Adult Mice After Ischemic Brain Damage Nerve Vascular Reconstruction Of Units And Study Of White Matter Damage Repair Time Compliance And Omega 3 Fatty Acids Promote Ischemic Brain Injury After Nerve Vascular Remodeling

Background and purpose:Stroke is the leading cause of serious long-term disability in adults in the US. Recent discoveries have demonstrated that ischemic stroke can trigger multiple processes of repair, including neurogenesis, angiogenesis and oligodendrogenesis in adult brain, aiming towards neurovascular remodeling in peri-infarct areas during stroke recovery. The understanding of theses endogenous restorative responses to stroke, however, is very limited. The present study aimed to clarify the temporal dynamics of neurogenesis, neovascularization and white matter injury/repair occurred in a murine cerebral ischemia-reperfusion injury model.Methods:Transient focal cerebral ischemia was induced in C57/BL6 mice by unilateral middle cerebral artery occlusion (MCAO) for 60 minutes. 5-bromo-2’-deoxyuridine (Brdu) was administered intraperitoneally to lable newly generated cells. Animals were sacrificed on day 1,3,7,14 or 28 of reperfusion (n=5 per group). Immunohistochemistry stainings of BrdU and cell-specific markers were used to determine the presence of neurogenesis (nestin, doublecortin (DCX)) and oligodendrogenesis (NG2). Functional vessels were identified by transcardial perfusion of FITC-conjugated tomato lectin, which labels endothelial cells only in perfused vessels. White matter injury was evaluated by immunohistochemistry staining of myelin basic protein (MBP) and neurofilament (NF) 200.Results:The number of BrdU+/nestin+ cells increased markedly in the ischemic brain up to 7 days after MCAO and decreased thereafter. The number of DCX+ cells in the ischemic hemisphere were increased compared to the contralateral hemisphere since 7 days after ischemia. The post-stroke neovasculation, as measured by total vascular branch points, total vascular number, and total vascular length per mm2, dramatically decreased in the peri-infarct regions at 1 day after ischemia. Vascular density was then partially recovered in the peri-infarct regions beginning at 3 days and further increased at 7,14 and 28 days after ischemia. Neovascularization was not observed in the ischemic core area. The post-stroke angiogenesis began to be observed at 3 days and further increased at 14 and 28 days after MCAO. Oligodendrogenesis, quantified as the number of BrdU+/NG2+ cells, significantly increased in the penumbra from day 3 until day 28 after ischemia. NF-200 immunoreactivity was essentially absent in the penumbra at day 1, while the loss of MBP immunoreactivity began at day 3 after ischemia. The loss of NF-200 and MBP continued until 28 days after ischemia, suggesting a persistent white matter injury.Conclusions:Our study provides a detailed temporal analysis of neurogenesis, angiogenesis and oligodendrogenesis in a rodent stroke model. Neurogenesis and neovascularization were substantially activated early after ischemic stroke and persisted for several weeks. Despite the sustained presence of newborn oligodendrocyte progenitors, white matter injury after ischemic stroke is almost irreversible without any intervention. These findings provide insight into the future development of therapeutic strategies targeting the establishment of integrated neurovascular units in the ischemic brain.