Immediate remote ischemic postconditioning reduces cerebral damage in ischemic stroke mice by enhancing leptomeningeal collateral circulation

Remote ischemic postconditioning (RIPC) is a promising neuroprotective strategy for ischemic stroke. Here, we employed a focal ischemic stroke mouse model to test the hypothesis that poststroke collateral circulation as a potent mechanism of action underlying the therapeutic effects of immediate RIPC. During reperfusion of cerebral ischemia, the mice were randomly assigned to receive RIPC, granulocyte colony-stimulating factor (G-CSF) as a positive control, or no treatment. At 24hr, we found RIPC and G-CSF increased monocytes/macrophages in the dorsal brain surface and in the spleen, coupled with enhanced leptomeningeal collateral flow compared with nontreatment group. Blood monocytes depletion by 5-fluorouracil (5-FU) significantly limited the neuroprotection of RIPC or G-CSF treatment. The protein expression of proangiogenic factors such as Ang-2 was increased by ischemia, but treatment with either RIPC or G-CSF showed no further upregulation. Thus, immediate RIPC confers neuroprotection, in part, by enhancing leptomeningeal collateral circulation in a mouse model of ischemic stroke.