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1.
Cell ; 180(5): 833-846.e16, 2020 03 05.
Article in English | MEDLINE | ID: mdl-32142677

ABSTRACT

Cognitive dysfunction and reactive microglia are hallmarks of traumatic brain injury (TBI), yet whether these cells contribute to cognitive deficits and secondary inflammatory pathology remains poorly understood. Here, we show that removal of microglia from the mouse brain has little effect on the outcome of TBI, but inducing the turnover of these cells through either pharmacologic or genetic approaches can yield a neuroprotective microglial phenotype that profoundly aids recovery. The beneficial effects of these repopulating microglia are critically dependent on interleukin-6 (IL-6) trans-signaling via the soluble IL-6 receptor (IL-6R) and robustly support adult neurogenesis, specifically by augmenting the survival of newborn neurons that directly support cognitive function. We conclude that microglia in the mammalian brain can be manipulated to adopt a neuroprotective and pro-regenerative phenotype that can aid repair and alleviate the cognitive deficits arising from brain injury.


Subject(s)
Brain Injuries, Traumatic/therapy , Interleukin-6/genetics , Receptors, Interleukin-6/genetics , Regeneration/genetics , Animals , Brain/growth & development , Brain/pathology , Brain Injuries, Traumatic/genetics , Brain Injuries, Traumatic/pathology , Cognitive Dysfunction/genetics , Cognitive Dysfunction/pathology , Cognitive Dysfunction/therapy , Disease Models, Animal , Humans , Inflammation/genetics , Inflammation/pathology , Mice , Microglia/metabolism , Microglia/pathology , Neurons/metabolism , Neurons/pathology , Neuroprotective Agents/therapeutic use , Signal Transduction/genetics
2.
Blood ; 143(10): 912-929, 2024 Mar 07.
Article in English | MEDLINE | ID: mdl-38048572

ABSTRACT

ABSTRACT: Chronic graft-versus-host disease (cGVHD) remains a significant complication of allogeneic hematopoietic stem cell transplantation. Central nervous system (CNS) involvement is becoming increasingly recognized, in which brain-infiltrating donor major histocompatibility complex (MHC) class II+ bone marrow-derived macrophages (BMDM) drive pathology. BMDM are also mediators of cutaneous and pulmonary cGVHD, and clinical trials assessing the efficacy of antibody blockade of colony-stimulating factor 1 receptor (CSF1R) to deplete macrophages are promising. We hypothesized that CSF1R antibody blockade may also be a useful strategy to prevent/treat CNS cGVHD. Increased blood-brain barrier permeability during acute GVHD (aGVHD) facilitated CNS antibody access and microglia depletion by anti-CSF1R treatment. However, CSF1R blockade early after transplant unexpectedly exacerbated aGVHD neuroinflammation. In established cGVHD, vascular changes and anti-CSF1R efficacy were more limited. Anti-CSF1R-treated mice retained donor BMDM, activated microglia, CD8+ and CD4+ T cells, and local cytokine expression in the brain. These findings were recapitulated in GVHD recipients, in which CSF1R was conditionally depleted in donor CX3CR1+ BMDM. Notably, inhibition of CSF1R signaling after transplant failed to reverse GVHD-induced behavioral changes. Moreover, we observed aberrant behavior in non-GVHD control recipients administered anti-CSF1R blocking antibody and naïve mice lacking CSF1R in CX3CR1+ cells, revealing a novel role for homeostatic microglia and indicating that ongoing clinical trials of CSF1R inhibition should assess neurological adverse events in patients. In contrast, transfer of Ifngr-/- grafts could reduce MHC class II+ BMDM infiltration, resulting in improved neurocognitive function. Our findings highlight unexpected neurological immune toxicity during CSF1R blockade and provide alternative targets for the treatment of cGVHD within the CNS.


Subject(s)
Graft vs Host Disease , Hematopoietic Stem Cell Transplantation , Humans , Mice , Animals , Neuroinflammatory Diseases , Graft vs Host Disease/etiology , Hematopoietic Stem Cell Transplantation/adverse effects , CD4-Positive T-Lymphocytes , Macrophages/pathology , Receptor Protein-Tyrosine Kinases , Receptors, Colony-Stimulating Factor
3.
J Neuroinflammation ; 21(1): 63, 2024 Mar 01.
Article in English | MEDLINE | ID: mdl-38429643

ABSTRACT

Next-generation humanised mouse models and single-cell RNA sequencing (scRNAseq) approaches enable in-depth studies into human immune cell biology. Here we used NSG-SGM3 mice engrafted with human umbilical cord haematopoietic stem cells to investigate how human immune cells respond to and/or are changed by traumatic spinal cord injury (SCI). We hypothesised that the use of such mice could help advance our understanding of spinal cord injury-induced immune depression syndrome (SCI-IDS), and also how human leukocytes change as they migrate from the circulation into the lesion site. Our scRNAseq experiments, supplemented by flow cytometry, demonstrate the existence of up to 11 human immune cell (sub-) types and/or states across the blood and injured spinal cord (7 days post-SCI) of humanised NSG-SGM3 mice. Further comparisons of human immune cell transcriptomes between naïve, sham-operated and SCI mice identified a total of 579 differentially expressed genes, 190 of which were 'SCI-specific' (that is, genes regulated only in response to SCI but not sham surgery). Gene ontology analysis showed a prominent downregulation of immune cell function under SCI conditions, including for T cell receptor signalling and antigen presentation, confirming the presence of SCI-IDS and the transcriptional signature of human leukocytes in association with this phenomenon. We also highlight the activating influence of the local spinal cord lesion microenvironment by comparing the transcriptomes of circulating versus infiltrated human immune cells; those isolated from the lesion site were enriched for genes relating to both immune cell activity and function (e.g., oxidative phosphorylation, T cell proliferation and antigen presentation). We lastly applied an integrated bioinformatics approach to determine where immune responses in humanised NSG-SGM3 mice appear congruent to the native responses of human SCI patients, and where they diverge. Collectively, our study provides a valuable resource and methodological framework for the use of these mice in translational research.


Subject(s)
Spinal Cord Diseases , Spinal Cord Injuries , Mice , Humans , Animals , Spinal Cord Injuries/metabolism , Leukocytes/pathology , Gene Expression , Sequence Analysis, RNA
4.
Brain Behav Immun ; 117: 181-194, 2024 03.
Article in English | MEDLINE | ID: mdl-38211634

ABSTRACT

Traumatic brain injury (TBI) results in prolonged and non-resolving activation of microglia. Forced turnover of these cells during the acute phase of TBI aids recovery, but the cell-intrinsic pathways that underpin the pro-repair phenotype of these repopulating microglia remain unclear. Here, we show that selective targeting of ROCK2 with the small molecule inhibitor KD025 impairs the proliferative response of microglia after TBI as well as during genetically induced turnover of microglia. KD025 treatment abolished the substantial neuroprotective and cognitive benefits conferred by repopulating microglia, preventing these cells from replenishing the depleted niche during the early critical time window post-injury. Delaying KD025 treatment to the subacute phase of TBI allowed microglial repopulation to occur, but this did not enhance the benefits conferred by repopulating microglia. Taken together, our data indicate that ROCK2 mediates neuronal survival and microglial population dynamics after TBI, including the emergence of repopulating microglia with a pro-repair phenotype.


Subject(s)
Brain Injuries, Traumatic , Microglia , Humans , Cell Proliferation , Cell Survival , Hydrolases , rho-Associated Kinases
5.
Brain Behav Immun ; 109: 37-50, 2023 03.
Article in English | MEDLINE | ID: mdl-36581304

ABSTRACT

Intravenous immunoglobulin (IVIG) is a promising immune-modulatory therapy for limiting harmful inflammation and associated secondary tissue loss in neurotrauma. Here, we show that IVIG therapy attenuates spatial learning and memory deficits following a controlled cortical impact mouse model of traumatic brain injury (TBI). These improvements in cognitive outcomes were associated with increased neuronal survival, an overall reduction in brain tissue loss, and a greater preservation of neural connectivity. Furthermore, we demonstrate that the presence of the main inhibitory FcγRIIB receptor is required for the beneficial effects of IVIG treatment in TBI, with our results simultaneously highlighting the role of this receptor in reducing secondary damage arising from brain injury.


Subject(s)
Brain Injuries, Traumatic , Brain Injuries , Mice , Animals , Immunoglobulins, Intravenous/pharmacology , Immunoglobulins, Intravenous/therapeutic use , Brain , Brain Injuries, Traumatic/complications , Brain Injuries/complications , Cognition
6.
J Neurosci ; 41(19): 4172-4186, 2021 05 12.
Article in English | MEDLINE | ID: mdl-33785644

ABSTRACT

Microglia, the resident immune cells of the CNS, have emerged as key regulators of neural precursor cell activity in the adult brain. However, the microglia-derived factors that mediate these effects remain largely unknown. In the present study, we investigated a role for microglial brain-derived neurotrophic factor (BDNF), a neurotrophic factor with well known effects on neuronal survival and plasticity. Surprisingly, we found that selective genetic ablation of BDNF from microglia increased the production of newborn neurons under both physiological and inflammatory conditions (e.g., LPS-induced infection and traumatic brain injury). Genetic ablation of BDNF from microglia otherwise also interfered with self-renewal/proliferation, reducing their overall density. In conclusion, we identify microglial BDNF as an important factor regulating microglia population dynamics and states, which in turn influences neurogenesis under both homeostatic and pathologic conditions.SIGNIFICANCE STATEMENT (1) Microglial BDNF contributes to self-renewal and density of microglia in the brain. (2) Selective ablation of BDNF in microglia stimulates neural precursor proliferation. (3) Loss of microglial BDNF augments working memory following traumatic brain injury. (4) Benefits of repopulating microglia on brain injury are not mediated via microglial BDNF.


Subject(s)
Brain-Derived Neurotrophic Factor/genetics , Hippocampus/physiology , Microglia/metabolism , Nerve Regeneration/genetics , Nerve Regeneration/physiology , Neurogenesis/genetics , Neurogenesis/physiology , Animals , Cell Proliferation , Cell Survival/genetics , Dendrites/ultrastructure , Dendritic Spines/ultrastructure , Encephalitis/chemically induced , Encephalitis/pathology , Learning/physiology , Memory/physiology , Mice , Mice, Inbred C57BL , Mice, Knockout , Neural Stem Cells/physiology , Neural Stem Cells/ultrastructure
7.
J Immunol ; 205(10): 2834-2839, 2020 11 15.
Article in English | MEDLINE | ID: mdl-33028618

ABSTRACT

Neutrophil infiltration to ischemic tissues following reperfusion worsens injury. A key driver of neutrophil recruitment and activation is the complement factor C5a, which signals through two receptors, C5aR1 and C5aR2. In this study, we used a neutrophil-dependent mouse model of intestinal ischemia-reperfusion (IR) injury to investigate the underexplored role of C5aR2 in neutrophil mobilization, recruitment, and disease outcomes. We show that intestinal IR induces rapid neutrophil mobilization along with a concomitant reduction in plasma C5a levels that is driven by both C5aR1 and C5aR2. Intestinal IR in C5aR2-/- mice led to worsened intestinal damage and increased neutrophil infiltration. Inhibition of C5aR1 signaling in C5aR2-/- mice with PMX53 prevented neutrophil accumulation and reduced IR pathology, suggesting a key requirement for enhanced neutrophil C5aR1 activation in the absence of C5aR2 signaling. Interestingly, C5aR2 deficiency also reduced circulating neutrophil numbers after IR, as well as following G-CSF-mediated bone marrow mobilization, which was independent of C5aR1, demonstrating that C5aR2 has unique and distinct functions from C5aR1 in neutrophil egress. Despite enhanced tissue injury in C5aR2-/- IR mice, there were significant reductions in intestinal proinflammatory cytokines, highlighting complicated dual protective/pathogenic roles for C5aR2 in pathophysiology. Collectively, we show that C5aR2 is protective in intestinal IR by inhibiting C5aR1-mediated neutrophil recruitment to the ischemic tissue. This is despite the potentially local pathogenic effects of C5aR2 in increasing intestinal proinflammatory cytokines and enhancing circulating neutrophil numbers in response to mobilizing signals. Our data therefore suggest that this balance between the dual pro- and anti-inflammatory roles of C5aR2 ultimately dictates disease outcomes.


Subject(s)
Mesenteric Ischemia/immunology , Neutrophil Infiltration , Receptor, Anaphylatoxin C5a/metabolism , Reperfusion Injury/immunology , Animals , Complement C5a/analysis , Complement C5a/metabolism , Disease Models, Animal , Humans , Jejunum/cytology , Jejunum/immunology , Jejunum/pathology , Male , Mesenteric Ischemia/blood , Mesenteric Ischemia/complications , Mesenteric Ischemia/pathology , Mice , Mice, Knockout , Receptor, Anaphylatoxin C5a/genetics , Reperfusion Injury/blood , Reperfusion Injury/pathology
8.
Curr Opin Neurol ; 34(6): 796-803, 2021 12 01.
Article in English | MEDLINE | ID: mdl-34608075

ABSTRACT

PURPOSE OF REVIEW: To date, prognostication of patients after acute traumatic spinal cord injury (SCI) mostly relies on the neurological assessment of residual function attributed to lesion characteristics. With emerging treatment candidates awaiting to be tested in early clinical trials, there is a need for wholistic high-yield prognostic biomarkers that integrate both neurogenic and nonneurogenic SCI pathophysiology as well as premorbid patient characteristics. RECENT FINDINGS: It is becoming clearer that effective prognostication after acute SCI would benefit from integrating an assessment of pathophysiological changes on a systemic level, and with that, extend from a lesion-centric approach. Immunological markers mirror tissue injury as well as host immune function and are easily accessible through routine blood sampling. New studies have highlighted the value of circulating white blood cells, neutrophils and lymphocytes in particular, as prognostic systemic indicators of SCI severity and outcomes. SUMMARY: We survey recent advances in methods and approaches that may allow for a more refined diagnosis and better prognostication after acute SCI, discuss how these may help deepen our understanding of SCI pathophysiology, and be of use in clinical trials.


Subject(s)
Spinal Cord Injuries , Biomarkers , Humans , Leukocytes , Prognosis , Spinal Cord , Spinal Cord Injuries/diagnosis
9.
J Neuroinflammation ; 18(1): 15, 2021 Jan 06.
Article in English | MEDLINE | ID: mdl-33407641

ABSTRACT

BACKGROUND: The acute phase response (APR) to CNS insults contributes to the overall magnitude and nature of the systemic inflammatory response. Aspects of this response are thought to drive secondary inflammatory pathology at the lesion site, and suppression of the APR can therefore afford some neuroprotection. In this study, we examined the APR in a mouse model of traumatic spinal cord injury (SCI), along with its relationship to neutrophil recruitment during the immediate aftermath of the insult. We specifically investigated the effect of IL-1 receptor antagonist (IL-1RA) administration on the APR and leukocyte recruitment to the injured spinal cord. METHODS: Adult female C57BL/6 mice underwent either a 70kD contusive SCI, or sham surgery, and tissue was collected at 2, 6, 12, and 24 hours post-operation. For IL-1RA experiments, SCI mice received two intraperitoneal injections of human IL-1RA (100mg/kg), or saline as control, immediately following, and 5 hours after impact, and animals were sacrificed 6 hours later. Blood, spleen, liver and spinal cord were collected to study markers of central and peripheral inflammation by flow cytometry, immunohistochemistry and qPCR. Results were analysed by two-way ANOVA or student's t-test, as appropriate. RESULTS: SCI induced a robust APR, hallmarked by elevated hepatic expression of pro-inflammatory marker genes and a significantly increased neutrophil presence in the blood, liver and spleen of these animals, as early as 2 hours after injury. This peripheral response preceded significant neutrophil infiltration of the spinal cord, which peaked 24 hours post-SCI. Although expression of IL-1RA was also induced in the liver following SCI, its response was delayed compared to IL-1ß. Exogenous administration of IL-1RA during this putative therapeutic window was able to suppress the hepatic APR, as evidenced by a reduction in CXCL1 and SAA-2 expression as well as a significant decrease in neutrophil infiltration in both the liver and the injured spinal cord itself. CONCLUSIONS: Our data indicate that peripheral administration of IL-1RA can attenuate the APR which in turn reduces immune cell infiltration at the spinal cord lesion site. We propose IL-1RA treatment as a viable therapeutic strategy to minimise the harmful effects of SCI-induced inflammation.


Subject(s)
Acute-Phase Reaction/immunology , Acute-Phase Reaction/prevention & control , Interleukin 1 Receptor Antagonist Protein/administration & dosage , Spinal Cord Injuries/drug therapy , Spinal Cord Injuries/immunology , Acute-Phase Reaction/metabolism , Animals , Female , Humans , Immunity, Cellular/drug effects , Immunity, Cellular/physiology , Inflammation/immunology , Inflammation/metabolism , Inflammation/prevention & control , Injections, Intraperitoneal , Mice , Mice, Inbred C57BL , Spinal Cord Injuries/metabolism , Thoracic Vertebrae/injuries , Treatment Outcome
10.
J Neurosci ; 39(40): 7976-7991, 2019 10 02.
Article in English | MEDLINE | ID: mdl-31363064

ABSTRACT

Alzheimer's disease (AD) is associated with the cleavage of the amyloid precursor protein (APP) to produce the toxic amyloid-ß (Aß) peptide. Accumulation of Aß, together with the concomitant inflammatory response, ultimately leads to neuronal death and cognitive decline. Despite AD progression being underpinned by both neuronal and immunological components, therapeutic strategies based on dual targeting of these systems remains unexplored. Here, we report that inactivation of the p110δ isoform of phosphoinositide 3-kinase (PI3K) reduces anterograde axonal trafficking of APP in hippocampal neurons and dampens secretion of the inflammatory cytokine tumor necrosis factor-alpha by microglial cells in the familial AD APPswe/PS1ΔE9 (APP/PS1) mouse model. Moreover, APP/PS1 mice with kinase-inactive PI3Kδ (δD910A) had reduced Aß peptides levels and plaques in the brain and an abrogated inflammatory response compared with APP/PS1 littermates. Mechanistic investigations reveal that PI3Kδ inhibition decreases the axonal transport of APP by eliciting the formation of highly elongated tubular-shaped APP-containing carriers, reducing the levels of secreted Aß peptide. Importantly, APP/PS1/δD910A mice exhibited no spatial learning or memory deficits. Our data highlight inhibition of PI3Kδ as a new approach to protect against AD pathology due to its dual action of dampening microglial-dependent neuroinflammation and reducing plaque burden by inhibition of neuronal APP trafficking and processing.SIGNIFICANCE STATEMENT During Alzheimer's disease (AD), the accumulation of the toxic amyloid-ß (Aß) peptide in plaques is associated with a chronic excessive inflammatory response. Uncovering new drug targets that simultaneously reduce both Aß plaque load and neuroinflammation holds therapeutic promise. Using a combination of genetic and pharmacological approaches, we found that the p110δ isoform of phosphoinositide 3-kinase (PI3K) is involved in anterograde trafficking of the amyloid precursor protein in neurons and in the secretion of tumor necrosis factor-alpha from microglial cells. Genetic inactivation of PI3Kδ reduces Aß plaque deposition and abrogates the inflammatory response, resulting in a complete rescue of the life span and spatial memory performance. We conclude that inhibiting PI3Kδ represents a novel therapeutic approach to ameliorate AD pathology by dampening plaque accumulation and microglial-dependent neuroinflammation.


Subject(s)
Alzheimer Disease/prevention & control , Amyloid beta-Protein Precursor/metabolism , Class I Phosphatidylinositol 3-Kinases/genetics , Cognitive Dysfunction/genetics , Cognitive Dysfunction/prevention & control , Encephalitis/genetics , Encephalitis/prevention & control , Plaque, Amyloid/genetics , Plaque, Amyloid/prevention & control , Tumor Necrosis Factor-alpha/metabolism , Alzheimer Disease/genetics , Alzheimer Disease/pathology , Animals , Axonal Transport/genetics , Cytokines/metabolism , Female , Male , Maze Learning , Mice , Mice, Inbred C57BL , Mice, Transgenic , Neurons/metabolism , Point Mutation , Primary Cell Culture , Spatial Memory
11.
Semin Immunol ; 28(3): 292-308, 2016 06.
Article in English | MEDLINE | ID: mdl-27049459

ABSTRACT

The recognition that complement proteins are abundantly present and can have pathological roles in neurological conditions offers broad scope for therapeutic intervention. Accordingly, an increasing number of experimental investigations have explored the potential of harnessing the unique activation pathways, proteases, receptors, complexes, and natural inhibitors of complement, to mitigate pathology in acute neurotrauma and chronic neurodegenerative diseases. Here, we review mechanisms of complement activation in the central nervous system (CNS), and explore the effects of complement inhibition in cerebral ischemic-reperfusion injury, traumatic brain injury, spinal cord injury, Alzheimer's disease, amyotrophic lateral sclerosis, Parkinson's disease and Huntington's disease. We consider the challenges and opportunities arising from these studies. As complement therapies approach clinical translation, we provide perspectives on how promising complement-targeted therapeutics could become part of novel and effective future treatment options to improve outcomes in the initiation and progression stages of these debilitating CNS disorders.


Subject(s)
Brain/pathology , Complement Inactivating Agents/therapeutic use , Complement System Proteins/metabolism , Neurodegenerative Diseases/therapy , Wounds and Injuries/therapy , Clinical Trials as Topic , Complement Activation , Disease Progression , Humans , Molecular Targeted Therapy , Neurodegenerative Diseases/immunology , Neuroprotection , Treatment Outcome , Wounds and Injuries/immunology
12.
Semin Cell Dev Biol ; 61: 60-70, 2017 01.
Article in English | MEDLINE | ID: mdl-27523920

ABSTRACT

Inflammation is a natural part of wound healing but it can also cause secondary (bystander) damage and/or negatively interfere with endogenous repair mechanisms if non-resolving. Regulation of inflammation is traditionally looked at from the perspective of danger signals, cytokines and chemokines, and their respective receptors. A neuronal contribution to the regulation of inflammation is, however, increasingly appreciated, and this has important implications for the bodily response under conditions where the nervous system itself may be damaged. In this review article, we provide an up-to-date overview of the current literature on neural innervation of primary and secondary lymphoid organs, focusing in particular on the bone marrow and spleen, its significance in relation to immune function and, lastly, also briefly discussing how a major neurotraumatic event like spinal cord injury (SCI) may impact on this.


Subject(s)
Bone Marrow/immunology , Bone Marrow/innervation , Spleen/immunology , Spleen/innervation , Animals , Humans , Models, Biological , Nervous System/immunology , Nervous System/pathology
13.
J Neurosci ; 35(16): 6517-31, 2015 Apr 22.
Article in English | MEDLINE | ID: mdl-25904802

ABSTRACT

This study investigated the role of the complement activation fragment C5a in secondary pathology following contusive spinal cord injury (SCI). C5ar(-/-) mice, which lack the signaling receptor for C5a, displayed signs of improved locomotor recovery and reduced inflammation during the first week of SCI compared with wild-type mice. Intriguingly, the early signs of improved recovery in C5ar(-/-) mice deteriorated from day 14 onward, with absence of C5aR ultimately leading to poorer functional outcomes, larger lesion volumes, reduced myelin content, and more widespread inflammation at 35 d SCI. Pharmacological blockade of C5aR with a selective antagonist (C5aR-A) during the first 7 d after SCI improved recovery compared with vehicle-treated mice, and this phenotype was sustained up to 35 d after injury. Consistent with observations made in C5ar(-/-) mice, these improvements were, however, lost if C5aR-A administration was continued into the more chronic phase of SCI. Signaling through the C5a-C5aR axis thus appears injurious in the acute period but serves a protective and/or reparative role in the post-acute phase of SCI. Further experiments in bone marrow chimeric mice suggested that the dual and opposing roles of C5aR on SCI outcomes primarily relate to its expression on CNS-resident cells and not infiltrating leukocytes. Additional in vivo and in vitro studies provided direct evidence that C5aR signaling is required during the postacute phase for astrocyte hyperplasia, hypertrophy, and glial scar formation. Collectively, these findings highlight the complexity of the inflammatory response to SCI and emphasize the importance of optimizing the timing of therapeutic interventions.


Subject(s)
Gliosis/physiopathology , Inflammation/physiopathology , Receptor, Anaphylatoxin C5a/physiology , Spinal Cord Injuries/physiopathology , Animals , Astrocytes/physiology , Cell Proliferation/drug effects , Cell Proliferation/physiology , Cells, Cultured , Complement Activation/drug effects , Complement Activation/physiology , Complement C5a/biosynthesis , Female , Gliosis/complications , Gliosis/drug therapy , Gliosis/pathology , Inflammation/complications , Inflammation/drug therapy , Inflammation/pathology , Mice , Mice, Knockout , Motor Activity/drug effects , Motor Activity/physiology , Peptides, Cyclic/pharmacology , Peptides, Cyclic/therapeutic use , Receptor, Anaphylatoxin C5a/antagonists & inhibitors , Receptor, Anaphylatoxin C5a/biosynthesis , Receptor, Anaphylatoxin C5a/genetics , Recovery of Function/physiology , Spinal Cord Injuries/complications , Spinal Cord Injuries/drug therapy , Spinal Cord Injuries/metabolism
14.
Glia ; 64(8): 1331-49, 2016 08.
Article in English | MEDLINE | ID: mdl-27189804

ABSTRACT

Under steady-state conditions the central nervous system (CNS) is traditionally thought to be devoid of antigen presenting cells; however, putative dendritic cells (DCs) expressing enhanced yellow fluorescent protein (eYFP) are present in the retina and brain parenchyma of CD11c-eYFP mice. We previously showed that these mice carry the Crb1(rd8) mutation, which causes retinal dystrophic lesions; therefore we hypothesized that the presence of CD11c-eYFP(+) cells within the CNS may be due to pathology associated with the Crb1(rd8) mutation. We generated CD11c-eYFP Crb1(wt/wt) mice and compared the distribution and immunophenotype of CD11c-eYFP(+) cells in CD11c-eYFP mice with and without the Crb1(rd8) mutation. The number and distribution of CD11c-eYFP(+) cells in the CNS was similar between CD11c-eYFP Crb1(wt/wt) and CD11c-eYFP Crb1(rd8/rd8) mice. CD11c-eYFP(+) cells were distributed throughout the inner retina, and clustered in brain regions that receive input from the external environment or lack a blood-brain barrier. CD11c-eYFP(+) cells within the retina and cerebral cortex of CD11c-eYFP Crb1(wt/wt) mice expressed CD11b, F4/80, CD115 and Iba-1, but not DC or antigen presentation markers, whereas CD11c-eYFP(+) cells within the choroid plexus and pia mater expressed CD11c, I-A/I-E, CD80, CD86, CD103, DEC205, CD8α and CD135. The immunophenotype of CD11c-eYFP(+) cells and microglia within the CNS was similar between CD11c-eYFP Crb1(wt/wt) and CD11c-eYFP Crb1(rd8/rd8) mice; however, CD11c and I-A/I-E expression was significantly increased in CD11c-eYFP Crb1(rd8/rd8) mice. This study demonstrates that the overwhelming majority of CNS CD11c-eYFP(+) cells do not display the phenotype of DCs or their precursors and are most likely a subpopulation of microglia. GLIA 2016. GLIA 2016;64:1331-1349.


Subject(s)
Bacterial Proteins/metabolism , Brain/cytology , CD11c Antigen/metabolism , Dendritic Cells/cytology , Luminescent Proteins/metabolism , Microglia/cytology , Retina/cytology , Animals , Bacterial Proteins/genetics , Brain/metabolism , Dendritic Cells/metabolism , Flow Cytometry , Fluorescent Antibody Technique , Immunoenzyme Techniques , Leukocyte Common Antigens/metabolism , Luminescent Proteins/genetics , Mice, Inbred C57BL , Mice, Transgenic , Microglia/metabolism , Microscopy, Confocal , Nerve Tissue Proteins/genetics , Nerve Tissue Proteins/metabolism , Pia Mater/cytology , Pia Mater/metabolism , Retina/metabolism
15.
Proc Natl Acad Sci U S A ; 110(23): 9439-44, 2013 Jun 04.
Article in English | MEDLINE | ID: mdl-23696668

ABSTRACT

C3a is a key complement activation fragment, yet its neutrophil-expressed receptor (C3aR) still has no clearly defined role. In this study, we used a neutrophil-dependent mouse model of intestinal ischemia-reperfusion (IR) injury to explore the role of C3aR in acute tissue injuries. C3aR deficiency worsened intestinal injury, which corresponded with increased numbers of tissue-infiltrating neutrophils. Circulating neutrophils were significantly increased in C3aR(-/-) mice after intestinal ischemia, and C3aR(-/-) mice also mobilized more circulating neutrophils after granulocyte colony-stimulating factor infusion compared with WT mice, indicating a specific role for C3aR in constraining neutrophil mobilization in response to intestinal injury. In support of this role, C3aR(-/-) mice reconstituted with WT bone marrow reversed IR pathology back to WT levels. Complement C5a receptor (C5aR) antagonism in C3aR(-/-) mice also rectified the worsened pathology after intestinal IR injury but had no effect on circulating neutrophils, highlighting the opposing roles of C3a and C5a in disease pathogenesis. Finally, we found that using a potent C3a agonist to activate C3aR in vivo reduced neutrophil mobilization and ameliorated intestinal IR pathology in WT, but not C3aR(-/-), mice. This study identifies a role for C3aR in regulating neutrophil mobilization after acute intestinal injury and highlights C3aR agonism as a potential treatment option for acute, neutrophil-driven pathologies.


Subject(s)
Intestines/immunology , Neutrophils/immunology , Receptors, Complement/immunology , Reperfusion Injury/prevention & control , Animals , Apoptosis/immunology , Cytokines/blood , Hemoglobins/metabolism , Histological Techniques , Intestines/cytology , Mice , Mice, Knockout , Receptors, Complement/genetics , Receptors, Complement/metabolism , Reperfusion Injury/immunology
16.
J Neurosci ; 33(15): 6603-13, 2013 Apr 10.
Article in English | MEDLINE | ID: mdl-23575857

ABSTRACT

It is now widely accepted that hippocampal neurogenesis underpins critical cognitive functions, such as learning and memory. To assess the behavioral importance of adult-born neurons, we developed a novel knock-in mouse model that allowed us to specifically and reversibly ablate hippocampal neurons at an immature stage. In these mice, the diphtheria toxin receptor (DTR) is expressed under control of the doublecortin (DCX) promoter, which allows for specific ablation of immature DCX-expressing neurons after administration of diphtheria toxin while leaving the neural precursor pool intact. Using a spatially challenging behavioral test (a modified version of the active place avoidance test), we present direct evidence that immature DCX-expressing neurons are required for successful acquisition of spatial learning, as well as reversal learning, but are not necessary for the retrieval of stored long-term memories. Importantly, the observed learning deficits were rescued as newly generated immature neurons repopulated the granule cell layer upon termination of the toxin treatment. Repeat (or cyclic) depletion of immature neurons reinstated behavioral deficits if the mice were challenged with a novel task. Together, these findings highlight the potential of stimulating neurogenesis as a means to enhance learning.


Subject(s)
Avoidance Learning/physiology , Gene Knock-In Techniques/psychology , Hippocampus/physiology , Memory/physiology , Microtubule-Associated Proteins/physiology , Neural Stem Cells/physiology , Neuropeptides/physiology , Reversal Learning/physiology , Animals , Cells, Cultured , Cerebral Cortex , Cytoskeletal Proteins/biosynthesis , Doublecortin Domain Proteins , Doublecortin Protein , Gene Knock-In Techniques/methods , Heparin-binding EGF-like Growth Factor , Intercellular Signaling Peptides and Proteins/genetics , Male , Memory, Long-Term/physiology , Mice , Mice, Inbred C57BL , Microtubule-Associated Proteins/genetics , Models, Animal , Nerve Degeneration/genetics , Nerve Tissue Proteins/biosynthesis , Neurogenesis/physiology , Neuropeptides/genetics , Space Perception/physiology
17.
Aging Cell ; 23(7): e14172, 2024 Jul.
Article in English | MEDLINE | ID: mdl-38747044

ABSTRACT

Slowing and/or reversing brain ageing may alleviate cognitive impairments. Previous studies have found that exercise may mitigate cognitive decline, but the mechanisms underlying this remain largely unclear. Here we provide unbiased analyses of single-cell RNA sequencing data, showing the impacts of exercise and ageing on specific cell types in the mouse hippocampus. We demonstrate that exercise has a profound and selective effect on aged microglia, reverting their gene expression signature to that of young microglia. Pharmacologic depletion of microglia further demonstrated that these cells are required for the stimulatory effects of exercise on hippocampal neurogenesis but not cognition. Strikingly, allowing 18-month-old mice access to a running wheel did by and large also prevent and/or revert T cell presence in the ageing hippocampus. Taken together, our data highlight the profound impact of exercise in rejuvenating aged microglia, associated pro-neurogenic effects and on peripheral immune cell presence in the ageing female mouse brain.


Subject(s)
Aging , Brain , Microglia , Physical Conditioning, Animal , T-Lymphocytes , Animals , Microglia/metabolism , Physical Conditioning, Animal/physiology , Mice , Female , T-Lymphocytes/immunology , T-Lymphocytes/metabolism , Aging/physiology , Brain/metabolism , Mice, Inbred C57BL
18.
J Neurosci ; 32(19): 6435-43, 2012 May 09.
Article in English | MEDLINE | ID: mdl-22573666

ABSTRACT

Exercise has been shown to positively augment adult hippocampal neurogenesis; however, the cellular and molecular pathways mediating this effect remain largely unknown. Previous studies have suggested that microglia may have the ability to differentially instruct neurogenesis in the adult brain. Here, we used transgenic Csf1r-GFP mice to investigate whether hippocampal microglia directly influence the activation of neural precursor cells. Our results revealed that an exercise-induced increase in neural precursor cell activity was mediated via endogenous microglia and abolished when these cells were selectively removed from hippocampal cultures. Conversely, microglia from the hippocampi of animals that had exercised were able to activate latent neural precursor cells when added to neurosphere preparations from sedentary mice. We also investigated the role of CX(3)CL1, a chemokine that is known to provide a more neuroprotective microglial phenotype. Intraparenchymal infusion of a blocking antibody against the CX(3)CL1 receptor, CX(3)CR1, but not control IgG, dramatically reduced the neurosphere formation frequency in mice that had exercised. While an increase in soluble CX(3)CL1 was observed following running, reduced levels of this chemokine were found in the aged brain. Lower levels of CX(3)CL1 with advancing age correlated with the natural decline in neural precursor cell activity, a state that could be partially alleviated through removal of microglia. These findings provide the first direct evidence that endogenous microglia can exert a dual and opposing influence on neural precursor cell activity within the hippocampus, and that signaling through the CX(3)CL1-CX(3)CR1 axis critically contributes toward this process.


Subject(s)
Aging/physiology , Hippocampus/cytology , Hippocampus/physiology , Microglia/physiology , Neural Stem Cells/physiology , Physical Conditioning, Animal/physiology , Animals , Female , Mice , Mice, Inbred C57BL , Mice, Knockout , Mice, Transgenic , Microglia/cytology , Neural Stem Cells/cytology , Neurogenesis/physiology
19.
Neuroimage ; 82: 574-85, 2013 Nov 15.
Article in English | MEDLINE | ID: mdl-23770410

ABSTRACT

This study examined the sensitivity of ultra-high field (16.4 T) diffusion tensor imaging (DTI; 70 µm in-plane resolution, 1mm slice thickness) to evaluate the spatiotemporal development of severe mid-thoracic contusive spinal cord injury (SCI) in mice. In vivo imaging was performed prior to SCI, then again at 2h, 1 day, 3 days, 7 days, and 30 days post-SCI using a Bruker 16.4 T small animal nuclear magnetic resonance spectrometer. Cross-sectional spinal cord areas were measured in axial slices and various DTI parameters, i.e. fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (λ||) and radial diffusivity (λ⊥), were calculated for the total spared white matter (WM), ventral funiculi (VF), lateral funiculi (LF) and dorsal columns (DCs) and then correlated with histopathology. Cross-sectional area measurements revealed significant atrophy (32% reduction) of the injured spinal cord at the lesion epicentre in the chronic phase of injury. Analysis of diffusion tensor parameters further showed that tissue integrity was most severely affected in the DCs, i.e. the site of immediate impact, which demonstrated a rapid and permanent decrease in FA and λ||. In contrast, DTI parameters for the ventrolateral white matter changed more gradually with time, suggesting that these regions are undergoing more delayed degeneration in a manner that may be amenable to therapeutic intervention. Of all the DTI parameters, λ⊥ was most closely correlated to myelin content whereas changes in FA and λ|| appeared more indicative of axonal integrity, Wallerian degeneration and associated presence of macrophages. We conclude that longitudinal DTI at 16.4T provides a clinically relevant, objective measure for assessing white matter pathology following contusive SCI in mice that may aid the translation of putative neuroprotective strategies into the clinic.


Subject(s)
Diffusion Tensor Imaging/methods , Nerve Fibers, Myelinated/pathology , Spinal Cord Injuries/pathology , Animals , Female , Mice , Mice, Inbred C57BL
20.
Neuroimage ; 68: 22-9, 2013 Mar.
Article in English | MEDLINE | ID: mdl-23246856

ABSTRACT

Accurate identification of spinal cord segments in relation to vertebral landmarks is essential to surgery aimed at experimental spinal cord injury. We have analyzed a complete series of high-resolution magnetic resonance (MR) images from the mouse spine in order to delineate the boundaries of spinal cord segments in relation to vertebral landmarks. The resulting atlas can be used to plan experimental approaches that require the accurate identification of a target spinal cord segment.


Subject(s)
Spinal Cord/anatomy & histology , Spine/anatomy & histology , Animals , Magnetic Resonance Imaging , Mice , Mice, Inbred C57BL
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