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Updated: May 28, 2026

Identifying Microglia and Peripheral Infiltrating Macrophages in the Injured Spinal Cords Using Flow Cytometry
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Identifying Microglia and Peripheral Infiltrating Macrophages in the Injured Spinal Cords Using Flow Cytometry

Published on: June 24, 2025

Site-specific subtypes of macrophages recruited after peripheral nerve injury

Tadasuke Komori1, Yoshihiro Morikawa, Takeshi Inada

  • 1Department of Anatomy and Neurobiology, Wakayama Medical University, Wakayama, Japan.

Neuroreport
|October 8, 2011
PubMed

Insights

Peripheral nerve injury causes distinct macrophage subtypes to infiltrate different tissues. M1 macrophages target the nerve, while M2 macrophages target the dorsal root ganglia, influencing neuropathic pain development.

Area of Science:

  • Neuroscience
  • Immunology
  • Cell Biology

Background:

  • Peripheral nerve injury triggers complex cellular responses.
  • Macrophages are key immune cells involved in tissue repair and inflammation.
  • Understanding macrophage subtypes and their roles is crucial for developing neuropathic pain treatments.

Purpose of the Study:

  • To investigate the subtypes and locations of macrophages infiltrating the sciatic nerve and dorsal root ganglia (DRGs) after injury.
  • To determine the temporal dynamics of macrophage infiltration and microglial activation.
  • To explore the potential roles of distinct macrophage populations in neuropathic pain development.

Main Methods:

  • Partial ligation of the mouse sciatic nerve model.
  • Immunohistochemical analysis to identify macrophage subtypes (M1 and M2) and neutrophils.
  • Examination of injured nerve, ipsilateral DRGs, and spinal cord dorsal horn.

Main Results:

  • M1 macrophages (iNOS-positive, Arg-1-negative) and neutrophils infiltrated the injured sciatic nerve.
  • M2 macrophages (iNOS-negative, Arg-1-positive) predominantly infiltrated the ipsilateral DRGs.
  • Macrophage infiltration preceded microglial activation in the spinal cord dorsal horn.

Conclusions:

  • Distinct macrophage subtypes (M1 and M2) exhibit site-specific infiltration following peripheral nerve injury.
  • Infiltrating macrophages may play unique, location-dependent roles in the pathogenesis of neuropathic pain.
  • These findings highlight macrophages as potential therapeutic targets for managing nerve injury-induced pain.

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