Expression of cystatin C in rat, monkey and human brains.

Expression of cystatin C and its mRNA in brain were investigated by use of immunohistochemical and polymerase chain-reaction techniques. High levels of cystatin C mRNA were detected in every region of rat brain examined, including the cerebral cortex, hippocampus, hypothalamus and cerebellum. Cystatin C-positive astrocytes were found by immunohistochemistry to be distributed throughout the brains of rat, monkey and human. Some neurons were also positive, but the staining was weak and variable. Intensely immunoreactive neurons were abundantly found in the cerebral cortex of some aged human cases and of all Alzheimer's disease patients. It is concluded that cystatin C is synthesized and expressed in the central nervous system, especially by astrocytes. Cystatin C might also be involved in the aging process of cortical neurons.