Junctions in the meninges and marginal glia

Area of Science:

• Neuroscience
• Cell Biology
• Anatomy

Background:

• The meninges form a protective barrier around the central nervous system.
• Understanding the meningeal barrier's structure is crucial for studying cerebrospinal fluid dynamics and drug delivery.

Purpose of the Study:

• To investigate the distribution of tight junctions within the meninges.
• To identify the cellular basis of the meningeal barrier between dural blood vessels and cerebrospinal fluid.

Main Methods:

• Electron microscopy (thin sectioning and freeze-fracturing) was used to examine meninges from various mammals.
• Focus was placed on identifying and characterizing intercellular junctions, particularly tight junctions.

Main Results:

• Endothelial cells of subarachnoid space blood vessels possess extensive tight junctions.
• A specialized arachnoid barrier layer exhibits a continuous system of tight junctions, identified as the primary meningeal barrier.
• Dural layers and astrocytes at the brain surface generally lack tight junctions but possess gap junctions and desmosomes.

Conclusions:

• The arachnoid barrier layer is the principal component responsible for the meningeal barrier function.
• The absence of tight junctions in other meningeal layers and between astrocytes suggests alternative mechanisms for intercellular communication and potential roles in substance exchange.