Enhancing remyelination in disease--can we wrap it up?

Transcriptional profiles of mouse oligodendrocyte precursor cells across the lifespan

Oligodendrocyte progenitor cells (OPCs) are highly dynamic, widely distributed glial cells of the central nervous system responsible for generating myelinating oligodendrocytes throughout life. However, the rates of OPC proliferation and differentiation decline dramatically with aging, which may impair homeostasis, remyelination and adaptive myelination during learning. To determine how aging influences OPCs, we generated a transgenic mouse line (Matn4-mEGFP) and performed single-cell RNA sequencing, providing enhanced resolution of transcriptional changes during key transitions from quiescence to proliferation and differentiation across the lifespan. We found that aging induces distinct transcriptomic changes in OPCs in different states, including enhanced activation of HIF-1α and WNT pathways. Pharmacological inhibition of these pathways in aged OPCs was sufficient to increase their ability to differentiate in vitro. Ultimately, Matn4-mEGFP mouse line and the sequencing dataset of cortical OPCs across ages will help to define the molecular changes guiding OPC behavior in various physiological and pathological contexts.

Design, current states, and challenges of nanomaterials in anti-neuroinflammation: A perspective on Alzheimer's disease

Alzheimer's disease (AD), an age-related neurodegenerative disease, brings huge damage to the society, to the whole family and even to the patient himself. However, until now, the etiological factor of AD is still unknown and there is no effective treatment for it. Massive deposition of amyloid-beta peptide(Aβ) and hyperphosphorylation of Tau proteins are acknowledged pathological features of AD. Recent studies have revealed that neuroinflammation plays a pivotal role in the pathology of AD. With the rise of nanomaterials in the biomedical field, researchers are exploring how the unique properties of these materials can be leveraged to develop effective treatments for AD. This article has summarized the influence of neuroinflammation in AD, the design of nanoplatforms, and the current research status and inadequacy of nanomaterials in improving neuroinflammation in AD.

Imaging Demyelinated Axons After Spinal Cord Injuries with PET Tracer [18F]3F4AP

Spinal cord injuries (SCIs) often lead to lifelong disability. Among the various types of injuries, incomplete and discomplete injuries, where some axons remain intact, offer potential for recovery. However, demyelination of these spared axons can worsen disability. Demyelination is a reversible phenomenon, and drugs such as 4-aminopyridine (4AP), which target K+ channels in demyelinated axons, show that conduction can be restored. Yet, accurately assessing and monitoring demyelination after SCI remains challenging because of the lack of suitable imaging methods. In this study, we introduce a novel approach using the PET tracer, 3-[18F]fluoro-4-aminopyridine ([18F]3F4AP), specifically targeting K+ channels in demyelinated axons for SCI imaging. Methods: Rats with incomplete contusion injuries were imaged with [18F]3F4AP PET up to 1 mo after injury, followed by further validation of PET imaging results with autoradiography and immunohistochemistry of postmortem spinal cord tissue. A proof-of-concept study in 2 human subjects with incomplete injuries of different severities and etiologies was also performed. Results: [18F]3F4AP PET of SCI rats revealed a more than 2-fold increase in tracer binding highly localized to the injured segment of the cord at 7 d after injury relative to baseline (SUV ratio = 2.49 ± 0.09 for 7 d after injury vs. 1.14 ± 0.10 for baseline), revealing [18F]3F4AP's exceptional sensitivity to injury and its ability to detect temporal changes. Autoradiography, histology, and immunohistochemistry confirmed [18F]3F4AP's targeting of demyelinated axons. In humans, [18F]3F4AP differentiated between a severe and a largely recovered incomplete injury, indicating axonal loss and demyelination, respectively. Moreover, alterations in tracer delivery were evident on dynamic PET images, suggestive of differences in spinal cord blood flow between the injuries. Conclusion: [18F]3F4AP demonstrates efficacy in detecting incomplete SCI in both animal models and humans. The potential for monitoring post-SCI demyelination changes and response to therapy underscores the utility of [18F]3F4AP in advancing our understanding and management of SCI.

Blood-brain barrier dysfunction in multiple system atrophy: A human postmortem study

Multiple system atrophy (MSA) is a rare neurodegenerative disease characterized by an accumulation of phosphorylated α-synuclein (p-αsyn) in oligodendrocytes in the form of glial cytoplasmic inclusions (GCIs). In MSA, not only mature oligodendrocytes but also oligodendrocyte precursor cells (OPCs) are affected. The latter play an important role in remyelination by differentiating into mature oligodendrocytes, as well as maintaining the blood-brain barrier (BBB) by promoting the expression of tight junction proteins. We have hypothesized that in MSA, the BBB is impaired as a result of aberrant interactions between affected OPCs and the cerebral vasculature. To verify this hypothesis, we conducted a neuropathological examination of postmortem brains from MSA patients and control subjects, focusing on the primary motor area, one of the main regions affected in MSA. Using double immunofluorescence, we quantified the expression of tight junction protein claudin-5 in capillary endothelial cells and found that it was significantly lower in MSA than in controls in both the gray matter and white matter. Furthermore, a significantly higher amount of fibrinogen was extravasated into the brain parenchyma in MSA patients than in controls. In addition, leakage of IgG was detected almost specifically in MSA brain parenchyma, as visualized in three dimensions by combining techniques of chemical tissue clearing and light sheet microscopy. Finally, we confirmed accumulation of p-αsyn-positive GCIs along the cerebral vasculature within OPCs. These results suggest that BBB dysfunction and associated fibrinogen extravasation are constant findings in MSA, presumably triggered by the deposition of p-αsyn in perivascular OPCs.

Brain white matter damage biomarkers

White matter (WM), constituting nearly half of the human brain's mass, is pivotal for the rapid transmission of neural signals across different brain regions, significantly influencing cognitive processes like learning, memory, and problem-solving. The integrity of WM is essential for brain function, and its damage, which can occur due to conditions such as multiple sclerosis (MS), stroke, and traumatic brain injury, results in severe neurological deficits and cognitive decline. The primary objective of this book chapter is to discuss the clinical significance of fluid biomarkers in assessing WM damage within the central nervous system (CNS). It explores the biological underpinnings and pathological changes in WM due to various neurological conditions and details how alterations can be detected and quantified through fluid biomarkers. By examining biomarkers like Myelin Basic Protein (MBP), Neurofilament light chain (NFL), and others, the chapter highlights their role in enhancing diagnostic precision, monitoring disease progression, and guiding therapeutic interventions, thus providing crucial insights into maintaining WM integrity and preventing cognitive and physical disabilities.

Transcriptional profiles of murine oligodendrocyte precursor cells across the lifespan

Oligodendrocyte progenitor cells (OPCs) are highly dynamic, widely distributed glial cells of the central nervous system (CNS) that are responsible for generating myelinating oligodendrocytes during development. By also generating new oligodendrocytes in the adult CNS, OPCs allow formation of new myelin sheaths in response to environmental and behavioral changes and play a crucial role in regenerating myelin following demyelination (remyelination). However, the rates of OPC proliferation and differentiation decline dramatically with aging, which may impair homeostasis, remyelination, and adaptive myelination during learning. To determine how aging influences OPCs, we generated a novel transgenic mouse line that expresses membrane-anchored EGFP under the endogenous promoter/enhancer of Matrilin-4 (Matn4-mEGFP) and performed high-throughput single-cell RNA sequencing, providing enhanced resolution of transcriptional changes during key transitions from quiescence to proliferation and differentiation across the lifespan. Comparative analysis of OPCs isolated from mice aged 30 to 720 days, revealed that aging induces distinct inflammatory transcriptomic changes in OPCs in different states, including enhanced activation of HIF-1α and Wnt pathways. Inhibition of these pathways in acutely isolated OPCs from aged animals restored their ability to differentiate, suggesting that this enhanced signaling may contribute to the decreased regenerative potential of OPCs with aging. This Matn4-mEGFP mouse line and single-cell mRNA datasets of cortical OPCs across ages help to define the molecular changes guiding their behavior in various physiological and pathological contexts.

Imaging demyelinated axons after spinal cord injuries with PET tracer [ 18 F]3F4AP

Spinal cord injuries (SCI) often lead to lifelong disability. Among the various types of injuries, incomplete and discomplete injuries, where some axons remain intact, offer potential for recovery. However, demyelination of these spared axons can worsen disability. Demyelination is a reversible phenomenon, and drugs like 4-aminopyridine (4AP), which target K+ channels in demyelinated axons, show that conduction can be restored. Yet, accurately assessing and monitoring demyelination post-SCI remains challenging due to the lack of suitable imaging methods. In this study, we introduce a novel approach utilizing the positron emission tomography (PET) tracer, [ 18 F]3F4AP, specifically targeting K+ channels in demyelinated axons for SCI imaging. Rats with incomplete contusion injuries were imaged up to one month post-injury, revealing [ 18 F]3F4AP's exceptional sensitivity to injury and its ability to detect temporal changes. Further validation through autoradiography and immunohistochemistry confirmed [ 18 F]3F4AP's targeting of demyelinated axons. In a proof-of-concept study involving human subjects, [ 18 F]3F4AP differentiated between a severe and a largely recovered incomplete injury, indicating axonal loss and demyelination, respectively. Moreover, alterations in tracer delivery were evident on dynamic PET images, suggestive of differences in spinal cord blood flow between the injuries. In conclusion, [ 18 F]3F4AP demonstrates efficacy in detecting incomplete SCI in both animal models and humans. The potential for monitoring post-SCI demyelination changes and response to therapy underscores the utility of [ 18 F]3F4AP in advancing our understanding and management of spinal cord injuries.

p38γ MAPK delays myelination and remyelination and is abundant in multiple sclerosis lesions

Multiple sclerosis is a chronic inflammatory disease in which disability results from the disruption of myelin and axons. During the initial stages of the disease, injured myelin is replaced by mature myelinating oligodendrocytes that differentiate from oligodendrocyte precursor cells. However, myelin repair fails in secondary and chronic progressive stages of the disease and with ageing, as the environment becomes progressively more hostile. This may be attributable to inhibitory molecules in the multiple sclerosis environment including activation of the p38MAPK family of kinases. We explored oligodendrocyte precursor cell differentiation and myelin repair using animals with conditional ablation of p38MAPKγ from oligodendrocyte precursors. We found that p38γMAPK ablation accelerated oligodendrocyte precursor cell differentiation and myelination. This resulted in an increase in both the total number of oligodendrocytes and the migration of progenitors ex vivo and faster remyelination in the cuprizone model of demyelination/remyelination. Consistent with its role as an inhibitor of myelination, p38γMAPK was significantly downregulated as oligodendrocyte precursor cells matured into oligodendrocytes. Notably, p38γMAPK was enriched in multiple sclerosis lesions from patients. Oligodendrocyte progenitors expressed high levels of p38γMAPK in areas of failed remyelination but did not express detectable levels of p38γMAPK in areas where remyelination was apparent. Our data suggest that p38γ could be targeted to improve myelin repair in multiple sclerosis.

Visual outcome measures in clinical trials of remyelinating drugs

One of the most promising approaches to delay, prevent or reverse disability progression in multiple sclerosis (MS) is to enhance endogenous remyelination and limit axonal degeneration. In clinical trials of remyelinating drugs, there is a need for reliable, sensitive and clinically relevant outcome measures. The visual pathway, which is frequently affected by MS, provides a unique model system to evaluate remyelination of acute and chronic MS lesions in vivo and non-invasively. In this review, we discuss the different measures that have been used and scrutinise visual outcome measure selection in current and future remyelination trials.

Transforming growth factor-β1 protects against white matter injury and reactive astrogliosis via the p38 MAPK pathway in rodent demyelinating model

In central nervous system (CNS), demyelination is a pathological process featured with a loss of myelin sheaths around axons, which is responsible for the diseases of multiple sclerosis, neuromyelitis optica, and so on. Transforming growth factor-beta1 (TGF-β1) is a multifunctional cytokine participating in abundant physiological and pathological processes in CNS. However, the effects of TGF-β1 on CNS demyelinating disease and its underlying mechanisms are controversial and not well understood. Herein, we evaluated the protective potential of TGF-β1 in a rodent demyelinating model established by lysophosphatidylcholine (LPC) injection. It was identified that supplement of TGF-β1 evidently rescued the cognitive deficit and motor dysfunction in LPC modeling mice assessed by novel object recognition and balance beam behavioral tests. Besides, quantified by luxol fast blue staining, immunofluorescence, and western blot, administration of TGF-β1 was found to significantly ameliorate the demyelinating lesion and reactive astrogliosis by suppressing p38 MAPK pathway. Mechanistically, the results of in vitro experiments indicated that treatment of TGF-β1 could directly promote the differentiation and migration of cultured oligodendrocytes. Our study revealed that modulating TGF-β1 activity might serve as a promising and innovative therapeutic strategy in CNS demyelinating diseases.

Potential of Nano-Engineered Stem Cells in the Treatment of Multiple Sclerosis: A Comprehensive Review

Multiple sclerosis (MS) is a chronic and degrading autoimmune disorder mainly targeting the central nervous system, leading to progressive neurodegeneration, demyelination, and axonal damage. Current treatment options for MS are limited in efficacy, generally linked to adverse side effects, and do not offer a cure. Stem cell therapies have emerged as a promising therapeutic strategy for MS, potentially promoting remyelination, exerting immunomodulatory effects and protecting against neurodegeneration. Therefore, this review article focussed on the potential of nano-engineering in stem cells as a therapeutic approach for MS, focusing on the synergistic effects of combining stem cell biology with nanotechnology to stimulate the proliferation of oligodendrocytes (OLs) from neural stem cells and OL precursor cells, by manipulating neural signalling pathways-PDGF, BMP, Wnt, Notch and their essential genes such as Sox, bHLH, Nkx. Here we discuss the pathophysiology of MS, the use of various types of stem cells in MS treatment and their mechanisms of action. In the context of nanotechnology, we present an overview of its applications in the medical and research field and discuss different methods and materials used to nano-engineer stem cells, including surface modification, biomaterials and scaffolds, and nanoparticle-based delivery systems. We further elaborate on nano-engineered stem cell techniques, such as nano script, nano-exosome hybrid, nano-topography and their potentials in MS. The article also highlights enhanced homing, engraftment, and survival of nano-engineered stem cells, targeted and controlled release of therapeutic agents, and immunomodulatory and tissue repair effects with their challenges and limitations. This visual illustration depicts the process of utilizing nano-engineering in stem cells and exosomes for the purpose of delivering more accurate and improved treatments for Multiple Sclerosis (MS). This approach targets specifically the creation of oligodendrocytes, the breakdown of which is the primary pathological factor in MS.

Oligodendrocyte progenitor cells differentiation induction with MAPK/ERK inhibitor fails to support repair processes in the chronically demyelinated CNS

Remyelination failure is considered a major obstacle in treating chronic-progressive multiple sclerosis (MS). Studies have shown blockage in the differentiation of resident oligodendrocyte progenitor cells (OPC) into myelin-forming cells, suggesting that pushing OPC into a differentiation program might be sufficient to overcome remyelination failure. Others stressed the need for a permissive environment to allow proper activation, migration, and differentiation of OPC. PD0325901, a MAPK/ERK inhibitor, was previously shown to induce OPC differentiation, non-specific immunosuppression, and a significant therapeutic effect in acute demyelinating MS models. We examined PD0325901 effects in the chronically inflamed central nervous system. Treatment with PD0325901 induced OPC differentiation into mature oligodendrocytes with high morphological complexity. However, treatment of Biozzi mice with chronic-progressive experimental autoimmune encephalomyelitis with PD0325901 showed no clinical improvement in comparison to the control group, no reduction in demyelination, nor induction of OPC migration into foci of demyelination. PD0325901 induced a direct general immunosuppressive effect on various cell populations, leading to a diminished phagocytic capability of microglia and less activation of lymph-node cells. It also significantly impaired the immune-modulatory functions of OPC. Our findings suggest OPC regenerative function depends on a permissive environment, which may include pro-regenerative inflammatory elements. Furthermore, they indicate that maintaining a delicate balance between the pro-myelinating and immune functions of OPC is of importance. Thus, the highly complex mission of creating a pro-regenerative environment depends upon an appropriate immune response controlled in time, place, and intensity. We suggest the need to employ a multi-systematic therapeutic approach, which cannot be achieved through a single molecule-based therapy.

Age-dependent changes on fractalkine forms and their contribution to neurodegenerative diseases

The chemokine fractalkine (FKN, CX3CL1), a member of the CX3C subfamily, contributes to neuron-glia interaction and the regulation of microglial cell activation. Fractalkine is expressed by neurons as a membrane-bound protein (mCX3CL1) that can be cleaved by extracellular proteases generating several sCX3CL1 forms. sCX3CL1, containing the chemokine domain, and mCX3CL1 have high affinity by their unique receptor (CX3CR1) which, physiologically, is only found in microglia, a resident immune cell of the CNS. The activation of CX3CR1contributes to survival and maturation of the neural network during development, glutamatergic synaptic transmission, synaptic plasticity, cognition, neuropathic pain, and inflammatory regulation in the adult brain. Indeed, the various CX3CL1 forms appear in some cases to serve an anti-inflammatory role of microglia, whereas in others, they have a pro-inflammatory role, aggravating neurological disorders. In the last decade, evidence points to the fact that sCX3CL1 and mCX3CL1 exhibit selective and differential effects on their targets. Thus, the balance in their level and activity will impact on neuron-microglia interaction. This review is focused on the description of factors determining the emergence of distinct fractalkine forms, their age-dependent changes, and how they contribute to neuroinflammation and neurodegenerative diseases. Changes in the balance among various fractalkine forms may be one of the mechanisms on which converge aging, chronic CNS inflammation, and neurodegeneration.

Selective PDE4 subtype inhibition provides new opportunities to intervene in neuroinflammatory versus myelin damaging hallmarks of multiple sclerosis

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system (CNS) characterized by focal inflammatory lesions and prominent demyelination. Even though the currently available therapies are effective in treating the initial stages of disease, they are unable to halt or reverse disease progression into the chronic progressive stage. Thus far, no repair-inducing treatments are available for progressive MS patients. Hence, there is an urgent need for the development of new therapeutic strategies either targeting the destructive immunological demyelination or boosting endogenous repair mechanisms. Using in vitro, ex vivo, and in vivo models, we demonstrate that selective inhibition of phosphodiesterase 4 (PDE4), a family of enzymes that hydrolyzes and inactivates cyclic adenosine monophosphate (cAMP), reduces inflammation and promotes myelin repair. More specifically, we segregated the myelination-promoting and anti-inflammatory effects into a PDE4D- and PDE4B-dependent process respectively. We show that inhibition of PDE4D boosts oligodendrocyte progenitor cells (OPC) differentiation and enhances (re)myelination of both murine OPCs and human iPSC-derived OPCs. In addition, PDE4D inhibition promotes in vivo remyelination in the cuprizone model, which is accompanied by improved spatial memory and reduced visual evoked potential latency times. We further identified that PDE4B-specific inhibition exerts anti-inflammatory effects since it lowers in vitro monocytic nitric oxide (NO) production and improves in vivo neurological scores during the early phase of experimental autoimmune encephalomyelitis (EAE). In contrast to the pan PDE4 inhibitor roflumilast, the therapeutic dose of both the PDE4B-specific inhibitor A33 and the PDE4D-specific inhibitor Gebr32a did not trigger emesis-like side effects in rodents. Finally, we report distinct PDE4D isoform expression patterns in human area postrema neurons and human oligodendroglia lineage cells. Using the CRISPR-Cas9 system, we confirmed that pde4d1/2 and pde4d6 are the key targets to induce OPC differentiation. Collectively, these data demonstrate that gene specific PDE4 inhibitors have potential as novel therapeutic agents for targeting the distinct disease processes of MS.

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.

Inhibition of CXCR2 enhances CNS remyelination via modulating PDE10A/cAMP signaling pathway

CXC chemokine receptor 2 (CXCR2) plays an important role in demyelinating diseases, but the detailed mechanisms were not yet clarified. In the present study, we mainly investigated the critical function and the potential molecular mechanisms of CXCR2 on oligodendrocyte precursor cell (OPC) differentiation and remyelination. The present study demonstrated that inhibiting CXCR2 significantly enhanced OPC differentiation and remyelination in primary cultured OPCs and ethidium bromide (EB)-intoxicated rats by facilitating the formation of myelin proteins, including PDGFRα, MBP, MAG, MOG, and Caspr. Further investigation identified phosphodiesterase 10A (PDE10A) as a main downstream protein of CXCR2, interacting with the receptor to regulate OPC differentiation, in that inhibition of CXCR2 reduced PDE10A expression while suppression of PDE10A did not affect CXCR2. Furthermore, inhibition of PDE10A promoted OPC differentiation, whereas overexpression of PDE10A down-regulated OPC differentiation. Our data also revealed that inhibition of CXCR2/PDE10A activated the cAMP/ERK1/2 signaling pathway, and up-regulated the expression of key transcription factors, including SOX10, OLIG2, MYRF, and ZFP24, that ultimately promoted remyelination and myelin protein biosynthesis. In conclusion, our findings suggested that inhibition of CXCR2 promoted OPC differentiation and enhanced remyelination by regulating PDE10A/cAMP/ERK1/2 signaling pathway. The present data also highlighted that CXCR2 may serve as a potential target for the treatment of demyelination diseases.

Uncovering mechanisms of brain inflammation in Alzheimer's disease with APOE4: Application of single cell-type lipidomics

A chronic state of unresolved inflammation in Alzheimer's disease (AD) is intrinsically involved with the remodeling of brain lipids. This review highlights the effect of carrying the apolipoprotein E ε4 allele (APOE4) on various brain cell types in promoting an unresolved inflammatory state. Among its pleotropic effects on brain lipids, we focus on APOE4's activation of Ca²⁺ -dependent phospholipase A2 (cPLA2) and its effects on arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid signaling cascades in the brain. During the process of neurodegeneration, various brain cell types, such as astrocytes, microglia, and neurons, together with the neurovascular unit, develop distinct inflammatory phenotypes that impact their functions and have characteristic lipidomic fingerprints. We propose that lipidomic phenotyping of single cell-types harvested from brains differing by age, sex, disease severity stage, and dietary and genetic backgrounds can be employed to probe mechanisms of neurodegeneration. A better understanding of the brain cellular inflammatory/lipidomic response promises to guide the development of nutritional and drug interventions for AD dementia.

Stem cell therapy for cuprizone model of multiple sclerosis focusing on the effectiveness of different injection methods and cell labeling

Multiple Sclerosis (MS) is a chronic and autoimmune disease of the central nervous system that causes inflammation in the brain and spinal cord, progressive degeneration of central nervous system tissue, damage to neuronal axons, and loss of function of central nervous system neurons. Experimental encephalomyelitis is an alternative animal model of MS that can simulate the symptoms of this disease. Cuprizone is one of the factors creating this model. Various researchers are testing the use of different cells to reduce the symptoms of cuprizone-demyelinated mice. The different injection methods explained in this article include intracerebral, intraperitoneal, intravenous, and intranasal. The intracerebral method, in contrast to the intranasal method, was widely employed by researchers. In each technique, the researchers try to inject a specific type of stem cell (SC) and monitor their efficiency. For monitoring SCs various labeling procedures are available, however, there is an upward trend in using magnetic resonance imaging (MRI). Two main barriers to using this method are high cost and complexity. In the current review, we try to make review cell therapy in the cuprizone model of MS.

Thyroid hormone-dependent oligodendroglial cell lineage genomic and non-genomic signaling through integrin receptors

Multiple sclerosis (MS) is a heterogeneous autoimmune disease whereby the pathological sequelae evolve from oligodendrocytes (OLs) within the central nervous system and are targeted by the immune system, which causes widespread white matter pathology and results in neuronal dysfunction and neurological impairment. The progression of this disease is facilitated by a failure in remyelination following chronic demyelination. One mediator of remyelination is thyroid hormone (TH), whose reliance on monocarboxylate transporter 8 (MCT8) was recently defined. MCT8 facilitates the entry of THs into oligodendrocyte progenitor cell (OPC) and pre-myelinating oligodendrocytes (pre-OLs). Patients with MS may exhibit downregulated MCT8 near inflammatory lesions, which emphasizes an inhibition of TH signaling and subsequent downstream targeted pathways such as phosphoinositide 3-kinase (PI3K)-Akt. However, the role of the closely related mammalian target of rapamycin (mTOR) in pre-OLs during neuroinflammation may also be central to the remyelination process and is governed by various growth promoting signals. Recent research indicates that this may be reliant on TH-dependent signaling through β1-integrins. This review identifies genomic and non-genomic signaling that is regulated through mTOR in TH-responsive pre-OLs and mature OLs in mouse models of MS. This review critiques data that implicates non-genomic Akt and mTOR signaling in response to TH-dependent integrin receptor activation in pre-OLs. We have also examined whether this can drive remyelination in the context of neuroinflammation and associated sequelae. Importantly, we outline how novel therapeutic small molecules are being designed to target integrin receptors on oligodendroglial lineage cells and whether these are viable therapeutic options for future use in clinical trials for MS.

Exploring the Pro-Phagocytic and Anti-Inflammatory Functions of PACAP and VIP in Microglia: Implications for Multiple Sclerosis

Multiple sclerosis (MS) is a chronic neuroinflammatory and demyelinating disease of the central nervous system (CNS), characterised by the infiltration of peripheral immune cells, multifocal white-matter lesions, and neurodegeneration. In recent years, microglia have emerged as key contributors to MS pathology, acting as scavengers of toxic myelin/cell debris and modulating the inflammatory microenvironment to promote myelin repair. In this review, we explore the role of two neuropeptides, pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP), as important regulators of microglial functioning during demyelination, myelin phagocytosis, and remyelination, emphasising the potential of these neuropeptides as therapeutic targets for the treatment of MS.

Emerging therapeutic role of chondroitinase (ChABC) in neurological disorders and cancer

Abstract:

Proteoglycans are essential biomacromolecules that participate in matrix structure and organization, cell proliferation and migration, and cell surface signal transduction. However, their roles in physiology, particularly in CNS remain incompletely deciphered. Numerous studies highlight the elevated levels of chondroitin sulphate proteoglycans (CSPGs) in various diseases like cancers and neurological disorders like spinal cord injury (SCI), traumatic brain damage, neurodegenerative diseases, and are mainly implicated to hinder tissue repair. In such a context, chondroitinase ABC (ChABC), a therapeutic enzyme has shown immense hope to treat these diseases in several preclinical studies, primarily attributed to the digestion of the side chains of the proteoglycan chondroitin sulphate (CS) molecule. Despite extensive research, the progress in evolving the concept of therapeutic targeting of proteoglycans is still in its infancy. This review thus provides fresh insights into the emerging therapeutic applications of ChABC in various diseases apart from SCI and the underlying mechanisms.

Newly Identified Deficiencies in the Multiple Sclerosis Central Nervous System and Their Impact on the Remyelination Failure

The pathogenesis of multiple sclerosis (MS) remains enigmatic and controversial. Myelin sheaths in the central nervous system (CNS) insulate axons and allow saltatory nerve conduction. MS brings about the destruction of myelin sheaths and the myelin-producing oligodendrocytes (ODCs). The conundrum of remyelination failure is, therefore, crucial in MS. In this review, the roles of epidermal growth factor (EGF), normal prions, and cobalamin in CNS myelinogenesis are briefly summarized. Thereafter, some findings of other authors and ourselves on MS and MS-like models are recapitulated, because they have shown that: (a) EGF is significantly decreased in the CNS of living or deceased MS patients; (b) its repeated administration to mice in various MS-models prevents demyelination and inflammatory reaction; (c) as was the case for EGF, normal prion levels are decreased in the MS CNS, with a strong correspondence between liquid and tissue levels; and (d) MS cobalamin levels are increased in the cerebrospinal fluid, but decreased in the spinal cord. In fact, no remyelination can occur in MS if these molecules (essential for any form of CNS myelination) are lacking. Lastly, other non-immunological MS abnormalities are reviewed. Together, these results have led to a critical reassessment of MS pathogenesis, partly because EGF has little or no role in immunology.

Microglia Impede Oligodendrocyte Generation in Aged Brain

Purpose

Age-related increase in myelin loss may be responsible for brain atrophy, and the mechanism is not completely understood. We aim to comprehensively delineate oligodendrocyte heterogeneity in young and aged mice and to reveal the underlying mechanism for myelin loss during aging.

Methods

Diffusion tensor imaging and immunofluorescent staining were performed to verify the demyelination in the aged brains of both rodents and human. Further, the single-cell RNA sequencing data of all brain cells from young and aged mice were deeply analyzed to identify the subsets of oligodendrocyte lineage cells. Cell-to-cell interaction analysis was performed to detect the mechanism of observed changes in oligodendrocyte generation.

Results

Oligodendrocytes were observed to up-regulate several senescence associated genes in aged brain. Four clusters of oligodendrocyte precursor cells (OPCs) were identified in both young and aged brains. The number of those OPCs in basal state was significantly increased, while the OPCs in the procedure of differentiation were immensely decreased in aged brain. Furthermore, it was identified that activated microglia in the aged brain released inflammatory factors to suppress OPC differentiation. Stat1 might be a potential target to transform senescent microglia into tissue repair type to promote oligodendrocyte generation.

Conclusion

These results provided a perspective on how age activated microglia could impede remyelination and might give a new therapeutic target for age-related remyelinating diseases.

Treatment With CD52 Antibody Protects Neurons in Experimental Autoimmune Encephalomyelitis Mice During the Recovering Phase

Multiple sclerosis (MS) is a chronic autoimmune disease driven by T and B lymphocytes. The remyelination failure and neurodegeneration results in permanent clinical disability in MS patients. A desirable therapy should not only modulate the immune system, but also promote neuroprotection and remyelination. To investigate the neuroprotective effect of CD52 antibody in MS, both C57BL/6J and SJL mice with experimental autoimmune encephalomyelitis (EAE) were treated with CD52 antibody at the peak of disease. Treatment with CD52 antibody depleted T but not B lymphocytes in the blood, reduced the infiltration of T lymphocytes and microglia/macrophages in the spinal cord. Anti-CD52 therapy attenuated EAE scores during the recovery phase. It protected neurons immediately after treatment (within 4 days) as shown by reducing the accumulation of amyloid precursor proteins. It potentially promoted remyelination as it increased the number of olig2/CC-1-positive mature oligodendrocytes and prevented myelin loss in the following days (e.g., 14 days post treatment). In further experiments, EAE mice with a conditional knockout of BDNF in neurons were administered with CD52 antibodies. Neuronal deficiency of BDNF attenuated the effect of anti-CD52 treatment on reducing EAE scores and inflammatory infiltration but did not affect anti-CD52 treatment-induced improvement of myelin coverage in the spinal cord. In summary, anti-CD52 therapy depletes CD4-positive T lymphocytes, prevents myelin loss and protects neurons in EAE mice. Neuronal BDNF regulates neuroprotective and anti-inflammatory effect of CD52 antibody in EAE mice.

Small molecule screening as an approach to encounter inefficient myelin repair

While current multiple sclerosis therapies are focused on immunomodulation, thereby slowing down disease progression, scientific interest has nowadays been shifted toward regenerative therapies aiming at reversing already existing deficits. The application of chemical compounds was proven to be valuable for the understanding of oligodendrogenesis and for exposing mechanisms that can boost remyelination. However, sufficient myelin repair has not been achieved yet, thus underscoring the need for more studies toward this unmet clinical goal. In this regard, many research groups have significantly contributed to the field via developing compound screening approaches or using single substances. We, here, present an overview of recent studies addressing the identification of myelin repair drugs and provide insights into technical aspects and identified substances.

Remyelination Trials: Are We Expecting the Unexpected?

Neuroaxonal loss is believed to underpin the progressive disability that characterizes multiple sclerosis (MS). While focal inflammatory demyelination is a principal cause of acute axonal transection and subsequent axonal degeneration, the gradual attrition of permanently demyelinated axons may also contribute to tissue damage, particularly in the progressive phase of the disease. Therefore, remyelination is considered a putative neuroprotective strategy. In this article, we review the potential pitfalls of remyelination trials, provide a framework for their appropriate design and temper the expectations, at times unrealistic, of researchers, regulators and the pharmaceutical industry.

Role of Multifocal Visually Evoked Potential as a Biomarker of Demyelination, Spontaneous Remyelination, and Myelin Repair in Multiple Sclerosis

Multiple sclerosis (MS) is a complex disease of the central nervous system (CNS), characterized by inflammation, demyelination, neuro-axonal loss, and gliosis. Inflammatory demyelinating lesions are a hallmark of the disease. Spontaneous remyelination, however, is often incomplete and strategies that promote remyelination are needed. As a result, accurate and sensitive in vivo measures of remyelination are necessary. The visual pathway provides a unique opportunity for in vivo assessment of myelin damage and repair in the MS-affected brain since it is highly susceptible to damage in MS and is a very frequent site of MS lesions. The visually evoked potential (VEP), an event-related potential generated by the striate cortex in response to visual stimulation, is uniquely placed to serve as a biomarker of the myelination along the visual pathway. The multifocal VEP (mfVEP) represents a most recent addition to the array of VEP stimulations. This article provides a current view on the role of mfVEP as a biomarker of demyelination, spontaneous remyelination, and myelin repair in MS.

Targeting innate immunity to protect and cure Alzheimer's disease: opportunities and pitfalls

Innate immunity has been the focus of many new directions to understand the mechanisms involved in the aetiology of brain diseases, especially Alzheimer's disease (AD). AD is a multifactorial disorder, with the innate immune response and neuroinflammation at the forefront of the pathology. Thus, microglial cells along with peripheral circulating monocytes and more generally the innate immune response have been the target of several pre-clinical and clinical studies. More than a decade ago, inhibiting innate immune cells was considered to be the critical angle for preventing and treating brain diseases. After the failing of numerous clinical trials and the discovery that it may actually be the opposite in various pre-clinical models, the field has changed considerably. Here, we present both sides of the story with a particular emphasis on the beneficial properties of innate immune cells and how they can be targeted to have neuroprotective properties.

Inhibition of Autophagy Flux Promotes Secretion of Chondroitin Sulfate Proteoglycans in Primary Rat Astrocytes

Following spinal cord injury (SCI), reactive astrocytes in the glial scar produce high levels of chondroitin sulfate proteoglycans (CSPGs), which are known to inhibit axonal regeneration. Transforming growth factor beta (TGFβ) is a well-known factor that induces the production of CSPGs, and in this study, we report a novel mechanism underlying TGFβ's effects on CSPG secretion in primary rat astrocytes. We observed increased TGFβ-induced secretion of the CSPGs neurocan and brevican, and this occurred simultaneously with inhibition of autophagy flux. In addition, we show that neurocan and brevican levels are further increased when TGFβ is administered in the presence of an autophagy inhibitor, Bafilomycin-A1, while they are reduced when cells are treated with a concentration of rapamycin that is not sufficient to induce autophagy. These findings suggest that TGFβ mediates its effects on CSPG secretion through autophagy pathways. They also represent a potential new approach to reduce CSPG secretion in vivo by targeting autophagy pathways, which could improve axonal regeneration after SCI.

ZEB2, the Mowat-Wilson Syndrome Transcription Factor: Confirmations, Novel Functions, and Continuing Surprises

After its publication in 1999 as a DNA-binding and SMAD-binding transcription factor (TF) that co-determines cell fate in amphibian embryos, ZEB2 was from 2003 studied by embryologists mainly by documenting the consequences of conditional, cell-type specific Zeb2 knockout (cKO) in mice. In between, it was further identified as causal gene causing Mowat-Wilson Syndrome (MOWS) and novel regulator of epithelial-mesenchymal transition (EMT). ZEB2's functions and action mechanisms in mouse embryos were first addressed in its main sites of expression, with focus on those that helped to explain neurodevelopmental and neural crest defects seen in MOWS patients. By doing so, ZEB2 was identified in the forebrain as the first TF that determined timing of neuro-/gliogenesis, and thereby also the extent of different layers of the cortex, in a cell non-autonomous fashion, i.e., by its cell-intrinsic control within neurons of neuron-to-progenitor paracrine signaling. Transcriptomics-based phenotyping of Zeb2 mutant mouse cells have identified large sets of intact-ZEB2 dependent genes, and the cKO approaches also moved to post-natal brain development and diverse other systems in adult mice, including hematopoiesis and various cell types of the immune system. These new studies start to highlight the important adult roles of ZEB2 in cell-cell communication, including after challenge, e.g., in the infarcted heart and fibrotic liver. Such studies may further evolve towards those documenting the roles of ZEB2 in cell-based repair of injured tissue and organs, downstream of actions of diverse growth factors, which recapitulate developmental signaling principles in the injured sites. Evident questions are about ZEB2's direct target genes, its various partners, and ZEB2 as a candidate modifier gene, e.g., in other (neuro)developmental disorders, but also the accurate transcriptional and epigenetic regulation of its mRNA expression sites and levels. Other questions start to address ZEB2's function as a niche-controlling regulatory TF of also other cell types, in part by its modulation of growth factor responses (e.g., TGFβ/BMP, Wnt, Notch). Furthermore, growing numbers of mapped missense as well as protein non-coding mutations in MOWS patients are becoming available and inspire the design of new animal model and pluripotent stem cell-based systems. This review attempts to summarize in detail, albeit without discussing ZEB2's role in cancer, hematopoiesis, and its emerging roles in the immune system, how intense ZEB2 research has arrived at this exciting intersection.

Targeting integrated stress response regulates microglial M1/M2 polarization and attenuates neuroinflammation following surgical brain injury in rat

Integrated stress response (ISR) contributes to various neuropathological processes and acting as a therapy target in CNS injuries. However, the fundamental role of ISR in regulating microglial polarization remains largely unknown. Currently no proper pharmacological approaches to reverse microglia-driven neuroinflammation in surgical brain injury (SBI) have been reported. Here we found that inhibition of the crucial ISR effector, activating transcription factor 4 (ATF4), using the RNA interference suppressed the lipopolysaccharide (LPS)-stimulated microglial M1 polarization in vitro. Interestingly, counteracting ISR with a small-molecule ISR inhibitor (ISRIB) resulted in a significant microglial M1 towards M2 phenotype switching after LPS treatment. The potential underlying mechanisms may related to downregulate the intracellular NADPH oxidase 4 (NOX4) expression under the neuroinflammatory microenvironment. Notably, ISRIB ameliorated the infiltration of microglia and improved the neurobehavioral outcomes in the SBI rat model. Overall, our findings suggest that targeting ISR exerts a novel anti-inflammatory effect on microglia via regulating M1/M2 phenotype and may represent a potential therapeutic target to overcome neuroinflammation following SBI.

FGF/FGFR Pathways in Multiple Sclerosis and in Its Disease Models

Multiple sclerosis (MS) is a chronic inflammatory and neurodegenerative disease of the central nervous system (CNS) affecting more than two million people worldwide. In MS, oligodendrocytes and myelin sheaths are destroyed by autoimmune-mediated inflammation, while remyelination is impaired. Recent investigations of post-mortem tissue suggest that Fibroblast growth factor (FGF) signaling may regulate inflammation and myelination in MS. FGF2 expression seems to correlate positively with macrophages/microglia and negatively with myelination; FGF1 was suggested to promote remyelination. In myelin oligodendrocyte glycoprotein (MOG)35-55-induced experimental autoimmune encephalomyelitis (EAE), systemic deletion of FGF2 suggested that FGF2 may promote remyelination. Specific deletion of FGF receptors (FGFRs) in oligodendrocytes in this EAE model resulted in a decrease of lymphocyte and macrophage/microglia infiltration as well as myelin and axon degeneration. These effects were mediated by ERK/Akt phosphorylation, a brain-derived neurotrophic factor, and downregulation of inhibitors of remyelination. In the first part of this review, the most important pharmacotherapeutic principles for MS will be illustrated, and then we will review recent advances made on FGF signaling in MS. Thus, we will suggest application of FGFR inhibitors, which are currently used in Phase II and III cancer trials, as a therapeutic option to reduce inflammation and induce remyelination in EAE and eventually MS.

Thrombin generation and activity in multiple sclerosis

The coagulation cascade and immune system are intricately linked, highly regulated and respond cooperatively in response to injury and infection. Increasingly, evidence of hyper-coagulation has been associated with autoimmune disorders, including multiple sclerosis (MS). The pathophysiology of MS includes immune cell activation and recruitment to the central nervous system (CNS) where they degrade myelin sheaths, leaving neuronal axons exposed to damaging inflammatory mediators. Breakdown of the blood-brain barrier (BBB) facilitates the entry of peripheral immune cells. Evidence of thrombin activity has been identified within the CNS of MS patients and studies using animal models of experimental autoimmune encephalomyelitis (EAE), suggest increased thrombin generation and activity may play a role in the pathogenesis of MS as well as inhibit remyelination processes. Thrombin is a serine protease capable of cleaving multiple substrates, including protease activated receptors (PARs), fibrinogen, and protein C. Cleavage of all three of these substrates represent pathways through which thrombin activity may exert immuno-regulatory effects and regulate permeability of the BBB during MS and EAE. In this review, we summarize evidence that thrombin activity directly, through PARs, and indirectly, through fibrin formation and activation of protein C influences neuro-immune responses associated with MS and EAE pathology.

Identification of novel myelin repair drugs by modulation of oligodendroglial differentiation competence

BACKGROUND

In multiple sclerosis loss of myelin and oligodendrocytes impairs saltatory signal transduction and leads to neuronal loss and functional deficits. Limited capacity of oligodendroglial precursor cells to differentiate into mature cells is the main reason for inefficient myelin repair in the central nervous system. Drug repurposing constitutes a powerful approach for identification of pharmacological compounds promoting this process.

METHODS

A phenotypic compound screening using the subcellular distribution of a potent inhibitor of oligodendroglial cell differentiation, namely p57kip2, as differentiation competence marker was conducted. Hit compounds were validated in terms of their impact on developmental cell differentiation and myelination using both rat and human primary cell cultures and organotypic cerebellar slice cultures, respectively. Their effect on spontaneous remyelination was then investigated following cuprizone-mediated demyelination of the corpus callosum.

FINDINGS

A number of novel small molecules able to promote oligodendroglial cell differentiation were identified and a subset was found to foster human oligodendrogenesis as well as myelination ex vivo. Among them the steroid danazol and the anthelminthic parbendazole were found to increase myelin repair.

INTERPRETATION

We provide evidence that early cellular processes involved in differentiation decisions are applicable for the identification of regeneration promoting drugs and we suggest danazol and parbendazole as potent therapeutic candidates for demyelinating diseases.

FUNDING

This work was supported by the Jürgen Manchot Foundation, Düsseldorf; Research Commission of the Medical Faculty of Heinrich-Heine-University Düsseldorf; Christiane and Claudia Hempel Foundation; Stifterverband/Novartisstiftung; James and Elisabeth Cloppenburg, Peek and Cloppenburg Düsseldorf Stiftung and International Progressive MS Alliance (BRAVEinMS).

Opposing and potentially antagonistic effects of BMP and TGF-β in multiple sclerosis: The "Yin and Yang" of neuro-immune Signaling

Bone Morphogenetic Proteins (BMP) and Transforming Growth Factor-beta (TGF-β) are cytokines with similar receptors and messengers. They are important for immune cell function, with BMPs exerting mainly proinflammatory but also anti-inflammatory effects, and TGF-β suppressing inflammation. Patients with Multiple Sclerosis exhibit BMP overactivity and suppressed TGF-β signaling. This dysregulated signaling participates in the crosstalk between infiltrating immune cells and glia, where BMP inhibits remyelination. Reciprocal antagonism between the two pathways takes place via a variety of mechanisms. Although this antagonism has not been studied in the setting of Multiple Sclerosis, it could inform further research and treatment discovery.

Leprosy piRnome: exploring new possibilities for an old disease

Leprosy, which is caused by the human pathogen Mycobacterium leprae, causes nerve damage, deformity and disability in over 200,000 people every year. Because of the long doubling time of M. leprae (13 days) and the delayed onset of detectable symptoms, which is estimated to be approximately 3-7 years after infection, there is always a large percentage of subclinically infected individuals in the population who will eventually develop the disease, mainly in endemic countries. piRNAs comprise the largest group of small noncoding RNAs found in humans, and they are distinct from microRNAs (miRNAs) and small interfering RNAs (siRNAs). piRNAs function in transposon silencing, epigenetic regulation, and germline development. The functional role of piRNAs and their associated PIWI proteins have started to emerge in the development of human cancers and viral infections, but their relevance to bacterial diseases has not been investigated. The present study reports the piRNome of human skin, revealing that all but one of the piRNAs examined are downregulated in leprosy skin lesions. Considering that one of the best characterized functions of piRNAs in humans is posttranscriptional mRNA silencing, their functions are similar to what we have described for miRNAs, including acting on apoptosis, M. leprae recognition and engulfment, Schwann cell (SC) demyelination, epithelial-mesenchymal transition (EMT), loss of sensation and neuropathic pain. In addition to new findings on leprosy physiopathology, the discovery of relevant piRNAs involved in disease processes in human skin may provide new clues for therapeutic targets, specifically to control nerve damage, a prominent feature of leprosy that has no currently available pharmaceutical treatment.

Secretome Analysis of Mesenchymal Stem Cell Factors Fostering Oligodendroglial Differentiation of Neural Stem Cells In Vivo

Mesenchymal stem cell (MSC)-secreted factors have been shown to significantly promote oligodendrogenesis from cultured primary adult neural stem cells (aNSCs) and oligodendroglial precursor cells (OPCs). Revealing underlying mechanisms of how aNSCs can be fostered to differentiate into a specific cell lineage could provide important insights for the establishment of novel neuroregenerative treatment approaches aiming at myelin repair. However, the nature of MSC-derived differentiation and maturation factors acting on the oligodendroglial lineage has not been identified thus far. In addition to missing information on active ingredients, the degree to which MSC-dependent lineage instruction is functional in vivo also remains to be established. We here demonstrate that MSC-derived factors can indeed stimulate oligodendrogenesis and myelin sheath generation of aNSCs transplanted into different rodent central nervous system (CNS) regions, and furthermore, we provide insights into the underlying mechanism on the basis of a comparative mass spectrometry secretome analysis. We identified a number of secreted proteins known to act on oligodendroglia lineage differentiation. Among them, the tissue inhibitor of metalloproteinase type 1 (TIMP-1) was revealed to be an active component of the MSC-conditioned medium, thus validating our chosen secretome approach.

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

BACKGROUND

Studies 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.

METHODS

Mice 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.

RESULTS

The 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.

CONCLUSIONS

Our 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.

Combinatory Multifactor Treatment Effects on Primary Nanofiber Oligodendrocyte Cultures

Multiple sclerosis (MS) is a chronic inflammatory demyelinating and neurodegenerative disease of the central nervous system. Neurological deficits are attributed to inflammatory demyelination, which compromises axonal function and survival. These are mitigated in experimental models by rapid and often complete remyelination of affected axons, but in MS this endogenous repair mechanism frequently fails, leaving axons increasingly vulnerable to the detrimental effects of inflammatory and metabolic stress. Understanding the molecular basis of remyelination and remyelination failure is essential to develop improved therapies for this devastating disease. However, recent studies suggest that this is not due to a single dominant mechanism, but rather represents the biological outcome of multiple changes in the lesion microenvironment that combine to disrupt oligodendrocyte differentiation. This identifies a pressing need to develop technical platforms to investigate combinatory and/or synergistic effects of factors differentially expressed in MS lesions on oligodendrocyte proliferation and differentiation. Here we describe protocols using primary oligodendrocyte cultures from Bl6 mice on 384-well nanofiber plates to model changes affecting oligodendrogenesis and differentiation in the complex signaling environment associated with multiple sclerosis lesions. Using platelet-derived growth factor (PDGF–AA), fibroblast growth factor 2 (FGF2), bone morphogenetic protein 2 (BMP2) and bone morphogenetic protein 4 (BMP4) as representative targets, we demonstrate that we can assess their combinatory effects across a wide range of concentrations in a single experiment. This in vitro model is ideal for assessing the combinatory effects of changes in availability of multiple factors, thus more closely modelling the situation in vivo and furthering high-throughput screening possibilities.

The Molecular Basis for Remyelination Failure in Multiple Sclerosis

Myelin sheaths in the central nervous system (CNS) insulate axons and thereby allow saltatory nerve conduction, which is a prerequisite for complex brain function. Multiple sclerosis (MS), the most common inflammatory autoimmune disease of the CNS, leads to the destruction of myelin sheaths and the myelin-producing oligodendrocytes, thus leaving behind demyelinated axons prone to injury and degeneration. Clinically, this process manifests itself in significant neurological symptoms and disability. Resident oligodendroglial precursor cells (OPCs) and neural stem cells (NSCs) are present in the adult brain, and can differentiate into mature oligodendrocytes which then remyelinate the demyelinated axons. However, for multiple reasons, in MS the regenerative capacity of these cell populations diminishes significantly over time, ultimately leading to neurodegeneration, which currently remains untreatable. In addition, microglial cells, the resident innate immune cells of the CNS, can contribute further to inflammatory and degenerative axonal damage. Here, we review the molecular factors contributing to remyelination failure in MS by inhibiting OPC and NSC differentiation or modulating microglial behavior.

Tissue Transglutaminase Promotes Early Differentiation of Oligodendrocyte Progenitor Cells

Demyelinated lesions of the central nervous system are characteristic for multiple sclerosis (MS). Remyelination is not very effective, particular at later stages of the disease, which results in a chronic neurodegenerative character with worsening of symptoms. Previously, we have shown that the enzyme Tissue Transglutaminase (TG2) is downregulated upon differentiation of oligodendrocyte progenitor cells (OPCs) into myelin-forming oligodendrocytes and that TG2 knock-out mice lag behind in remyelination after cuprizone-induced demyelination. Here, we examined whether astrocytic or oligodendroglial TG2 affects OPCs in a cell-specific manner to modulate their differentiation, and therefore myelination. Our findings indicate that human TG2-expressing astrocytes did not modulate OPC differentiation and myelination. In contrast, persistent TG2 expression upon OPC maturation or exogenously added recombinant TG2 accelerated OPC differentiation and myelin membrane formation. Continuous exposure of recombinant TG2 to OPCs at different consecutive developmental stages, however, decreased OPC differentiation and myelin membrane formation, while it enhanced myelination in dorsal root ganglion neuron-OPC co-cultures. In MS lesions, TG2 is absent in OPCs, while human OPCs show TG2 immunoreactivity during brain development. Exposure to the MS-relevant pro-inflammatory cytokine IFN-γ increased TG2 expression in OPCs and prolonged expression of endogenous TG2 upon differentiation. However, despite the increased TG2 levels, OPC maturation was not accelerated, indicating that TG2-mediated OPC differentiation may be counteracted by other pathways. Together, our data show that TG2, either endogenously expressed, or exogenously supplied to OPCs, accelerates early OPC differentiation. A better understanding of the role of TG2 in the OPC differentiation process during MS is of therapeutic interest to overcome remyelination failure.

Yoga as an intervention to manage multiple sclerosis symptoms

Multiple sclerosis (MS) is an autoimmune, demyelinating, inflammatory disease of central nervous system (CNS) which is characterized by spasticity, fatigue, depression, anxiety, bowel and bladder dysfunction, impaired mobility, cognitive impairment etc. and affects approximately 2.5 million people worldwide. Disease modifying therapies for MS which help in preventing accumulation of lesions in white matter of CNS are costly and have significant adverse effects. Therefore, patients with MS are using complementary and alternative medicine (CAM) and Yoga is one of the most popular form of CAM which is being used immensely to reduce or overcome the symptoms of MS. In the current review attempted to present the potential impact of yoga practices on reducing MS related symptoms.

Inhibiting Bone Morphogenetic Protein 4 Type I Receptor Signaling Promotes Remyelination by Potentiating Oligodendrocyte Differentiation

Blocking inhibitory factors within CNS demyelinating lesions is regarded as a promising strategy to promote remyelination. Bone morphogenetic protein 4 (BMP4) is an inhibitory factor present in demyelinating lesions. Noggin, an endogenous antagonist to BMP, has previously been shown to increase the number of oligodendrocytes and promote remyelination in vivo. However, it remains unclear how BMP4 signaling inhibits remyelination. Here we investigated the downstream signaling pathway that mediates the inhibitory effect that BMP4 exerts upon remyelination through pharmacological and transgenic approaches. Using the cuprizone mouse model of central demyelination, we demonstrate that selectively blocking BMP4 signaling via the pharmacological inhibitor LDN-193189 significantly promotes oligodendroglial differentiation and the extent of remyelination in vivo. This was accompanied by the downregulation of transcriptional targets that suppress oligodendrocyte differentiation. Further, selective deletion of BMP receptor type IA (BMPRIA) within primary mouse oligodendrocyte progenitor cells (OPCs) significantly enhanced their differentiation and subsequent myelination in vitro. Together, the results of this study identify that BMP4 signals via BMPRIA within OPCs to inhibit oligodendroglial differentiation and their capacity to myelinate axons, and suggest that blocking the BMP4/BMPRIA pathway in OPCs is a promising strategy to promote CNS remyelination.

Oligodendroglial Lineage Cells in Thyroid Hormone-Deprived Conditions

Oligodendrocytes are supporting glial cells that ensure the metabolism and homeostasis of neurons with specific synaptic axoglial interactions in the central nervous system. These require key myelinating glial trophic signals important for growth and metabolism. Thyroid hormone (TH) is one such trophic signal that regulates oligodendrocyte maturation, myelination, and oligodendroglial synaptic dynamics via either genomic or nongenomic pathways. The intracellular and extracellular transport of TH is facilitated by a specific transmembrane transporter known as the monocarboxylate transporter 8 (MCT8). Dysfunction of the MCT8 due to mutation, inhibition, or downregulation during brain development leads to inherited hypomyelination, which manifests as psychomotor retardation in the X-linked inherited Allan-Herndon-Dudley syndrome (AHDS). In particular, oligodendroglial-specific MCT8 deficiency may restrict the intracellular T3 availability, culminating in deficient metabolic communication between the oligodendrocytes and the neurons they ensheath, potentially promulgating neurodegenerative adult diseases such as multiple sclerosis (MS). Based on the therapeutic effects exhibited by TH in various preclinical studies, particularly related to its remyelinating potential, TH has now entered the initial stages of a clinical trial to test the therapeutic efficacy in relapsing-remitting MS patients (NCT02506751). However, TH analogs, such as DITPA or Triac, may well serve as future therapeutic options to rescue mature oligodendrocytes and/or promote oligodendrocyte precursor cell differentiation in an environment of MCT8 deficiency within the CNS. This review outlines the therapeutic strategies to overcome the differentiation blockade of oligodendrocyte precursors and maintain mature axoglial interactions in TH-deprived conditions.

Phagocytosis in the Brain: Homeostasis and Disease

Microglia are resident macrophages of the central nervous system and significantly contribute to overall brain function by participating in phagocytosis during development, homeostasis, and diseased states. Phagocytosis is a highly complex process that is specialized for the uptake and removal of opsonized and non-opsonized targets, such as pathogens, apoptotic cells, and cellular debris. While the role of phagocytosis in mediating classical innate and adaptive immune responses has been known for decades, it is now appreciated that phagocytosis is also critical throughout early neural development, homeostasis, and initiating repair mechanisms. As such, modulating phagocytic processes has provided unexplored avenues with the intent of developing novel therapeutics that promote repair and regeneration in the CNS. Here, we review the functional consequences that phagocytosis plays in both the healthy and diseased CNS, and summarize how phagocytosis contributes to overall pathophysiological mechanisms involved in brain injury and repair.

The formation of a glial scar does not prohibit remyelination in an animal model of multiple sclerosis

The role of astrocytes in the pathophysiology of multiple sclerosis (MS) is discussed controversially. Especially the formation of the glial scar is often believed to act as a barrier for remyelination. At the same time, astrocytes are known to produce factors that influence oligodendrocyte precursor cell (OPC) survival. To explore these mechanisms, we investigated the astrocytic reaction in an animal model induced by immunization with myelin oligodendrocyte glycoprotein (MOG) in Dark Agouti (DA) rats, which mimics most of the histological features of MS. We correlated the astroglial reaction by immunohistochemistry (IHC) for glial fibrillary acidic protein (GFAP) to the remyelination capacity by in situ hybridization for mRNA of proteolipid protein (PLP), indicative of OPCs, over the full course of the disease. PLP mRNA peaked in early remyelinating lesions while the amount of GFAP positive astrocytes was highest in remyelinated lesions. In shadow plaques, we found at the same time all features of a glial scar and numbers of OPCs and mature oligodendrocytes, which were nearly equal to that in unaffected white matter areas. To assess the plaque environment, we furthermore quantitatively analyzed factors expressed by astrocytes previously suggested to influence remyelination. From our data, we conclude that remyelination occurs despite an abundant glial reaction in this animal model. The different patterns of astrocytic factors and the occurrence of different astrocytic phenotypes during lesion evolution furthermore indicate a finely regulated, balanced astrocytic involvement leading to successful repair.

Myelination in Multiple Sclerosis Lesions Is Associated with Regulation of Bone Morphogenetic Protein 4 and Its Antagonist Noggin

Remyelination is a central aspect of new multiple sclerosis (MS) therapies, in which one aims to alleviate disease symptoms by improving axonal protection. However, a central problem is mediators expressed in MS lesions that prevent effective remyelination. Bone morphogenetic protein4 (BMP4) inhibits the development of mature oligodendrocytes in cell culture and also blocks the expression of myelin proteins. Additionally, numerous studies have shown that Noggin (SYM1)—among other physiological antagonists of BMP4—plays a prominent role in myelin formation in the developing but also the adult central nervous system. Nonetheless, neither BMP4 nor Noggin have been systematically studied in human MS lesions. In this study, we demonstrated by transcript analysis and immunohistochemistry that BMP4 is expressed by astrocytes and microglia/macrophages in association with inflammatory infiltrates in MS lesions, and that astrocytes also express BMP4 in chronic inactive lesions that failed to remyelinate. Furthermore, the demonstration of an increased expression of Noggin in so-called shadow plaques (i.e., remyelinated lesions with thinner myelin sheaths) in comparison to chronically inactive demyelinated lesions implies that antagonizing BMP4 is associated with successful remyelination in MS plaques in humans. However, although BMP4 is strongly overexpressed in inflammatory lesion areas, its levels are also elevated in remyelinated lesion areas, which raises the possibility that BMP4 signaling itself may be required for remyelination. Therefore, remyelination might be influenced by a small number of key factors. Manipulating these molecules, i.e., BMP4 and Noggin, could be a promising therapeutic approach for effective remyelination.

Co-administration of aspirin and adipose-derived stem cell conditioned medium improves the functional recovery of the optic pathway in a lysolecithin-induced demyelination model

INTRODUCTION

Based on beneficial effects of aspirin and mesenchymal stem cells (MSCs) on myelin repair, in a preset study, effects of co-administration of aspirin and conditioned medium from adipose tissue-derived stem cells (ADSC-CM) on functional recovery of optic pathway, demyelination levels, and astrocytes' activation were evaluated in a lysolecithin (LPC)-induced demyelination model of optic chiasm.

METHODS

LPC (1%, 2 µL) was injected into the rat optic chiasm and animals underwent daily intraperitoneal (i.p.) injections of ADSCs-CM and oral gavage of aspirin at a dose of 25 mg/kg for 14 days post LPC injection. The conductivity of visual signals was assessed using visual evoked potential recordings (VEPs) before LPC injection and on days 7 and 14 post lesion. Immunostaining against PDGFRα as oligodendrocyte precursor cells marker, MOG as mature myelin marker, and GFAP as astrocyte marker was performed on brain sections at day 14 post LPC injection. FluoroMyelin staining was also used to measure the extent of demyelination areas.

RESULTS

Our results showed that administration of ADSCs-CM and aspirin significantly reduced the latency of VEP waves in LPC receiving animals. In addition, demyelination levels and GFAP expressing cells were attenuated while the number of oligodendrocyte precursor cells significantly increased in rats treated with ADSCs-CM and aspirin.

CONCLUSION

Overall, our results suggest that co-administration of ADSCs-CM and aspirin improves the functional recovery of optic pathway through amelioration of astrocyte activation and attenuation of demyelination level.