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

The APPSwe/PSEN1 dE9（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/PS1 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/PS1 mice and normal C57 BL/6 mice aged 3 and 6 months. Luxol fast blue staining of the corpus callosum and quantitative reverse transcription-polymerase chain reaction（q RT-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 C57 BL/6 mice, there was a downregulation of MBP mRNA in APP/PS1 mice aged 3 months. This became more obvious in APP/PS1 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 MCT1 mRNA. These findings indicate that the involvement of early demyelination at 3 months and the oligodendrocyte dysfunction at 6 months in APP/PS1 mice are in association with Alzheimer＇s disease pathogenesis.

Neuroimaging of corpus callosum in central nervous system demyelinating disorders

Corpus callosum (CC) is the largest white matter structure in the brain, consisting of 200-250 million contralateral axonal projections. It is the major commissural pathway connecting the hemispheres of human brain. The pathology of CC includes wide variety of entities that arise from different causes such as congenital, inflammatory, tumoral, degenerative, infectious, etc. This study reviews the most reliable neuroimaging data of human CC in central nervous system (CNS) demyelinating diseases to facilitate the understanding of different pathological entities of the CC and their role in anticipation of probable prognostic findings. After a brief description of normal anatomy and functions of CC, this review examines the most valuable findings obtained using conventional and functional magnetic resonance imaging. It also demonstrates the most well organized findings of how CC features influence prognostic factors of demyelinating disorders, which could have a great value for choosing proper therapy methods. The authors also provided a brief review of other demyelinating disorders which are primarily caused by other pathological factors other than autoimmunity. As a conclusion, the authors showed the importance of CC as an critical part of the brain, which should be explored by different methods of imaging, correspondent to clinical evaluation of CNS demyelinating disorder to widen our knowledge on pathology and clinical patterns of such disorders.