Does Hypoxic Preconditioning Induce Angiogenesis and Protect against Focal Cerebral Ischemic Damage in Rats ?

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Background and Aims : This study investigated whether hypoxic preconditioning (HP) induces ischemic tolerance in an established experimental model of permanent middle cerebral artery occlusion using rats. Methods : Animals were divided into the normoxia (control) and HP groups. HP was performed under normobaric conditions ( 7% O₂ for 2 hours), 14 days before focal cerebral ischemia induction. The infarct volume was evaluated by quantitative histopathology. Immunofluorescence analysis was assessed at 24 hours after HP to examine the effect on proliferating cell and microglia/macrophage activation. Brain microvessel density was assessed 14 days after HP. Furthermore, the expression was evaluated of angiogenesis-related proteins such as hypoxia-inducible factor-1α and vascular endothelial growth factor proteins. Results : Hemisphere infarct volume in the HP group was significantly smaller than in the control group. Vascular endothelial growth factor and proliferating cell nuclear antigen expression was not increased after HP. HP tended to increase vessel density relative to the control group, but this did not achieve statistical significance. Conclusion : HP attenuated the infarct volume in rats. The phenomenon of ischemic tolerance may link HP with vascular remodeling.