Differential degeneration of the cerebral microvasculature in Alzheimer's disease.

We used immunocytochemical methods to define abnormalities in the cerebral endothelium and the vascular basement membrane in patients with Alzheimer's disease (AD) and in aging control subjects. Double immunostaining with antibodies to the endothelial cell markers CD34 and CD31 revealed an absence of endothelial staining in many capillary profiles that still appeared to retain their basement membranes stained by antibodies to collagen IV. Such differential labeling, clearly suggesting capillaries with collapsed or degenerated endothelium, was frequently (> 90% of cases) evident in AD but relatively lacking in brain regions or other diseases and controls (< 30%) free of amyloid beta (A beta) deposits. We suggest that this profound vascular phenomenon is concomitant with A beta deposition and implies abnormalities in the integrity of brain microvasculature related to neuronal degeneration in AD.