The role of CD11C positive and negative microglia populations in Neuromyelitis optica
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ABSTRACT: Background: Tissue macrophages contribute to development and protection, both requiring appropriately timed and located source(s) of factors controlling growth, cell differentiation and migration. Goal: To understand the role of microglia (tissue macrophages of the central nervous system), in promoting neurodevelopment and controlling neuroinflammation. Summary of findings: We show that microglia fulfill both these roles. In contrast to adult cells, neonatal microglia show a unique neurogenic phenotype with stem cell-like potential. Neonatal microglia are protective against neuroinflammation, and their transplantation ameliorates experimental autoimmune encephalomyelitis. A CD11c+ microglial subset predominates in primary myelinating areas of the developing brain and expresses genes for neuronal and glial survival, migration and differentiation. CD11c+ microglia are also found in clusters of repopulating microglia after experimental ablation and in neuroinflammation in adult mice, but despite some similarities, they do not recapitulate neurogenic neonatal microglia characteristics. Conclusions: We therefore identify a unique phenotype of neonatal microglia that deliver signals necessary for neurogenesis and myelination and suppress neuroinflammation.
Project description:Background: Tissue macrophages contribute to development and protection, both requiring appropriately timed and located source(s) of factors controlling growth, cell differentiation and migration. Goal: To understand the role of microglia (tissue macrophages of the central nervous system), in promoting neurodevelopment and controlling neuroinflammation. Summary of findings: We show that microglia fulfill both these roles. In contrast to adult cells, neonatal microglia show a unique neurogenic phenotype with stem cell-like potential. Neonatal microglia are protective against neuroinflammation, and their transplantation ameliorates experimental autoimmune encephalomyelitis. A CD11c+ microglial subset predominates in primary myelinating areas of the developing brain and expresses genes for neuronal and glial survival, migration and differentiation. CD11c+ microglia are also found in clusters of repopulating microglia after experimental ablation and in neuroinflammation in adult mice, but despite some similarities, they do not recapitulate neurogenic neonatal microglia characteristics. Conclusions: We therefore identify a unique phenotype of neonatal microglia that deliver signals necessary for neurogenesis and myelination and suppress neuroinflammation.
Project description:Understanding the respective role of microglia and infiltrating monocytes in neuroinflammatory conditions has recently seemed possible by the identification of a specific microglia signature. Here instead we provide evidence that peripheral macrophages may express some of the most commonly described microglia markers at some developmental stages or pathological conditions, in particular during chronic neuroinflammation. Further, our data support the hypothesis about phenotypic plasticity and convergence among distinct myeloid cells so that they may act as a functional unit rather than as different entities, boosting their mutual functions in different phases of disease. This holds relevant implications in the view of the growing use of myeloid cell therapies to treat brain disease in humans.
Project description:Huntington's Disease (HD) is a fatal neurodegenerative disorder caused by an extended polyglutamine repeat in the N-terminus of the huntingtin (Htt) protein. Reactive microglia and elevated cytokine levels are observed in the brains of HD patients, but the extent to which neuroinflammation results from extrinsic or cell-autonomous mechanisms is unknown. Furthermore, the impact of microglia activation on the pathogenesis of HD remains to be established. Using genome-wide approaches, we show that expression of mutant Htt in microglia promotes cell-autonomous pro-inflammatory transcriptional activation within microglia by increasing the expression and transcriptional activities of the myeloid lineage-determining factors PU.1 and C/EBPs. Elevated levels of PU.1 and its target genes are observed in the brains of mouse models and HD individuals. Moreover, mutant Htt expressing microglia exhibit an increased capacity to induce neuronal death ex vivo and in vivo in the presence of sterile inflammation. These findings suggest that expression of mutant Htt in microglia may contribute to neuronal pathology in Huntingtin disease. RNA-Seq and ChIP-Seq for PU.1, C/EBP, and H3K4me2 in BV2 cells and RNA-Seq in primary microglia and macrophages
Project description:Microglia in the spinal dorsal horn have been implicated in the pathogenesis of neuropathic pain following peripheral nerve injury. We have revently found that CD11c-expressing spinal microglia appear after the development of behavioral pain hypersensitivity following nerve injury and are essential for recovery from neuropathic pain. In order to better understand the gene expression profiles of CD11c-expressing microglia, we performed quantitative bulk RNA sequencing of microglia isolated from mice expressing Venus fluorescent protein under the control of CD11c promoter. We found that CD11c-expressing microglia show distinct gene expression profile compared to CD11c-negative microglia following nerve injury.
Project description:Microglia, the parenchymal macrophage of the central nervous system serve crucial remodeling functions throughout development in response to developmental cues. Microglia are transcriptionally heterogenous, suggesting that distinct microglial states confer distinct roles. Currently, little is known about how dynamic these states are, the cues that promote them, or how they impact microglial function. In the developing retina, we previously found a significant proportion of microglia that express CD11c (Integrin αX, complement receptor 4, Itgax). which has also been reported in other developmental and disease contexts. Here, we sought to understand the regulation and function of CD11c+ microglia by examining the developmental contexts and dynamics for the emergence of CD11c+ microglia. We find that microglial CD11c expression tracks with prominent waves of neuronal apoptosis in postnatal retina. Using genetic fate mapping, we provide evidence that microglia transition out of the CD11c state to return to homeostasis. We show that CD11c+ microglia have elevated lysosomal content and contribute to the clearance of apoptotic neurons, and found that acquisition of CD11c expression is, in part, dependent upon the TAM receptor Axl. Using selective ablation, we find similar effects on apoptotic cell clearance with depletion of CD11c+ versus non-CD11c microglia, suggesting that CD11c+ microglia are not uniquely critical for phagocytic clearance. Together, our data suggests CD11c+ microglia are a transient state induced in response to developmental apoptosis rather than a specialized subset mediating phagocytic elimination.
Project description:A phenotypically and functinoally distinct subset of human blood dendritic cells expressing CD11b is specific of the neonatal environment. We have employed whole genome microarray expression profiling to identify the specific gene signature of CD11b+ cord blood dendritic cells as compared to their adult peripheral blood counterparts. Peripheral blood adult cDC2 (CD20- CD11c+ CD14- BDCA1+ CD11b- ), neonatal cord blood cDC2 (CD20- CD11c+ CD14- BDCA1+ CD11b-) and neonatal cord blood cDC2b (CD20- CD11c+ CD14- BDCA1+ CD11b+) were FACS purified from BDCA1+ magnetically. Neonatal monocytes (CD11c+ CD14+) and neonatal naive T cells (CD3+ CD4+ CD56- CD25- CD45RO-) were used as controls.
Project description:Purpose: We purified spinal cord microglia utilizing percoll gradients and magnetic beads, followed by transcriptome profiling (RNA-seq) to define microglia expression profiles against other neural, immune cell-types. We next observed how the microglial transcriptomes change during activation in the SOD1-G93A mouse model of motor neuron degeneration at 3 time points. We also compared these profiles with that induced by LPS injection. Results and conclusions: ALS microglia were found to differ substantially from those activated by LPS and from M1/M2 macrophages by comparison with published datasets. These ALS microglia showing substantial induction of a neurodegeneration-tailored phenotype, with induction of lysosomal, RNA splicing, and Alzheimer's disease pathway genes. Overall they express a mixture of neuroprotective and neurotoxic factors during activation in ALS mice, showing that neuro-immune activation in the spinal cord is a double-edged sword. We also detected the transcriptional nature of surface marker expression in microglia (CD11b, CD86, CD11c), and substantial T-cell microglia cross-talk using correlative microglia transcriptome/FACS analysis. 42 total RNA samples from purified spinal cord microglia were subjected to paired-end RNA-sequencing. Parallel flow cytometry data was collected from the same spinal cords.
Project description:Analysis of LRRK2-regulation of microglia responce to the LPS at gene expression level. The hypothesis tested in the present study was whether LRRK2 influence the microglial phagocytosis- and neuroinflammation- related gene expression at mRNA level. Total RNA obtained from microglia cells isolated from Ntg or LRRK2KO mouse brain subjected to 6 or 24 hours of LPS treatment in vitro
Project description:Microglia are the primary phagocytes in the central nervous system and are responsible for clearing dead cells generated during development or disease. The phagocytic process shapes the phenotype of the microglia, which affects the local environment. A unique population of microglia reside in the ventricular-subventricular zone (V-SVZ) of neonatal mice, but how they influence this neurogenic niche is not well-understood. Here, we demonstrate that phagocytosis creates a pro-neurogenic microglial phenotype in the V-SVZ and that these microglia phagocytose apoptotic cells via the engulfment receptor Jedi-1. Deletion of Jedi-1 decreases apoptotic cell clearance, triggering the development of a neuroinflammatory phenotype, reminiscent of neurodegenerative and-age-associated microglia, that reduces neural precursor proliferation via elevated interleukin (IL)-1β signaling; inhibiton of IL-1 receptor rescues precursor proliferation in vivo. Together, these results reveal a critical role for Jedi-1 in connecting microglial phagocytic activity to a phenotype that promotes neurogenesis in the developing V-SVZ. We performed RNAseq on MACS-sorted microglia from V-SVZ and Cortex of WT and Jedi-1 knockout P7 mice.
Project description:Traumatic Brain injury-induced disturbances in mitochondrial fission-and-fusion dynamics have been linked to the onset and propagation of neuroinflammation and neurodegeneration. However, cell-type-specific contributions and crosstalk between neurons, microglia, and astrocytes in mitochondria-driven neurodegeneration after brain injury remain undefined. We developed a human three-dimensional in vitro triculture tissue model of a contusion injury composed of neurons, microglia, and astrocytes and examined the contributions of mitochondrial dysregulation to neuroinflammation and progression of injury-induced neurodegeneration. Pharmacological studies presented here suggest that fragmented mitochondria released by microglia are a key contributor to secondary neuronal damage progression after contusion injury, a pathway that requires astrocyte-microglia crosstalk. Controlling mitochondrial dysfunction thus offers an exciting option for developing therapies for TBI patients.