ABSTRACT Neuronal loss in multiple sclerosis (MS) is a key factor in the progression of disability. Axonal degeneration within MS lesions is central to progressive MS pathology, yet its mechanisms are not fully understood. Excess extracellular l‐glutamate (GLUT) is neurotoxic due to overstimulation of GLUT receptors. Excitotoxicity, driven by GLUT, is a suspected contributor to several central nervous system (CNS) diseases. Astrocytic glutamate transporters EAAT‐1 and EAAT‐2 play crucial roles in managing extracellular GLUT, yet their role in chronic MS remains underexplored. Using the animal model experimental autoimmune encephalomyelitis (EAE) and advanced microscopy in live anesthetized mice, we examined GLUT‐mediated neurotoxicity and protective mechanisms in chronic CNS lesions. By employing genetically encoded fluorescent biosensors, we visualized extracellular GLUT levels and axonal Ca 2+ dynamics within the live mouse brain during EAE. In acute EAE, extracellular GLUT levels were high, while in chronic lesions, normalized GLUT levels together with sustained EAAT‐2 upregulation were consistent with a protective astrocytic response. EAAT‐2 inhibition in chronic lesions led to higher intra‐axonal Ca 2+ levels and morphological changes consistent with neuroaxonal injury, indicating that EAAT‐2 upregulation may counter excitotoxicity and support neuroprotection. Post‐mortem MS brain tissue analysis provided complementary evidence, showing elevated EAAT‐1 and EAAT‐2 expression in chronic MS lesions with expression patterns varying according to lesion type and cellularity. This study highlights astrocytic mechanisms that may contribute to neuroaxonal protection in MS tissue and suggests targeting GLUT transporters as a promising strategy to limit neurodegeneration in progressive MS.
ABSTRACT The etiological heterogeneity of autism spectrum disorder (ASD) complicates identifying core molecular mechanisms. We systematically integrated scRNA‐seq data from 11 diverse genetic and environmental mouse ( Mus musculus ) models, encompassing > 300,000 cells across multiple brain regions and developmental stages. Using advanced computational harmonization (RPCA), we identified robust convergent transcriptomic signatures that transcend model‐specific variability. Our findings reveal widespread alterations in neuronal communication pathways, specifically increased excitatory‐inhibitory signaling involving PTN, SLIT, and PTPR pathways. Furthermore, cell–cell communication analysis via NicheNet prioritized ligand‐receptor pairs associated with altered circuit excitability, offering a predictive blueprint of dysregulated intercellular crosstalk. Crucially, we identified significant glial involvement characterized by astrocyte function inhibition, marked by Aqp4 and Kcnj10 downregulation related to impaired water/potassium homeostasis and mature oligodendrocyte metabolic dysregulation through Olig family upregulation and enhanced oxidative phosphorylation. Differentially expressed genes (DEGs) significantly overlapped with SFARI‐listed high‐confidence risk genes, particularly within excitatory neuronal subtypes. Comparison with human postmortem single‐nucleus data from the prefrontal and parietal cortices demonstrated conserved signatures related to impaired synaptic protein synthesis (GRIN2B, CAMK2A) and oligodendrocyte‐mediated neurodevelopmental deficits (NRXN, DLGAP). This study confirms that E/I imbalance and glial dysfunction are universal cellular pathologies in ASD, providing a robust, large‐scale reference for identifying novel therapeutic targets with single‐cell resolution.
ABSTRACT Adult hippocampal neurogenesis (AHN)—the lifelong generation of new neurons in the dentate gyrus (DG)—depends on the integrity of the subgranular zone (SGZ) neurogenic niche, which comprises astrocytes, microglia, oligodendroglial cells, and a dense vascular network. Although AHN declines during aging and is impaired in Alzheimer's disease (AD), the cell‐type‐specific alterations within the DG underlying this decline remain poorly characterized. Given the critical role of glycogen synthase kinase‐3β (GSK‐3β) in AD pathogenesis and AHN regulation, we studied how the overexpression of this kinase in dentate granule cells (DGCs) remodels the cellular and vascular composition of the DG throughout life. Using a layer‐resolved approach (SGZ vs. granule cell layer (GCL)) and mice of distinct ages (4–30 months), we quantified glial densities, cellular contacts, vascular architecture, and cytokine profiles in wild‐type (WT) and GSK‐3β‐overexpressing (GSK‐3β‐OE) mice. In the former, aging was associated with a layer‐specific reorganization, characterized by progressive astrocyte loss in the SGZ, midlife increases in GCL microglia, a reduction in oligodendroglial progenitors, and enhanced SGZ vascularization. GSK‐3β overexpression accelerated age‐related changes, triggering premature SGZ astrocyte depletion by 4 months, broader disruption featuring reduced SGZ microglial and mature oligodendrocyte densities accompanied by increased microglial morphological complexity, vascular restructuring, and a shift toward a pro‐inflammatory environment. Therefore, neuronal GSK‐3β overexpression promoted a non‐cell‐autonomous reorganization of the DG, consistent with premature remodeling of the neurogenic niche. These results provide mechanistic insights into AHN failure in AD and point to the modulation of GSK‐3β activity as a strategy to preserve DG integrity.
ABSTRACT The mechanisms by which pathogenic T cells enter the immune‐privileged retina at the onset of uveitis remain unclear. To identify regulatory targets that promote retinal inflammation, we established an experimental autoimmune uveoretinitis (EAU) model by immunizing C57BL/6J mice with IRBP 651–670 and dynamically evaluated retinal inflammation after induction; fundus lesions were prominent, with the first 14 days representing the initiation phase, Days 14–28 the amplification phase, Days 28–35 the peak phase, and Days 35–42 the regression phase. We characterized retinal cellular alterations from the pre‐inflammatory stage to the peak stage using single‐cell transcriptomic analysis, and found that retinal immune cells changed in parallel with EAU severity, while immune‐cell interactions were strongest on Day 14, especially between microglia and T cells through multiple chemokine‐related pathways. We then identified key cell populations and candidate targets through integrated analyses and functional validation, and Ifi27l2a emerged as a core gene associated with inflammatory and immune responses in retinal microglia on Day 14. In vitro knockdown of Ifi27l2a in LPS‐activated BV‐2 cells reduced inflammatory mediator production and abolished Th1/Th17 induction. In vivo targeting of Ifi27l2a attenuated EAU severity and restored the balance of T‐cell subsets. These findings indicate that microglia are highly activated before retinal inflammation becomes prominent and that Ifi27l2a regulates this early pathogenic process.
ABSTRACT Traumatic spinal cord injury (SCI) is a complex and disabling condition with no curative therapy currently available. The mechanical damage of the primary injury phase is followed and exacerbated by a secondary injury phase, characterized by the release of free radicals and pro‐inflammatory cytokines that lead to chronic inflammation. Microglia, as the resident immune cells of the central nervous system, play a critical role in orchestrating this inflammatory response. Studying their dynamics after SCI not only deepens our understanding of injury pathology but also advances the development of microglia‐targeted immunotherapies. However, trauma‐induced transcriptional and phenotypic changes mean that markers used to identify homeostatic microglia may be unreliable when applied to their reactive counterparts. Another major challenge lies within discriminating resident microglia from infiltrating monocyte‐derived macrophages (MDM), which permeate the blood‐spinal cord barrier (BSCB) after injury. In this review, we examine three key variables for selecting appropriate strategies for labeling microglia in mice: (i) time (in relation to injury); (ii) efficacy (within the chosen murine SCI model); and (iii) specificity (to microglia). We discuss the transcriptional landscape of murine microglia pre‐injury and its alteration post‐injury, evaluate the strengths and limitations of commonly used markers, and highlight emerging tools and approaches for studying microglia in preclinical murine SCI research.
