Objective: To investigate the therapeutic effect of vascular endothelial growth factor (VEGF) gene expression mediated by recombinant AAV1 (rAAV1) vector in brain ischemia and the mechanism thereof.
Methods: Sixty-four SD rats were randomly divided into 2 equal groups and received intra-ventricular injection with rAAV1-VEGF or rAAV1-lacZ as controls. 21 days later the rats underwent transient middle cerebral artery occlusion (MCAO). Neurological severity score (NSS) was recorded 1, 2, 3, 7, 14, and 21 days after MCAO. 48 rats were sacrificed 21 days after MCAO and brains were taken out from 48 rats. Immune quantitative analysis was used to identify the quantity of VEGF expression. Immunohistochemistry was used to identify the site of VEGF expression. Immunofluorescence double labeling of von Willebrand factor (vWF) and 5-bromodeoxy-uridine (BrdU) was performed to detect the proliferation of endothelial cells. Fluorescein isothiocyanate (FITC)-dextran was infused into the caudal vein of 8 rats from each group and then the rats were killed with their brains taken out to evaluate the cerebral microvessel perfusion and microvessel density.
Results: The NSSs of the VEGF group 7, 14, and 21 days after MCAO were all significantly lower than those of the control group (all P < 0.05), and the VEGF165 protein expression quantity was 27 times as that of the control group (P < 0.05). Immunohistochemistry demonstrated that VEGF expression was distributed mainly in the caudate putamen, corpus callosum, choroid plexus, and hippocampus in the VEGF group, while no expression was detected in the control group. The microvessel density of the VEGF group was 157 +/- 13, significantly higher than that of the control group [(89 +/- 9), P < 0.05]. BrdU +/vWF + endothelial cells were detected in the area adjacent to the MCAO. The density of microvessel infused with FITC-dextran was (152,617 +/- 13,076) microm2/mm2 in the VEGF group, significantly higher than that of the control group [(91,658 +/- 6577) microm2/mm2 P < 0.05].
Conclusion: rAAV1 mediates the VEGF gene expression in multiple structures in the brain and attenuates the neurological deficit of MCAO. VEGF gene transfer may stimulate angiogenesis and improves blood supply in brain. Neovascularization may be a therapeutic strategy for brain ischemia.