Human embryonic neural stem cell transplantation increases subventricular zone cell proliferation and promotes peri-infarct angiogenesis after focal cerebral ischemia

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.