Perivascular astrocytes within Alzheimer's disease plaques.

The association of astrocytes with plaques is a well-established feature of Alzheimer's disease (AD) and has generally been interpreted as a secondary reaction to amyloid deposition or neuronal degeneration. Astrocytes in brain tissue from six non-demented controls and six patients with AD were investigated using enhanced immunohistochemistry for glial fibrillary acid protein (GFAP) in serial sections from cortex, basal forebrain, amygdala, putamen and diencephalon. Astrocytes colocalized with all diffuse and non-diffuse plaques in AD and control brain tissue. All plaque-associated astrocytes contacted microvessels, and despite having greater numbers of hypertrophic and fine calibre processes, the cells maintained the perivascular arrangement characteristic of control brain tissue. These observations suggest that plaques form at the site of microvascular aberrations followed by reactive and degenerative changes in perivascular astrocytes.