Induction of angiogenesis in the β-amyloid peptide-injected rat hippocampus

Angiogenesis, the formation of new capillary blood vessels, has been studied following the stereotaxic injection of β-amyloid peptide (Aβ_1-42) into rat hippocampus. Immunohistochemical analysis for laminin showed that neovascularization was only slightly increased, relative to control, in the hippocampus 1 day post-Aβ_1-42 injection. However, 7 days following peptide injection neovascularization was markedly up-regulated (by 2.2-fold) compared to control. Immunoreactivity for the angiogenic stimulatory agent vascular endothelial growth factor (VEGF) was also significantly increased in the hippocampus 7 days after Aβ_1-42 injection. Double immunofluorescence staining demonstrated that the increased level of VEGF immunoreactivity was localized to both astrocytes and microglia, suggesting inflammatory responses contributed to angiogenesis. The findings of β-amyloid stimulated angiogenesis and the involvement of peptide-induced inflammatory processes may have relevance to the pathology of Alzheimer's disease.