Glial reaction in the hippocampal formation is highly correlated with aging in human brain.

Glial fibrillary acidic protein (GFAP), a biochemical marker of astrocytes and glial reaction, was quantified by immunoblotting in different brain areas from 33 non-demented patients with a Mini Mental State Examination score above 26 and aged from 12 to 98 years. An increase of GFAP with age was first found in the hippocampus and then in the entorhinal cortex. In both regions, GFAP amounts were correlated with age (r = 0.768). In the isocortex, the increase of GFAP as a function of age was also significant (r = 0.672), but less than for the hippocampal region. GFAP levels increased dramatically after the age of 65 years, and more especially in the hippocampal formation. This glial reaction was observed in aged controls that do not show cognitive impairment and the neuropathological hallmarks of Alzheimer's disease.