Abstract
Purpose :
A primary challenge during optic neuropathies is to promote Retinal Ganglion Cell (RGC) survival and axon growth during or after axon degeneration. Although the role of canonical Wnt ligands such as Wnt3a was studied in RGC axon regeneration, the effect of non-canonical Wnt ligands such as Wnt5a on RGC protection and axon growth and regeneration was not analyzed. In the current study, we explored the role of Wnt5a in RGC protection and optic nerve regeneration in a mouse model of traumatic optic neuropathy.
Methods :
Primary RGC cultures were treated with different concentrations of recombinant Wnt5a to identify its effect on RGC neurite growth and complexity. Optic nerve crush mouse model was used to identify the effect of intravitreal injections of Wnt5a on RGC protection and optic nerve regeneration after 2 weeks of injury. Western blots and IHC were performed with Wnt5a intravitreally injected retinal lysates and retinal sections respectively, to identify the induced signaling mechanisms in retinal cells. PERG was used for the functional assessment of RGC.
Results :
Primary RGCs treated with 20ng (Average neurite length (ANL); 138±11.6 mean±SD, p=0.0003), 50ng (ANL; 236.5±11.9, p<0.0001) and 100ng (ANL; 407.6±29.5, p<0.0001) concentration of Wnt5a protein showed significantly increased average neurite length and neurite complexity compared to BSA treated RGCs (ANL; 35.16±2.63). The optic nerve sections also showed significant increase in axon length and axon number in Wnt5a injected eyes compared to saline injected eyes. The western blots showed a significant increase in phosphorylation of CamKII (p<0.0001), phosphorylation of JNK (p=0.0007) and phosphorylation of STAT3 (p<0.0001) in Wnt5a 20ng and 50ng injected eyes in comparison with PBS injected eyes. The IHC of retinal sections identified the activation of CamKII and JNK in RGCs.
Conclusions :
For the first time, this study identified Wnt5a, a non-canonical Wnt ligand as a regulator of RGC protection, neurite growth and optic nerve regeneration. The induced CamKII and JNK/STAT3 signaling mechanisms in RGC and other retinal cells such as Muller glia by Wnt5a could be responsible for RGC protection and optic nerve regeneration. This study identifies the importance of Wnt5a and non-canonical Wnt signaling mechanisms to induce RGC protection and RGC axon regeneration that could be useful as therapeutic targets.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.