Age-associated changes of cerebrospinal fluid amyloid-β and tau in cynomolgus monkeys.

Nonhuman primates (NHPs) are useful for the study of age-associated changes in the brain as a model that is biologically closely related to humans. For example, with age, all NHPs analyzed to date, develop β-amyloid (Aβ) plaques as seen in humans. Nevertheless, it is still unclear if NHPs have human-like age-associated changes in Aβ and tau protein in cerebrospinal fluid. The present study was an attempt to specifically address these issues. Cerebrospinal fluid levels of Aβ and phosphorylated tau were measured in 37 and 22 cynomolgus monkeys, respectively, with ages ranging from 4 to 22-year-old. The result from the present study revealed significant age-associated declines in Aβ42 levels but not in Aβ40 and phosphorylated tau levels. This finding appears to parallel changes seen with human aging, in which decreased levels of Aβ42 can be seen in normal older adults, and supporting that cynomolgus monkeys would be a useful model for studying age-related neurologic disorders associated with Alzheimer-like cerebral proteopathy.