Demyelination induces transport of ribosome-containing vesicles from glia to axons: evidence from animal models and MS patient brains

Transfer of nuclear and ribosomal material from Sox10-lineage cells to neurons in the mouse brain

Material transfer is an essential form of intercellular communication to exchange information and resources between cells. Material transfer between neurons and from glia to neurons has been demonstrated to support neuronal survival and activity. Understanding the extent of material transfer in the healthy nervous system is limited. Here we report that in the mouse central nervous system (CNS), neurons receive nuclear and ribosomal material of Sox10-lineage cell (SOL) origin. We show that transfer of SOL-derived material to neurons is region dependent, establishes during postnatal brain maturation, and dynamically responds to LPS-induced neuroinflammation in the adult mouse brain. We identified satellite oligodendrocyte-neuron pairs with loss of plasma membrane integrity between nuclei, suggesting direct material transfer. Together, our findings provide evidence of regionally coordinated transfer of SOL-derived nuclear and ribosomal material to neurons in the mouse CNS, with potential implications for the understanding and modulation of neuronal function and treatment of neurological disorders.

Oligodendroglia-to-neuron material transfer lights up the mouse CNS

Intercellular material transfer in the central nervous system (CNS) supports neuronal survival and activity. Mayrhofer et al. (2023. J. Exp. Med.https://doi.org/10.1084/jem.20221632) characterize extensive regionally coordinated transfer of oligodendroglial ribosomal and nuclear material toward neurons, linked to satellite oligodendrocyte-neuron pairs in the mouse CNS.

Effect of Carvacrol on histological analysis and expression of genes involved in an animal model of multiple sclerosis

BACKGROUND

The most common non-traumatic neurological disease in young- and middle-aged adults is multiple sclerosis (MS), leading to central nervous system (CNS) atrophy and neurological disorders with loss of myelin and axonal degeneration. Due to the inadequate efficiency of common treatments, some natural products with antioxidant properties such as Carvacrol have been considered.

OBJECTIVE

the present study aimed to investigate carvacrol's anti-inflammatory and therapeutic effects on MS symptoms in healthy and experimental autoimmune encephalomyelitis (EAE) induced female Lewis rats.

METHODS

The study was performed in three groups of Lewis rats: control group, EAE model, and EAE treated with carvacrol (carvacrol-treated group). The treatment group received 25 mg/kg of carvacrol intraperitoneally daily. Histologic examination and expression analysis of pro-inflammatory genes (Interleukin-1 and 17 (IL-1 and IL-17), Nuclear Factor Kappa B Cells (NF-κB) and Tumor Necrosis Factor-α (TNF-α)), myelin repair, and also regeneration genes (Myelin basic protein (MBP), Oligodendrocyte Transcription Factor 2 (OLIG2) and Platelet-Derived Growth Factor Receptor α (PDGFR-α)) were carried out. Gene studies, Hematoxylin and Eosin (H&E), and Luxol fast blue stain were performed in the lumbar region of the spinal cord.

RESULTS

The EAE clinical scores in the carvacrol-treated group were lower than in untreated rats (P < 0.001). The expression of two genes, IL-17 and MBP, was confirmed using fluorescence immunohistochemistry (FIHC). A significant decrease was observed in NF-κB and IL-17, and IL-1 gene expression. The MBP and OLIG2 gene expression was increased in the carvacrol-treated group (p < 0.001). In EAE, PDGFR-α expression increased about four times. However, carvacrol administration did not affect PDGFR-α and TNF-α gene expression. In this treatment, H&E staining of spinal cord regions showed a significant decrease in inflammatory cell infiltration. Moreover, immunostaining analysis demonstrated a considerable increase in MBP and a reduction in IL-17 secretion.

CONCLUSION

The results showed that carvacrol administration reduces the entry of inflammatory cells into the CNS by stimulating myelination-related processes employing increasing the expression of genes involved in myelin repair and reducing the expression of inflammatory genes. Our findings confirm that carvacrol improves the clinical and pathological symptoms of EAE through its therapeutic and modification properties as a potential adjunctive therapy and needs to be studied more.

Age-related loss of axonal regeneration is reflected by the level of local translation

Regeneration capacity is reduced as CNS axons mature. Using laser-mediated axotomy, proteomics and puromycin-based tagging of newly-synthesized proteins in a human embryonic stem cell-derived neuron culture system that allows isolation of axons from cell bodies, we show here that efficient regeneration in younger axons (d45 in culture) is associated with local axonal protein synthesis (local translation). Enhanced regeneration, promoted by co-culture with human glial precursor cells, is associated with increased axonal synthesis of proteins, including those constituting the translation machinery itself. Reduced regeneration, as occurs with the maturation of these axons by d65 in culture, correlates with reduced levels of axonal proteins involved in translation and an inability to respond by increased translation of regeneration promoting axonal mRNAs released from stress granules. Together, our results provide evidence that, as in development and in the PNS, local translation contributes to CNS axon regeneration.

Association of microtubules and axonal RNA transferred from myelinating Schwann cells in rat sciatic nerve

Transference of RNAs and ribosomes from Schwann cell-to-axon was demonstrated in normal and regenerating peripheral nerves. Previously, we have shown that RNAs transfer is dependent on F-actin cytoskeleton and Myosin Va. Here, we explored the contribution of microtubules to newly synthesized RNAs transport from Schwann cell nuclei up to nodal microvilli in sciatic nerves. Results using immunohistochemistry and quantitative confocal FRET analysis indicate that Schwann cell-derived RNAs co-localize with microtubules in Schwann cell cytoplasm. Additionally, transport of Schwann cell-derived RNAs is nocodazole and colchicine sensitive demonstrating its dependence on microtubule network integrity. Moreover, mRNAs codifying neuron-specific proteins are among Schwann cell newly synthesized RNAs population, and some of them are associated with KIF1B and KIF5B microtubules-based motors.

Cell-to-Cell Communication in Learning and Memory: From Neuro- and Glio-Transmission to Information Exchange Mediated by Extracellular Vesicles

Most aspects of nervous system development and function rely on the continuous crosstalk between neurons and the variegated universe of non-neuronal cells surrounding them. The most extraordinary property of this cellular community is its ability to undergo adaptive modifications in response to environmental cues originating from inside or outside the body. Such ability, known as neuronal plasticity, allows long-lasting modifications of the strength, composition and efficacy of the connections between neurons, which constitutes the biochemical base for learning and memory. Nerve cells communicate with each other through both wiring (synaptic) and volume transmission of signals. It is by now clear that glial cells, and in particular astrocytes, also play critical roles in both modes by releasing different kinds of molecules (e.g., D-serine secreted by astrocytes). On the other hand, neurons produce factors that can regulate the activity of glial cells, including their ability to release regulatory molecules. In the last fifteen years it has been demonstrated that both neurons and glial cells release extracellular vesicles (EVs) of different kinds, both in physiologic and pathological conditions. Here we discuss the possible involvement of EVs in the events underlying learning and memory, in both physiologic and pathological conditions.

Central Nervous System Remyelination: Roles of Glia and Innate Immune Cells

In diseases such as multiple sclerosis (MS), inflammation can injure the myelin sheath that surrounds axons, a process known as demyelination. The spontaneous regeneration of myelin, called remyelination, is associated with restoration of function and prevention of axonal degeneration. Boosting remyelination with therapeutic intervention is a promising new approach that is currently being tested in several clinical trials. The endogenous regulation of remyelination is highly dependent on the immune response. In this review article, we highlight the cell biology of remyelination and its regulation by innate immune cells. For the purpose of this review, we discuss the roles of microglia, and also astrocytes and oligodendrocyte progenitor cells (OPCs) as they are being increasingly recognized to have immune cell functions.

Identification of key target genes and biological pathways in multiple sclerosis brains using microarray data obtained from the Gene Expression Omnibus database

OBJECTIVE

The purpose of this study was to investigate critical genes in multiple sclerosis (MS) using microarray data from brain tissue in MS.

MATERIALS

The expression profile data set of MS (GSE38010) downloaded from the Gene Expression Omnibus database contained gene information from five plaque tissues from MS brains and two white matter tissues from healthy controls. An R package was applied to process these raw chip data. Gene Ontology (GO) functional analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis and protein-protein interaction (PPI) network analysis were performed to investigate interactions between differentially expressed genes (DEGs) in MS brain tissues.

RESULTS

This study identified a total of 1065 DEGs, including 530 up-regulated genes and 535 down-regulated genes, in MS brain tissue samples compared to those in normal white matter tissue samples. GO and KEGG pathway enrichment analyses showed that the up-regulated DEGs were mainly related to neuron development, neuron projection morphogenesis and neuron differentiation. Furthermore, the down-regulated DEGs were largely related to axon ensheathment, ensheathment of neurons and nervous system development. Seven key genes were found as hub genes in the maintenance of the PPI network.

CONCLUSION

Several key target genes and their GO and KEGG pathway enrichment identified in the present study may serve as feasible targets for MS therapies.

Remyelination therapies: a new direction and challenge in multiple sclerosis

Multiple sclerosis is characterized by inflammatory activity that results in destruction of the myelin sheaths that enwrap axons. The currently available medications for multiple sclerosis are predominantly immune-modulating and do not directly promote repair. White matter regeneration, or remyelination, is a new and exciting potential approach to treating multiple sclerosis, as remyelination repairs the damaged regions of the central nervous system. A wealth of new strategies in animal models that promote remyelination, including the repopulation of oligodendrocytes that produce myelin, has led to several clinical trials to test new reparative therapies. In this Review, we highlight the biology of, and obstacles to, remyelination. We address new strategies to improve remyelination in preclinical models, highlight the therapies that are currently undergoing clinical trials and discuss the challenges of objectively measuring remyelination in trials of repair in multiple sclerosis.