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Updated: Jul 11, 2025
Partial Sciatic Nerve Ligation: A Mouse Model of Chronic Neuropathic Pain to Study the Antinociceptive Effect of Novel Therapies
Published on: October 6, 2022
Switching Rat Resident Macrophages from M1 to M2 Phenotype by Iba1 Silencing Has Analgesic Effects in SNL-Induced
Roxana-Olimpia Gheorghe1, Andreea Violeta Grosu1, Melania Magercu1
1Department of Anatomy, Animal Physiology and Biophysics, Faculty of Biology, University of Bucharest, 91-95 Splaiul Independentei, District 5, 050095 Bucharest, Romania.
Abstract:
Resident macrophages from dorsal root ganglia are important for the development of traumatic-induced neuropathic pain. In the first 5-7 days after a traumatic sciatic nerve injury (i.e., spinal nerve ligation (SNL), spared nerve injury (SNI), sciatic nerve transection or sciatic nerve ligation and transection), Ionized binding adapter protein 1 (Iba1) (+) resident macrophages cluster around dorsal root ganglia neurons, possibly contributing to nerve injury-induced hypersensitivity. Since infiltrating macrophages gradually recruited to the lesion site peak at about 7 days, the first few days post-lesion offer a window of opportunity when the contribution of Iba1 (+) resident macrophages to neuropathic pain pathogenesis could be investigated. Iba1 is an actin cross-linking cytoskeleton protein, specifically located only in macrophages and microglia. In this study, we explored the contribution of rat Iba1 (+) macrophages in SNL-induced neuropathic pain by using intra-ganglionic injections of naked Iba1-siRNA, delivered at the time the lesion occurred. The results show that 5 days after Iba1 silencing, Iba1 (+) resident macrophages are switched from an M1 (pro-inflammatory) phenotype to an M2 (anti-inflammatory) phenotype, which was confirmed by a significant decrease of M1 markers (CD32 and CD86), a significant increase of M2 markers (CD163 and Arginase-1), a reduced secretion of pro-inflammatory cytokines (IL-6, TNF-α and IL-1β) and an increased release of pro-regenerative factors (BDNF, NGF and NT-3) which initiated the regrowth of adult DRG neurites and reduced SNL-induced neuropathic pain. Our data show for the first time, that it is possible to induce macrophages towards an anti-inflammatory phenotype by interacting with their cytoskeleton.
Insights
Resident macrophages in dorsal root ganglia contribute to neuropathic pain. Silencing Ionized binding adapter protein 1 (Iba1) shifts these macrophages to an anti-inflammatory state, reducing pain and promoting nerve regeneration.
Area of Science:
- Neuroscience
- Immunology
- Pain Research
Background:
- Resident macrophages in dorsal root ganglia (DRG) play a crucial role in the development of neuropathic pain following nerve injury.
- Ionized binding adapter protein 1 (Iba1) is a marker for macrophages and microglia, and Iba1-positive macrophages accumulate around DRG neurons after injury.
- The early post-injury period presents a therapeutic window to investigate the role of resident macrophages in neuropathic pain.
Purpose of the Study:
- To investigate the contribution of Iba1-positive macrophages in spinal nerve ligation (SNL)-induced neuropathic pain in rats.
- To explore the potential of modulating macrophage phenotype from pro-inflammatory (M1) to anti-inflammatory (M2) via targeting Iba1.
Main Methods:
- Intra-ganglionic injection of Iba1-siRNA in rats at the time of sciatic nerve injury (SNL).
- Assessment of macrophage phenotype by analyzing M1 (CD32, CD86) and M2 (CD163, Arginase-1) markers.
- Quantification of pro-inflammatory cytokines (IL-6, TNF-α, IL-1β) and pro-regenerative factors (BDNF, NGF, NT-3).
- Evaluation of neuropathic pain and DRG neurite regrowth.
Main Results:
- Iba1 silencing successfully shifted resident macrophages from an M1 to an M2 phenotype.
- This phenotypic switch was confirmed by decreased M1 markers and increased M2 markers.
- Reduced secretion of pro-inflammatory cytokines and increased release of neurotrophic factors were observed.
- SNL-induced neuropathic pain was significantly reduced, and DRG neurite regrowth was initiated.
Conclusions:
- Targeting the cytoskeleton protein Iba1 can modulate macrophage phenotype towards an anti-inflammatory and pro-regenerative state.
- Modulating resident macrophage phenotype offers a potential therapeutic strategy for neuropathic pain.
- This study demonstrates a novel approach to treat neuropathic pain by reprogramming macrophages.
