Abstract 3830: Wnt/ beta-catenin Signaling is Upregulated Early Post-stroke and Exogenous Activation of the Pathway Promotes Neurogenesis, Enhances Functional Recovery and has Potential Neuroprotective Effects

Abstract

Introduction and Objectives: Wnt/ beta-catenin signaling has been identified as an essential component of adult neurogenesis within the hippocampus. Its role within the adult Subventricular Zone, SVZ, is less well understood, as is its role in the context of post-stroke neurogenesis. With this work we aim to 1) compare the levels of Wnt/ beta-catenin signaling at the neurogenic subventricular zone, SVZ, at 1, 3, 5 and 7 day post-stroke or SHAM surgery 2) to determine the cell types that upregulate the Wnt/ beta-catenin signaling pathway post-stroke 3) to determine the effect on neurogenesis and post-stroke recovery following 3.1 an intraparenchymal injection of a Wnt-3a liposomes able to activate the pathway and 3.2 ablation of the pathway through a conditional knock-out model. Methods and Results: - Wnt/ beta-catenin signaling is upregulated within the adult neurogenic subventricular zone, SVZ, at 1 and 3 days post 30 min MCAO but is unchanged compared to SHAM operated animals at 5 and 7 days post-stroke. Strokes were performed on adult male Axin2 +/- animals, reporter for Wnt/ beta-catenin signaling. - Doublecortin, DCX, positive immature neurons both at the SVZ and migrating towards the injury site were positive for the pathway, as were reactive astrocytes, expressing GFAP, and mature NeuN expressing neurons in both the cortex and striatum - Intraparenchymal injections of Wnt-3a liposomes, able to activate the Wnt/ beta-catenin pathway both in vivo and in vitro, significantly increased the levels of neurogenesis at the SVZ post-stroke, when compared to PBS liposomes (p<0.001, t-test). Wnt-3a or PBS liposomes were injected at 3, 5 and 7 days post-stroke and animals were sacrificed at the 2 week time point for histology and 6 weeks post-stroke for infarct size analyses. A trend in reduced infract size, as measured by MRI and silver staining, and a significant score improvement on the ladder test at 4 weeks post-stroke were also observed (p<0.01, t-test). - Conditional ablation of the Wnt/ beta-catenin pathway using the GLAST/ beta-catenin knock out mice, generated in collaboration with Dr. Magdalena Goetz laboratory at Heidelberg, resulted in a trend of larger stroke sizes, which is being reconfirmed. Conclusions: We have demonstrated that the Wnt/ beta-catenin signaling pathway is upregulated early post-stroke and is present within immature neurons, reactive astrocytes and mature neurons. Exogenous activation of the pathway post-stroke promotes neurogenesis and has beneficial effects on functional recovery as well as potential neuroprotective effects.