IL-33 promotes sciatic nerve regeneration in mice by modulating macrophage polarization

Area of Science:

• Neuroscience
• Immunology
• Regenerative Medicine

Background:

• Peripheral nerve injuries often result in incomplete sensorimotor recovery due to insufficient regeneration.
• Interleukin-33 (IL-33) is a chemokine known to promote tissue healing via type 2 immune responses and M2 macrophage polarization, but its role in nerve regeneration is not well understood.

Purpose of the Study:

• To investigate the neuroprotective effects and efficacy of IL-33 treatment on sciatic nerve regeneration and sensorimotor recovery in a mouse model.
• To elucidate the mechanisms underlying IL-33's effects, including macrophage polarization and modulation of inflammatory and neurotrophic factors.

Main Methods:

• Sciatic nerve crush injury was induced in male C57BL/6 mice.
• Mice received intraperitoneal injections of IL-33 (10, 25, or 50 µg/kg) or vehicle for seven days.
• Sensorimotor recovery was assessed eight weeks post-injury.
• Immunohistochemistry, ELISA, and real-time PCR were employed to analyze macrophage polarization, cytokine levels, and neurotrophic factor expression (NGF, VEGF, BDNF) at the injury site.

Main Results:

• IL-33 administration at 25 and 50 µg/kg significantly enhanced nerve regeneration and sensorimotor recovery compared to the control and 10 µg/kg groups.
• IL-33 treatment promoted a shift in macrophage populations towards the pro-healing M2 phenotype.
• Pro-inflammatory cytokine levels were reduced, while mRNA expression of neurotrophic factors (NGF, VEGF, BDNF) was increased in the injured nerves following IL-33 treatment.
• A seven-day IL-33 treatment demonstrated neuroprotective effects in the sciatic nerve crush model.

Conclusions:

• IL-33 treatment effectively promotes peripheral nerve regeneration and sensorimotor recovery in mice.
• The therapeutic benefits of IL-33 are likely mediated by the induction of M2 macrophage polarization and the regulation of the inflammatory microenvironment.
• IL-33 represents a promising therapeutic candidate for enhancing recovery from sciatic nerve injuries.