Search

Neurogenesis and angiogenesis are two important processes that may contribute to the repair of brain injury after stroke. This study was designed to investigate whether transplantation of human embryonic neural stem cells (NSCs) into cortical peri-infarction 24h after ischemia effects cell proliferation in the subventricular zone (SVZ) and angiogenesis in the peri-infarct zone. NSCs were prepared from embryonic human brains at 8 weeks gestation. Focal cerebral ischemia was induced by permanent occlusion of the middle cerebral artery of adult rats. Animals were randomly divided into two groups (n=30, each) at 24h after ischemia: NSC-grafted and medium-grafted groups. Toluidine blue staining and 5'-bromo-2'-deoxyuridine (BrdU) or von Willebrand factor (vWF) immunohistochemistry were performed at 7, 14 and 28 days after transplantation. NSC transplantation increased the number of BrdU-positive cells in the ischemic ipsilateral SVZ compared with the medium control at 7 days (P<0.01). This difference in SVZ cell proliferation persisted at 14 days (P<0.01), but was not significant at 28 days (P>0.05). In addition, angiogenesis, as indicated by BrdU and vWF staining in cortical peri-infarct regions, was augmented by 46% and 65% in NSC-grafted rats versus medium-grafted rats at 7 and 14 days, respectively (P<0.05). However, this increase became non-significant at 28 days (P>0.05). Our results indicate that NSC transplantation enhances endogenous cell proliferation in the SVZ and promotes angiogenesis in the peri-infarct zone, even if it is performed in the acute phase of ischemic injury., (© 2010 Japanese Society of Neuropathology.)

Neuronal nitric oxide synthase (nNOS) regulates neurogenesis in the normal developing brain, but the role of nNOS in neurogenesis of the adult ischemic brain remains unclear. The aim of this study was to investigate the temporal and spatial relationship between cell migration from the ependymal/subventricular zone (SVZ) to periinfarction and nNOS expression in the rat. Ependymal/subventricular zone cells were prelabeled with fluorescence dye DiI. Focal cerebral ischemia was induced by occlusion of the left middle cerebral artery. At 1, 3, 7, 14 and 21 days after ischemia, the rats were killed in order to determine the number of migrating cells, the colocalization of DiI and nNOS as well as nNOS quantity in specific regions. Compared to non-ischemic control and 1 day post-ischemia, the number of DiI-labeled cells in the selected regions increased at 3 days and peaked 14 days following ischemia. During 3-7 days post-ischemia, none of the migrating cells expressed nNOS and decreased nNOS expression was observed in the regions where migrating cells passed through. These results suggest the possible association between ependymal/SVZ cell migration and decreased nNOS expression within the areas including the migrating routes towards the peri-infarction.

Neuronal nitric oxide synthase (nNOS) regulates neurogenesis in normal developing brain, but the role of nNOS in neurogenesis in the ischemic brain remains unclear. To investigate the temporal and spatial relationship between cell proliferation of the ependymal/subventricular zone (SVZ), a principal neuroproliferative region in the adult brain, and nNOS expression, the male Sprague-Dawley rats weighing 250-350 g were used. The focal cerebral ischemia was induced by middle cerebral artery occlusion (MCAO). 10 microl of 0.2% fluorescence dye DiI was injected into the right lateral ventricle to prelabel ependymal/subventricular zone cells before ischemia. The rats were killed immediately after ischemia and days 1, 3, 7, 11, 14, 21 and 28 after ischemia. DiI-labeled cell counting was employed to assess cell proliferation. Immunohistochemistry and grayscale analysis were performed to determine nNOS localization and its quantity in the specific regions. Compared with control, the density of DiI-labeled cells in the ipsilateral ependyma/SVZ was significantly higher at days 1, 3, 7 and 11 after ischemia, whereas the quantity of nNOS expression in the ependyma/SVZ adjacent regions was significantly lower at the above time points. Additionally, nNOS positive cells were largely excluded from SVZ, and their long processes did not enter the ependyma/SVZ. Our results indicate that after focal cerebral ischemia, decreased nNOS expression in the ipsilateral ependymal/SVZ adjacent regions might be related to cell proliferation in the ependymal/SVZ.