Glial fibrillary acidic protein-immunoreactive astrocytosis in elderly patients with schizophrenia and dementia

Clinical and neuropsychological studies of chronically institutionalized patients with schizophrenia indicate that severe cognitive impairment and functional disability in late life are very prevalent. The biological substrates for this dementia remain unknown. While subtle cytoarchitectural and morphometric abnormalities have been described in patients with schizophrenia and interpreted as reflecting aberrant neurodevelopment, post-maturational injury or neurodegeneration associated with gliosis remain as plausible explanations of at least some of the clinical manifestations of schizophrenia. We monitored astrocytosis and neurofibrillary tangle (NFT) formation in 21 elderly patients with schizophrenia (14 with concurrent dementia, 7 without), and in 12 normal and 5 Alzheimer's disease (AD) control cases. Astrocytes in ventromedial temporal, frontal, and calcarine cortices were immunohistochemically identified with monoclonal antibodies directed at glial fibrillary acidic protein (GFAP) and vimentin, and NFTs were labeled with an anti-tau antibody specific for paired helical filaments. There were no increases in GFAP- or vimentin-immunoreactive astrocyte counts, GFAP optical density, or NFT counts for the schizophrenic group as a whole compared to the non-neuropsychiatric group, while both groups differed from AD. When patients with schizophrenia were divided into demented and non-demented subtypes, those with dementia demonstrated significantly greater numbers of GFAP-positive astrocytes than those without dementia. These data may reflect an up-regulation of GFAP in normal astrocytes or the presence of reactive astrocytosis in a subgroup of schizophrenics. In the absence of any diagnostic neuropathological findings in this subgroup, the implications of these observations for the pathogenesis of schizophrenia remain to be determined.