Association between Alzheimer's disease pathogenesis and early demyelination and oligodendrocyte dysfunction

The APPSwc/PSEN1dE9 (APP/PS1) transgenic mouse model is an Alzheimer's disease mouse model exhibiting symptoms of dementia, and is commonly used to explore pathological changes in the development of Alzheimer's disease. Previous clinical autopsy and imaging studies suggest that Alzheimer's disease patients have white matter and oligodendrocyte damage, but the underlying mechanisms of these have not been revealed. Therefore, the present study used APP/PSI mice to assess cognitive change, myelin loss, and corresponding changes in oligodendrocytes, and to explore the underlying mechanisms. Morris water maze tests were performed to evaluate cognitive change in APP/PSI mice and normal C57BL/6 mice aged 3 and 6 months. Luxol fast blue staining of the corpus callosum and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) for myelin basic protein (MBP) mRNA were carried out to quantify myelin damage. Immunohistochemistry staining for NG2 and qRT-PCR for monocarboxylic acid transporter 1 (MCT1) mRNA were conducted to assess corresponding changes in oligodendrocytes. Our results demonstrate that compared with C5761/6 mice, there was a downregulation of MBP mRNA in APP/PSI mice aged 3 months. This became more obvious in APP/PSI mice aged 6 months accompanied by other abnormalities such as prolonged escape latency in the Morris water maze test, shrinkage of the corpus callosum, upregulation of NG2-immunoreactive cells, and downregulation of MCTI mRNA. These findings indicate that the involvement of early demyelination at 3 months and the oligodendrocyte dysfunction at 6 months in APP/PSI mice are in association with Alzheimer's disease pathogenesis.