Wnt expression in the adult rat subventricular zone after stroke

Neurogenesis occurs in adult brain neural progenitor cells (NPCs) located in the subventricular zone (SVZ) of the lateral ventricle and the subgrandular zone of the hippocampal dentate gyrus. After ischemic stroke, NPCs in the SVZ proliferate and migrate towards the ischemic boundary region to replenish damaged neurons. During development, the Wnt pathways contribute to stem cell maintenance and promote neurogenesis. We hypothesized that stroke up regulates Wnt family genes in SVZ cells. Non-ischemic and ischemic cultured SVZ cells and a single population of non-ischemic and ischemic SVZ cells isolated by laser capture microdissection (LCM) were analyzed for Wnt pathway expression using real-time RT-PCR and immunostaining. The number of neurospheres increased significantly (p<0.05) in SVZ cells derived from ischemic (32+/-4.7/rat) compared with the number in non-ischemic SVZ cells (18+/-3/rat). Wnt family gene mRNA levels were detected in SVZ cells isolated from both cultured and LCM SVZ cells, however there was no up regulation between non-ischemic and ischemic SVZ cells. Immunostaining on brain sections also demonstrated no up regulation of Wnt pathway protein between ischemic and non-ischemic SVZ cells. Expression of the Wnt family genes in SVZ cells support the hypothesis that the Wnt pathway may be involved in neurogenesis in the adult brain. However, ischemia does not up regulate Wnt family gene expression.