyte process extensions interacting with reticulospinal axons. Furthermore, blocking synaptic vesicle release increased the frequency that new interactions formed and retracted. In contrast, tracking the movements of all process extensions of singly-labeled oligodendrocytes revealed that synaptic vesicle release does not regulate overall process motility or exploratory behavior. Blocking synaptic vesicle release influenced the density of oligodendrocyte process extensions interacting with reticulospinal and serotonergic axons, but not commissural interneuron or dopaminergic axons. Taken together, these data indicate that alterations to synaptic vesicle release cause changes to oligodendrocyte-axon interactions that are neuron subtype specific.

Intranasal administration is an efficient strategy for bypassing the BBB, favoring drug accumulation in the brain, and improving its efficiency. Lipid nanocapsules (LNC) are suitable nanocarriers for the delivery of lipophilic drugs via this route and can be used to encapsulate lipophilic molecules such as retinoic acid (RA) and calcitriol (Cal). As the hallmarks of multiple sclerosis (MS) are neuroinflammation and oligodendrocyte loss, our hypothesis was that by combining two molecules known for their pro-differentiating properties, encapsulated in LNC, and delivered by intranasal administration, we would stimulate oligodendrocyte progenitor cells (OPC) differentiation into oligodendrocytes and provide a new pro-remyelinating therapy. LNC loaded with RA (LNC-RA) and Cal (LNC-Cal) were stable for at least 8 weeks. The combination of RA and Cal was more efficient than the molecules alone, encapsulated or not, on OPC differentiation in vitro and decreased microglia cell activation in a dose-dependent manner. After the combined intranasal administration of LNC-RA and LNC-Cal in a mouse cuprizone model of demyelination, increased MBP staining was observed in the corpus callosum. In conclusion, intranasal delivery of lipophilic drugs encapsulated in LNC is a promising strategy for myelinating therapies.

UNASSIGNED: Demyelination is one of the hallmarks of multiple sclerosis (MS). While remyelination occurs during the disease, it is incomplete from the start and strongly decreases with its progression, mainly due to the harm to oligodendrocyte progenitor cells (OPCs), causing irreversible neurological deficits and contributing to neurodegeneration. Therapeutic strategies promoting remyelination are still very preliminary and lacking within the current treatment panel for MS.
UNASSIGNED: In a previous study, we identified 21 microRNAs dysregulated mostly in the CSF of relapsing and/or remitting MS patients. In this study we transfected the mimics/inhibitors of several of these microRNAs separately in an OPC cell line, called CG-4. We aimed (1) to phenotypically characterize their effect on OPC differentiation and (2) to identify corroborating potential mRNA targets via immunocytochemistry, RT-qPCR analysis, RNA sequencing, and Gene Ontology enrichment analysis.
UNASSIGNED: We observed that the majority of 13 transfected microRNA mimics decreased the differentiation of CG-4 cells. We demonstrate, by RNA sequencing and independent RT-qPCR analyses, that miR-33-3p, miR-34c-5p, and miR-124-5p arrest OPC differentiation at a late progenitor stage and miR-145-5p at a premyelinating stage as evidenced by the downregulation of premyelinating oligodendrocyte (OL) [Tcf7l2, Cnp (except for miR-145-5p)] and mature OL (Plp1, Mbp, and Mobp) markers, whereas only miR-214-3p promotes OPC differentiation. We further propose a comprehensive exploration of their change in cell fate through Gene Ontology enrichment analysis. We finally confirm by RT-qPCR analyses the downregulation of several predicted mRNA targets for each microRNA that possibly support their effect on OPC differentiation by very distinctive mechanisms, of which some are still unexplored in OPC/OL physiology.
UNASSIGNED: miR-33-3p, miR-34c-5p, and miR-124-5p arrest OPC differentiation at a late progenitor stage and miR-145-5p at a premyelinating stage, whereas miR-214-3p promotes the differentiation of CG-4 cells. We propose several potential mRNA targets and hypothetical mechanisms by which each microRNA exerts its effect. We hereby open new perspectives in the research on OPC differentiation and the pathophysiology of demyelination/remyelination, and possibly even in the search for new remyelinating therapeutic strategies in the scope of MS.

BACKGROUND: Prenatal infection has been implicated in the development of neuropsychiatric disorders in children. We hypothesised that exposure to lipopolysaccharide during prenatal development could induce anxiety-like behaviour and sensorineural hearing loss in offspring, as well as disrupt neural differentiation during embryonic neural development.
METHODS: We simulated prenatal infection in FVB mice and mouse embryonic stem cell (ESC) lines, specifically 46C and E14Tg2a, through lipopolysaccharide treatment. Gene expression profiling analyses and behavioural tests were utilized to study the effects of lipopolysaccharide on the offspring and alterations in toll-like receptor (TLR) 2-positive and TLR4-positive cells during neural differentiation in the ESCs.
RESULTS: Exposure to lipopolysaccharide (25 µg/kg) on gestation day 9 resulted in anxiety-like behaviour specifically in male offspring, while no effects were detected in female offspring. We also found significant increases in the expression of GFAP and CNPase, as well as higher numbers of GFAP + astrocytes and O4+ oligodendrocytes in the prefrontal cortex of male offspring. Furthermore, increased scores for genes related to oligodendrocyte and lipid metabolism, particularly ApoE, were observed in the prefrontal cortex regions. Upon exposure to lipopolysaccharide during the ESC-to-neural stem cell (NSC) transition, Tuj1, Map2, Gfap, O4, and Oligo2 mRNA levels increased in the differentiated neural cells on day 14. In vitro experiments demonstrated that lipopolysaccharide exposure induced inflammatory responses, as evidenced by increased expression of IL1b and ApoB mRNA.
CONCLUSIONS: Our findings suggest that prenatal infection at different stages of neural differentiation may result in distinct disturbances in neural differentiation during ESC-NSC transitions. Furthermore, early prenatal challenges with lipopolysaccharide selectively induce anxiety-like behaviour in male offspring. This behaviour may be attributed to the abnormal differentiation of astrocytes and oligodendrocytes in the brain, potentially mediated by ApoB/E signalling pathways in response to inflammatory stimuli.

How neuronal signaling affects brain myelination remains poorly understood. We show dysregulated neuronal RHEB-mTORC1-DLK1 axis impairs brain myelination. Neuronal Rheb cKO impairs oligodendrocyte differentiation/myelination, with activated neuronal expression of the imprinted gene Dlk1. Neuronal Dlk1 cKO ameliorates myelination deficit in neuronal Rheb cKO mice, indicating that activated neuronal Dlk1 expression contributes to impaired myelination caused by Rheb cKO. The effect of Rheb cKO on Dlk1 expression is mediated by mTORC1; neuronal mTor cKO and Raptor cKO and pharmacological inhibition of mTORC1 recapitulate elevated neuronal Dlk1 expression. We demonstrate that both a secreted form of DLK1 and a membrane-bound DLK1 inhibit the differentiation of cultured oligodendrocyte precursor cells into oligodendrocytes expressing myelin proteins. Finally, neuronal expression of Dlk1 in transgenic mice reduces the formation of mature oligodendrocytes and myelination. This study identifies Dlk1 as an inhibitor of oligodendrocyte myelination and a mechanism linking altered neuronal signaling with oligodendrocyte dysfunction.

Accumulating evidences suggest a strong correlation between metabolic changes and neurodegeneration in CNS demyelinating diseases such as multiple sclerosis (MS). Biotin, an essential cofactor for five carboxylases, is expressed by oligodendrocytes and involved in fatty acid synthesis and energy production. The metabolic effect of biotin or high-dose-biotin (MD1003) has been reported on rodent oligodendrocytes in vitro, and in neurodegenerative or demyelinating animal models. However, clinical studies, showed mild or no beneficial effect of MD1003 in amyotrophic lateral sclerosis (ALS) or MS. Here, we took advantage of a mouse model of myelin deficiency to study the effects of MD1003 on the behavior of murine and grafted human oligodendrocytes in vivo. We show that MD1003 increases the number and the differentiation potential of endogenous murine oligodendroglia over time. Moreover, the levels of MD1003 are increased in the plasma and brain of pups born to treated mothers, indicating that MD1003 can pass through the mother\'s milk. The histological analysis of the grafted animals shows that MD1003 increased proliferation and accelerates differentiation of human oligodendroglia, but without enhancing their myelination potential. These findings provide important insights into the role of MD1003 on murine and human oligodendrocyte maturation/myelination that may explain the mitigated outcome of ALS/MS clinical trials.

Oligodendrocyte (OL) death and remyelination failure lead to progressive neurological deficits in multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). Matrine (MAT), a quinolizidine alkaloid component derived from the root of Sophora flavescens, has the capacity to effectively inhibit central nervous system (CNS) inflammation and to promote neuroregeneration. In the present study we explored its regulatory mechanism on the Wnt/β-catenin/TCF7L2 pathway, a negative modulator for myelination, in MOG35--55 peptide-induced EAE. Our results clearly indicate that MAT treatment reduced the activation of Wnt3a and β-catenin in the CNS of EAE mice, accompanied by the activation of GSK3β and decreased expression of cyclin D1 and Axin2, two target genes of the Wnt3a/β-catenin pathway. In addition, MAT increased OL maturation and myelination, as evidenced by the decreased number of NG2+Olig2+ cells and the increased numbers of MBP+ and CC1+Olig2+ cells. Taken together, these findings indicate that MAT treatment promoted the maturation of OLs and myelin repair, which is closely related to the modulation of the Wnt/β-catenin/TCF7L2 signaling pathway.

Leucine-rich glioma-inactivated protein 1 (LGI1) is known to play a key role in autosomal dominant lateral temporal lobe epilepsy (ADLTE). The ADLTE is an inherited disease characterized by focal seizures with distinctive auditory or aphasic symptoms. A large number of mutations on the Lgi1 gene have been reported and are believed to be the genetic cause for ADLTE. We identified a novel missense mutation, c.152A>G (p.Asp51Gly), on Lgi1 from a Chinese ADLTE patient who manifests locomotor imbalance and white matter reduction. However, it remains unknown how mutant LGI1 causes white matter abnormalities at molecular and cellular levels. Here, we generated a knock-in mouse bearing this Lgi1 mutation. We found that Lgi1D51G / D51G mice exhibited impaired defective white matter and motor coordination. We observed that Lgi1D51G / D51G mice displayed a reduced number of mature oligodendrocytes (OLs) and deficient OL differentiation in the white matter. However, the population of oligodendrocyte precursor cells was not affected in Lgi1D51G / D51G mice. Mechanistically, we showed that the Lgi1D51G mutation resulted in altered mTOR signaling and led to decreased levels of Sox10. Given that Sox10 is a key transcriptional factor to control OL differentiation, our results strongly suggest that the Lgi1D51G mutation may cause white matter abnormalities via inhibiting Sox10-dependent OL differentiation and myelination in the central nervous system.