Reaction of peripheral nerves to vascular and bacterial injuries

Area of Science:

• Neuroscience
• Infectious Diseases
• Pathology

Background:

• Peripheral nerve damage is a hallmark of leprosy.
• Understanding the specific pathological changes in nerve tissue is crucial for developing effective treatments.

Purpose of the Study:

• To investigate the pathological changes in mouse sciatic nerves following devascularization, Mycobacterium leprae inoculation, and a combination of both insults.
• To compare the temporal progression of nerve damage in different experimental conditions.

Main Methods:

• Induction of devascularization and/or Mycobacterium leprae footpad inoculation (FPI) in mouse sciatic nerves.
• Histopathological examination of nerve tissues at various time points post-insult.
• Analysis of changes in nerve fibers, Schwann cells, blood vessels, and inflammatory cell infiltration.

Main Results:

• Combined devascularization and FPI led to rapid nerve changes within hours, while FPI alone showed changes after eight months.
• Both groups exhibited initial loss of small myelinated fibers.
• Schwann cell proliferation was observed in the combined insult group, peaking at two weeks, but M. leprae appeared to arrest this activity later.
• Endoneurial blood vessels displayed characteristic changes, including increased endothelial cell cytoplasm and basement membrane proliferation.
• Increased mast cells were noted in devascularized and FPI nerves, while macrophages indicated low immunity in devascularized nerves.
• Eosinophils migrated to the endoneurium due to axoplasm leakage.

Conclusions:

• The combination of nerve devascularization and M. leprae inoculation accelerates peripheral nerve pathology compared to FPI alone.
• Specific vascular and cellular changes in endoneurial blood vessels are indicative of leprosy nerve involvement.
• The study highlights the complex interplay between vascular integrity, microbial presence, and host immune response in leprosy neuropathy.