Immunohistochemical changes related to ageing in the mouse hippocampus and subventricular zone

We investigated mainly immunohistochemical changes of nestin (a marker of neuroepithelial stem cells) and Ki-67 (a marker of proliferating cells) proteins related to ageing in the mouse hippocampus and subventricular zone (SVZ) using young adult (8 weeks old) and middle-aged (40 weeks old) mice. In the present study, no significant changes in neurons and astrocytes of the hippocampal CAI sector were found in a middle-aged male ICR mice without severe senile weakness, as compared with young adult animals. In contrast, a significant change in the number of microglia was found in the hippocampal CAI sector of the middle-aged mice. Furthermore, no significant changes in the number of nestin- and Ki-67-positive cells were observed in the hippocampal CAI sector of the middle-aged mice. On the other hand, decreases in the number of nestin- and Ki67-immuno-positive cells were observed in the SVZ of the middle-aged mice. Furthermore, a migration of nestin- and Ki-67-immuno-reactive cells in the corpus callosum was not observed in the SVZ of the middle-aged mice. In the dentate gyrus, significant decreases in the number of Ki-67immunopositive cells were observed in the middle-aged mice. Our study also showed that nestin immunoreactivity was observed in both Ki-67-postive cells and astrocytes in the SVZ of young adult mice. These findings emphasize the need to recognize ageing as important factors in studies of microglia, which may help to clarify the role of glial cell structure and function during ageing processes. Furthermore, the present findings suggest that ageing processes may decrease neurogenesis in the corpus callosurn, SVZ and dentate gyrus. Thus our present findings provide valuable information for the neurogenesis during ageing processes. (C) 2007 Elsevier Ireland Ltd. All rights reserved.