Glialfrumur

Glial fibers, also known as glial fibrils, are the filamentous networks inside glial cells that form part of the cells’ cytoskeleton. In the central nervous system, these filaments are most prominent in astrocytes and are made mainly of intermediate filament proteins such as glial fibrillary acidic protein (GFAP) and, in development, vimentin. In mature tissue, GFAP is the primary component of the astrocytic intermediate filament system.

The distribution and composition of glial fibers reflect development and cell type. Astrocytes contain dense GFAP-positive filaments that support cell shape, stabilize processes, and help organize interactions with blood vessels and synapses. During development, radial glia use similar filaments to provide a scaffold for migrating neurons; later, these filaments help maintain the astrocyte architecture in the mature brain. Other glial cells, such as oligodendrocytes and Schwann cells, express GFAP to varying degrees, especially during development or in response to injury.

Functionally, glial fibers contribute to mechanical support and the structural integrity of glial networks. They participate in maintaining tissue architecture, supporting astrocyte processes around capillaries and synapses, and modulating astrocyte signaling and ion homeostasis. While they are not the primary drivers of metabolism, they support the broader roles of glial cells in neuronal function and homeostasis.

Pathologically, GFAP expression and glial filament organization change after CNS injury or disease. Reactive gliosis involves upregulation of GFAP and remodeling of glial filaments, which can lead to the formation of glial scars that influence regeneration and inflammation.

Glial fibers are commonly visualized with GFAP immunostaining in histology, which highlights the astrocytic network and the overall glial architecture of nervous tissue.