Whisker stimulation enhances angiogenesis in the barrel cortex following focal ischemia in mice

Post-ischemia angiogenesis and vascular plasticity help to restore blood flow to ischemic tissue and likely benefit long-term functional recovery. Physical activity has been shown to cause morphologic and functional effects, including promoting angiogenesis in normal or injured animals. A therapeutic effect of peripheral activity on central angiogenesis after cerebral ischemia, however, has not been studied. In the present study of whisker-barrel cortex ischemia in the mouse model, we tested the hypothesis that enhancing whisker activity and sensory input to the ischemic barrel cortex might promote post-ischemia cerebral angiogenesis. Three days after focal ischemia in adult mice, the whiskers corresponding to the ischemic barrel cortex were stimulated by two methods: (1) whiskers on the right side of the mouse face were trimmed away, so the left whiskers were overused by the animals, (2) left whiskers were manually stimulated to enhance input signals to the ischemic barrel cortex. Western blot analysis showed that whisker stimulation increased expression of the angiogenic factors vascular endothelial growth factor, basic fibroblast growth factor, Tie-1, angiopoietin-2 (Ang-2), and possibly Ang-1. Co-immunostaining with markers for proliferation (5-bromo-2'-deoxyuridine (BrdU)) and vascular endothelial cells (Glut-1/CD-31) identified vessel proliferation in the penumbra region. Whisker stimulation increased BrdU-positive endothelial cells and vessels in this region 7 and 14 days after ischemia. Whisker stimulation also attenuated endothelial cell death and increased local cerebral blood flow. Our data suggest that appropriately enhanced peripheral activity and afferent signals to the ischemic cortex can promote post-ischemic angiogenesis, which may imply beneficial effects of specific physical therapy on long-term recovery from ischemic stroke.