Transperineurial arterioles in human sural nerve

Area of Science:

• Neuroscience
• Vascular Biology
• Histology

Background:

• The perineurial sheath separates nerve fascicle layers, endoneurium and epineurium.
• Transperineurial arterioles (TPA) link endoneurial capillaries to the epineurial arterial supply.
• Understanding TPA structure is key to nerve blood flow regulation.

Purpose of the Study:

• To investigate the anatomical structure and pathway of transperineurial arterioles (TPA) within human sural nerves.
• To determine the role of TPA and post-arteriolar capillaries (PAC) in the neurovascular supply of the endoneurium.

Main Methods:

• Three-dimensional reconstruction of one-micron sections from biopsied human sural nerves.
• Ultrastructural analysis of step serials to examine TPA morphology.
• Correlative light and electron microscopy to identify TPA and associated nerve fibers.

Main Results:

• Transperineurial arterioles (TPA) are confirmed to reside within open-ended perineurial sleeves, traversing from the epineurium to the endoneurium.
• Most TPAs are terminal arterioles (10-25 microns) connecting to capillaries, gradually transitioning to post-arteriolar capillaries (PAC).
• TPAs and PACs are frequently associated with unmyelinated nerve fiber plexuses, suggesting neurovascular interaction.

Conclusions:

• Transperineurial arterioles (TPA) possess a unique anatomical pathway through perineurial sleeves, facilitating endoneurial vascular access.
• The association of TPA and PAC with nerve fibers suggests a role in neurogenic control of endoneurial blood flow.
• These findings enhance our understanding of the microvasculature within peripheral nerves and its regulation.