Wed | 20 14:00 - 16:00

In vivo selective manipulation of microglia

Lorena Rela

IFIBIO Houssay, Universidad de Buenos Aires Facultad de Medicina y CONICET

Microglial cell physiology has become a topic of interest, because they have been identified as key modulators of neuroinflammation and nervous system plasticity. In order to disentangle their roles it is crucial to manipulate microglial cells in vivo using selective tools.This symposium will cover the applications of a variety of genetic and pharmacological tools that have become available in in the recent years to interfere with microglia functions in animal models of healthy and diseased nervous systems.

The use of CSF1R inhibitors to manipulate microglia in the healthy and diseased brain.

Kim Green

Department of Neurobiology and Behavior, University of California, Irvine, USA

Microglia, the brain’s immune sentinels, have garnered much attention in recent years as their roles in maintaining brain homeostasis and as critical enactors of brain disease and injury have come to light. We previously discovered that microglia were dependent on signaling through the colony-stimulating factor 1 receptor (CSF1R) for their survival and developed CSF1R inhibitor paradigms that allow for the rapid and sustained elimination of the microglial tissue from the CNS. The varying degrees of spatiotemporal manipulation afforded by this pharmacological approach allows for microglial ablation prior to, during, and/or following insult, injury or disease. Here, we will show the various ways that CSF1R inhibitors can be employed to manipulate microglia in vivo – from extended depletion to elucidate their functions in the healthy and diseased brains, to repopulation of a replacement tissue from a variety of myeloid cell sources, and in normalization of dyshomeostatic microglia in disease.

Neurovascular Interactions: Unlocking drivers of neurodegeneration

Katerina Akassoglou

Gladstone Institutes and University of California, San Francisco (UCSF), USA

The communication between the brain, immune and vascular systems is a key contributor to the onset and progression of neurological diseases. We discovered the coagulation factor fibrinogen as a blood-derived driver for neuroinflammation in a wide range of neurologic diseases, such as multiple sclerosis, Alzheimer’s disease and brain trauma 1 . We showed that fibrinogen is necessary and sufficient for neurodegeneration and a new culprit for microglia-mediated oxidative stress-dependent spine elimination and cognitive impairment 2 . Microglial surveillance is a key feature of brain physiology and disease. We showed that G i -dependent microglial dynamics prevent neuronal network hyperexcitability 3 . By generating Mg-PTX mice to genetically inhibit G i in microglia, we showed that sustained reduction of microglia brain surveillance and directed process motility induced spontaneous seizures and increased hypersynchrony after physiologically evoked neuronal activity in awake adult mice, suggesting that G i -dependent microglia dynamics may prevent hyperexcitability in neurological diseases. By developing Tox-Seq, we reported the oxidative stress innate immune cell atlas in neuroinflammation. We discovered a first-in-class fibrin-targeting immunotherapy to selectively target inflammatory functions of fibrin without interference with clotting with potent therapeutic effects in autoimmune- and amyloid-driven neurotoxicity 4 . These findings could be a common thread

Microglial activation influences the affective state.

David Engblom

Department of Biomedical and Clinical Sciences (BKV), Center for Social and Affective Neuroscience (CSAN), Linköpking University, Sweden

Many diseases are inflammatory or have an inflammatory component. In these diseases, patients often experience a feeling of sickness that severely reduce their quality of life. Several lines of evidence indicate that inflammatory signaling is a key driver of the depressive mood associated with “classic” inflammatory diseases but also contribute to emotional and cognitive symptoms in neurodegenerative and psychiatric diseases including major depression. The molecular and cellular nature of the “inflammatory signaling” that is critical for the symptoms are in most cases not known but microglia are obvious candidates. To investigate how microglial activation influences affective functions, we have used a model in which we activate microglia in a highly selective way with genetic techniques in mice. Using injection of viral vectors in combination with Cre/loxP methodology, we expressed activating DREADDs (Designer Receptors Exclusively Activated by Designer Drugs) selectively in microglial cells in the striatum. Activation of these receptors with the designer drug CNO induced a negative affective state. Furthermore, inhibition of microglial activation using inhibitory DREADDs (or microglia-specific intervention with IL-6 or prostaglandin synthesis) blocked inflammation-induced aversion. Collectively, these findings show that microglial activation induces a negative affective state and that DREADDs are efficient tools for the study of microglia function.

Effect of microglial depletion on neurodegeneration in a multiple sclerosis model

Laura Andrea Pasquini

Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Biológica. Cátedra de Química Biológica Patológica. Buenos Aires, Argentina. 2Universidad de Buenos Aires-CONICET. Instituto de Química y Fisicoquímica Biológicas (IQUIFIB). Buenos Aires, Argentina

Multiple sclerosis (MS), especially in its progressive pattern, involves early axonal damage resulting from demyelination and loss of trophic support, in association with astrocyte- and microglia-mediated inflammation in the central nervous system (CNS). Prolonged cuprizone (CPZ) intoxication is widely used as a MS model, as it triggers chronic demyelination, neurodegeneration, astrogliosis and microgliosis. While reactive MG can damage tissue, exacerbate deleterious effects and contribute to neurodegeneration, their role in myelin debris phagocytosis during demyelination proves crucial in enabling oligodendroglial differentiation and bringing about remyelination. As MG are physiologically dependent on colony-stimulating factor 1 receptor (CSF-1R) signaling, MG can be almost completely eliminated from the brain using CSF-1R inhibitors. Therefore, we aimed to evaluate the effects of CSF-1R inhibitor BLZ945 on myelin status, neurodegeneration and astrogliosis during chronic CPZ demyelination. Mice were fed either control or CPZ chow for 12 weeks and orally gavaged vehicle or BLZ945 as from the 2nd week of CPZ treatment. BLZ945 induced a reduction in the microglial population in all structures evaluated. Moreover, the recovery in myelin basic protein (MBP) and myelin lipids showed BLZ945 to protect myelin. However, no significant correlation was found between myelin and axonal protection, as axonal degeneration was more prominent upon BLZ945 treatment along with astroglial activ