Sampling and Evaluating the Peripheral Nervous System.

Area of Science:

• Neuroscience
• Toxicology
• Pathology

Background:

• Preclinical peripheral nervous system (PNS) evaluation often relies on limited sciatic nerve sections.
• This approach overlooks critical toxicity mechanisms and anatomical variations affecting peripheral neurons.
• Current methods inadequately assess demyelination and differentiate axonal versus myelin degeneration.

Purpose of the Study:

• To highlight limitations in current PNS preclinical evaluation methods.
• To propose an enhanced strategy for assessing test article effects on peripheral neurons and neurites.
• To improve the characterization of peripheral neuropathies.

Main Methods:

• Critique of standard paraffin-embedded, hematoxylin and eosin-stained sciatic nerve sections.
• Discussion of anatomical factors influencing test article distribution (e.g., capillary permeability).
• Emphasis on length-dependent neuropathy mechanisms and myelin assessment challenges.

Main Results:

• Paraffin sections are suboptimal for evaluating myelin changes and demyelination.
• Distinguishing axonal from myelin degeneration is difficult with current standard methods.
• Anatomical differences and exposure variations impact peripheral neuron susceptibility.

Conclusions:

• A comprehensive PNS assessment requires methods beyond basic sciatic nerve histology.
• Optimized tissue harvesting, fixation, and combined resin/paraffin embedding are crucial.
• Enhanced strategies improve the pathologist's ability to detect and characterize PNS effects.