Which glial cell forms the blood-brain barrier?

Which glial cell forms the blood-brain barrier?

• A. Microglia
• B. Astrocytes
• C. Oligodendrocytes
• D. Schwann Cells

Answer: (B)

Astrocytes are the glial cells that form and maintain the blood-brain barrier. Their endfeet wrap around CNS capillaries, creating the glial limitans and shaping the neurovascular unit. These endfeet interact with endothelial cells and release signaling molecules that promote and regulate tight junction proteins (like claudins and occludins) in the cerebral microvasculature, helping to restrict paracellular leak and control what passes into the brain. They also help with ion and water homeostasis, notably via aquaporin-4 channels in their endfeet, which supports barrier function. Microglia are the resident immune cells of the CNS and do not form the barrier. Oligodendrocytes create myelin for CNS axons, not a barrier. Schwann cells perform myelination in the peripheral nervous system, not the CNS barrier.

Astrocytes are the glial cells that form and maintain the blood-brain barrier. Their endfeet wrap around CNS capillaries, creating the glial limitans and shaping the neurovascular unit. These endfeet interact with endothelial cells and release signaling molecules that promote and regulate tight junction proteins (like claudins and occludins) in the cerebral microvasculature, helping to restrict paracellular leak and control what passes into the brain. They also help with ion and water homeostasis, notably via aquaporin-4 channels in their endfeet, which supports barrier function.

Microglia are the resident immune cells of the CNS and do not form the barrier. Oligodendrocytes create myelin for CNS axons, not a barrier. Schwann cells perform myelination in the peripheral nervous system, not the CNS barrier.