Axonally transported peripheral signals regulate alpha-internexin expression in regenerating motoneurons

Area of Science:

• Neuroscience
• Cell Biology
• Regenerative Medicine

Background:

• Class IV neuronal intermediate filament (IF) proteins include the neurofilament (NF) triplet (NF-L, NF-M, NF-H) and alpha-internexin.
• NF-L, -M, and -H are downregulated post-peripheral nerve injury.
• The role of alpha-internexin in neuronal injury and regeneration remains less understood.

Purpose of the Study:

• To investigate alpha-internexin protein and mRNA expression following facial nerve injury.
• To explore the relationship between alpha-internexin expression, nerve regeneration, and axonal transport.

Main Methods:

• Facial nerve injury models (crush, transection, resection) in rats.
• Immunohistochemistry for alpha-internexin.
• In situ hybridization for alpha-internexin mRNA.
• Retrograde tracing (Fluorogold) to assess reinnervation.
• Axonal transport blockage using colchicine.
• Central axotomy of rubrospinal neurons.

Main Results:

• Alpha-internexin immunoreactivity significantly increased in facial motoneurons after all injury types, peaking at 7 days.
• Sustained high alpha-internexin levels were observed after nerve resection, which impedes regeneration.
• Increased alpha-internexin mRNA expression occurred post-injury.
• Alpha-internexin expression was inversely correlated with successful target reinnervation and axonal transport.

Conclusions:

• Upregulation of alpha-internexin in injured motoneurons suggests a role in neuronal regeneration.
• Alpha-internexin expression is dynamically regulated by peripheral nerve injury, axonal transport, and reinnervation status.
• Alpha-internexin may serve as a marker for neuronal injury and a potential factor in the regenerative process.