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Published on: March 30, 2018
Effect of modulating macrophage phenotype on peripheral nerve repair
Nassir Mokarram1, Alishah Merchant, Vivek Mukhatyar
1Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA 30332, USA.
Biomaterials
|September 18, 2012
Summary
Modulating macrophage phenotypes using cytokines like Interferon-gamma (IFN-γ) and Interleukin-4 (IL-4) enhances nerve regeneration. Pro-healing macrophages significantly improve Schwann cell migration and axonal growth across nerve gaps.
Area of Science:
- Biomedical Engineering
- Regenerative Medicine
- Neuroscience
Background:
- Peripheral nerve repair across long gaps is a significant clinical challenge.
- Current nerve guidance scaffolds struggle to match autograft repair outcomes.
- Macrophage polarization is a potential therapeutic target for nerve regeneration.
Purpose of the Study:
- To investigate the effect of cytokine-mediated macrophage polarization on Schwann cell migration and axonal regeneration.
- To evaluate the efficacy of modulating macrophage phenotypes within nerve guidance channels for peripheral nerve repair.
Main Methods:
- Utilized polymeric nerve guidance channels for local delivery of Interferon-gamma (IFN-γ) or Interleukin-4 (IL-4) to modulate macrophage phenotypes.
- Assessed Schwann cell infiltration and axonal regeneration in vitro and in a 15 mm rat sciatic nerve gap model.
- Quantified macrophage populations using CD206 (pro-healing) and CCR7 (pro-inflammatory) markers.
Main Results:
- Local delivery of IL-4 successfully polarized macrophages towards pro-healing M2a and M2c phenotypes.
- M2a and M2c macrophage polarization led to enhanced Schwann cell infiltration and accelerated axonal growth.
- A linear relationship was observed between the regenerative bias (CD206+/CCR7+ ratio) and distal axonal regeneration.
Conclusions:
- Macrophage phenotype, not just presence, is critical for regulating peripheral nerve regeneration outcomes.
- Cytokine-mediated 'biasing' of macrophages towards a pro-healing phenotype offers a promising strategy for enhancing nerve repair.
- This approach holds potential for improving clinical strategies for long-gap peripheral nerve injuries.
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