Misfolding protein pathology detected in a chronic mouse model of multiple sclerosis

Multiple sclerosis (MS) is one of the most common causes of neurological disability in young adults. The pathobiology of MS includes both autoimmune inflammation and underlying degeneration, with the current challenge being to better understand and treat MS progression. The cuprizone (CPZ) mouse model is commonly used to study de- and remyelination. Despite initial robust myelin repair after toxin withdrawal, mice display progressive callosal atrophy, myelin loss, and gliosis. We tested the hypothesis that this delayed demyelination is due to a progressive degenerative proteopathy. Male C57BL/6 mouse brain sections harvested 8 months after a demyelinating CPZ insult followed by repair were positive for anti-oligomer and anti-fibril epitopes using the antibodies A11 and LOC (p < 0.05 and p < 0.001, respectively). Tissues were also stained with the fluorescent amyloid probes Thioflavin-S (ThS) or pFTAA. Quantitative spectral analysis of the corpus callosum (CC) indicated a subtle but widespread accumulation of ß-sheet-rich material (p < 0.001 and p < 0.0001, respectively). Taken together, our results are consistent with deposition of misfolded proteins facilitating chronic degeneration of axons and myelin in the post-CPZ CC leading to a progressive MS-like pathology. This "late post-CPZ" model could shed light on mechanisms of progressive late degeneration in the MS brain and represents a new animal model of progressive MS, allowing development of novel therapies for this phase of the disease. Our data also raise the possibility that the underlying cytodegenerative component of MS may be driven by subtle toxic amyloid accumulation as in many other traditional neurodegenerative disorders.