Investigating mechanical behaviour at a core-sheath interface in peripheral nerve

Area of Science:

• Neuroscience
• Biomechanical Engineering
• Anatomy

Background:

• Peripheral nerve function relies on internal component movement during deformation.
• The specific mechanisms of intraneural component interaction remain poorly understood.
• Previous research identified distinct core and sheath structures in the rat sciatic nerve, offering a model for investigation.

Purpose of the Study:

• To characterize the mechanical and anatomical properties of the interface between the core and sheath in the rat sciatic nerve.
• To elucidate the nature of interactions between nerve core and sheath structures.

Main Methods:

• Rat sciatic nerves (15-20 mm) were harvested and subjected to tensile testing.
• A custom jig and tensile testing machine were used to pull the nerve core from the sheath.
• Transmission electron microscopy (TEM) was employed to analyze anatomical features of the core-sheath interface.

Main Results:

• Mechanical tests showed that pre-stretching the core-sheath interface by 25% reduced the pull-out force by approximately six times compared to intact controls.
• TEM analysis indicated that the sheath originates from the epineurium and outer perineurium, while the core comprises endoneurium and inner perineurium.
• The plane of separation during mechanical testing involved the innermost perineurial cell layer.

Conclusions:

• The results support the hypothesis that core-sheath interactions are mediated by physical connections rather than a viscous fluid interface.
• Understanding these physical connections is crucial for comprehending peripheral nerve biomechanics and injury mechanisms.