Bundles of amyloid precursor protein-immunoreactive axons in human cerebrovascular white matter lesions

Cerebral white matter lesions commonly observed in Binswanger's disease, multi-infarct encephalopathy and elderly people are neuropathologically characterized by diffuse incomplete demyelination and considered to be ischemic in nature. Arteriolosclerosis in the white matter is a common feature in these white matter lesions. To investigate a possible alteration of the distribution of amyloid precursor protein (APP), chromogranin A (CgA) and synaptophysin (Syn) in such white matter lesions, we examined 15 cases with white matter lesions and 5 without white matter lesions. Many bundles of axons with APP-like immunoreactivity (LI) were observed particularly in mild white matter lesions. Such bundles of axons showed similar but less intense CgA-LI and Syn-LI. They appeared to occur in areas with many ameboid or ramified microglia labeled with anti-leukocyte common antigen and few astrocytes labeled with anti-glial fibrillary acidic protein. In the center of moderate of severe white matter lesions bundles of axons with APP-LI were never observed. Since APP, CgA and Syn undergo fast axonal transport, and since following ischemic insults to central nervous system microglial reaction occurs earlier than astroglial changes, our results suggest that axonal damage, which induces disturbance of fast axonal transport, can occur even in the early stage of white matter lesions.