Astrocyte reactivity

Published on July 31, 2023   51 min

A selection of talks on Immunology & Inflammation

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Hello my name is Michael Sofroniew from UCLA. Welcome to this Henry Stewart Talk on Astrocyte Reactivity.
Astrocytes are a main cell type in the brain and spinal cord where they constitute about 30-40% of the cells. Astrocytes tile the entire central nervous system which we'll refer to as the CNS. The image shows this tiling in the mouse hippocampus and cerebral cortex. White dots represent astrocyte nuclei selectively stained for the transcription factor Sox9 and shows that they are evenly spaced throughout the tissue. The green stain is for GFAP which is visible in the main astrocyte branches in the hippocampus but GFAP is not detectably expressed by cortical astrocytes in healthy tissue. Astrocytes are highly branched cells and their branches interact with multiple other cell types, in particular with neurons and synapses where astrocytes contribute many functions that are essential for maintaining and influencing synapse function. As shown in the schematic on the right these functions include taking up and recycling neurotransmitters and maintaining potassium homeostasis. Astrocytes also contact blood vessels and help to regulate blood flow and interstitial fluid levels and lymphatic flow. In addition, astrocytes form an important border around the entire surface of the brain and spinal cord that separates neural tissue from the non-neural tissue of the meninges.
In addition to their functions in the healthy central nervous system astrocytes respond to all forms of injury and disease with changes that are referred to as astrocyte reactivity. These responses include many variable changes in gene expression and protein expression as well as changes in cell structure and potentially also cell proliferation. In histological tissue sections as seen in the images on this slide, increased staining for the protein GFAP is a prototypical sign of astrocyte reactivity. This slide shows examples of astrocyte changes in various human disorders or mouse models including stroke, traumatic injury, neurodegenerative diseases like Alzheimer's disease, tumors, autoimmune inflammatory diseases like multiple sclerosis, and their models and infections.