Glia最新文献

Cerebral organoids derived from human induced pluripotent stem cells (iPSCs) are increasingly becoming essential tools to study the human brain, from understanding pathological mechanisms in neurodevelopmental, neurodegenerative, and infectious diseases to identifying genetic risks and biomarkers. To resemble the brain environment, cerebral organoids must contain microglia, the resident macrophages of the brain parenchyma that are essential for its homeostasis. As microglia derive from the yolk sac, they are not present in conventional brain organoids, which are generated by reprogramming iPSCs towards the neuroectodermal lineage and must be exogenously incorporated through a variety of strategies. Once in the organoid parenchyma, microglia must recapitulate their developmental milestones to achieve full immunocompetence, reaching a mature transcriptional profile and morphology, a tessellated distribution, efficient phagocytosis, and controlled inflammatory responses. In this review, we will summarize recent protocols that have been developed to generate human microglial-containing cerebral organoids (MCCOs), focusing on the methods used to assess the level of microglial maturation compared to their in vivo counterparts. We provide a series of recommendations to assess microglial immunocompetence using stringent quantitative approaches that will promote developing standardized protocols to culture MCCOs.

Aberrant activation of multiple cellular processes and signaling pathways is a hallmark of many neurological disorders. Understanding how these processes interact is crucial for elucidating the neuropathogenesis of these diseases. Among these, endoplasmic reticulum (ER) stress, activation of the unfolded protein response (UPR), and neuroinflammation are frequently implicated. Previously, we demonstrated that ER stress synergizes with tumor necrosis factor (TNF)-α to amplify interleukin (IL)-6 and C-C motif chemokine ligand (CCL)20 production in astrocytes through a Janus kinase 1 (JAK1)-dependent mechanism. Here, we expand on this finding by defining the scope and underlying mechanisms of this phenomenon. We show that ER stress and TNF-α cooperatively enhance inflammatory gene expression in astrocytes via a signaling axis that requires both protein kinase R (PKR)-like ER kinase (PERK) and JAK1. PERK-mediated phosphorylation of eukaryotic translation initiation factor (eIF)2α suppresses protein translation, delaying the expression of negative regulators such as NF-κB inhibitor (IκB)α and suppressor of cytokine signaling (SOCS)3 following TNF-α or oncostatin M (OSM) stimulation, respectively. Pharmacological reversal of p-eIF2α-dependent translational suppression using the small molecule integrated stress response inhibitor (ISRIB) restored IκBα and SOCS3 expression and attenuated the ER stress-induced enhancement of TNF-α- or OSM-driven inflammatory responses. Notably, astrocytes harboring a vanishing white matter-associated EIF2B5 mutation revealed that translational attenuation alone is insufficient to amplify cytokine-induced gene expression. Together, these findings identify a PERK/eIF2α/JAK1 signaling axis that sensitizes astrocytes to inflammatory cytokines, providing new mechanistic insights into the interactions between ER stress and neuroinflammation.

Cover Illustration: Oligodendrocyte binds to laminin on the perivascular basement membrane in the murine cortex at the age of postnatal day 16 (red: CC-1; green: laminin alpha-2; blue: DAPI). (See Sasaki, B., et al, https://doi.org/10.1002/glia.70027)

Spinal cord injury (SCI) results in significant disruption of nerve fibers responsible for transmitting signals between the brain and body, often leading to partial or complete motor, sensory, and autonomic dysfunction below the injury site. Astrocytes are an important component in scar formation, crucial for suppression of injury propagation, effective wound healing, and the regulation of neuronal plasticity. Here, we identify the role of the actin-binding protein Drebrin (DBN) in reactive astrogliosis following SCI. SCI induces the upregulation of DBN in astrocytes, which controls immediate injury containment but also the long-term preservation of tissue integrity and healing in the spinal cord. DBN knockout results in enlarged spinal cord lesions, increased immune cell infiltration, and neurodegeneration. Mechanistically, DBN loss disrupts the polarization of scar border-forming astrocytes, leading to impaired encapsulation of the injury. In summary, DBN serves as a pivotal regulator of SCI outcome by modulating astrocytic polarity, which is essential for establishing a protective barrier confining the lesion site.

Electrical signaling, driven by ion fluxes between intra- and extracellular compartments, is central to brain functioning. Astrocytes provide crucial support by maintaining the homeostasis of water and ions in the brain. This is disrupted in the leukodystrophy Megalencephalic Leukoencephalopathy with subcortical Cysts (MLC). Studies on cultured primary astrocytes and other isolated cell lines point to a central defect in astrocyte volume regulation in MLC. However, cell culture severely alters the properties and polarity of astrocytes. Therefore, whether astrocytes in the intact MLC brain exhibit aberrant physiology related to water and ion homeostasis remains unknown. To investigate astrocyte physiology in intact astrocytes, we performed experiments in acute brain slices from a validated MLC mouse model, the Glialcam-null mouse. We combined viral sensor delivery with two-photon microscopy to study astrocyte volume regulation and associated chloride dynamics. Cortical Glialcam-null astrocytes showed normal intracellular chloride dynamics but reduced volume recovery upon potassium-induced cell swelling. Whole-cell patch-clamp recordings revealed a modestly depolarized resting membrane potential and slower glutamate uptake in Glialcam-null astrocytes. Gap junction coupling of the astrocyte syncytium was modestly reduced, but it remained sufficient to preserve functional electrical isopotentiality. In conclusion, our findings confirm that the previously observed disturbance of astrocyte volume regulation observed in cultured cells is also observed in intact astrocytes in situ, and we uncover additional changes in astrocyte electrophysiological properties. These findings support the concept that dysfunctional astrocyte volume regulation is central to the MLC disease mechanism.

Cover Illustration: Stochastically labeled astrocytes (cyan) and Müller glia (magenta) contacting blood vessels (orange) and neural cell bodies and axons bundles (green) in a mouse retina. (See Holden, JM, et al, https://doi.org/10.1002/glia.70022)