Human choroid plexus growth factors: What are the implications for CSF dynamics in Alzheimer's disease?

The choroid plexus plays a key role in supporting neuronal function by secreting cerebrospinal fluid (CSF) and may be involved in the regulation of various soluble factors. Because the choroid plexus is involved in growth factor secretion as well as CSF dynamics, it is important to understand how growth factors in CSF interact with the brain parenchyma as well as with cells in direct contact with the flowing CSF, i.e., choroid plexus and arachnoid villi. While the existence of growth factors in the choroid plexus has been documented in several animal models, the presence and distribution of growth factors in the human choroid plexus has not been extensively examined. This study describes the general distribution and possible functions of a number of key proteins in the human choroid plexus and arachnoid villi, including basic fibroblast growth factor, FGF receptor, and vascular endothelial growth factor. FGF and VEGF could both be readily demonstrated in choroid plexus epithelial cells. The presence of FGF and VEGF within the choroid plexus was also confirmed by ELISA analysis. Since Alzheimer's disease (AD) is known to be associated with a number of growth factor abnormalities, we examined the choroid plexus and arachnoid villi from AD patients. Immunohistochemical studies revealed the presence of FGF and VEGF within the AD choroid plexus and an increased density of FGFr in both the choroid plexus and the arachnoid villi of AD patients. No qualitative changes in the distribution of FGF and VEGF were observed in the AD choroid plexus. The appearance of FGFr in AD arachnoid was associated with robust amyloid and vimentin immunoreactivity. These findings confirm the presence of FGF and VEGF within the normal and AD choroid plexus and suggest that the alteration of growth factors and their receptors may contribute to the pathogenesis of the hydrocephalus ex vacuo that is characteristically seen in AD.