Increase of acidic fibroblast growth factor in the brains of hamsters infected with either 263K or 139H strains of scrapie

Scrapie is the archetypal unconventional slow infection disease. It has been shown that hamsters injected intracerebrally with scrapie strains 139H or 263K show extensive astrocytosis and that the induced reactive astrocytes produce a variety of factors that can affect brain function. Acidic fibroblast growth factor (aFGF) belongs to a family of growth factors that show a high affinity for heparin sulfate proteoglycans. In the current study, we have used immunohistochemistry to investigate the distribution of aFGF in scrapie-infected brain; we observed a low level of aFGF immunoreactivity (ir-aFGF) in ependymal cells and in a few neurons in the hypothalamus of control hamsters. In contrast, in scrapie-infected hamsters, there was an increase of ir-aFGF in a number of cell types, including neurons, pericytes, astrocytes, and ependymal cells. In 139H-infected hamsters, ir-aFGF staining in astrocytes, neurons and neuropil areas of the cortex, hippocampus, thalamus, and hypothalamus was greater than the staining in control animals. For 263K animals, astrocytic ir-aFGF staining was significantly greater than in either control or 139H-infected hamsters in the following regions: cortex, putamen, corpus callosum, thalamus, hypothalamus, fimbria, hippocampus, subependymal areas, and amygdala. In addition, there was a significant increase in neuronal ir-aFGF in the CA1 hippocampal area and in the amygdala. Our results suggest that neurons and astrocytes can produce and/or absorb aFGF during scrapie infection. These findings indicate that aFGF might play an important role in neuronal protection and in astrocytosis in scrapie-infected hamsters.