A time course for the focal elevation of synthesis of basic fibroblast growth factor and one of its high-affinity receptors (flg) following a localized cortical brain injury

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Abstract
Traumatic injury to the CNS initiates transient and unsuccessful regeneration of damaged neural pathways, accompanied by reactive gliosis, angiogenesis, and deposition of a dense fibrous glial/meningeal scar at the wound site. Basic fibroblast growth factor (basic FGF) is a CNS protein with potent effects on neurons, glia, fibroblasts, and vascular endothelial cells. Hybridization and immunocytochemical methods were used to examine temporal and spatial changes in distribution and levels of basic FGF protein and mRNA and also of its receptor mRNA (flg), following a defined wound to the cerebral cortex of adult rat brains. In the injured brain, a rapid, transient increase in basic FGF mRNA and protein is readily detectable within 7 d of surgery and thereafter declines in the tissues bordering the lesion. The increased expression is localized to multiple cell types including macrophages, neurons, astrocytes, and vascular endothelial cells. The changes in immunoreactive basic FGF parallel changes in the bioactivity of extracted heparin-binding proteins, which include basic FGF. Focal increases in flg mRNA appear 7 d after injury and subside by 14 d. The changes in local basic FGF synthesis, concentration, localization, and bioactivity suggest that this growth factor may contribute to the cascade of cellular events that occur in CNS wound repair.