Neural precursor cell-secreted TGF-β2 redirects inflammatory monocyte-derived cells in CNS autoimmunity

Neural precursor cells rescue symptoms of Rett syndrome by activation of the Interferon γ pathway

The beneficial effects of Neural Precursor Cell (NPC) transplantation in several neurological disorders are well established and they are generally mediated by the secretion of immunomodulatory and neurotrophic molecules. We therefore investigated whether Rett syndrome (RTT), that represents the first cause of severe intellectual disability in girls, might benefit from NPC-based therapy. Using in vitro co-cultures, we demonstrate that, by sensing the pathological context, NPC-secreted factors induce the recovery of morphological and synaptic defects typical of Mecp2 deficient neurons. In vivo, we prove that intracerebral transplantation of NPCs in RTT mice significantly ameliorates neurological functions. To uncover the molecular mechanisms underpinning the mediated benefic effects, we analyzed the transcriptional profile of the cerebellum of transplanted animals, disclosing the possible involvement of the Interferon γ (IFNγ) pathway. Accordingly, we report the capacity of IFNγ to rescue synaptic defects, as well as motor and cognitive alterations in Mecp2 deficient models, thereby suggesting this molecular pathway as a potential therapeutic target for RTT.

The Research Progress in Transforming Growth Factor-β2

Transforming growth factor-beta 2 (TGF-β2), an important member of the TGF-β family, is a secreted protein that is involved in many biological processes, such as cell growth, proliferation, migration, and differentiation. TGF-β2 had been thought to be functionally identical to TGF-β1; however, an increasing number of recent studies uncovered the distinctive features of TGF-β2 in terms of its expression, activation, and biological functions. Mice deficient in TGF-β2 showed remarkable developmental abnormalities in multiple organs, especially the cardiovascular system. Dysregulation of TGF-β2 signalling was associated with tumorigenesis, eye diseases, cardiovascular diseases, immune disorders, as well as motor system diseases. Here, we provide a comprehensive review of the research progress in TGF-β2 to support further research on TGF-β2.

Age-induced alterations of granulopoiesis generate atypical neutrophils that aggravate stroke pathology

Aging accounts for increased risk and dismal outcome of ischemic stroke. Here, we investigated the impact of age-related changes in the immune system on stroke. Upon experimental stroke, compared with young mice, aged mice had increased neutrophil clogging of the ischemic brain microcirculation, leading to worse no-reflow and outcomes. Aged mice showed an enhanced granulopoietic response to stroke that led to the accumulation of CD101+CD62Llo mature and CD177hiCD101loCD62Llo and CD177loCD101loCD62Lhi immature atypical neutrophils in the blood, endowed with increased oxidative stress, phagocytosis and procoagulant features. Production of CXCL3 by CD62Llo neutrophils of the aged had a key role in the development and pathogenicity of aging-associated neutrophils. Hematopoietic stem cell rejuvenation reverted aging-associated neutropoiesis and improved stroke outcome. In elderly patients with ischemic stroke, single-cell proteome profile of blood leukocytes identified CD62Llo neutrophil subsets associated with worse reperfusion and outcome. Our results unveil how stroke in aging leads to a dysregulated emergency granulopoiesis impacting neurological outcome.

Transforming growth factor β (TGF-β) pathway in the immunopathogenesis of multiple sclerosis (MS); molecular approaches

INTRODUCTION

Multiple sclerosis (MS) is an acute demyelinating disease with an autoimmune nature, followed by gradual neurodegeneration and enervating scar formation. Dysregulated immune response is a crucial dilemma contributing to the pathogenesis of MS. The role of chemokines and cytokines, such as transforming growth factor-β (TGF-β), have been recently highlighted regarding their altered expressions in MS. TGF-β has three isoforms, TGF-β1, TGF-β2, and TGF-β3, that are structurally similar; however, they can show different functions.

RESULTS

All three isoforms are known to induce immune tolerance by modifying Foxp3⁺ regulatory T cells. Nevertheless, there are controversial reports concerning the role of TGF-β1 and 2 in the progression of scar formation in MS. At the same time, these proteins also improve oligodendrocyte differentiation and have shown neuroprotective behavior, two cellular processes that suppress the pathogenesis of MS. TGF-β3 shares the same properties but is less likely contributes to scar formation, and its direct role in MS remains elusive.

DISCUSSION

To develop novel neuroimmunological treatment strategies for MS, the optimal strategy could be the one that causes immune modulation, induces neurogenesis, stimulates remyelination, and prevents excessive scar formation. Therefore, regarding its immunological properties, TGF-β could be an appropriate candidate; however, contradictory results of previous studies have questioned its role and therapeutic potential in MS. In this review article, we provide an overview of the role of TGF-β in immunopathogenesis of MS, related clinical and animal studies, and the treatment potential of TGF-β in MS, emphasizing the role of different TGF-β isoforms.

Eliminating METTL1-mediated accumulation of PMN-MDSCs prevents hepatocellular carcinoma recurrence after radiofrequency ablation

BACKGROUND AND AIMS

Radiofrequency ablation (RFA) is an important curative therapy in hepatocellular carcinoma (HCC), but recurrence rate remains as high as all the other HCC therapeutic modalities. Methyltransferase 1 (METTL1), an enzyme for m 7 G tRNA modification, was reported to promote HCC development. Here, we assessed the role of METTL1 in shaping the immunosuppressive tumor microenvironment after insufficient RFA (iRFA).

APPROACH AND RESULTS

By immunohistochemistry and multiplex immunofluorescence (mIF) staining, we showed that METTL1 expression was enhanced in post-RFA recurrent HCC, accompanied by increased CD11b + CD15 + polymorphonuclear-myeloid-derived suppressor cells (PMN-MDSCs) and decreased CD8 + T cells. Mechanistically, heat-mediated METTL1 upregulation enhanced TGF-β2 translation to form the immunosuppressive environment by induction of myeloid-derived suppressor cell. Liver-specific overexpression or knockdown of Mettl1 significantly affected the accumulation of PMN-MDSCs and subsequently affected CD8 + T cell infiltration. Complete RFA successfully eliminated the tumor, whereas iRFA-treated mice exhibited enhanced tumor growth and metastasis with increased PMN-MDSC accumulation and decreased CD8 + T cells compared to sham surgery. Interrupting METTL1-TGF-β2-PMN-MDSC axis by anti-Ly6G antibody, or knockdown of hepatoma-intrinsic Mettl1 or Tgfb2 , or TGF-β signaling blockade significantly mitigated tumor progression induced by iRFA and restored CD8 + T cell population.

CONCLUSIONS

Our study sheds light on the pivotal role of METTL1 in modulating an immunosuppressive microenvironment and demonstrated that interrupting METTL1-TGF-β2-PMN-MDSC axis could be a therapeutic strategy to restore antitumor immunity and prevent HCC recurrence after RFA treatment, meriting further clinical studies.

Immunomodulatory and Anti-inflammatory effect of Neural Stem/Progenitor Cells in the Central Nervous System

Neuroinflammation is a critical event that responds to disturbed homeostasis and governs various neurological diseases in the central nervous system (CNS). The excessive inflammatory microenvironment in the CNS can adversely affect endogenous neural stem cells, thereby impeding neural self-repair. Therapies with neural stem/progenitor cells (NSPCs) have shown significant inhibitory effects on inflammation, which is mainly achieved through intercellular contact and paracrine signalings. The intercellular contact between NSPCs and immune cells, the activated CNS- resident microglia, and astrocyte plays a critical role in the therapeutic NSPCs homing and immunomodulatory effects. Moreover, the paracrine effect mainly regulates infiltrating innate and adaptive immune cells, activated microglia, and astrocyte through the secretion of bioactive molecules and extracellular vesicles. However, the molecular mechanism involved in the immunomodulatory effect of NSPCs is not well discussed. This article provides a systematic analysis of the immunomodulatory mechanism of NSPCs, discusses efficient ways to enhance its immunomodulatory ability, and gives suggestions on clinical therapy.

Stem Cells Attenuate the Inflammation Crosstalk Between Ischemic Stroke and Multiple Sclerosis: A Review

The immense neuroinflammation induced by multiple sclerosis (MS) promotes a favorable environment for ischemic stroke (IS) development, making IS a deadly complication of MS. The overlapping inflammation in MS and IS is a prelude to the vascular pathology, and an inherent cell death mechanism that exacerbates neurovascular unit (NVU) impairment in the disease progression. Despite this consequence, no therapies focus on reducing IS incidence in patients with MS. To this end, the preclinical and clinical evidence we review here argues for cell-based regenerative medicine that will augment the NVU dysfunction and inflammation to ameliorate IS risk.

Neural stem cell transplantation in patients with progressive multiple sclerosis: an open-label, phase 1 study

Innovative pro-regenerative treatment strategies for progressive multiple sclerosis (PMS), combining neuroprotection and immunomodulation, represent an unmet need. Neural precursor cells (NPCs) transplanted in animal models of multiple sclerosis have shown preclinical efficacy by promoting neuroprotection and remyelination by releasing molecules sustaining trophic support and neural plasticity. Here we present the results of STEMS, a prospective, therapeutic exploratory, non-randomized, open-label, single-dose-finding phase 1 clinical trial ( NCT03269071 , EudraCT 2016-002020-86), performed at San Raffaele Hospital in Milan, Italy, evaluating the feasibility, safety and tolerability of intrathecally transplanted human fetal NPCs (hfNPCs) in 12 patients with PMS (with evidence of disease progression, Expanded Disability Status Scale ≥6.5, age 18-55 years, disease duration 2-20 years, without any alternative approved therapy). The safety primary outcome was reached, with no severe adverse reactions related to hfNPCs at 2-year follow-up, clearly demonstrating that hfNPC therapy in PMS is feasible, safe and tolerable. Exploratory secondary analyses showed a lower rate of brain atrophy in patients receiving the highest dosage of hfNPCs and increased cerebrospinal fluid levels of anti-inflammatory and neuroprotective molecules. Although preliminary, these results support the rationale and value of future clinical studies with the highest dose of hfNPCs in a larger cohort of patients.

Magnetic labeling of primary murine monocytes using very small superparamagnetic iron oxide nanoparticles

Due to their very small size, nanoparticles can interact with all cells in the central nervous system. One of the most promising nanoparticle subgroups are very small superparamagnetic iron oxide nanoparticles (VSOP) that are citrate coated for electrostatic stabilization. To determine their influence on murine blood-derived monocytes, which easily enter the injured central nervous system, we applied VSOP and carboxydextran-coated superparamagnetic iron oxide nanoparticles (Resovist). We assessed their impact on the viability, cytokine, and chemokine secretion, as well as iron uptake of murine blood-derived monocytes. We found that (1) the monocytes accumulated VSOP and Resovist, (2) this uptake seemed to be nanoparticle- and time-dependent, (3) the decrease of monocytes viability was treatment-related, (4) VSOP and Resovist incubation did not alter cytokine homeostasis, and (5) overall a 6-hour treatment with 0.75 mM VSOP-R1 was probably sufficient to effectively label monocytes for future experiments. Since homeostasis is not altered, it is safe to label blood-derived monocles with VSOP. VSOP labeled monocytes can be used to study injured central nervous system sites further, for example with drug-carrying VSOP.

Promoting exogenous repair in multiple sclerosis: myelin regeneration

PURPOSE OF THE REVIEW

Despite the significant progress in the development of disease-modifying treatments for multiple sclerosis (MS), repair of existing damage is still poorly addressed. Current research focuses on stem cell-based therapies as a suitable alternative or complement to current drug therapies.

RECENT FINDINGS

Myelin damage is a hallmark of multiple sclerosis, and novel approaches leading to remyelination represent a promising tool to prevent neurodegeneration of the underlying axon. With increasing evidence of diminishing remyelination capacity of the MS brain with ageing and disease progression, exogenous cell transplantation is a promising therapeutic approach for restoration of oligodendrocyte precursor cell pool reserve and myelin regeneration.

SUMMARY

The present review summarizes recent developments of remyelinating therapies in multiple sclerosis, focusing on exogenous cell-based strategies and discussing related scientific, practical, and ethical concerns.

Failure of Alzheimer’s Mice Brain Resident Neural Precursor Cells in Supporting Microglia-Mediated Amyloid β Clearance

The failure of brain microglia to clear excess amyloid β (Aβ) is considered a leading cause of the progression of Alzheimer’s disease pathology. Resident brain neural precursor cells (NPCs) possess immune-modulatory and neuro-protective properties, which are thought to maintain brain homeostasis. We have recently showed that resident mouse brain NPCs exhibit an acquired decline in their trophic properties in the Alzheimer’s disease brain environment. Therefore, we hypothesized that functional NPCs may support microglial phagocytic activity, and that NPCs derived from the adult AD mouse brain may fail to support the clearance of Aβ by microglia. We first identified in the AD brain, in vivo and ex vivo, a subpopulation of microglia that express high Aβ phagocytic activity. Time-lapse microscopy showed that co-culturing newborn NPCs with microglia induced a significant increase in the fraction of microglia with high Aβ phagocytic activity. Freshly isolated NPCs from adult wild type, but not AD, mouse brain, induced an increase in the fraction of microglia with high Aβ phagocytic activity. Finally, we showed that NPCs also possess the ability to promote Aβ degradation within the microglia with high Aβ phagocytic activity. Thus, resident brain NPCs support microglial function to clear Aβ, but NPCs derived from the AD environment fail to do so. We suggest that the failure of AD brain NPCs to support Aβ clearance from the brain by microglia may accelerate disease pathology.

Lumbar spine intrathecal transplantation of neural precursor cells promotes oligodendrocyte proliferation in hot spots of chronic demyelination

Experimental autoimmune encephalomyelitis (EAE) is a basic and reliable model used to study clinical and pathological hallmarks of multiple sclerosis (MS) in rodents. Several studies suggest neural precursor cells (NPCs) as a significant research tool while reporting that transplanted NPCs are a promising therapeutic approach to treating neurological disorders, such as MS. The main objective was to approach a preclinical, in vivo scenario of oligodendrogenesis with NPCs, targeting the main chronic demyelinated lumbosacral milieu of EAE, via the least invasive delivery method which is lumbar puncture. We utilized MOG_35‐55 peptide to induce EAE in C57BL/6 mice and prior to the acute relapse, we intervened with either the traceable GFP⁺ cellular therapy or saline solution in the intrathecal space of their lumbar spine. A BrdU injection, which enabled us to monitor endogenous proliferation, marked the endpoint 50 days post‐induction (50 dpi). Neuropathology with high‐throughput, triple immunofluorescent, and transmission electron microscopy (TEM) data were extracted and analyzed. The experimental treatment attenuated the chronic phase of EAE (50 dpi; score <1) following an acute, clinical relapse. Myelination and axonal integrity were rescued in the NPC‐treated animals along with suppressed immune populations. The differentiation profile of the exogenous NPCs and endogenous BrdU⁺ cells was location‐dependent where GFP⁺‐rich areas drove undifferentiated phenotypes toward the oligodendrocyte lineage. In situ oligodendrocyte enrichment was demonstrated through increased (p < 0.001) gap junction channels of Cx32 and Cx47, reliable markers for proliferative oligodendroglia syncytium. TEM morphometric analysis ultimately manifested an increased g‐ratio in lumbosacral fibers of the recovered animals (p < 0.001). Herein, we suggest that a single, lumbar intrathecal administration of NPCs capacitated a viable cellular load and resulted in clinical and pathological amelioration, stimulating resident OPCs to overcome the remyelination failure in EAE demyelinating locale.

Stem Cell Therapies for Progressive Multiple Sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system characterized by demyelination and axonal degeneration. MS patients typically present with a relapsing-remitting (RR) disease course, manifesting as sporadic attacks of neurological symptoms including ataxia, fatigue, and sensory impairment. While there are several effective disease-modifying therapies able to address the inflammatory relapses associated with RRMS, most patients will inevitably advance to a progressive disease course marked by a gradual and irreversible accrual of disabilities. Therapeutic intervention in progressive MS (PMS) suffers from a lack of well-characterized biological targets and, hence, a dearth of successful drugs. The few medications approved for the treatment of PMS are typically limited in their efficacy to active forms of the disease, have little impact on slowing degeneration, and fail to promote repair. In looking to address these unmet needs, the multifactorial therapeutic benefits of stem cell therapies are particularly compelling. Ostensibly providing neurotrophic support, immunomodulation and cell replacement, stem cell transplantation holds substantial promise in combatting the complex pathology of chronic neuroinflammation. Herein, we explore the current state of preclinical and clinical evidence supporting the use of stem cells in treating PMS and we discuss prospective hurdles impeding their translation into revolutionary regenerative medicines.

Niche Cells Crosstalk In Neuroinflammation After Traumatic Brain Injury

Traumatic brain injury (TBI) is recognized as the disease with high morbidity and disability around world in spite of the work ongoing in neural protection. Due to heterogeneity among the patients, it's still hard to acquire satisfying achievements in clinic. Neuroinflammation, which exists since primary injury occurs, with elusive duality, appear to be of significance from recovery of injury to neurogenesis. In recent years, studied have revealed that communication in neurogenic niche is more than “cell to cell” communication, and study on NSCs represent it as central role in the progress of neural regeneration. Hence, the neuroinflammation-affecting crosstalk after TBI, and clarifying definitive role of NSCs in the course of regeneration is a promising subject for researchers, for its great potential in overcoming the frustrating status quo in clinic, promoting welfare of TBI patient.

Harnessing the Neural Stem Cell Secretome for Regenerative Neuroimmunology

Increasing evidence foresees the secretome of neural stem cells (NSCs) to confer superimposable beneficial properties as exogenous NSC transplants in experimental treatments of traumas and diseases of the central nervous system (CNS). Naturally produced secretome biologics include membrane-free signaling molecules and extracellular membrane vesicles (EVs) capable of regulating broad functional responses. The development of high-throughput screening pipelines for the identification and validation of NSC secretome targets is still in early development. Encouraging results from pre-clinical animal models of disease have highlighted secretome-based (acellular) therapeutics as providing significant improvements in biochemical and behavioral measurements. Most of these responses are being hypothesized to be the result of modulating and promoting the restoration of key inflammatory and regenerative programs in the CNS. Here, we will review the most recent findings regarding the identification of NSC-secreted factors capable of modulating the immune response to promote the regeneration of the CNS in animal models of CNS trauma and inflammatory disease and discuss the increased interest to refine the pro-regenerative features of the NSC secretome into a clinically available therapy in the emerging field of Regenerative Neuroimmunology.

Modulation of Immune Infiltration of Ovarian Cancer Tumor Microenvironment by Specific Subpopulations of Fibroblasts

Tumor immune infiltration plays a key role in the progression of solid tumors, including ovarian cancer, and immunotherapies are rapidly emerging as effective treatment modalities. However, the role of cancer-associated fibroblasts (CAFs), a predominant stromal constituent, in determining the tumor-immune microenvironment and modulating efficacy of immunotherapies remains poorly understood. We have conducted an extensive bioinformatic analysis of our and other publicly available ovarian cancer datasets (GSE137237, GSE132289 and GSE71340), to determine the correlation of fibroblast subtypes within the tumor microenvironment (TME) with the characteristics of tumor-immune infiltration. We identified (1) four functional modules of CAFs in ovarian cancer that are associated with the TME and metastasis of ovarian cancer, (2) immune-suppressive function of the collagen 1,3,5-expressing CAFs in primary ovarian cancer and omental metastases, and (3) consistent positive correlations between the functional modules of CAFs with anti-immune response genes and negative correlation with pro-immune response genes. Our study identifies a specific fibroblast subtype, fibroblast functional module (FFM)2, in the ovarian cancer tumor microenvironment that can potentially modulate a tumor-promoting immune microenvironment, which may be detrimental toward the effectiveness of ovarian cancer immunotherapies.

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.

TGF-β2 interfering oligonucleotides used as adjuvants for microbial vaccines

The success of using immune checkpoint inhibitors to treat cancers implies that inhibiting an immunosuppressive cytokine, such as TGF-β2, could be a strategy to develop novel adjuvants for microbial vaccines. To develop nucleic acid based TGF-β2 inhibitors, we designed three antisense oligonucleotides, designated as TIO1, TIO2, and TIO3, targeting the conserve regions identical in human and mouse TGF-β2 mRNA 3'-untranslated region. In cultured immune cells, TIO3 and TIO1 significantly reduced the TGF-β2 mRNA expression and protein production. In mice, the TIO3 and TIO1, when formulated in various microbial vaccines, significantly enhanced the antibody response to the vaccines, and the TIO3-adjuvanted influenza virus vaccine induced effective protection against the influenza virus challenge. In the immunized mice, TIO3 formulated in microbial vaccines dramatically reduced surface-bound TGF-β2 expression on CD4⁺ T cells and CD19⁺ B cells in the lymph node (LN) cells and spleen cells; up-regulated the expression of CD40, CD80, CD86, and MHC II molecules on CD19⁺ B cells and CD11c⁺ dendritic cells; and promoted IFN-γ production in CD4⁺ T cells and CD8⁺ T cells in the LN cells. Overall, TIO3 or TIO1 could be used as a novel type of adjuvant for facilitating the microbial vaccines to elicit more vigorous and persistent antibody response by interfering with TGF-β2 expression.

Promises and Limitations of Neural Stem Cell Therapies for Progressive Multiple Sclerosis

Multiple disease-modifying medications with regulatory approval to treat multiple sclerosis (MS) are unable to prevent inflammatory tissue damage in the central nervous system (CNS), and none directly promote repair. Thus, there is an unmet clinical need for therapies that can arrest and reverse the persistent accumulation of disabilities associated with progressive forms of MS (P-MS). Preclinical research has revealed an unexpected ability of neural stem cell (NSC) therapies to provide neurotrophic support and inhibit detrimental host immune responses in vivo following transplantation into the chronically inflamed CNS. We discuss NSC transplantation as a promising therapy for P-MS, elaborate on the necessities of clinical trial validation and formalized usage guidelines, and caution about unscrupulous 'clinics' marketing unproven therapies to patients.

T follicular helper cells are elevated in a rat model of autoimmune myocarditis

Myocarditis is an inflammatory disease of the myocardium that is associated with immune dysfunction. Earlier studies have suggested that T helper 1/2 cell imbalance plays an important role in the development of myocarditis, but the role of T follicular helper (Tfh) cells in the development of autoimmune myocarditis has not previously been reported. Here, we investigated this involvement by using a rat model of experimental autoimmune myocarditis (EAM). Inflammatory cell infiltration, myocardial structure destruction and tissue necrosis were observed in EAM myocardial tissues, and the percentages of CD4⁺ CXCR5⁺ Tfh cells and CD19⁺ B cells were both significantly higher in spleen and myocardial tissues of the EAM model as compared with the control group. Furthermore, the expression levels of interleukin-21, CXCL13 and myosin antibody were significantly higher in the serum of rats with EAM compared with the control group on days 14 and 35 after immunization. Fourteen or 35 days after immunization, the expression levels of interleukin-21 and CXCL13 were both significantly higher in myocardial tissues of rats with EAM as compared with the control group. Our findings suggest that Tfh cell balance is disrupted during the pathological process of autoimmune myocarditis.

The proportion of myeloid-derived suppressor cells in the spleen is related to the severity of the clinical course and tissue damage extent in a murine model of multiple sclerosis

Multiple Sclerosis (MS) is the second cause of paraplegia among young adults, after all types of CNS traumatic lesions. In its most frequent relapsing-remitting form, the severity of the disease course is very heterogeneous, and its reliable evaluation remains a key issue for clinicians. Myeloid-Derived sSuppressor Cells (MDSCs) are immature myeloid cells that suppress the inflammatory response, a phenomenon related to the resolution or recovery of the clinical symptoms associated with experimental autoimmune encephalomyelitis (EAE), the most common model for MS. Here, we establish the severity index as a new parameter for the clinical assessment in EAE. It is derived from the relationship between the maximal clinical score and the time elapsed since disease onset. Moreover, we relate this new index with several histopathological hallmarks in EAE and with the peripheral content of MDSCs. Based on this new parameter, we show that the splenic MDSC content is related to the evolution of the clinical course of EAE, ranging from mild to severe. Indeed, when the severity index indicates a severe disease course, EAE mice display more intense lymphocyte infiltration, demyelination and axonal damage. A direct correlation was drawn between the MDSC population in the peripheral immune system, and the preservation of myelin and axons, which was also correlated with T cell apoptosis within the CNS (being these cells the main target for MDSC suppression). The data presented clearly indicated that the severity index is a suitable tool to analyze disease severity in EAE. Moreover, our data suggest a clear relationship between circulating MDSC enrichment and disease outcome, opening new perspectives for the future targeting of this population as an indicator of MS severity.

Vaccines targeting the primary amino acid sequence and conformational epitope of amyloid-β had distinct effects on neuropathology and cognitive deficits in EAE/AD mice

BACKGROUND AND PURPOSE

Immunotherapeutic intervention is one of the most promising strategies for the prevention and treatment of Alzheimer's disease (AD). Although they showed great success in AD mouse models, the clinical trials of many immune approaches failed due to low efficacy and safety. Thus, an animal model which can show the potential side effects of vaccines or antibodies is urgently needed. In this study, we generated EAE/AD mice by crossing APP/PS1 mice with experimental autoimmune encephalomyelitis (EAE) mice. We then investigated the efficacy and safety of two vaccines: the immunogens of which were Aβ1-42 aggregates (Aβ42 vaccine) and an oligomer-specific conformational epitope (AOE1 vaccine), respectively.

EXPERIMENTAL APPROACH

EAE/AD mice were immunized with the Aβ42 vaccine or AOE1 vaccine five times at biweekly intervals. After the final immunization, cognitive function was evaluated by the Morris water maze, Y maze, and object recognition tests. Neuropathological changes in the mouse brains were analysed by immunohistochemistry and ELISA.

KEY RESULTS

In contrast to previous findings in conventional AD animal models, Aβ42 immunization promoted neuroinflammation, enhanced Aβ levels and plaque burden, and failed to restore cognitive deficits in EAE/AD mice. By contrast, AOE1 immunization dramatically attenuated neuroinflammation, reduced Aβ levels, and improved cognitive performance in EAE/AD mice.

CONCLUSION AND IMPLICATIONS

These results suggest that the EAE/AD mouse model can exhibit the potential side effects of AD immune approaches that conventional AD animal models fail to display. Furthermore, strategies specifically targeting Aβ oligomers may be safe and show clinical benefit for AD treatment.

Therapeutic Plasticity of Neural Stem Cells

Neural stem cells (NSCs) have garnered significant scientific and commercial interest in the last 15 years. Given their plasticity, defined as the ability to develop into different phenotypes inside and outside of the nervous system, with a capacity of almost unlimited self-renewal, of releasing trophic and immunomodulatory factors, and of exploiting temporal and spatial dynamics, NSCs have been proposed for (i) neurotoxicity testing; (ii) cellular therapies to treat CNS diseases; (iii) neural tissue engineering and repair; (iv) drug target validation and testing; (v) personalized medicine. Moreover, given the growing interest in developing cell-based therapies to target neurodegenerative diseases, recent progress in developing NSCs from human-induced pluripotent stem cells has produced an analog of endogenous NSCs. Herein, we will review the current understanding on emerging conceptual and technological topics in the neural stem cell field, such as deep characterization of the human compartment, single-cell spatial-temporal dynamics, reprogramming from somatic cells, and NSC manipulation and monitoring. Together, these aspects contribute to further disentangling NSC plasticity to better exploit the potential of those cells, which, in the future, might offer new strategies for brain therapies.

Endogenous neural precursor cells in health and disease

Neurogenesis persists in the adult brain of mammals in the subventricular zone (SVZ) of the lateral ventricles and in the subgranular zone (SGZ) of the dentate gyrus (DG). The complex interactions between intrinsic and extrinsic signals provided by cells in the niche but also from distant sources regulate the fate of neural stem/progenitor cells (NPCs) in these sites. This fine regulation is perturbed in aging and in pathological conditions leading to a different NPC behavior, tailored to the specific physio-pathological features. Indeed, NPCs exert in physiological and pathological conditions important neurogenic and non-neurogenic regulatory functions and participate in maintaining and protecting brain tissue homeostasis. In this review, we discuss intrinsic and extrinsic signals that regulate NPC activation and NPC functional role in various homeostatic and non-homeostatic conditions.

Molecular signature of different lesion types in the brain white matter of patients with progressive multiple sclerosis

To identify pathogenetic markers and potential drivers of different lesion types in the white matter (WM) of patients with progressive multiple sclerosis (PMS), we sequenced RNA from 73 different WM areas. Compared to 25 WM controls, 6713 out of 18,609 genes were significantly differentially expressed in MS tissues (FDR < 0.05). A computational systems medicine analysis was performed to describe the MS lesion endophenotypes. The cellular source of specific molecules was examined by RNAscope, immunohistochemistry, and immunofluorescence. To examine common lesion specific mechanisms, we performed de novo network enrichment based on shared differentially expressed genes (DEGs), and found TGFβ-R2 as a central hub. RNAscope revealed astrocytes as the cellular source of TGFβ-R2 in remyelinating lesions. Since lesion-specific unique DEGs were more common than shared signatures, we examined lesion-specific pathways and de novo networks enriched with unique DEGs. Such network analysis indicated classic inflammatory responses in active lesions; catabolic and heat shock protein responses in inactive lesions; neuronal/axonal specific processes in chronic active lesions. In remyelinating lesions, de novo analyses identified axonal transport responses and adaptive immune markers, which was also supported by the most heterogeneous immunoglobulin gene expression. The signature of the normal-appearing white matter (NAWM) was more similar to control WM than to lesions: only 465 DEGs differentiated NAWM from controls, and 16 were unique. The upregulated marker CD26/DPP4 was expressed by microglia in the NAWM but by mononuclear cells in active lesions, which may indicate a special subset of microglia before the lesion develops, but also emphasizes that omics related to MS lesions should be interpreted in the context of different lesions types. While chronic active lesions were the most distinct from control WM based on the highest number of unique DEGs (n = 2213), remyelinating lesions had the highest gene expression levels, and the most different molecular map from chronic active lesions. This may suggest that these two lesion types represent two ends of the spectrum of lesion evolution in PMS. The profound changes in chronic active lesions, the predominance of synaptic/neural/axonal signatures coupled with minor inflammation may indicate end-stage irreversible molecular events responsible for this less treatable phase.

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.

GABA-stimulated adipose-derived stem cells suppress subcutaneous adipose inflammation in obesity

Accumulating evidence suggests that subcutaneous and visceral adipose tissues are differentially associated with metabolic disorders. In obesity, subcutaneous adipose tissue is beneficial for metabolic homeostasis because of repressed inflammation. However, the underlying mechanism remains unclear. Here, we demonstrate that γ-aminobutyric acid (GABA) sensitivity is crucial in determining fat depot-selective adipose tissue macrophage (ATM) infiltration in obesity. In diet-induced obesity, GABA reduced monocyte migration in subcutaneous inguinal adipose tissue (IAT), but not in visceral epididymal adipose tissue (EAT). Pharmacological modulation of the GABA_B receptor affected the levels of ATM infiltration and adipose tissue inflammation in IAT, but not in EAT, and GABA administration ameliorated systemic insulin resistance and enhanced insulin-dependent glucose uptake in IAT, accompanied by lower inflammatory responses. Intriguingly, compared with adipose-derived stem cells (ADSCs) from EAT, IAT-ADSCs played key roles in mediating GABA responses that repressed ATM infiltration in high-fat diet-fed mice. These data suggest that selective GABA responses in IAT contribute to fat depot-selective suppression of inflammatory responses and protection from insulin resistance in obesity.

Neural Stem Cells of the Subventricular Zone Contribute to Neuroprotection of the Corpus Callosum after Cuprizone-Induced Demyelination

Myelin loss occurring in demyelinating diseases, including multiple sclerosis, is the leading cause of long-lasting neurological disability in adults. While endogenous remyelination, driven by resident oligodendrocyte precursor cells (OPCs), might partially compensate myelin loss in the early phases of demyelinating disorders, this spontaneous reparative potential fails at later stages. To investigate the cellular mechanisms sustaining endogenous remyelination in demyelinating disorders, we focused our attention on endogenous neural precursor cells (eNPCs) located within the subventricular zone (SVZ) since this latter area is considered one of the primary sources of new OPCs in the adult forebrain. First, we fate mapped SVZ-eNPCs in cuprizone-induced demyelination and found that SVZ endogenous neural stem/precursor cells are recruited during the remyelination phase to the corpus callosum (CC) and are capable of forming new oligodendrocytes. When we ablated SVZ-derived eNPCs during cuprizone-induced demyelination in female mice, the animals displayed reduced numbers of oligodendrocytes within the lesioned CC. Although this reduction in oligodendrocytes did not impact the ensuing remyelination, eNPC-ablated mice experienced increased axonal loss. Our results indicate that, in toxic models of demyelination, SVZ-derived eNPCs contribute to support axonal survival.SIGNIFICANCE STATEMENT One of the significant challenges in MS research is to understand the detrimental mechanisms leading to the failure of CNS tissue regeneration during disease progression. One possible explanation is the inability of recruited oligodendrocyte precursor cells (OPCs) to complete remyelination and to sustain axonal survival. The contribution of endogenous neural precursor cells (eNPCs) located in the subventricular zone (SVZ) to generate new OPCs in the lesion site has been debated. Using transgenic mice to fate map and to selectively kill SVZ-derived eNPCs in the cuprizone demyelination model, we observed migration of SVZ-eNPCs after injury and their contribution to oligodendrogenesis and axonal survival. We found that eNPCs are dispensable for remyelination but protect partially from increased axonal loss.

Absence of TGFβ signaling in retinal microglia induces retinal degeneration and exacerbates choroidal neovascularization

Constitutive TGFβ signaling is important in maintaining retinal neurons and blood vessels and is a factor contributing to the risk for age-related macular degeneration (AMD), a retinal disease involving neurodegeneration and microglial activation. How TGFβ signaling to microglia influences pathological retinal neuroinflammation is unclear. We discovered that ablation of the TGFβ receptor, TGFBR2, in retinal microglia of adult mice induced abnormal microglial numbers, distribution, morphology, and activation status, and promoted a pathological microglial gene expression profile. TGFBR2-deficient retinal microglia induced secondary gliotic changes in Müller cells, neuronal apoptosis, and decreased light-evoked retinal function reflecting abnormal synaptic transmission. While retinal vasculature was unaffected, TGFBR2-deficient microglia demonstrated exaggerated responses to laser-induced injury that was associated with increased choroidal neovascularization, a hallmark of advanced exudative AMD. These findings demonstrate that deficiencies in TGFβ-mediated microglial regulation can drive neuroinflammatory contributions to AMD-related neurodegeneration and neovascularization, highlighting TGFβ signaling as a potential therapeutic target.

Progression in migraine: Role of mast cells and pro-inflammatory and anti-inflammatory cytokines

Migraine is a common painful neurovascular disorder usually associated with several symptoms, such as photophobia, phonophobia, nausea, vomiting and inflammation, and involves immune cells. Mast cells (MCs) are immune cells derived from hematopoietic pluripotent stem cells which migrate and mature close to epithelial, blood vessels, and nerves. In almost all vascularized tissues there are MCs that produce, contain and release biologically active products including cytokines, arachidonic acid compounds, and proteases. In addition, MCs participate in innate and adaptive immune responses. Innate responses in the central nervous system (CNS) occur during neuroinflammatory phenomena, including migraine. Antigens found in the environment have a crucial role in inflammatory response, causing a broad range of diseases including migraine. They can be recognized by several innate immune cells, such as macrophages, microglia, dendritic cells and MCs, which can be activated trough Toll-like receptor (TLR) signaling. MCs reside close to primary nociceptive neurons, associate with nerves, and are capable of triggering local inflammation. MCs are involved in the pathophysiology of various tissues and organs, especially where there is an increase of angiogenesis. Activated MCs release preformed mediators include histamine, heparin, proteases (tryptase, chimase), hydrolases, cathepsin, carboxypeptidases, and peroxidase, and they also generate pro-inflammatory cytokines/chemokines. In addition, activated macrophages, microglia and MCs in the CNS release pro-inflammatory cytokines which provoke an increase of arachidonic acid product levels and lead to migraine and other neurological manifestations including fatigue, nausea, headaches and brain fog. Innate immunity and pro-inflammatory interleukin (IL)-1 cytokine family members can be inhibited by IL-37, a relatively new member of the IL-1 family. In this article, we report that some pro-inflammatory cytokines inducing migraine may be inhibited by IL-37, a natural suppressor of inflammation, and innate and acquired immunity.

Neural stem cell derived extracellular vesicles: Attributes and prospects for treating neurodegenerative disorders

Neural stem cell (NSC) grafting in conditions such as aging, brain injury, and neurodegenerative diseases promotes regeneration, plasticity and functional recovery. Recent studies have revealed that administration of NSC-derived extracellular vesicles (NSC-EVs) via non-invasive approaches can also afford therapeutic benefits. This review confers the properties and therapeutic promise of EVs secreted by NSCs. NSC-EVs enriched with specific miRNAs mediate multiple functions in physiological and pathological conditions, which include modulation of the proximate microenvironment, facilitating the entry of viruses into cells, functioning as independent metabolic units, operating as a microglial morphogen and influencing the diverse aspects of brain function in adulthood including the process of aging. Due to their anti-inflammatory, neurogenic and neurotrophic effects, NSC-EVs are also useful for treating multiple neurodegenerative diseases. Although only a few studies have demonstrated the efficacy of NSC-EVs to treat brain impairments, the promise is enormous. Moving forward, the use of well-characterized NSC-EVs generated in specific culture conditions and NSC-EVs that are engineered to carry the desired miRNAs, mRNAs and proteins have great promise for treating brain injury and neurogenerative diseases. Notably, the possibility of targeting NSC-EVs to specific neuronal types or brain regions would enable managing of diverse neurodegenerative conditions with minimal side effects.

How to reprogram microglia toward beneficial functions

Microglia, brain cells of nonneural origin, orchestrate the inflammatory response to diverse insults, including hypoxia/ischemia or maternal/fetal infection in the perinatal brain. Experimental studies have demonstrated the capacity of microglia to recognize pathogens or damaged cells activating a cytotoxic response that can exacerbate brain damage. However, microglia display an enormous plasticity in their responses to injury and may also promote resolution stages of inflammation and tissue regeneration. Despite the critical role of microglia in brain pathologies, the cellular mechanisms that govern the diverse phenotypes of microglia are just beginning to be defined. Here we review emerging strategies to drive microglia toward beneficial functions, selectively reporting the studies which provide insights into molecular mechanisms underlying the phenotypic switch. A variety of approaches have been proposed which rely on microglia treatment with pharmacological agents, cytokines, lipid messengers, or microRNAs, as well on nutritional approaches or therapies with immunomodulatory cells. Analysis of the molecular mechanisms relevant for microglia reprogramming toward pro‐regenerative functions points to a central role of energy metabolism in shaping microglial functions. Manipulation of metabolic pathways may thus provide new therapeutic opportunities to prevent the deleterious effects of inflammatory microglia and to control excessive inflammation in brain disorders.

Extracellular Vesicles Containing IL-4 Modulate Neuroinflammation in a Mouse Model of Multiple Sclerosis

Extracellular vesicles (EVs) play a major role in cell-to-cell communication in physiological and pathological conditions, and their manipulation may represent a promising therapeutic strategy. Microglia, the parenchymal mononuclear phagocytes of the brain, modulate neighboring cells also through the release of EVs. The production of custom EVs filled with desired molecules, possibly targeted to make their uptake cell specific, and their administration in biological fluids may represent a valid approach for drug delivery. We engineered a murine microglia cell line, BV-2, to release EVs overexpressing the endogenous "eat me" signal Lactadherin (Mfg-e8) on the surface to target phagocytes and containing the anti-inflammatory cytokine IL-4. A single injection of 10⁷ IL-4⁺Mfg-e8⁺ EVs into the cisterna magna modulated established neuroinflammation and significantly reduced clinical signs in the mouse model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE). Injected IL-4⁺Mfg-e8⁺ EVs target mainly phagocytes (i.e., macrophages and microglia) surrounding liquoral spaces, and their cargo promote the upregulation of anti-inflammatory markers chitinase 3-like 3 (ym1) and arginase-1 (arg1), significantly reducing tissue damage. Engineered EVs may represent a biological drug delivery tool able to deliver multiple functional molecules simultaneously to treat neuroinflammatory diseases.