WNT SIGNALING PROMOTES AXONAL REGENERATION FOLLOWING OPTIC NERVE INJURY IN THE MOUSE

Adult mammalian CNS axons generally do not regenerate, creating an obstacle to effective repair and recovery after neuronal injury. The canonical Wnt/beta-catenin signaling pathway is an essential signal transduction cascade that regulates axon growth and neurite extension in the developing mammalian embryo. In this study, we investigated whether a Wnt/beta-catenin signaling activator could be repurposed to induce regeneration in the adult CNS after axonal injury. We used a retinal ganglion cell (RGC) axon crush injury model in a transgenic Wnt reporter mouse, and intravitreal injections were used to deliver Wnt3a or saline to the RGC cell bodies within the retina. Our findings demonstrated that Wnt3a induced Wnt signaling in RGCs and resulted in significant axonal regrowth past the lesion site when measured at two and four weeks post-injury. Furthermore, Wnt3a-injected eyes showed increased survival of RGCs and significantly higher pattern electroretinography (PERG) amplitudes compared to the control. Additionally, Wnt3a-induced axonal regeneration and RGC survival were associated with elevated activation of the transcription factor Stat3, and reducing expression of Stat3 using a conditional Stat3 knock-out mouse line led to diminished Wnt3a-dependent axonal regeneration and RGC survival. Therefore, these findings reveal a novel role for retinal Wnt signaling in axonal regrowth and RGC survival following axonal injury, which may lead to the development of novel therapies for axonal regeneration. (C) 2016 IBRO. Published by Elsevier Ltd. All rights reserved.