Meninges Of Mice Research Articles

300 Intracranial Tumors Hijack the Meningeal Venolymphatic Network Through VEGFR-2 Signaling

INTRODUCTION: Glioblastoma and other intracranial neoplasms have been associated with breakdown of the blood brain barrier. Other protective CNS barriers have sparsely been studied in brain tumors. Here, we identify the ability of intracranial neoplasms to hijack the meningeal venolymphatic network, which is driven through VEGFR-2/VEGF-A signaling. METHODS: C57BL/6J mice were stereotactically injected with syngeneic SB28 (glioblastoma) cell lines. Mice were treated with either isotype control or a VEGFR-2 inhibitor. Two-photon microscopy was used to visualize vascular cytoarchitecture and dynamics in vivo. Meningeal whole mounts, brains and spleens were also collected and analyzed by confocal microscopy and high parameter flow cytometry. Human dura mater from glioblastoma patients underwent multiplex immunohistochemistry to confirm the translatability of our findings. RESULTS: Our imaging studies revealed that glioblastomas can generate an extensive de novo network of meningeal blood vessels and lymphatics both in mice and humans. Lymphatic vessels were often observed developing in parallel to the newly formed vasculature. Intravital two-photon microscopy further revealed that the peritumoral vascular bed in the meninges of mice was leaky, dysfunctional, and generated a hypoxic microenvironment. Importantly, inhibition of VEGFR signaling impeded formation of this faulty venolymphatic network, which slowed tumor growth, reduced peritumoral hypoxia, enhanced immune infiltration, and increased survival. CONCLUSIONS: Our results demonstrate that glioblastomas can invade the meninges and hijack the venolymphatic network through VEGFR-2 and PECAM-1 signaling. While VEGFR-2 is associated with angiogenesis, our data suggest that it may also have an important role in regulating the simultaneous development of de novo meningeal venous and lymphatic drainage during glioblastoma.

MODL-01. INTRACRANIAL TUMORS HIJACK THE MENINGEAL VENOLYMPHATIC NETWORK THROUGH VEGFR-2 SIGNALING

Abstract INTRODUCTION Glioblastoma and other intracranial neoplasms have been associated with breakdown of the blood brain barrier. Other protective CNS barriers have sparsely been studied in brain tumors. Here, we identify the ability of intracranial neoplasms to hijack the meningeal venolymphatic network, which is driven through VEGFR-2/VEGF-A signaling. METHODS C57BL/6J mice were stereotactically injected with syngeneic SB28 (glioblastoma) cell lines. Mice were treated with either isotype control or a VEGFR-2 inhibitor. Two-photon microscopy was used to visualize vascular cytoarchitecture and dynamics in vivo. Meningeal whole mounts, brains and spleens were also collected and analyzed by confocal microscopy and high parameter flow cytometry. Similar experiments were conducted with a PECAM-1 inhibitor to assess the role of endothelial cell crosstalk in venolymphatic expansion. Human dura mater from glioblastoma patients underwent multiplex immunohistochemistry to confirm the translatability of our findings. RESULTS Our imaging studies revealed that glioblastomas can generate an extensive de novo network of meningeal blood vessels and lymphatics both in mice and humans. Lymphatic vessels were often observed developing in parallel to the newly formed vasculature. Intravital two-photon microscopy further revealed that the peritumoral vascular bed in the meninges of mice was leaky, dysfunctional, and generated a hypoxic microenvironment. Importantly, inhibition of VEGFR signaling impeded formation of this faulty venolymphatic network, which slowed tumor growth, reduced peritumoral hypoxia, enhanced immune infiltration, and increased survival. PECAM-1 (CD31) inhibition had a similar effect on the tumor microenvironment, suggesting that endothelial cell crosstalk is required for glioblastomas to optimally invade the meninges. CONCLUSION Our results demonstrate that glioblastomas can invade the meninges and hijack the venolymphatic network through VEGFR-2 and PECAM-1 signaling. While VEGFR-2 is associated with angiogenesis, our data suggest that it may also have an important role in regulating the simultaneous development of de novo meningeal venous and lymphatic drainage during glioblastoma.

Dendritic cell expansion and activation enhances the adaptive immune response against TNBC brain metastases

Abstract Despite initial control by chemotherapy, Triple Negative Breast Cancer (TNBC) quickly acquires resistance and metastasizes to distal organs, including the brain. Median survival following diagnosis of TNBC brain metastases is a meager 7.3 months—indicative of a substantial unmet clinical need, with only a small subpopulation responding to checkpoint immunotherapy. As suboptimal antigen presentation can contribute to the weak T lymphocyte response to intracranial tumors, we hypothesized that enhancing dendritic cell (DC) presence in tumors may support intracranial T cell responses to tumors. Using a murine model of intracranial metastasis, we assessed immune cell frequency and function and in vivocytokine staining for flow cytometry to test whether Flt3L can be used to promote DC presence within tumors, and whether the addition of polyIC further enhances subsequent T cell responses. Flt3L treatment effectively increases the number of DC within the brains and meninges of mice, however these newly expanded populations exhibit lower proportions of the costimulatory molecule CD86 than the untreated control group, indicative of an immature phenotype. 24 hours after polyIC treatment, a higher percentage of DCs in brain tumors express CD86 but do not produce IL-12. Despite the lack of intratumoral IL-12, the combination of Flt3L and polyIC treatments led to a higher presence of T cells within tumors and their production of IFN-γ in the TME than either treatment alone. In conclusion, simply increasing the presence of DC within intracranial tumors is insufficient to promote T cell immunity; rather, deliberate activation of de novo DC is required for this full effect. Supported by grants from NIH (2T32CA009109-46 and 1R21CA226607-01A1) and the Schiff Foundation

461 Intracranial Tumors Hijack the Meningeal Venolymphatic Network Through VEGFR-2 Signaling

INTRODUCTION: Glioblastoma and other intracranial neoplasms have been associated with breakdown of the blood brain barrier. Other protective CNS barriers have sparsely been studied in brain tumors. Here, we identify the ability of intracranial neoplasms to hijack the meningeal venolymphatic network, which is driven through VEGFR-2/VEGF-A signaling. METHODS: C57BL/6J mice were stereotactically injected with syngeneic SB28 (glioblastoma) cell lines. Mice were treated with either isotype control or a VEGFR-2 inhibitor. Two-photon microscopy was used to visualize vascular cytoarchitecture and dynamics in vivo. Meningeal whole mounts, brains and spleens were also collected and analyzed by confocal microscopy and high parameter flow cytometry. Similar experiments were conducted with a PECAM-1 inhibitor to assess the role of endothelial cell crosstalk in venolymphatic expansion. Human dura mater from glioblastoma patients underwent multiplex immunohistochemistry to confirm the translatability of our findings. RESULTS: Our imaging studies revealed that glioblastomas can generate an extensive de novo network of meningeal blood vessels and lymphatics both in mice and humans. Lymphatic vessels were often observed developing in parallel to the newly formed vasculature. Intravital two-photon microscopy further revealed that the peritumoral vascular bed in the meninges of mice was leaky, dysfunctional, and generated a hypoxic microenvironment. Importantly, inhibition of VEGFR signaling impeded formation of this faulty venolymphatic network, which slowed tumor growth, reduced peritumoral hypoxia, enhanced immune infiltration, and increased survival. PECAM-1 (CD31) inhibition had a similar effect on the tumor microenvironment, suggesting that endothelial cell crosstalk is required for glioblastomas to optimally invade the meninges. CONCLUSIONS: Our results demonstrate that glioblastomas can invade the meninges and hijack the venolymphatic network through VEGFR-2 and PECAM-1 signaling. While VEGFR-2 is associated with angiogenesis, our data suggest that it may also have an important role in regulating the simultaneous development of de novo meningeal venous and lymphatic drainage during glioblastoma.

196 Multi-omic Convergence of Human Craniosynostosis Genes Within a Developmental Bone-Dura-Brain Nexus

INTRODUCTION: Craniosynostosis (CS) is the premature fusion of the calvarial sutures and has long been considered mostly an aesthetic disorder, despite many affected children experiencing neurocognitive deficiencies and seizures. The two types of CS, syndromic and non-syndromic, present with significant genetic clinical heterogeneity, suggesting a complex interplay of genetic and environmental causes. Given the neurodevelopmental symptoms observed in CS patients, we hypothesized the genes involved in the pathophysiology of CS may play a key role in the functional development of the brain. METHODS: We applied a multimodal integrative genomic approach to examine the functional relationships as well as the spatiotemporal and cellular interactions of all currently known craniosynostosis-associated genes (CSGs) and also explored whether they are linked to other neurodevelopmental disorders (NDD). To this end, we constructed gene co-expression modules using a bulk-RNA expression dataset with 27 human brains encompassing 16 human brain regions across fetal development into early childhood. We further used scRNA-seq datasets derived from embryonic mouse meninges, calvarial sutures and developmental human brain to identify cell-types enriched with CSGs. RESULTS: The set of co-expression modules significantly enriched with CSGs were highly expressed during mid-gestation and in primary motor, somatosensory and prefrontal cortices, and the ganglionic eminence. Moreover, some of these modules were also significantly enriched with autism-spectrum disorder (ASD) and NDD genes. The most significant modules were associated with histone-3 lysine-4 methylation, neural crest differentiation, endochondral ossification and reactive astrogliosis. The mouse meninges scRNAseq analysis showed enrichment in pial and dural fibroblasts. The whole-brain scRNA-seq analysis showed CSGs were enriched in medial ganglionic eminence (MGE)-derived cortical interneurons, astrocytes and oligodendrocyte precursors during mid-fetal brain development. CONCLUSION: CSGs may contribute to pathogenesis through epigenetic dysregulation, disrupted neural crest differentiation facilitated by neuroglial cells and MGE interneuron migration very early during development. These processes are in confluence with premature suture fusion mediated by dural and pial fibroblasts.

Targeting the Meningeal Compartment to Resolve Chemobrain and Neuropathy via Nasal Delivery of Functionalized Mitochondria.

Cognitive deficits (chemobrain) and peripheral neuropathy occur in ∼75% of patients treated for cancer with chemotherapy and persist long-term in >30%of survivors. Without preventive or curative interventions and with increasing survivorship rates, the population debilitated by these neurotoxicities is rising. Platinum-based chemotherapeutics, including cisplatin, induce neuronal mitochondrial defects leading to chemobrain and neuropathic pain. This study investigates the capacity of nasally administered mesenchymal stem cell-derived mitochondria coated with dextran-triphenylphosphonium polymer (coated mitochondria) to reverse these neurotoxicities. Nasally administered coated mitochondria are rapidly detectable in macrophages in the brain meninges but do not reach the brain parenchyma. The coated mitochondria change expression of >2400genes regulating immune, neuronal, endocrine and vascular pathways in the meninges of mice treated with cisplatin. Nasal administration of coated mitochondria reverses cisplatin-induced cognitive deficits and resolves neuropathic pain at a >55-timeslower dose compared to uncoated mitochondria. Reversal of these neuropathologies is associated with resolution of cisplatin-induced deficits in myelination, synaptosomal mitochondrial integrity and neurogenesis. These findings demonstrate that nasally administered coated mitochondria promote resolution of chemobrain and peripheral neuropathy, thereby identifying a novel facile strategy for clinical application of mitochondrial donation and treating central and peripheral nervous system pathologies by targeting the brain meninges.

Migraine-relevant sex-dependent activation of mouse meningeal afferents by TRPM3 agonists

BackgroundMigraine is a common brain disorder that predominantly affects women. Migraine pain seems mediated by the activation of mechanosensitive channels in meningeal afferents. Given the role of transient receptor potential melastatin 3 (TRPM3) channels in mechanical activation, as well as hormonal regulation, these channels may play a role in the sex difference in migraine. Therefore, we investigated whether nociceptive firing induced by TRPM3 channel agonists in meningeal afferents was different between male and female mice. In addition, we assessed the relative contribution of mechanosensitive TRPM3 channels and that of mechanosensitive Piezo1 channels and transient receptor potential vanilloid 1 (TRPV1) channels to nociceptive firing relevant to migraine in both sexes.MethodsTen- to 13-week-old male and female wildtype (WT) C57BL/6 J mice were used. Nociceptive spikes were recorded directly from nerve terminals in the meninges in the hemiskull preparations.ResultsSelective agonists of TRPM3 channels profoundly activated peripheral trigeminal nerve fibres in mouse meninges. A sex difference was observed for nociceptive firing induced by either PregS or CIM0216, both agonists of TRPM3 channels, with the induced firing being particularly prominent for female mice. Application of Yoda1, an agonist of Piezo1 channels, or capsaicin activating TRPV1 channels, although also leading to increased nociceptive firing of meningeal fibres, did not reveal a sex difference. Cluster analyses of spike activities indicated a massive and long-lasting activation of TRPM3 channels with preferential induction of large-amplitude spikes in female mice. Additional spectral analysis revealed ​a dominant contribution of spiking activity in the α- and β-ranges following TRPM3 agonists in female mice.ConclusionsTogether, we revealed a specific mechanosensitive profile of nociceptive firing in females and suggest TRPM3 channels as a potential novel candidate for the generation of migraine pain, with particular relevance to females.

DuraBle tolerance to CNS antigens.

B cell development occurs in the meninges of mice and primates, and central nervous system antigen–specific B cells are negatively selected there but not in bone marrow.

Early developing B cells undergo negative selection by central nervous system-specific antigens in the meninges

Self-reactive B cell progenitors are eliminated through central tolerance checkpoints, a process thought to be restricted to the bone marrow in mammals. Here, we identified a consecutive trajectory of B cell development in the meninges of mice and non-human primates. The meningeal B cells were located predominantly at the dural sinuses, where endothelial cells expressed essential niche factors to support B cell development. Parabiosis experiments together with lineage tracing showed that meningeal developing B cells were replenished continuously from hematopoietic stem cell (HSC)-derived progenitors via a circulation-independent route. Autoreactive immature B cells that recognized myelin oligodendrocyte glycoprotein (MOG), a central nervous system-specific antigen, were eliminated specifically from the meninges. Furthermore, genetic deletion of the Mog gene restored the self-reactive B cell population in the meninges. These findings identify the meninges as a distinct reservoir for B cell development, allowing in situ negative selection to ensure a locally non-self-reactive immune repertoire.

Cells with Many Talents: Lymphatic Endothelial Cells in the Brain Meninges.

The lymphatic system serves key functions in maintaining fluid homeostasis, the uptake of dietary fats in the small intestine, and the trafficking of immune cells. Almost all vascularized peripheral tissues and organs contain lymphatic vessels. The brain parenchyma, however, is considered immune privileged and devoid of lymphatic structures. This contrasts with the notion that the brain is metabolically extremely active, produces large amounts of waste and metabolites that need to be cleared, and is especially sensitive to edema formation. Recently, meningeal lymphatic vessels in mammals and zebrafish have been (re-)discovered, but how they contribute to fluid drainage is still not fully understood. Here, we discuss these meningeal vessel systems as well as a newly described cell population in the zebrafish and mouse meninges. These cells, termed brain lymphatic endothelial cells/Fluorescent Granular Perithelial cells/meningeal mural lymphatic endothelial cells in fish, and Leptomeningeal Lymphatic Endothelial Cells in mice, exhibit remarkable features. They have a typical lymphatic endothelial gene expression signature but do not form vessels and rather constitute a meshwork of single cells, covering the brain surface.

Radiation Disrupts the Protective Function of the Spinal Meninges in a Mouse Model of Tumor-induced Spinal Cord Compression.

Radiation Disrupts the Protective Function of the Spinal Meninges in a Mouse Model of Tumor-induced Spinal Cord Compression.

PF150 ADAM28 OVEREXPRESSION IN ACUTE LYMPHOBLASTIC LEUKEMIA PROMOTE ITS INVASION IN CENTRAL NEURAL SYSTEM VIA CROSS TALKING WITH CXCR4 PATHWAY

Background:ADAM28 has been shown to relate with tumor proliferation, metastasis and prognosis. Our previous work showed that overexpression of ADAM28 in bone marrow of acute lymphoblastic leukemia (ALL) patients is related with poor prognosis. Central neural system (CNS) involvement is still a challenge in treatment of ALL and the mechanism is unknown. Our study revealed that the overexpression of ADAM28 might be one of the indicator and key mechanism in the occurrence of CNS leukemia.Aims:To explore the effect and mechanism of ADAM28 expression in ALL blast cell on its CNS metastasis.Methods:Bone marrow samples were collected from 50 ALL patients and 10 healthy donors. The expression of ADAM28 in BM were detected through flow cytometry. The tumor xenograft mouse model was established via the femoral vein injection of primary ALL cells or Nalm‐6 cell line after a sublethally irradiation and intraperitoneal injection with CD122 in male 8‐week‐old NOD/SCID mice. CNS symptoms such as seizures and paraplegia were observed after the injection of ALL cells. The mice were sacrificed on days 1, 3, 5, and 7 after injection respectively, and the brain, liver, spleen, kidney and BM were collected, samples were then embedded in paraffin. Sections were mounted on slides, deparaffinized and stained with hematoxylin and eosin (HE) or anti‐CD45 antibody. Knock‐down and overexpression of ADAM28 in primary ALL cells and cell line were achieved by transfection of ADAM28‐shRNA or ADAM28 plasmid. Ly294002 as ADAM28 inhibitor and CXCR4 Inhibitory antibody were added in the in vitro culture of primary ALL cells and cell lines. Transwell chambers were used to verify the migration and invasion ability of ALL cells. Western blot (WB) and RT‐PCR was performed to verify the expression level of ADAM28, CXCR4, IGFBP3 in order to analysis the cross talk between the two pathways.Results:The expression of ADAM28 in BM of ALL patients with CNSL were significantly higher than that in ALL patients without CNSL. In the xenograft mouse model, mice injected with ALL cells in which ADAM28 was overexpressed showed a significant higher incidence rate of seizures or paraplegia. The HE stain results showed that the involvement of brain and meninges in ADAM28 overexpress group was significantly higher than control, while there was no difference in liver, spleen and kidney invasion in the two groups. Clonal tracking experiments results that most of the ALL cells observed in brain and meninges of mice injected the mixture of ADAM28‐overexpression‐GFP ALL cells and empty plasmid ALL cells were GFP positive, which demonstrated that the invasion of ALL cells was increased when ADAM28 overexpressing. In vitro, transwell chamber results showed that the migration ability of ALL cells with high ADAM28 level was significantly higher than that of controls, and the migration ability was decreased when ADAM28 was knocked down or treated with ADAM28 inhibitor. Additional, when ADAM28 was knocked down, the expression of CXCR4 in mRNA level and protein level were decreased, and the ADAM28 expression level was decreased when decreased when treated with CXCR4 inhibitory antibodies, which suggested that there might be a cross talk between ADAM28 and CXCR4 signaling pathway.Summary/Conclusion:The incidence of CNSL in ADAM28 overexpressing ALL patients was increased. The invasion into CNS of ALL cells was increased when ADAM28 was overexpressed in xenograft mouse model. ADAM28 might promote the migration and invasion ability via cross talking with CXCR4 pathway.

Overcoming Acute Lymphoblastic Leukemia Chemoresistance Induced By the Meninges

Central nervous system (CNS) relapse is a leading cause of treatment failure in acute lymphoblastic leukemia (ALL). We have shown that the meninges provide a unique leukemia niche in the CNS that enhances leukemia chemoresistance through effects on apoptosis and quiescence. We now describe our work to leverage this new knowledge of the CNS leukemia niche into novel CNS-directed leukemia therapies that 1) target vulnerabilities unique to leukemia cells in the meninges, 2) inhibit the meningeal pathways that contribute to leukemia chemoresistance, and 3) disrupt the interactions between leukemia and meningeal cells.First, we focused on identifying and targeting vulnerabilities unique to leukemia cells in the meninges. We used a leukemia-meningeal co-culture system and tested the ability of drugs targeting pathways important for leukemia biology to overcome meningeal-mediated leukemia resistance to cytarabine and methotrexate. Intriguingly, we found that pre-treatment of leukemia cells with ruxolitinib, a JAK1/2 inhibitor, prior to co-culture with primary meningeal cells diminished leukemia chemoresistance. Ruxolitinib had no effect on the chemosensitivity of leukemia cells in suspension. Other JAK1/2 inhibitors, such as CHZ868, yielded comparable results and we are currently testing the ability of JAK2 knockdown by shRNA in leukemia cells to overcome chemoresistance. As a potential explanation for the mechanism by which ruxolitinib overcomes meningeal-mediated leukemia resistance, we found that ruxolitinib decreases leukemia quiescence and enhances proliferation in co-culture, as measured by FxCycle and Ki67 staining. Finally, preliminary experiments in xenotransplanted mice showed that ruxolitinib significantly enhanced the efficacy of cytarabine in treating leukemia in the meninges.Second, we also identified and therapeutically targeted meningeal signaling pathways that contribute to leukemia chemoresistance. We used reverse phase protein arrays (RPPA; MD Anderson) to assess the effects of co-culture on protein expression and phosphorylation in primary meningeal cells. RPPA determines the levels of >300 proteins involved in multiple signaling pathways. Amongst other findings, we identified activation of the AKT pathway in primary meningeal cells in the presence of leukemia cells. Furthermore, pre-treatment of primary meningeal cells with INK128, an inhibitor that acts downstream of AKT and targets mTOR, prior to co-culture with leukemia cells diminished leukemia chemoresistance.Third, we tested whether disrupting meningeal-leukemia adhesion overcomes leukemia chemoresistance. Leukemia cells were dissociated from meningeal cells with trypsin and manual pipetting after co-culture for 48-72 hours. Leukemia cells were then purified with magnetic beads and placed back in suspension prior to further characterization and drug testing. We found leukemia cells placed back into suspension after co-culture with meningeal cells, or isolated from the meninges of mice, reverted back to baseline cell cycle, quiescence, and apoptosis balance characteristics. Moreover, leukemia cells removed from co-culture exhibited similar sensitivity to methotrexate and cytarabine as leukemia cells in suspension. These results suggest that drugs or biologic agents that disrupt adhesion between leukemia and meningeal cells may restore leukemia chemosensitivity in the CNS niche. Accordingly, we next identified several cell adhesion inhibitors that effectively disrupted leukemia-meningeal adhesion in co-culture. The more promising agents are currently being characterized more extensively in co-culture and tested in combination with chemotherapy in xenotransplanted mice.In summary, in order to address the need for more efficacious and less toxic therapies for CNS leukemia, we have identified mechanisms by which the meninges enhance leukemia chemoresistance. We are now testing novel strategies for overcoming leukemia chemoresistance that by targeting different components of the CNS leukemia niche (leukemia cells, meningeal cells, or the interactions between the two cell types) may be complementary or even synergistic. DisclosuresNo relevant conflicts of interest to declare.

Leptin Receptor Expression in Mouse Intracranial Perivascular Cells.

Past studies have suggested that non-neuronal brain cells express the leptin receptor. However, the identity and distribution of these leptin receptor-expressing non-neuronal brain cells remain debated. This study assessed the distribution of the long form of the leptin receptor (LepRb) in non-neuronal brain cells using a reporter mouse model in which LepRb-expressing cells are permanently marked by tdTomato fluorescent protein (LepRb-CretdTomato). Double immunohistochemistry revealed that, in agreement with the literature, the vast majority of tdTomato-tagged cells across the mouse brain were neurons (i.e., based on immunoreactivity for NeuN). Non-neuronal structures also contained tdTomato-positive cells, including the choroid plexus and the perivascular space of the meninges and, to a lesser extent, the brain. Based on morphological criteria and immunohistochemistry, perivascular cells were deduced to be mainly pericytes. Notably, tdTomato-positive cells were immunoreactive for vitronectin and platelet derived growth factor receptor beta (PDGFBR). In situ hybridization studies confirmed that most tdTomato-tagged perivascular cells were enriched in leptin receptor mRNA (all isoforms). Using qPCR studies, we confirmed that the mouse meninges were enriched in Leprb and, to a greater extent, the short isoforms of the leptin receptor. Interestingly, qPCR studies further demonstrated significantly altered expression for Vtn and Pdgfrb in the meninges and hypothalamus of LepRb-deficient mice. Collectively, our data demonstrate that the only intracranial non-neuronal cells that express LepRb in the adult mouse are cells that form the blood-brain barrier, including, most notably, meningeal perivascular cells. Our data suggest that pericytic leptin signaling plays a role in the integrity of the intracranial perivascular space and, consequently, may provide a link between obesity and numerous brain diseases.

The amazing brain drain.

In this issue of JEM, Antila et al. (https://doi.org/10.1084/jem.20170391) demonstrate that central nervous system lymphatics develop in the mouse meninges during early postnatal periods and display remarkable plasticity in adult periods through manipulation of VEGF-C-VEGFR3 signaling.

Characterization of meningeal type 2 innate lymphocytes and their response to CNS injury.

The meningeal space is occupied by a diverse repertoire of immune cells. Central nervous system (CNS) injury elicits a rapid immune response that affects neuronal survival and recovery, but the role of meningeal inflammation remains poorly understood. Here, we describe type 2 innate lymphocytes (ILC2s) as a novel cell type resident in the healthy meninges that are activated after CNS injury. ILC2s are present throughout the naive mouse meninges, though are concentrated around the dural sinuses, and have a unique transcriptional profile. After spinal cord injury (SCI), meningeal ILC2s are activated in an IL-33-dependent manner, producing type 2 cytokines. Using RNAseq, we characterized the gene programs that underlie the ILC2 activation state. Finally, addition of wild-type lung-derived ILC2s into the meningeal space of IL-33R-/- animals partially improves recovery after SCI. These data characterize ILC2s as a novel meningeal cell type that responds to SCI and could lead to new therapeutic insights for neuroinflammatory conditions.

Meningeal Melanocytes in the Mouse: Distribution and Dependence on Mitf.

Summary: Melanocytes are pigment producing cells derived from the neural crest. They are primarily found in the skin and hair follicles, but can also be found in other tissues including the eye, ear and heart. Here, we describe the distribution of pigmented cells in C57BL/6J mouse meninges, the membranes that envelope the brain. These cells contain melanosomes of all four stages of development and they depend on Microphthalmia associated transcription factor (MITF), the master regulator of melanocyte development, suggesting that they are bona-fide melanocytes. The location of these pigmented cells is consistent with the location of meningeal melanomas in humans and animal models.Significance: Here, we document and define pigmented cells in the meninges of the mouse brain and confirm that they are melanocytes. This is important for understanding the role of this cell type and for understanding primary meningeal melanoma, a rare disease that likely arises from normal meningeal melanocytes.

Characterization of resident plasma cells in and their migration to the inflamed central nervous system during experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is one of the most abundant neurological diseases causing disability in young adults. Immunological aspects of MS include intrathecal antibody production. These antibodies might have disease-promoting effects like directly affecting the integrity of the myelin sheath of the central nervous system (CNS). In our study we were able to show the presence of antigen producing plasma cells in the subarachnoidal space in the meninges of mice with ongoing experimental autoimmune encephalomyelitis (EAE).

Dynamics of the meningeal CD4+ T-cell repertoire are defined by the cervical lymph nodes and facilitate cognitive task performance in mice

The traditional view of the central nervous system (CNS) as an immune-privileged organ yielded a longstanding perception of such interactions—as seen for example in multiple sclerosis (MS) 1, 2—as intrinsically destructive. This notion is changing with the identification of several homeostatic functions attributable to beneficial T-cell/CNS interaction 3, for example in hippocampal-dependent learning 4 and stress response paradigms 5, and in models of neurodegeneration and CNS injury 6. Here we provide insights into the maintenance, and dynamics of the meningeal T-cell repertoire. We show that meningeal T-cell composition is coupled to the CNS-draining deep cervical lymph nodes (dCLNs), whose surgical removal interrupted the normal flow of meningeal T-cells and resulted in cognitive impairment.

Spontaneous locomotor activity correlates with the degranulation of mast cells in the meninges rather than in the thalamus: Disruptive effect of cocaine

Mast cells are located in the central nervous system (CNS) of many mammals and stress induces their degranulation. We postulated that mast cells are associated with wakefulness and stimulatory tone in the CNS, as reflected by spontaneous motor activity. Because stress also precipitates drug-seeking behavior in cocaine addicts, we also postulated that cocaine manifests its effects through this relationship. We investigated the influence of single and repeated injections of cocaine on circulating corticosterone, motor activity and degranulation of mast cells in both the thalamus and meninges of mice. Mice were subjected to 5 consecutive days of cocaine or saline followed by a single injection of cocaine or saline 11 days later. Spontaneous locomotor activity was measure for 1 h after the final injection before death. Neither a single injection nor prior treatment with cocaine increased motor activity compared to saline-injected controls, however, repeated administration of cocaine induced a significant sensitization to its behavioral effect when delivered 11 days later. In mice that received only saline, motor activity correlated positively with mast cell degranulation in the meninges but not in the thalamus. Cocaine, regardless of the treatment schedule, disrupted this correlation. The concentration of corticosterone did not differ amongst groups and did not correlate with either behavior or mast cell parameters in any group. The correlation between behavioral activity and the mast cell degranulation in the meninges suggests that these parameters are linked. The disruptive effect of cocaine on this relationship indicates a role downstream from mast cells in the regulation of motor activity.