Project description:We subjected old (21-22 month) and young (3-4 month) male C57BL/6 mice to 45 min transient oclusion of the middle cerebral artery and obtained the brain four days later. We obtained bodipy+ microglia from the ischemic brain tissue by FACS.
Project description:To address whether, after depletion by Csf1r inhibition, microglia repopulating the CNS revert to a “younger” phenotype, we treated a group of 23 months old mice with the Csf1r inhibitor for 5 days and let microglia repopulate the central nervous system for 7 days. Young (3 months old) and old (23 months old) mice were included as controls. After the repopulation time, whole spinal cord samples and Fluorescence Activated Sorting (FACS)-sorted microglia cells from brain tissue were collected to perform bulk transcriptome (RNAseq) analysis. Analysis of whole spinal cord suggested that repopulating microglia tend to re-acquire its original aged phenotype. Gene expression in FACS-sorted microglia was then analyzed to better characterize its intrinsic phenotype after repopulation. In contrast to the whole spinal cord samples, old and old-treated replicates separated in Principal Component Analysis, suggesting that repopulating microglia displayed a different phenotype compared to old microglia.
Project description:Microglia are resident CNS immune cells that are active sensors in healthy brain and versatile effectors under pathological conditions. Cerebral ischemia induces a robust neuroinflammatory response that includes marked changes in the gene expression and phenotypic profile of a variety of endogenous CNS cell types (astrocytes, neurons, microglia) as well as an influx of leukocytic cells (neutrophils, macrophages, T-cells) from the periphery. Many molecules and conditions can trigger a transformation of ârestingâ (or surveying) microglia to an âactivatedâ (alerted/reactive) state. Here we review recent developments in the literature that relate to microglial activation in the experimental setting of in vitro and in vivo ischemia. We also present new data from our own laboratory demonstrating the direct effects of in vitro ischemic conditions on the microglial phenotype and genomic profile. Emphasis is placed on the role of specific molecular signaling systems such as hypoxia inducible factor-1 (HIF-1) and toll-like receptor-4 (TLR4) in regulating the microglial response in this setting. We then review histological and recent novel radiological data that confirms a key role for microglial activation in the setting of ischemic stroke in humans. We discuss recent progress in the pharmacological and molecular targeting of microglia in acute ischemic stroke. Finally, we explore how recent studies on ischemic preconditioning have increased interest in preemptively targeting microglial activation in order to reduce stroke severity. 12 arrays, 4 experimental groups, 3 replicates in each group, CN is control normoxia, CH is control hypoxia, TN is TLR4 knockout normoxia, TH is TLR4 knockout hypoxia.
Project description:Senescence-associated alterations in microglia may have profound impact on cerebral homeostasis and stroke outcomes. However, the lack of a transcriptome-wide comparison between young and aged microglia in the context of ischemia limits our understanding of aging-related mechanisms. Herein, we performed bulk RNA sequencing analysis of microglia purified from cerebral hemispheres of young adult (10-week-old) and aged (18-month-old) mice 5 days after distal middle cerebral artery occlusion or sham operation. Considerable transcriptional differences were observed between young and aged microglia in healthy brains, indicating heightened chronic inflammation in aged microglia. Following stroke, the overall transcriptional activation was more robust in young microglia than in aged microglia. Gene clusters with functional implications in immune inflammatory responses, immune cell chemotaxis, tissue remodeling, and cell-cell interactions were markedly activated in microglia of young but not aged stroke mice. These alterations in microglial gene response may contribute to aging-driven vulnerability and poorer recovery after ischemic stroke.
Project description:Microglia are resident CNS immune cells that are active sensors in healthy brain and versatile effectors under pathological conditions. Cerebral ischemia induces a robust neuroinflammatory response that includes marked changes in the gene expression and phenotypic profile of a variety of endogenous CNS cell types (astrocytes, neurons, microglia) as well as an influx of leukocytic cells (neutrophils, macrophages, T-cells) from the periphery. Many molecules and conditions can trigger a transformation of “resting” (or surveying) microglia to an “activated” (alerted/reactive) state. Here we review recent developments in the literature that relate to microglial activation in the experimental setting of in vitro and in vivo ischemia. We also present new data from our own laboratory demonstrating the direct effects of in vitro ischemic conditions on the microglial phenotype and genomic profile. Emphasis is placed on the role of specific molecular signaling systems such as hypoxia inducible factor-1 (HIF-1) and toll-like receptor-4 (TLR4) in regulating the microglial response in this setting. We then review histological and recent novel radiological data that confirms a key role for microglial activation in the setting of ischemic stroke in humans. We discuss recent progress in the pharmacological and molecular targeting of microglia in acute ischemic stroke. Finally, we explore how recent studies on ischemic preconditioning have increased interest in preemptively targeting microglial activation in order to reduce stroke severity.
Project description:RNA-Seq transcriptome comparison of the following cell populations (n=4 independent samples per cell population): a) CD11c-eYFP+ cells FACS sorted from brain of adult mice 4 days after cerebral ischemia, b) CX3CR1+ microglia sorted from the ischemic brain of CX3CR1CreERT2-ROSA26 tdTomato mice; c) CD11c-rYFP+ cells sorted from the spleen of control mice; d) CX3CR1+ microglia sorted from the brain of control mice. Purpose: The goal of this study is to compare the transcriptome profile (RNA-Seq) of cD11c-eYFP+ cells and microglia, both collected from ischemic brains of mice, and with reference cell populations, i.e. Steady-stated microglia from brain of corresponding control mice and steady-state CD11c-eYFP cells sorted from the spleen of control mice. Methods: RNA samples were obtained from FACS sorted eYFP+ cells of the ipsilateral brain hemisphere of CD11c-eYFP mice 4 days post-ischemia, the spleen of control CD11c-eYFP mice, and from microglial cells sorted from control brain and the ipsilateral brain hemisphere 4 days post-ischemia of Cx3cr1CreERT2:ROSA26dTomato mice. NGS was perfomed (RNA-Seq) to compare the transcriptome of these populations. Results: the populations we compared clearly separated the differentially expressed genes in an unsupervised cluster analysis. 950 genes were overrepresented in microglia and 1469 genes were overrepresented in CD11c-eYFP+ cells in the ischemic brain. Conclusions: Our study is the first comparative analysis of the transcriptomes of microglia and the infiltrating CD11c-eYFP+ cells derived from the ischemic brain of mice. The results show that the infiltrating CD11c-eYFP cell population in the ischemic brain tissue of parabiotic mice displays overrepresentation of genes typical of dendritic cells, immune functions, and ClassII antigen presentation, amongst others, that are not found represented in microglia.