astroglia

Astroglia, or astrocytes, are a major class of glial cells in the central nervous system. They are typically star-shaped, with numerous processes contacting neurons, synapses, and blood vessels. In gray matter, protoplasmic astrocytes predominate, while fibrous astrocytes are common in white matter. During development, astroglia arise from radial glia and contribute to neural circuit formation as well as later repair and remodeling.

Astroglia perform diverse homeostatic and regulatory roles. They buffer extracellular potassium and clear neurotransmitters such as glutamate and GABA via specific transporters, helping to prevent excitotoxicity. They participate in brain energy metabolism by supplying neurons with substrates like lactate. They contribute to the integrity of the blood-brain barrier and regulate cerebral blood flow through endfeet on capillaries. They modulate synaptic transmission and plasticity, release neurotrophic factors, and influence synaptogenesis. They also participate in immune responses and can adopt reactive phenotypes after injury.

Identification and markers: astroglia express proteins such as GFAP, S100β, and ALDH1L1, although marker expression varies with state and region and no single marker uniquely identifies all astroglia.

Clinical and pathological relevance: in injury and disease, astroglia often become reactive in a process called astrogliosis, which can form a glial scar and alter tissue repair, inflammation, and water and ion homeostasis. Dysregulation of astroglial functions, including impaired glutamate uptake and disrupted neurovascular coupling, is implicated in neurodegenerative and neuropsychiatric disorders.