Axonal pathology and loss precede demyelination and accompany chronic lesions in a spontaneously occurring animal model of multiple sclerosis

Brain Pathol. 2010 May;20(3):551-9. doi: 10.1111/j.1750-3639.2009.00332.x. Epub 2009 Aug 26.


Axonal damage has been highlighted recently as a cause of neurological disability in various demyelinating diseases, including multiple sclerosis, either as a primary pathological change or secondary due to myelin loss. To characterize and quantify axonal damage and loss in canine distemper demyelinating leukoencephalomyelitis (DL), formalin-fixed paraffin-embedded cerebella were investigated histochemically and immunohistochemically using the modified Bielschowsky's silver stain as well as antibodies against nonphosphorylated (n-NF), phosphorylated neurofilament (p-NF) and beta-amyloid precursor protein (beta-APP). Injured axons characterized by immunoreactivity against n-NF and beta-APP were detected in early distemper lesions without demyelination. In subacute and chronic demyelinating lesions the number of injured axons increased. Moreover, a significant decrease in axonal density was observed within lesions and in the normal appearing white matter in DL as determined by morphometric analyses using Bielschowsky's silver stain and p-NF immunohistochemistry. Summarized, the observed findings indicate that axonal damage (i) occurs early in DL; (ii) can be detected before myelin loss; and (iii) represents a pivotal feature in advanced lesions. It must be postulated that axonal damage plays an important role in the initial phase as a primary event and during progression of nervous distemper as a result of demyelination.

MeSH terms

  • Animals
  • Axons / pathology*
  • Brain / pathology*
  • Chronic Disease
  • Disease Models, Animal
  • Distemper / pathology*
  • Dogs
  • Leukoencephalopathies / pathology*
  • Multiple Sclerosis / pathology*
  • Nerve Fibers, Myelinated / pathology*
  • Wallerian Degeneration / etiology
  • Wallerian Degeneration / pathology*