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Unmyelinated nerve fiber estimation by immunocytochemistry. Correlation with electron microscopy
P C Johnson1, J L Beggs, A G Olafsen
1Division of Neuropathology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona 85013.
Journal of Neuropathology and Experimental Neurology
|March 1, 1994
Summary
Quantifying unmyelinated nerve fibers (UMNF) is faster and cheaper using PGP 9.5 immunocytochemistry on paraffin-embedded biopsies. This method shows excellent correlation with electron microscopy for UMNF and myelinated nerve fiber densities.
Area of Science:
- Neurology
- Histology
- Biotechnology
Background:
- Electron microscopy (EM) is the standard for quantifying unmyelinated nerve fiber (UMNF) densities but is resource-intensive.
- Current EM methods analyze only a nerve's fraction, are time-consuming, and costly.
- A need exists for more efficient methods to assess nerve fiber densities.
Purpose of the Study:
- To evaluate the efficacy of PGP 9.5 immunocytochemistry in paraffin-embedded human sural nerve biopsies for quantifying UMNF densities.
- To compare UMNF and myelinated nerve fiber (MNF) densities obtained via PGP 9.5 staining with traditional EM and morphometric methods.
- To determine if PGP 9.5 immunocytochemistry offers a viable, cost-effective alternative to EM for nerve fiber analysis.
Main Methods:
- Human sural nerve biopsies were fixed in glutaraldehyde and embedded in paraffin.
- Immunocytochemistry was performed using anti-PGP 9.5 antibody to identify unmyelinated axons.
- Nerves were counterstained with Luxol fast blue, and UMNF and MNF densities were quantified and compared to EM and morphometric estimates.
Main Results:
- PGP 9.5 immunocytochemistry demonstrated excellent correlation with EM-derived UMNF densities (p < 0.0001).
- Estimates of MNF densities using this method also showed excellent correlation with traditional morphometric analyses (p = 0.0026).
- The technique successfully detects small axons and multiple axons per Schwann cell subunit, though it has limitations in fiber size histogram preparation and pathology analysis.
Conclusions:
- PGP 9.5 immunocytochemistry provides a quicker, less expensive, and highly accurate method for UMNF quantitation compared to EM.
- This method serves as a valuable tool for both quantitative and qualitative assessment of UMNF populations in nerve biopsies.
- While not replacing EM for all aspects (e.g., pathology, fiber size distribution), it offers a significant advancement in diagnostic efficiency.