CXCR4 promotes differentiation of oligodendrocyte progenitors and remyelination

Activation of CXCR7 exerts an inhibitory effect on adipogenesis through regulation of β-arrestin2/Wnt and AKT signalling

CXCR7, an alternative receptor for the inflammatory chemokine SDF-1, is involved in cell proliferation and migration. Recent studies have reported that CXCR7 also plays a role in adipose tissue. However, evidence regarding the role of CXCR7 and its ligands in adipocyte differentiation is limited. In this study, we aimed to elucidate changes in CXCR7 expression during adipocyte differentiation and the role of the SDF-1/CXCR7/CXCR4 axis in adipogenesis using recombinant SDF-1, the CXCR7 ligand CCX771, and small interfering RNAs. The results indicated that the levels of SDF-1 and its receptors, CXCR7 and CXCR4, decreased during the early stages of adipogenesis. Treatment with recombinant SDF-1 and CCX771 inhibited adipogenesis and lipid accumulation by inducing β-arrestin2, Wnt expression, and AKT phosphorylation and downregulating C/EBPα, PPARγ, and FABP4 expression. In contrast, knockdown of SDF-1 and CXCR7 in preadipocytes downregulated the β-arrestin2/Wnt and AKT pathway, leading to the induction of adipogenesis. Meanwhile, knockdown of CXCR4 had no significant effect. In mice, basal gene expression levels of SDF-1 and CXCR7 were higher in the stromal vascular fraction compared to mature adipocytes and were significantly upregulated by a high-fat diet. Our results provide new insights into the local role of the SDF-1-CXCR7 axis in adipocytes and offer additional benefits for the prevention of obesity-related metabolic disorders.

A Sox2 enhancer cluster regulates region-specific neural fates from mouse embryonic stem cells

Sex-determining region Y box 2 (Sox2) is a critical transcription factor for embryogenesis and neural stem and progenitor cell (NSPC) maintenance. While distal enhancers control Sox2 in embryonic stem cells (ESCs), enhancers closer to the gene are implicated in Sox2 transcriptional regulation in neural development. We hypothesize that a downstream enhancer cluster, termed Sox2 regulatory regions 2-18 (SRR2-18), regulates Sox2 transcription in neural stem cells and we investigate this in NSPCs derived from mouse ESCs. Using functional genomics and CRISPR-Cas9-mediated deletion analyses, we investigate the role of SRR2-18 in Sox2 regulation during neural differentiation. Transcriptome analyses demonstrate that the loss of even 1 copy of SRR2-18 disrupts the region-specific identity of NSPCs, reducing the expression of genes associated with more anterior regions of the embryonic nervous system. Homozygous deletion of this Sox2 neural enhancer cluster causes reduced SOX2 protein, less frequent interaction with transcriptional machinery, and leads to perturbed chromatin accessibility genome-wide further affecting the expression of neurodevelopmental and anterior-posterior regionalization genes. Furthermore, homozygous NSPC deletants exhibit self-renewal defects and impaired differentiation into cell types found in the brain. Altogether, our data define a cis-regulatory enhancer cluster controlling Sox2 transcription in NSPCs and highlight the sensitivity of neural differentiation processes to decreased Sox2 transcription, which causes differentiation into posterior neural fates, specifically the caudal neural tube. This study highlights the importance of precise Sox2 regulation by SRR2-18 in neural differentiation.

Distant origin of glioblastoma recurrence: neural stem cells in the subventricular zone serve as a source of tumor reconstruction after primary resection

Glioblastoma (GBM) is the most aggressive and common type of primary malignant brain cancer in adults. GBM often recurs locally near the resection cavity (RC) following the surgical removal of primary tumors. Recent research has reported that neural stem cells (NSCs) in the subventricular zone (SVZ) harboring cancer-driving mutations serve as the cells of origin for human GBM. However, the pathological role of tumor-initiating NSCs in the SVZ in tumor recurrence remains to be elucidated. Here, we explore the potential contribution of mutation-harboring NSCs in the SVZ to tumor recurrence around the RC following surgical resection. Our hypothesis emerged from performing deep sequencing of longitudinal tissues from 10 patients with GBM, including (i) tumor-free SVZ tissue, (ii) primary tumor tissue, (iii) recurrent tumor tissue, and (iv) blood. As a result of this sequencing, we observed evidence suggesting that recurrent tumors show genetic links to the SVZ in 60% (6/10) of patients, which are distinct from the primary tumors. Using a genome-edited mouse model, we further identified that mutation-harboring NSCs appeared to migrate to the RC through the aberrant growth of oligodendrocyte progenitor cells, potentially contributing to the reconstruction of high-grade malignant gliomas in the RC. This process was associated with the CXCR4/CXCL12 axis, as supported by RNA sequencing data from human recurrent GBM. Taken together, our findings suggest that NSCs in human SVZ tissue may play a role in GBM recurrence, potentially highlighting a novel distant contributor of recurrence.

Multiple Sclerosis and Other Acquired Demyelinating Diseases of the Central Nervous System

Acquired demyelinating diseases of the central nervous system (CNS) comprise inflammatory conditions, including multiple sclerosis (MS) and related diseases, as well as noninflammatory conditions caused by toxic, metabolic, infectious, traumatic, and neurodegenerative insults. Here, we review the spectrum of diseases producing acquired CNS demyelination before focusing on the prototypical example of MS, exploring the pathologic mechanisms leading to myelin injury in relapsing and progressive MS and summarizing the mechanisms and modulators of remyelination. We highlight the complex interplay between the immune system, oligodendrocytes and oligodendrocyte progenitor cells (OPCs), and other CNS glia cells such as microglia and astrocytes in the pathogenesis and clinical course of MS. Finally, we review emerging therapeutic strategies that exploit our growing understanding of disease mechanisms to limit progression and promote remyelination.

Patient-centered brain transcriptomic and multimodal imaging determinants of clinical progression, physical activity, and treatment needs in Parkinson's disease

We continue to lack a clear understanding on how the biological and clinical complexity of Parkinson's disease emerges from molecular to macroscopic brain interactions. Here, we use personalized multiscale spatiotemporal computational brain models to characterize for the first time the synergistic links between genes, several multimodal neuroimaging-derived biological factors, clinical profiles, and therapeutic needs in PD. We identified genes modulating PD-caused brain reorganization in dopamine transporter level, neuronal activity integrity, microstructure, dendrite density and tissue atrophy. Inter-individual heterogeneity in the identified gene-mediated biological mechanisms was associated with five distinct configurations of PD motor and non-motor symptoms. Notably, the protein-protein interaction networks underlying both brain phenotypic and symptom configurations in PD revealed distinct hub genes including MYC, CCNA2, CCDK1, SRC, STAT3 and PSMD4. We also studied the biological mechanisms associated with physical activities performance, observing that leisure and work activities are strongly related to neurotypical cholesterol homeostasis and inflammatory response processes, respectively. Finally, patient-tailored in silico gene perturbations revealed a set of putative disease-modifying drugs with potential to effectively treat PD across different biological levels, most of which are associated with dopamine reuptake and anti-inflammation. Our study constitutes the first self-contained multiscale spatiotemporal computational approach providing comprehensive insights into the complex multifactorial pathogenesis of PD, unraveling key biological modulators of physical and clinical deterioration, and serving as a blueprint for optimum drug selection at personalized level.

Oligodendrocytes, the Forgotten Target of Gene Therapy

If the billions of oligodendrocytes (OLs) populating the central nervous system (CNS) of patients could express their feelings, they would undoubtedly tell gene therapists about their frustration with the other neural cell populations, neurons, microglia, or astrocytes, which have been the favorite targets of gene transfer experiments. This review questions why OLs have been left out of most gene therapy attempts. The first explanation is that the pathogenic role of OLs is still discussed in most CNS diseases. Another reason is that the so-called ubiquitous CAG, CBA, CBh, or CMV promoters-widely used in gene therapy studies-are unable or poorly able to activate the transcription of episomal transgene copies brought by adeno-associated virus (AAV) vectors in OLs. Accordingly, transgene expression in OLs has either not been found or not been evaluated in most gene therapy studies in rodents or non-human primates. The aims of the current review are to give OLs their rightful place among the neural cells that future gene therapy could target and to encourage researchers to test the effect of OL transduction in various CNS diseases.

Should We Consider Neurodegeneration by Itself or in a Triangulation with Neuroinflammation and Demyelination? The Example of Multiple Sclerosis and Beyond

Neurodegeneration is preeminent in many neurological diseases, and still a major burden we fail to manage in patient's care. Its pathogenesis is complicated, intricate, and far from being completely understood. Taking multiple sclerosis as an example, we propose that neurodegeneration is neither a cause nor a consequence by itself. Mitochondrial dysfunction, leading to energy deficiency and ion imbalance, plays a key role in neurodegeneration, and is partly caused by the oxidative stress generated by microglia and astrocytes. Nodal and paranodal disruption, with or without myelin alteration, is further involved. Myelin loss exposes the axons directly to the inflammatory and oxidative environment. Moreover, oligodendrocytes provide a singular metabolic and trophic support to axons, but do not emerge unscathed from the pathological events, by primary myelin defects and cell apoptosis or secondary to neuroinflammation or axonal damage. Hereby, trophic failure might be an overlooked contributor to neurodegeneration. Thus, a complex interplay between neuroinflammation, demyelination, and neurodegeneration, wherein each is primarily and secondarily involved, might offer a more comprehensive understanding of the pathogenesis and help establishing novel therapeutic strategies for many neurological diseases and beyond.

Phospholipase D Family Member 4 Regulates Microglial Phagocytosis and Remyelination via the AKT Pathway in a Cuprizone-Induced Multiple Sclerosis Mouse Model

AIMS

Remyelination is an endogenous repair process that is often deficient in multiple sclerosis (MS). Stimulation of remyelination is thought to help limit the progression of MS. This study aimed to investigate the expression pattern and function of a microglial phagocytosis-related gene, phospholipase D family member 4 (PLD4), in a cuprizone (CPZ)-induced MS mouse model.

METHODS

The extent of remyelination was assessed using LFB staining. Myelin phagocytosis assay was used to investigate the effect of Pld4 on microglial phagocytic activity.

RESULTS

Pld4 was upregulated in the corpus callosum during demyelination and remyelination. AAV9-mediated Pld4 deficiency impaired remyelination and reduced the number of Olig2-positive cells. In the corpus callosum of Pld4-deficient mice, the microglial phagocytosis marker MAC2 was reduced, accompanied by inhibition of TrkA/AKT signaling. Similarly, the phagocytosis assay showed that Pld4 knockdown significantly inhibited myelin debris phagocytosis by BV2 cells. The AKT activator SC79 reversed the Pld4 deficiency-induced inhibition of microglial phagocytic activity and rescued the impaired remyelination in Pld4-deficient mice.

CONCLUSION

PLD4 is upregulated in CPZ-induced MS and modulates microglial phagocytosis and remyelination via the AKT pathway. Our findings provide experimental evidence for a better understanding of the molecular mechanism of MS.

Oligodendrocytes in central nervous system diseases: the effect of cytokine regulation

Cytokines including tumor necrosis factor, interleukins, interferons, and chemokines are abundantly produced in various diseases. As pleiotropic factors, cytokines are involved in nearly every aspect of cellular functions such as migration, survival, proliferation, and differentiation. Oligodendrocytes are the myelin-forming cells in the central nervous system and play critical roles in the conduction of action potentials, supply of metabolic components for axons, and other functions. Emerging evidence suggests that both oligodendrocytes and oligodendrocyte precursor cells are vulnerable to cytokines released under pathological conditions. This review mainly summarizes the effects of cytokines on oligodendrocyte lineage cells in central nervous system diseases. A comprehensive understanding of the effects of cytokines on oligodendrocyte lineage cells contributes to our understanding of central nervous system diseases and offers insights into treatment strategies.

Glial Cells as Key Regulators in Neuroinflammatory Mechanisms Associated with Multiple Sclerosis

Even though several highly effective treatments have been developed for multiple sclerosis (MS), the underlying pathological mechanisms and drivers of the disease have not been fully elucidated. In recent years, there has been a growing interest in studying neuroinflammation in the context of glial cell involvement as there is increasing evidence of their central role in disease progression. Although glial cell communication and proper function underlies brain homeostasis and maintenance, their multiple effects in an MS brain remain complex and controversial. In this review, we aim to provide an overview of the contribution of glial cells, oligodendrocytes, astrocytes, and microglia in the pathology of MS during both the activation and orchestration of inflammatory mechanisms, as well as of their synergistic effects during the repair and restoration of function. Additionally, we discuss how the understanding of glial cell involvement in MS may provide new therapeutic targets either to limit disease progression or to facilitate repair.

Oxygen and HIF1α-dependent SDF1 expression in primary astrocytes

In the naturally hypoxic in utero fetal environment of preterm infants, oxygen and oxygen-sensitive signaling pathways play an important role in brain development, with hypoxia-inducible factor-1α (HIF1α) being an important regulator. Early exposure to nonphysiological high oxygen concentrations by birth in room can induce HIF1α degradation and may affect neuronal and glial development. This involves the dysregulation of astroglial maturation and function, which in turn might contribute to oxygen-induced brain injury. In this study, we investigated the effects of early high oxygen exposure on astroglial maturation and, specifically, on astroglial stromal cell-derived factor 1 (SDF1) expression in vivo and in vitro. In our neonatal mouse model of hyperoxia preterm birth brain injury in vivo, high oxygen exposure affected astroglial development and cortical SDF1 expression. These results were further supported by reduced Sdf1 expression, impaired proliferation, decreased total cell number, and altered expression of astroglial markers in astrocytes in primary cultures grown under high oxygen conditions. Moreover, to mimic the naturally hypoxic in utero fetal environment, astroglial Sdf1 expression was increased after low oxygen exposure in vitro, which appears to be regulated by HIF1α activity. Additionally, the knockdown of Hif1α revealed HIF1α-dependent Sdf1 expression in vitro. Our results indicate HIF1α and oxygen-dependent chemokine expression in primary astrocytes and highlight the importance of oxygen conditions for brain development.

Fibulin-2 is an extracellular matrix inhibitor of oligodendrocytes relevant to multiple sclerosis

Impairment of oligodendrocytes and myelin contributes to neurological disorders including multiple sclerosis (MS), stroke, and Alzheimer's disease. Regeneration of myelin (remyelination) decreases the vulnerability of demyelinated axons, but this repair process commonly fails with disease progression. A contributor to inefficient remyelination is the altered extracellular matrix (ECM) in lesions, which remains to be better defined. We have identified fibulin-2 (FBLN2) as a highly upregulated ECM component in lesions of MS and stroke and in proteome databases of Alzheimer's disease and traumatic brain injury. Focusing on MS, the inhibitory role of FBLN2 was suggested in the experimental autoimmune encephalomyelitis (EAE) model, in which genetic FBLN2 deficiency improved behavioral recovery by promoting the maturation of oligodendrocytes and enhancing remyelination. Mechanistically, when oligodendrocyte progenitors were cultured in differentiation medium, FBLN2 impeded their maturation into oligodendrocytes by engaging the Notch pathway, leading to cell death. Adeno-associated virus deletion of FBLN2 in astrocytes improved oligodendrocyte numbers and functional recovery in EAE and generated new myelin profiles after lysolecithin-induced demyelination. Collectively, our findings implicate FBLN2 as a hitherto unrecognized injury-elevated ECM, and a therapeutic target, that impairs oligodendrocyte maturation and myelin repair.

Interplay between androgen and CXCR4 chemokine signaling in myelin repair

In men, reduced levels of testosterone are associated with the prevalence and progression of multiple sclerosis (MS), a chronic and disabling demyelinating disorder. Testosterone has been shown to promote myelin repair. Here, we demonstrate that the cooperation between testosterone and CXCR4 signaling involving astrocytes is required for myelin regeneration after focal demyelination produced in the ventral mouse spinal cord by the infusion of lysolecithin. The testosterone-dependent remyelination of axons by oligodendrocytes was accompanied by an increase in astrocytes expressing CXCR4, its ligand CXCL12 and the androgen receptor (AR) within the demyelinated area. Depriving males of their testosterone or pharmacological inhibition of CXCR4, with the selective antagonist AMD3100, prevented the appearance of astrocytes expressing CXCR4, CXCL12 and AR within the demyelinated area and the concomitant recruitment of myelin forming oligodendrocytes. Conditional genetic ablation of either CXCR4 or AR in astrocytes also completely blocked the formation of new myelin by oligodendrocytes. Interestingly, the gain of function mutation in CXCR4 causing WHIM syndrome allows remyelination to take place, even in the absence of testosterone, but its potentiating effects remained observable. After testosterone deprivation or CXCR4 inhibition, the absence of astrocytes within the demyelinated area led to the incursion of Schwann cells, most likely derived from spinal nerves, and the formation of peripheral nerve type myelin. In patients with progressive MS, astrocytes expressing CXCR4 and AR surrounded myelin lesions, and their presence opposed the incursion of Schwann cells. These results highlight a mechanism of promyelinating testosterone signaling and the importance of normalizing its levels in combined myelin repair therapies.

Astrocytes: Lessons Learned from the Cuprizone Model

A diverse array of neurological and psychiatric disorders, including multiple sclerosis, Alzheimer's disease, and schizophrenia, exhibit distinct myelin abnormalities at both the molecular and histological levels. These aberrations are closely linked to dysfunction of oligodendrocytes and alterations in myelin structure, which may be pivotal factors contributing to the disconnection of brain regions and the resulting characteristic clinical impairments observed in these conditions. Astrocytes, which significantly outnumber neurons in the central nervous system by a five-to-one ratio, play indispensable roles in the development, maintenance, and overall well-being of neurons and oligodendrocytes. Consequently, they emerge as potential key players in the onset and progression of a myriad of neurological and psychiatric disorders. Furthermore, targeting astrocytes represents a promising avenue for therapeutic intervention in such disorders. To gain deeper insights into the functions of astrocytes in the context of myelin-related disorders, it is imperative to employ appropriate in vivo models that faithfully recapitulate specific aspects of complex human diseases in a reliable and reproducible manner. One such model is the cuprizone model, wherein metabolic dysfunction in oligodendrocytes initiates an early response involving microglia and astrocyte activation, culminating in multifocal demyelination. Remarkably, following the cessation of cuprizone intoxication, a spontaneous process of endogenous remyelination occurs. In this review article, we provide a historical overview of studies investigating the responses and putative functions of astrocytes in the cuprizone model. Following that, we list previously published works that illuminate various aspects of the biology and function of astrocytes in this multiple sclerosis model. Some of the studies are discussed in more detail in the context of astrocyte biology and pathology. Our objective is twofold: to provide an invaluable overview of this burgeoning field, and, more importantly, to inspire fellow researchers to embark on experimental investigations to elucidate the multifaceted functions of this pivotal glial cell subpopulation.

Prophylactic effect of chronic immunosuppression in a mouse model of CSF-1 receptor-related leukoencephalopathy

Mutations leading to colony-stimulating factor-1 receptor (CSF-1R) loss-of-function or haploinsufficiency cause CSF1R-related leukoencephalopathy (CRL), an adult-onset disease characterized by loss of myelin and neurodegeneration, for which there is no effective therapy. Symptom onset usually occurs in the fourth decade of life and the penetrance of disease in carriers is high. However, familial studies have identified a few carriers of pathogenic CSF1R mutations that remain asymptomatic even in their seventh decade of life, raising the possibility that the development and severity of disease might be influenced by environmental factors. Here we report new cases in which long-term glucocorticoid treatment is associated with asymptomatic status in elder carriers of pathogenic CSF-1R mutations. The main objective of the present study was to investigate the link between chronic immunosuppression initiated pre-symptomatically and resistance to the development of symptomatic CRL, in the Csf1r+/- mouse model. We show that chronic prednisone administration prevents the development of memory, motor coordination and social interaction deficits, as well as the demyelination, neurodegeneration and microgliosis associated with these deficits. These findings are in agreement with the preliminary clinical observations and support the concept that pre-symptomatic immunosuppression is protective in patients carrying pathogenic CSF1R variants associated with CRL. Proteomic analysis of microglia and oligodendrocytes indicates that prednisone suppresses processes involved in microglial activation and alleviates senescence and improves fitness of oligodendrocytes. This analysis also identifies new potential targets for therapeutic intervention.

Glia Cells Control Olfactory Neurogenesis by Fine-Tuning CXCL12

Olfaction depends on lifelong production of sensory neurons from CXCR4 expressing neurogenic stem cells. Signaling by CXCR4 depends on the concentration of CXCL12, CXCR4's principal ligand. Here, we use several genetic models to investigate how regulation of CXCL12 in the olfactory stem cell niche adjusts neurogenesis. We identify subepithelial tissue and sustentacular cells, the olfactory glia, as main CXCL12 sources. Lamina propria-derived CXCL12 accumulates on quiescent gliogenic stem cells via heparan sulfate. Additionally, CXCL12 is secreted within the olfactory epithelium by sustentacular cells. Both sustentacular-cell-derived and lamina propria-derived CXCL12 are required for CXCR4 activation. ACKR3, a high-affinity CXCL12 scavenger, is expressed by mature glial cells and titrates CXCL12. The accurate adjustment of CXCL12 by ACKR3 is critical for CXCR4-dependent proliferation of neuronal stem cells and for proper lineage progression. Overall, these findings establish precise regulation of CXCL12 by glia cells as a prerequisite for CXCR4-dependent neurogenesis and identify ACKR3 as a scavenger influencing tissue homeostasis beyond embryonic development.

Research progress of neuroinflammation-related cells in traumatic brain injury: A review

Neuroinflammation after traumatic brain injury (TBI) is related to chronic neurodegenerative diseases and is one of the causes of acute secondary injury after TBI. Therefore, it is particularly important to clarify the role of cellular mechanisms in the neuroinflammatory response after TBI. The objective of this article is to understand the involvement of cells during the TBI inflammatory response (for instance, astrocytes, microglia, and oligodendrocytes) and shed light on the recent progress in the stimulation and interaction of granulocytes and lymphocytes, to provide a novel approach for clinical research. We searched articles in PubMed published between 1950 and 2023, using the following keywords: TBI, neuroinflammation, inflammatory cells, neuroprotection, clinical. Articles for inclusion in this paper were finalized based on their novelty, representativeness, and relevance to the main arguments of this review. We found that the neuroinflammatory response after TBI includes the activation of glial cells, the release of inflammatory mediators in the brain, and the recruitment of peripheral immune cells. These inflammatory responses not only induce secondary brain damage, but also have a role in repairing the nervous system to some extent. However, not all of the mechanisms of cell-to-cell interactions have been well studied. After TBI, clinical treatment cannot simply suppress the inflammatory response, and the inflammatory phenotype of patients' needs to be defined according to their specific conditions after injury. Clinical trials of personalized inflammation regulation therapy for specific patients should be carried out in order to improve the prognosis of patients.

Shaping the brain vasculature in development and disease in the single-cell era

The CNS critically relies on the formation and proper function of its vasculature during development, adult homeostasis and disease. Angiogenesis - the formation of new blood vessels - is highly active during brain development, enters almost complete quiescence in the healthy adult brain and is reactivated in vascular-dependent brain pathologies such as brain vascular malformations and brain tumours. Despite major advances in the understanding of the cellular and molecular mechanisms driving angiogenesis in peripheral tissues, developmental signalling pathways orchestrating angiogenic processes in the healthy and the diseased CNS remain incompletely understood. Molecular signalling pathways of the 'neurovascular link' defining common mechanisms of nerve and vessel wiring have emerged as crucial regulators of peripheral vascular growth, but their relevance for angiogenesis in brain development and disease remains largely unexplored. Here we review the current knowledge of general and CNS-specific mechanisms of angiogenesis during brain development and in brain vascular malformations and brain tumours, including how key molecular signalling pathways are reactivated in vascular-dependent diseases. We also discuss how these topics can be studied in the single-cell multi-omics era.

Upregulation of C-X-C motif chemokine 12 in the spinal cord alleviated the symptoms of experimental autoimmune encephalomyelitis in Lewis rats

Background

C-X-C motif chemokine 12 (CXCL12) is a chemokine that performs many functions. Studies have shown that CXCL12 can aggravate inflammatory symptoms in the central nervous system (CNS). Evidence also indicates that CXCL12 can promote the repair of myelin sheaths in the CNS in experimental autoimmune encephalomyelitis (EAE). Here, we investigated the function of CXCL12 in CNS inflammation by upregulating CXCL12 in the spinal cord and subsequently inducing EAE.

Materials and methods

CXCL12 upregulation in the spinal cords of Lewis rats was induced by the injection of adeno-associated virus 9 (AAV9)/eGFP-P2A-CXCL12 after intrathecal catheter implantation. Twenty-one days after AAV injection, EAE was induced and clinical score was collected; Immunofluorescence staining, WB and LFB-PAS staining were used to evaluate the effect of CXCL12 upregulation. In the in vitro study, oligodendrocyte precursor cells (OPCs) were harvested, cultured with CXCL12 and AMD3100, and subjected to immunofluorescence staining for functional assessment.

Results

CXCL12 was upregulated in the lumbar enlargement of the spinal cord by AAV injection. In each stage of EAE, upregulation of CXCL12 significantly alleviated clinical scores by inhibiting leukocyte infiltration and promoting remyelination. In contrast, the addition of AMD3100, which is a CXCR4 antagonist, inhibited the effect of CXCL12. In vitro, 10 ng/ml CXCL12 promoted the differentiation of OPCs into oligodendrocytes.

Conclusion

AAV-mediated upregulation of CXCL12 in the CNS can alleviate the clinical signs and symptoms of EAE and significantly decrease the infiltration of leukocytes in the peak stage of EAE. CXCL12 can promote the maturation and differentiation of OPCs into oligodendrocytes in vitro. These data indicate that CXCL12 effectively promotes remyelination in the spinal cord and decreases the signs and symptoms of EAE.

Heterochronic parabiosis reprograms the mouse brain transcriptome by shifting aging signatures in multiple cell types

Aging is a complex process involving transcriptomic changes associated with deterioration across multiple tissues and organs, including the brain. Recent studies using heterochronic parabiosis have shown that various aspects of aging-associated decline are modifiable or even reversible. To better understand how this occurs, we performed single-cell transcriptomic profiling of young and old mouse brains after parabiosis. For each cell type, we cataloged alterations in gene expression, molecular pathways, transcriptional networks, ligand-receptor interactions and senescence status. Our analyses identified gene signatures, demonstrating that heterochronic parabiosis regulates several hallmarks of aging in a cell-type-specific manner. Brain endothelial cells were found to be especially malleable to this intervention, exhibiting dynamic transcriptional changes that affect vascular structure and function. These findings suggest new strategies for slowing deterioration and driving regeneration in the aging brain through approaches that do not rely on disease-specific mechanisms or actions of individual circulating factors.

CNS remyelination and inflammation: From basic mechanisms to therapeutic opportunities

Remyelination, the myelin regenerative response that follows demyelination, restores saltatory conduction and function and sustains axon health. Its declining efficiency with disease progression in the chronic autoimmune disease multiple sclerosis (MS) contributes to the currently untreatable progressive phase of the disease. Although some of the bona fide myelin regenerative medicine clinical trials have succeeded in demonstrating proof-of-principle, none of these compounds have yet proceeded toward approval. There therefore remains a need to increase our understanding of the fundamental biology of remyelination so that existing targets can be refined and new ones discovered. Here, we review the role of inflammation, in particular innate immunity, in remyelination, describing its many and complex facets and discussing how our evolving understanding can be harnessed to translational goals.

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

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

Can the administration of platelet lysates to the brain help treat neurological disorders?

Neurodegenerative disorders of the central nervous system (CNS) and brain traumatic insults are characterized by complex overlapping pathophysiological alterations encompassing neuroinflammation, alterations of synaptic functions, oxidative stress, and progressive neurodegeneration that eventually lead to irreversible motor and cognitive dysfunctions. A single pharmacological approach is unlikely to provide a complementary set of molecular therapeutic actions suitable to resolve these complex pathologies. Recent preclinical data are providing evidence-based scientific rationales to support biotherapies based on administering neurotrophic factors and extracellular vesicles present in the lysates of human platelets collected from healthy donors to the brain. Here, we present the most recent findings on the composition of the platelet proteome that can activate complementary signaling pathways in vivo to trigger neuroprotection, synapse protection, anti-inflammation, antioxidation, and neurorestoration. We also report experimental data where the administration of human platelet lysates (HPL) was safe and resulted in beneficial neuroprotective effects in established rodent models of neurodegenerative diseases such as Parkinson's disease, Alzheimer's disease, traumatic brain injury, and stroke. Platelet-based biotherapies, prepared from collected platelet concentrates (PC), are emerging as a novel pragmatic and accessible translational therapeutic strategy for treating neurological diseases. Based on this assumption, we further elaborated on various clinical, manufacturing, and regulatory issues that need to be addressed to ensure the ethical supply, quality, and safety of HPL preparations for treating neurodegenerative and traumatic pathologies of the CNS. HPL made from PC may become a unique approach for scientifically based treatments of neurological disorders readily accessible in low-, middle-, and high-income countries.

Chemokine-Driven Migration of Pro-Inflammatory CD4+ T Cells in CNS Autoimmune Disease

Pro-inflammatory CD4⁺ T helper (Th) cells drive the pathogenesis of many autoimmune conditions. Recent advances have modified views of the phenotype of pro-inflammatory Th cells in autoimmunity, extending the breadth of known Th cell subsets that operate as drivers of these responses. Heterogeneity and plasticity within Th1 and Th17 cells, and the discovery of subsets of Th cells dedicated to production of other pro-inflammatory cytokines such as GM-CSF have led to these advances. Here, we review recent progress in this area and focus specifically upon evidence for chemokine receptors that drive recruitment of these various pro-inflammatory Th cell subsets to sites of autoimmune inflammation in the CNS. We discuss expression of specific chemokine receptors by subsets of pro-inflammatory Th cells and highlight which receptors may be tractable targets of therapeutic interventions to limit pathogenic Th cell recruitment in autoimmunity.

Oligodendrocyte Precursor Cells Transplantation Improves Stroke Recovery via Oligodendrogenesis, Neurite Growth and Synaptogenesis

Ischemic-induced white matter injury is strongly correlated with the poor neurological outcomes in stroke patients. The transplantation of oligodendrocyte precursor cells (OPCs) is an effective candidate for enhancing re-myelination in congenitally dysmyelinated brain and spinal cord. Nevertheless, mechanisms governing the recovery of white matter and axon after OPCs transplantation are incompletely understood in ischemic stroke. In this study, OPCs were transplanted into the ischemic brain at 7 days after transient middle cerebral artery occlusion (tMCAO). We observed improved behavior recovery and reduced brain atrophy volume at 28 days after OPCs transplantation. Moreover, our results identified that myelin sheath integrity and endogenous OPCs proliferation and migration were promoted after OPCs transplantation. By contrast, AMD3100, an antagonist of C-X-C chemokine receptor type 4, eliminated the beneficial effects of OPCs transplantation on white matter integrity and endogenous oligodendrogenesis. In addition, the improvement of neurite growth and synaptogenesis after OPCs transplantation in ischemic brain or OPC co-cultured neurons, potentially through the upregulation of Netrin-1, was indicated by increased protein levels of synaptophysin and postsynaptic density protein 95. Knockdown of Deleted in Colorectal Carcinoma, a receptor of Netrin-1, prevented increased neurite growth and synaptogenesis in neurons co-cultured with OPCs. In conclusion, our studies suggested that engrafted OPCs promoted the recovery after ischemic stroke by enhancing endogenous oligodendrogenesis, neurite growth, and synaptogenesis; the last two being mediated by the Netrin-1/DCC axis.

Subacute AMD3100 Treatment Is Not Efficient in Neonatal Hypoxic-Ischemic Rats

BACKGROUND AND PURPOSE

Despite the advances in treating neonatal hypoxic-ischemic encephalopathy (HIE) with induced hypothermia, the rates of severe disability are still high among survivors. Preclinical studies have indicated that cell therapies with hematopoietic stem/progenitor cells could improve neurological outcomes in HIE. In this study, we investigated whether the administration of AMD3100, a CXCR4 antagonist that mobilizes hematopoietic stem/progenitor cells into the circulation, has therapeutic effects in HIE.

METHODS

P10 Wistar rats of both sexes were subjected to right common carotid artery occlusion or sham procedure, and then were exposed to hypoxia for 120 minutes. Two subcutaneous injections of AMD3100 or vehicle were given on the third and fourth day after HIE. We first assessed the interindividual variability in brain atrophy after experimental HIE and vehicle treatment in a small cohort of rats. Based on this exploratory analysis, we designed and conducted an experiment to test the efficacy of AMD3100. Brain atrophy on day 21 after HIE was defined as the primary end point. Secondary efficacy end points were cognitive (T-water maze) and motor function (rotarod) on days 17 and 18 after HIE, respectively.

RESULTS

AMD3100 did not decrease the brain atrophy in animals of either sex. Cognitive impairments were not observed in the T-water maze, but male hypoxic-ischemic animals exhibited motor coordination deficits on the rotarod, which were not improved by AMD3100. A separate analysis combining data from animals of both sexes also revealed no evidence of the effectiveness of AMD3100 treatment.

CONCLUSIONS

These results indicate that the subacute treatment with AMD3100 does not improve structural and functional outcomes in a rat HIE model.

Mechanisms of oligodendrocyte progenitor developmental migration

Oligodendrocytes, the myelinating cells of the central nervous system (CNS), develop from oligodendrocyte progenitor cells (OPCs) that must first migrate extensively throughout the developing brain and spinal cord. Specified at particular times from discrete regions in the developing CNS, OPCs are one of the most migratory of cell types and disperse rapidly. A variety of factors act on OPCs to trigger intracellular changes that regulate their migration. We will discuss factors that act as long-range guidance cues, those that act to regulate cellular motility, and those that are critical in determining the final positioning of OPCs. In addition, recent evidence has identified the vasculature as the physical substrate used by OPCs for their migration. Several new findings relating to this oligodendroglial-vascular signaling axis reveal new insight on the relationship between OPCs and blood vessels in the developing and adult brain.

Glial PAMPering and DAMPening of Adult Hippocampal Neurogenesis

Adult neurogenesis represents a mature brain's capacity to integrate newly generated neurons into functional circuits. Impairment of neurogenesis contributes to the pathophysiology of various mood and cognitive disorders such as depression and Alzheimer's Disease. The hippocampal neurogenic niche hosts neural progenitors, glia, and vasculature, which all respond to intrinsic and environmental cues, helping determine their current state and ultimate fate. In this article we focus on the major immune communication pathways and mechanisms through which glial cells sense, interact with, and modulate the neurogenic niche. We pay particular attention to those related to the sensing of and response to innate immune danger signals. Receptors for danger signals were first discovered as a critical component of the innate immune system response to pathogens but are now also recognized to play a crucial role in modulating non-pathogenic sterile inflammation. In the neurogenic niche, viable, stressed, apoptotic, and dying cells can activate danger responses in neuroimmune cells, resulting in neuroprotection or neurotoxicity. Through these mechanisms glial cells can influence hippocampal stem cell fate, survival, neuronal maturation, and integration. Depending on the context, such responses may be appropriate and on-target, as in the case of learning-associated synaptic pruning, or excessive and off-target, as in neurodegenerative disorders.

Aberrant oligodendroglial LDL receptor orchestrates demyelination in chronic cerebral ischemia

Oligodendrocytes express low-density lipoprotein receptor (LDLR) to endocytose cholesterol for the maintenance of adulthood myelination. However, the potential role of LDLR in chronic cerebral ischemia-related demyelination remains unclear. We used bilateral carotid artery stenosis (BCAS) to induce sustained cerebral ischemia in mice. This hypoxic-ischemic injury caused a remarkable decrease in oligodendroglial LDLR, with impaired oligodendroglial differentiation and survival. Oligodendroglial cholesterol levels, however, remained unchanged. Mouse miR-344e-3p and the human homolog miR-410-3p, 2 miRNAs directly targeting Ldlr, were identified in experimental and clinical leukoaraiosis and were thus implicated in the LDLR reduction. Lentiviral delivery of LDLR ameliorated demyelination following chronic cerebral ischemia. By contrast, Ldlr-/- mice displayed inadequate myelination in the corpus callosum. Ldlr-/- oligodendrocyte progenitor cells (OPCs) exhibited reduced ability to differentiate and myelinate axons in vitro. Transplantation with Ldlr-/- OPCs could not rescue the BCAS-induced demyelination. Such LDLR-dependent myelin restoration might involve a physical interaction of the Asn-Pro-Val-Tyr (NPVY) motif with the phosphotyrosine binding domain of Shc, which subsequently activated the MEK/ERK pathway. Together, our findings demonstrate that the aberrant oligodendroglial LDLR in chronic cerebral ischemia impairs myelination through intracellular signal transduction. Preservation of oligodendroglial LDLR may provide a promising approach to treat ischemic demyelination.

Diversity of Adult Neural Stem and Progenitor Cells in Physiology and Disease

Adult neural stem and progenitor cells (NSPCs) contribute to learning, memory, maintenance of homeostasis, energy metabolism and many other essential processes. They are highly heterogeneous populations that require input from a regionally distinct microenvironment including a mix of neurons, oligodendrocytes, astrocytes, ependymal cells, NG2+ glia, vasculature, cerebrospinal fluid (CSF), and others. The diversity of NSPCs is present in all three major parts of the CNS, i.e., the brain, spinal cord, and retina. Intrinsic and extrinsic signals, e.g., neurotrophic and growth factors, master transcription factors, and mechanical properties of the extracellular matrix (ECM), collectively regulate activities and characteristics of NSPCs: quiescence/survival, proliferation, migration, differentiation, and integration. This review discusses the heterogeneous NSPC populations in the normal physiology and highlights their potentials and roles in injured/diseased states for regenerative medicine.

Exosomes derived from astrocytes after oxygen-glucose deprivation promote differentiation and migration of oligodendrocyte precursor cells in vitro

BACKGROUND

Excessive release of glutamate, oxidative stress, inflammation after ischemic brain injury can lead to demyelination. Astrocytes participate in the maturation and differentiation of oligodendrocyte precursor cells (OPCs), and play multiple roles in the process of demyelination and remyelination. Here, we studied the role of Astrocyte-derived exosomes (AS-Exo) under ischemic conditions in proliferation, differentiation and migration of OPCs in vitro.

METHODS AND RESULTS

Exosomes were collected from astrocytes supernatant by differential centrifugation from control astrocytes (CT^exo), mild hypoxia astrocytes (O2R24^exo) which were applied oxygen-glucose deprivation for 2 h and reperfusion for 24 h (OGD2hR24h) and severe hypoxia astrocytes (O4R24^exo) which were applied oxygen-glucose deprivation for 4 h and reperfusion for 24 h (OGD4hR24h). Exosomes (20 µg/ml) were co-cultured with OPCs for 24 h and their proliferation, differentiation and migration were detected. The results showed that AS-Exo under severe hypoxia (O4R24^exo) inhibit the proliferation of OPCs. Meanwhile, all exosomes from three groups can promote OPCs differentiation and migration. Compared to control, the expressions of MAG and MBP, markers of mature oligodendrocytes, were significantly increased in AS-Exo treatment groups. AS-Exo treatment significantly increased chemotaxis for OPCs.

CONCLUSIONS

AS-Exo improve OPCs' differentiation and migration, whereas AS-Exo with severe hypoxic precondition suppress OPCs' proliferation. AS-Exo may be a potential therapeutic target for myelin regeneration and repair in white matter injury or other demyelination related diseases.

Specific Blockade of Bone Morphogenetic Protein-2/4 Induces Oligodendrogenesis and Remyelination in Demyelinating Disorders

Oligodendrocyte precursor cells (OPCs) are present in demyelinated lesions of multiple sclerosis (MS) patients. However, their differentiation into functional oligodendrocytes is insufficient, and most lesions evolve into nonfunctional astroglial scars. Blockade of bone morphogenetic protein (BMP) signaling induces differentiation of OPCs into myelin-producing oligodendrocytes. We studied the effect of specific blockade of BMP-2/4 signaling, by intravenous (IV) treatment with anti-BMP-2/4 neutralizing mAb in both the inflammatory model of relapsing experimental autoimmune encephalomyelitis (R-EAE) and the cuprizone-toxic model of demyelination in mice. Administration of anti-BMP-2/4 to R-EAE-induced mice, on day 9 post-immunization (p.i.), ameliorated R-EAE signs, diminished the expression of phospho-SMAD1/5/8, primarily within the astrocytic lineage, increased the numbers of de novo immature and mature oligodendrocytes, and reduced the numbers of newly generated astrocytes within the spinal cord as early as day 18 p.i. This effect was accompanied with elevated remyelination, manifested by increased density of remyelinating axons (0.8 < g-ratios < 1), and reduced fully demyelinated and demyelinating axons, in the anti-BMP-2/4-treated R-EAE mice, studied by electron microscopy. No significant immunosuppressive effect was observed in the CNS and in the periphery, during the peak of the first attack, or at the end of the experiment. Moreover, IV treatment with anti-BMP-2/4 mAb in the cuprizone-challenged mice augmented the numbers of mature oligodendrocytes and remyelination in the corpus callosum during the recovery phase of the disease. Based on our findings, the specific blockade of BMP-2/4 has a therapeutic potential in demyelinating disorders such as MS, by inducing early oligodendrogenesis-mediated remyelination in the affected tissue.

Connecting Neuroinflammation and Neurodegeneration in Multiple Sclerosis: Are Oligodendrocyte Precursor Cells a Nexus of Disease?

The pathology in neurodegenerative diseases is often accompanied by inflammation. It is well-known that many cells within the central nervous system (CNS) also contribute to ongoing neuroinflammation, which can promote neurodegeneration. Multiple sclerosis (MS) is both an inflammatory and neurodegenerative disease in which there is a complex interplay between resident CNS cells to mediate myelin and axonal damage, and this communication network can vary depending on the subtype and chronicity of disease. Oligodendrocytes, the myelinating cell of the CNS, and their precursors, oligodendrocyte precursor cells (OPCs), are often thought of as the targets of autoimmune pathology during MS and in several animal models of MS; however, there is emerging evidence that OPCs actively contribute to inflammation that directly and indirectly contributes to neurodegeneration. Here we discuss several contributors to MS disease progression starting with lesion pathology and murine models amenable to studying particular aspects of disease. We then review how OPCs themselves can play an active role in promoting neuroinflammation and neurodegeneration, and how other resident CNS cells including microglia, astrocytes, and neurons can impact OPC function. Further, we outline the very complex and pleiotropic role(s) of several inflammatory cytokines and other secreted factors classically described as solely deleterious during MS and its animal models, but in fact, have many neuroprotective functions and promote a return to homeostasis, in part via modulation of OPC function. Finally, since MS affects patients from the onset of disease throughout their lifespan, we discuss the impact of aging on OPC function and CNS recovery. It is becoming clear that OPCs are not simply a bystander during MS progression and uncovering the active roles they play during different stages of disease will help uncover potential new avenues for therapeutic intervention.

Therapeutic Potential of Cytokines in Demyelinating Lesions After Stroke

White matter damage is a component of most human stroke and usually accounts for at least half of the lesion volume. Subcortical white matter stroke (WMS) accounts for 25% of all strokes and causes severe motor and cognitive dysfunction. The adult brain has a very limited ability to repair white matter damage. Pathological analysis shows that demyelination or myelin loss is the main feature of white matter injury and plays an important role in long-term sensorimotor and cognitive dysfunction. This suggests that demyelination is a major therapeutic target for ischemic stroke injury. An acute inflammatory reaction is triggered by brain ischemia, which is accompanied by cytokine production. The production of cytokines is an important factor affecting demyelination and myelin regeneration. Different cytokines have different effects on myelin damage and myelin regeneration. Exploring the role of cytokines in demyelination and remyelination after stroke and the underlying molecular mechanisms of demyelination and myelin regeneration after ischemic injury is very important for the development of rehabilitation treatment strategies. This review focuses on recent findings on the effects of cytokines on myelin damage and remyelination as well as the progress of research on the role of cytokines in ischemic stroke prognosis to provide a new treatment approach for amelioration of white matter damage after stroke.

Opioid Modulation of Neuronal Iron and Potential Contributions to NeuroHIV

Opioid use has substantially increased over recent years and remains a major driver of new HIV infections worldwide. Clinical studies indicate that opioids may exacerbate the symptoms of HIV-associated neurocognitive disorders (HAND), but the mechanisms underlying opioid-induced cognitive decline remain obscure. We recently reported that the μ-opioid agonist morphine increased neuronal iron levels and levels of ferritin proteins that store iron, suggesting that opioids modulate neuronal iron homeostasis. Additionally, increased iron and ferritin heavy chain protein were necessary for morphine's ability to reduce the density of thin and mushroom dendritic spines in cortical neurons, which are considered critical mediators of learning and memory, respectively. As altered iron homeostasis has been reported in HAND and related neurocognitive disorders like Alzheimer's, Parkinson's, and Huntington's disease, understanding how opioids regulate neuronal iron metabolism may help identify novel drug targets in HAND with potential relevance to these other neurocognitive disorders. Here, we review the known mechanisms of opioid-mediated regulation of neuronal iron and corresponding cellular responses and discuss the implications of these findings for patients with HAND. Furthermore, we discuss a new molecular approach that can be used to understand if opioid modulation of iron affects the expression and processing of amyloid precursor protein and the contributions of this pathway to HAND.

ACT-1004-1239, a first-in-class CXCR7 antagonist with both immunomodulatory and promyelinating effects for the treatment of inflammatory demyelinating diseases

Current strategies for the treatment of demyelinating diseases such as multiple sclerosis (MS) are based on anti-inflammatory or immunomodulatory drugs. Those drugs have the potential to reduce the frequency of new lesions but do not directly promote remyelination in the damaged central nervous system (CNS). Targeting CXCR7 (ACKR3) has been postulated as a potential therapeutic approach in demyelinating diseases, leading to both immunomodulation by reducing leukocyte infiltrates and promyelination by enhancing myelin repair. ACT-1004-1239 is a potent, selective, insurmountable, and orally available first-in-class CXCR7 receptor antagonist. The effect of ACT-1004-1239 was evaluated in the myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE) and the cuprizone-induced demyelination mouse models. In addition, ACT-1004-1239 was assessed in a rat oligodendrocyte precursor cell (OPC) differentiation assay in vitro. In the MOG-induced EAE model, ACT-1004-1239 treatment (10-100 mg/kg, twice daily, orally) showed a significant dose-dependent reduction in disease clinical scores, resulting in increased survival. At the highest dose tested (100 mg/kg, twice daily), ACT-1004-1239 delayed disease onset and significantly reduced immune cell infiltrates into the CNS and plasma neurofilament light chain concentration. Treatment with ACT-1004-1239 dose-dependently increased plasma CXCL12 concentration, which correlated with a reduction of the cumulative disease score. Furthermore, in the cuprizone model, ACT-1004-1239 treatment significantly increased the number of mature myelinating oligodendrocytes and enhanced myelination in vivo. In vitro, ACT-1004-1239 promoted the maturation of OPCs into myelinating oligodendrocytes. These results provide evidence that ACT-1004-1239 both reduces neuroinflammation and enhances myelin repair substantiating the rationale to explore its therapeutic potential in a clinical setting.

A comprehensive review on the role of chemokines in the pathogenesis of multiple sclerosis

Multiple sclerosis (MS) as a chronic inflammatory disorder of the central nervous system (CNS) is thought to be caused by the abnormal induction of immune responses. Chemokines as molecules that can engage leukocytes into the location of inflammation, actively participate in the pathogenesis of MS. Several members of this family of chemo attractants have been shown to be dysregulated in the peripheral blood, cerebrospinal fluid or CNS lesions of MS patients. Studies in animal models of MS particularly experimental autoimmune encephalomyelitis have indicated the critical roles of chemokines in the pathophysiology of MS. In the current review, we summarize the data regarding the role of CCL2, CCL3, CCL4, CCL11, CCL20, CXCL1, CXCL2, CXCL8, CXCL10, CXCL12 and CXCL13 in the pathogenesis of MS.

Regeneration using endogenous neural stem cells following neonatal brain injury

Despite recent advancements in perinatal care, the incidence of neonatal brain injury has not decreased. No therapies are currently available to repair injured brain tissues. In the postnatal brain, neural stem cells reside in the ventricular-subventricular zone (V-SVZ) and continuously generate new immature neurons (neuroblasts). After brain injury in rodents, V-SVZ-derived neuroblasts migrate toward the injured area using blood vessels as a scaffold. Notably, the neonatal V-SVZ has a remarkable neurogenic capacity. Furthermore, compared with the adult brain, after neonatal brain injury, larger numbers of neuroblasts migrate toward the lesion, raising the possibility that the V-SVZ could be a source for endogenous neuronal regeneration after neonatal brain injury. We recently demonstrated that efficient migration of V-SVZ-derived neuroblasts toward a lesion is supported by neonatal radial glia via neural cadherin (N-cadherin)-mediated neuron-fiber contact, which promotes RhoA activity. Moreover, providing blood vessel- and radial glia-mimetic scaffolds for migrating neuroblasts promotes neuronal migration and improves functional gait behaviors after neonatal brain injury. In the V-SVZ, oligodendrocyte progenitor cells (OPCs) are also generated and migrate toward the surrounding white matter, where they differentiate and form myelin. After white matter injury in rodents, the production and subsequent migration of V-SVZ-derived OPCs are enhanced. In the neonatal period, administration of growth factors at a specific time promotes oligodendrocyte regeneration and functional recovery after brain injury. These findings suggest that activating the high regenerative capacity that is specific to the neonatal period could lead to the development of new therapeutic strategies for neonatal brain injury.

Mesenchymal stem cell-derived neural progenitors in progressive MS: Two-year follow-up of a phase I study

Objective

To determine the long-term safety and efficacy of repeated intrathecal (IT) administration of autologous mesenchymal stem cell-derived neural progenitors (MSC-NPs) in patients with progressive MS by evaluating subjects 2 years after treatment.

Methods

Twenty subjects were enrolled as part of a phase I, open-label single-arm study of 3 IT injections of MSC-NPs spaced 3 months apart. Subjects were evaluated for adverse events and disability outcomes including the Expanded Disability Status Scale (EDSS) and the timed 25-foot walk (T25FW). Long-term evaluation was conducted 2 years after the third treatment. CSF was collected before and 3 months after treatment.

Results

Eighteen of the 20 study participants completed the full 2-year follow-up protocol. There were no long-term adverse events associated with repeated IT-MSC-NP treatment. Seven subjects showed sustained improvement in EDSS after 2 years, although the degree of improvement was not maintained in 5 of the subjects. Three of the 10 ambulatory subjects showed sustained improvement in the T25FW after 2 years. CSF biomarker analysis revealed a decrease in C-C motif chemokine ligand 2 (CCL2) and an increase in interleukin 8, hepatocyte growth factor, and C-X-C motif chemokine ligand 12 (CXCL12) after treatment.

Conclusions

Safety and efficacy of repeated IT-MSC-NP treatment was sustained for 2 years; however, the degree of disability reversal was not sustained in a subset of patients. CSF biomarkers altered in response to IT-MSC-NP treatment may reflect specific immunoregulatory and trophic mechanisms of therapeutic response in MS.

Classification of evidence

This study provides Class IV evidence that for patients with progressive MS, IT administration of MSC-NPs is safe and effective. The study is rated Class IV because of the absence of a non–IT-MSC-NP-treated control group.

Clinicaltrials.gov identifier

NCT01933802.

The impact of trophic and immunomodulatory factors on oligodendrocyte maturation: Potential treatments for encephalopathy of prematurity

Encephalopathy of prematurity (EoP) is a major cause of morbidity in preterm neonates, causing neurodevelopmental adversities that can lead to lifelong impairments. Preterm birth-related insults, such as cerebral oxygen fluctuations and perinatal inflammation, are believed to negatively impact brain development, leading to a range of brain abnormalities. Diffuse white matter injury is a major hallmark of EoP and characterized by widespread hypomyelination, the result of disturbances in oligodendrocyte lineage development. At present, there are no treatment options available, despite the enormous burden of EoP on patients, their families, and society. Over the years, research in the field of neonatal brain injury and other white matter pathologies has led to the identification of several promising trophic factors and cytokines that contribute to the survival and maturation of oligodendrocytes, and/or dampening neuroinflammation. In this review, we discuss the current literature on selected factors and their therapeutic potential to combat EoP, covering a wide range of in vitro, preclinical and clinical studies. Furthermore, we offer a future perspective on the translatability of these factors into clinical practice.

Increased C-X-C Motif Chemokine Ligand 12 Levels in Cerebrospinal Fluid as a Candidate Biomarker in Sporadic Amyotrophic Lateral Sclerosis

Sporadic amyotrophic lateral sclerosis (sALS) is a fatal progressive neurodegenerative disease affecting upper and lower motor neurons. Biomarkers are useful to facilitate the diagnosis and/or prognosis of patients and to reveal possible mechanistic clues about the disease. This study aimed to identify and validate selected putative biomarkers in the cerebrospinal fluid (CSF) of sALS patients at early disease stages compared with age-matched controls and with other neurodegenerative diseases including Alzheimer disease (AD), spinal muscular atrophy type III (SMA), frontotemporal dementia behavioral variant (FTD), and multiple sclerosis (MS). SWATH acquisition on liquid chromatography-tandem mass spectrometry (LC-MS/MS) for protein quantitation, and ELISA for validation, were used in CSF samples of sALS cases at early stages of the disease. Analysis of mRNA and protein expression was carried out in the anterior horn of the lumbar spinal cord in post-mortem tissue of sALS cases (terminal stage) and controls using RTq-PCR, and Western blotting, and immunohistochemistry, respectively. SWATH acquisition on liquid chromatography-tandem mass spectrometry (LC-MS/MS) revealed 51 differentially expressed proteins in the CSF in sALS. Receiver operating characteristic (ROC) curves showed CXCL12 to be the most valuable candidate biomarker. We validated the values of CXCL12 in CSF with ELISA in two different cohorts. Besides sALS, increased CXCL12 levels were found in MS but were not altered in AD, SMA, and FTD. Therefore, increased CXCL12 levels in the CSF can be useful in the diagnoses of MS and sALS in the context of the clinical settings. CXCL12 immunoreactivity was localized in motor neurons in control and sALS, and in a few glial cells in sALS at the terminal stage; CXCR4 was in a subset of oligodendroglial-like cells and axonal ballooning of motor neurons in sALS; and CXCR7 in motor neurons in control and sALS, and reactive astrocytes in the pyramidal tracts in terminal sALS. CXCL12/CXCR4/CXCR7 axis in the spinal cord probably plays a complex role in inflammation, oligodendroglial and astrocyte signaling, and neuronal and axonal preservation in sALS.

Intranasal mesenchymal stem cell therapy to boost myelination after encephalopathy of prematurity

Encephalopathy of prematurity (EoP) is a common cause of long-term neurodevelopmental morbidity in extreme preterm infants. Diffuse white matter injury (dWMI) is currently the most commonly observed form of EoP. Impaired maturation of oligodendrocytes (OLs) is the main underlying pathophysiological mechanism. No therapies are currently available to combat dWMI. Intranasal application of mesenchymal stem cells (MSCs) is a promising therapeutic option to boost neuroregeneration after injury. Here, we developed a double-hit dWMI mouse model and investigated the therapeutic potential of intranasal MSC therapy. Postnatal systemic inflammation and hypoxia-ischemia led to transient deficits in cortical myelination and OL maturation, functional deficits and neuroinflammation. Intranasal MSCs migrated dispersedly into the injured brain and potently improved myelination and functional outcome, dampened cerebral inflammationand rescued OL maturation after dWMI. Cocultures of MSCs with primary microglia or OLs show that MSCs secrete factors that directly promote OL maturation and dampen neuroinflammation. We show that MSCs adapt their secretome after ex vivo exposure to dWMI milieu and identified several factors including IGF1, EGF, LIF, and IL11 that potently boost OL maturation. Additionally, we showed that MSC-treated dWMI brains express different levels of these beneficial secreted factors. In conclusion, the combination of postnatal systemic inflammation and hypoxia-ischemia leads to a pattern of developmental brain abnormalities that mimics the clinical situation. Intranasal delivery of MSCs, that secrete several beneficial factors in situ, is a promising strategy to restore myelination after dWMI and subsequently improve the neurodevelopmental outcome of extreme preterm infants in the future.

Microglia depletion exacerbates demyelination and impairs remyelination in a neurotropic coronavirus infection

Microglia are considered both pathogenic and protective during recovery from demyelination, but their precise role remains ill defined. Here, using an inhibitor of colony stimulating factor 1 receptor (CSF1R), PLX5622, and mice infected with a neurotropic coronavirus (mouse hepatitis virus [MHV], strain JHMV), we show that depletion of microglia during the time of JHMV clearance resulted in impaired myelin repair and prolonged clinical disease without affecting the kinetics of virus clearance. Microglia were required only during the early stages of remyelination. Notably, large deposits of extracellular vesiculated myelin and cellular debris were detected in the spinal cords of PLX5622-treated and not control mice, which correlated with decreased numbers of oligodendrocytes in demyelinating lesions in drug-treated mice. Furthermore, gene expression analyses demonstrated differential expression of genes involved in myelin debris clearance, lipid and cholesterol recycling, and promotion of oligodendrocyte function. The results also demonstrate that microglial functions affected by depletion could not be compensated by infiltrating macrophages. Together, these results demonstrate that microglia play key roles in debris clearance and in the initiation of remyelination following infection with a neurotropic coronavirus but are not necessary during later stages of remyelination.

Relevance of the CXCR4/CXCR7-CXCL12 axis and its effect in pathophysiological conditions

The impact of the C-X-C receptor (CXCR) 7 and its close co-player CXCR4 in different physiological and pathophysiological processes has been extensively investigated within the last decades. Following activation by their shared ligand C-X-C ligand (CXCL) 12, both chemokine receptors can induce various routes of cell signaling and/or scavenge CXCL12 from the extracellular environment. This contributes to organ development and maintenance of homeostasis. Alterations of the CXCR4/CXCR7-CXCL12 axis have been detected in diseases such as cancer, central nervous system and cardiac disorders, and autoimmune diseases. These alterations include changes of the expression pattern, distribution, or downstream effects. The progression of the diseases can be regulated in preclinical models by the use of various modulators suggesting that this axis serves as a promising therapeutic target. It is therefore of great interest to investigate CXCR4/CXCR7/CXCL12 modulators in clinical development, with several CXCR4 and CXCL12 modulators such as plerixafor, ulocuplumab, balixafortide, and olaptesed pegol having already reached this stage. An overview is presented of the most important diseases whose outcomes can be positively or negatively regulated by the CXCR4/CXCR7-CXCL12 axis and summarizes preclinical and clinical data of modulators of that axis. Contrary to CXCR4 and CXCL12 modulators, CXCR7 modulators have, thus far, not been extensively studied. Therefore, more (pre)clinical investigations are needed.

Regulation of Neurogenesis in Mouse Brain by HMGB1

The High Mobility Group Box 1 (HMGB1) is the most abundant nuclear nonhistone protein that is involved in transcription regulation. In addition, HMGB1 has previously been found as an extracellularly acting protein enhancing neurite outgrowth in cultured neurons. Although HMGB1 is widely expressed in the developing central nervous system of vertebrates and invertebrates, its function in the developing mouse brain is poorly understood. Here, we have analyzed developmental defects of the HMGB1 null mouse forebrain, and further examined our findings in ex vivo brain cell cultures. We find that HMGB1 is required for the proliferation and differentiation of neuronal stem cells/progenitor cells. Enhanced apoptosis is also found in the neuronal cells lacking HMGB1. Moreover, HMGB1 depletion disrupts Wnt/β-catenin signaling and the expression of transcription factors in the developing cortex, including Foxg1, Tbr2, Emx2, and Lhx6. Finally, HMGB1 null mice display aberrant expression of CXCL12/CXCR4 and reduced RAGE signaling. In conclusion, HMGB1 plays a critical role in mammalian neurogenesis and brain development.

Astrocyte-T cell crosstalk regulates region-specific neuroinflammation

During multiple sclerosis (MS), an inflammatory and neurodegenerative disease of the central nervous system (CNS), symptoms, and outcomes are determined by the location of inflammatory lesions. While we and others have shown that T cell cytokines differentially regulate leukocyte entry into perivascular spaces and regional parenchymal localization in murine models of MS, the molecular mechanisms of this latter process are poorly understood. Here, we demonstrate that astrocytes exhibit region-specific responses to T cell cytokines that promote hindbrain versus spinal cord neuroinflammation. Analysis of cytokine receptor expression in human astrocytes showed region-specific responsiveness to Th1 and Th17 inflammatory cytokines. Consistent with this, human and murine astrocytes treated with these cytokines exhibit differential expression of the T cell localizing molecules VCAM-1 and CXCR7 that is both cytokine and CNS region-specific. Using in vivo models of spinal cord versus brain stem trafficking of myelin-specific T cells and astrocyte-specific deletion strategies, we confirmed that Th1 and Th17 cytokines differentially regulate astrocyte expression of VCAM-1 and CXCR7 in these locations. Finally, stereotaxic injection of individual cytokines into the hindbrain or spinal cord revealed region- and cytokine-specific modulation of localizing cue expression by astrocytes. These findings identify a role for inflammatory cytokines in mediating local astrocyte-dependent mechanisms of immune cell trafficking within the CNS during neuroinflammation.

Absence of miRNA-146a Differentially Alters Microglia Function and Proteome

Background: MiR-146a is an important regulator of innate inflammatory responses and is also implicated in cell death and survival.

Methods: By sorting CNS resident cells, microglia were the main cellular source of miR-146a. Therefore, we investigated microglia function and phenotype in miR-146a knock-out (KO) mice, analyzed the proteome of KO and wild-type (WT) microglia by LC-MS/MS, and examined miR-146a expression in different brain lesions of patients with multiple sclerosis (MS).

Results: When stimulated with LPS or myelin in vitro, microglia from KO mice expressed higher levels of IL-1β, TNF, IL-6, IL-10, CCL3, and CCL2 compared to WT. Stimulation increased migration and phagocytosis of WT but not KO microglia. CD11c⁺ microglia were induced by cuprizone (CPZ) in the WT mice but less in the KO. The proteome of ex vivo microglia was not different in miR-146a KO compared to WT mice, but CPZ treatment induced differential and reduced protein responses in the KO: GOT1, COX5b, CRYL1, and cystatin-C were specifically changed in KO microglia. We explored discriminative features of microglia proteomes: sparse Partial Least Squares-Discriminant Analysis showed the best discrimination when control and CPZ-treated conditions were compared. Cluster of ten proteins separated WT and miR-146a KO microglia after CPZ: among them were sensomes allowing to perceive the environment, Atp1a3 that belongs to the signature of CD11c⁺ microglia, and proteins related to inflammatory responses (S100A9, Ppm1g). Finally, we examined the expression of miR-146a and its validated target genes in different brain lesions of MS patients. MiR-146 was upregulated in all lesion types, and the highest expression was in active lesions. Nineteen of 88 validated target genes were significantly changed in active lesions, while none were changed in NAWM.

Conclusion: Our data indicated that microglia is the major source of miR-146a in the CNS. The absence of miR-146a differentially affected microglia function and proteome, and miR-146a may play an important role in gene regulation of active MS lesions.

Potential microglia-based interventions for stroke

A large number of families worldwide suffer from the physical and mental burden posed by stroke. An increasing number of studies aimed at the prevention and treatment of stroke have been conducted. Specifically, manipulating the immune response to stroke is under intense investigation. Microglia are the principal immune cells in the brain and are the first line of defense against the pathophysiology induced by stroke. Increasing evidence has suggested that microglia play diverse roles that depend on dynamic interactions with neurons, astrocytes, and other neighboring cells both in the normal brain and under pathological conditions, including stroke. Moreover, there are dynamic alterations in microglial functions with respect to aging and sex differences in the human brain, which offer a deep understanding of the conditions of stroke patients of different ages and sex. Hence, we review the dynamic microglial reactions caused by aging, sex, and crosstalk with neighboring cells both in normal conditions and after stroke and relevant potential interventions.